Tidy HTML

05-03.html

@@ -1,234 +1,232 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: Crossing the Border</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=05//-->
-<!--PAGES=118-121//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="05-02.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="05-04.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P><B>LISTING 5.1 SEARCH.C</B></P>
-<!-- CODE //-->
-<PRE>
-/* Program to search the file specified by the first command-line
- * argument for the string specified by the second command-line
- * argument. Performs the search by reading and searching blocks
- * of size BLOCK_SIZE. */
-
-#include &lt;stdio.h&gt;
-#include &lt;fcntl.h&gt;
-#include &lt;string.h&gt;
-#include &lt;alloc.h&gt;   /* alloc.h for Borland compilers,
-                        malloc.h for Microsoft compilers */
-
-#define BLOCK_SIZE  0x4000   /* we&rsquo;ll process the file in 16K blocks */
-
-/* Searches the specified number of sequences in the specified
-   buffer for matches to SearchString of SearchStringLength. Note
-   that the calling code should already have shortened SearchLength
-   if necessary to compensate for the distance from the end of the
-   buffer to the last possible start of a matching sequence in the
-   buffer.
-*/
-
-int SearchForString(unsigned char *Buffer, int SearchLength,
-   unsigned char *SearchString, int SearchStringLength)
-{
-   unsigned char *PotentialMatch;
-
-   /* Search so long as there are potential-match locations
-      remaining */
-   while ( SearchLength ) {
-     /* See if the first character of SearchString can be found */
-     if ( (PotentialMatch =
-           memchr(Buffer, *SearchString, SearchLength)) == NULL ) {
-        break;   /* No matches in this buffer */
-     }
-      /* The first character matches; see if the rest of the string
-         also matches */
-      if ( SearchStringLength == 1 ) {
-         return(1);  /* That one matching character was the whole
-                        search string, so we&rsquo;ve got a match */
-      }
-      else {
-         /* Check whether the remaining characters match */
-         if ( !memcmp(PotentialMatch + 1, SearchString + 1,
-               SearchStringLength - 1) ) {
-            return(1);  /* We&rsquo;ve got a match */
-         }
-      }
-      /* The string doesn&rsquo;t match; keep going by pointing past the
-         potential match location we just rejected */
-      SearchLength -= PotentialMatch - Buffer + 1;
-      Buffer = PotentialMatch + 1;
-   }
-
-   return(0);  /* No match found */
-}
-
-main(int argc, char *argv[]) {
-   int Done;               /* Indicates whether search is done */
-   int Handle;             /* Handle of file being searched */
-   int WorkingLength;      /* Length of current block */
-   int SearchStringLength; /* Length of string to search for */
-   int BlockSearchLength;  /* Length to search in current block */
-   int Found;              /* Indicates final search completion
-                              status */
-   int NextLoadCount;      /* # of bytes to read into next block,
-                              accounting for bytes copied from the
-                              last block */
-   unsigned char *WorkingBlock; /* Block storage buffer */
-   unsigned char *SearchString; /* Pointer to the string to search for */
-   unsigned char *NextLoadPtr;  /* Offset at which to start loading
-                                   the next block, accounting for
-                                   bytes copied from the last block */
-
-   /* Check for the proper number of arguments */
-   if ( argc != 3 ) {
-      printf(&ldquo;usage: search filename search-string\n&rdquo;);
-      exit(1);
-   }
-
-   /* Try to open the file to be searched */
-   if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
-      printf(&ldquo;Can&rsquo;t open file: %s\n&rdquo;, argv[1]);
-      exit(1);
-   }
-   /* Calculate the length of text to search for */
-   SearchString = argv[2];
-   SearchStringLength = strlen(SearchString);
-   /* Try to get memory in which to buffer the data */
-   if ( (WorkingBlock = malloc(BLOCK_SIZE)) == NULL ) {
-      printf(&ldquo;Can&rsquo;t get enough memory\n&rdquo;);
-      exit(1);
-   }
-
-   /* Load the first block at the start of the buffer, and try to
-      fill the entire buffer */
-   NextLoadPtr = WorkingBlock;
-   NextLoadCount = BLOCK_SIZE;
-   Done = 0;      /* Not done with search yet */
-   Found = 0;     /* Assume we won&rsquo;t find a match */
-   /* Search the file in BLOCK_SIZE chunks */
-   do {
-      /* Read in however many bytes are needed to fill out the block
-         (accounting for bytes copied over from the last block), or
-         the rest of the bytes in the file, whichever is less */
-      if ( (WorkingLength = read(Handle, NextLoadPtr,
-            NextLoadCount)) == -1 ) {
-         printf(&ldquo;Error reading file %s\n&rdquo;, argv[1]);
-         exit(1);
-      }
-      /* If we didn&rsquo;t read all the bytes we requested, we&rsquo;re done
-         after this block, whether we find a match or not */
-      if ( WorkingLength != NextLoadCount ) {
-         Done = 1;
-      }
-
-      /* Account for any bytes we copied from the end of the last
-         block in the total length of this block */
-      WorkingLength += NextLoadPtr - WorkingBlock;
-      /* Calculate the number of bytes in this block that could
-         possibly be the start of a matching sequence that lies
-         entirely in this block (sequences that run off the end of
-         the block will be transferred to the next block and found
-         when that block is searched)
-      */
-      if ( (BlockSearchLength =
-               WorkingLength - SearchStringLength + 1) &lt;= 0 ) {
-            Done = 1;  /* Too few characters in this block for
-                          there to be any possible matches, so this
-                          is the final block and we&rsquo;re done without
-                          finding a match
-                       */
-      }
-      else {
-         /* Search this block */
-         if ( SearchForString(WorkingBlock, BlockSearchLength,
-               SearchString, SearchStringLength) ) {
-            Found = 1;     /* We&rsquo;ve found a match */
-            Done = 1;
-         }
-         else {
-            /* Copy any bytes from the end of the block that start
-               potentially-matching sequences that would run off
-               the end of the block over to the next block */
-            if ( SearchStringLength &gt; 1 ) {
-               memcpy(WorkingBlock,
-                  WorkingBlock+BLOCK_SIZE - SearchStringLength + 1,
-                  SearchStringLength - 1);
-            }
-            /* Set up to load the next bytes from the file after the
-               bytes copied from the end of the current block */
-            NextLoadPtr = WorkingBlock + SearchStringLength - 1;
-            NextLoadCount = BLOCK_SIZE - SearchStringLength + 1;
-         }
-      }
-   } while ( !Done );
-
-   /* Report the results */
-   if ( Found ) {
-      printf(&ldquo;String found\n&rdquo;);
-   } else {
-      printf(&ldquo;String not found\n&rdquo;);
-   }
-   exit(Found);   /* Return the found/not found status as the
-                     DOS errorlevel */
-}
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="05-02.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="05-04.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-
-<hr width="90%" size="1" noshade>
-<div align="center">
-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
-<!-- all of the reference materials (books) have the footer and subfoot reveresed -->
-<!-- reference_subfoot = footer -->
-<!-- reference_footer = subfoot -->
-
-<!-- BEGIN SUB FOOTER -->
-</BODY>
-</HTML>
-
-<!-- END FOOTER -->
-
-
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: Crossing the Border</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=05//-->
+  <!--PAGES=118-121//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="05-02.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="05-04.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p><b>LISTING 5.1 SEARCH.C</b></p><!-- CODE //-->
+  <pre>
+/* Program to search the file specified by the first command-line
+ * argument for the string specified by the second command-line
+ * argument. Performs the search by reading and searching blocks
+ * of size BLOCK_SIZE. */
+
+#include &lt;stdio.h&gt;
+#include &lt;fcntl.h&gt;
+#include &lt;string.h&gt;
+#include &lt;alloc.h&gt;   /* alloc.h for Borland compilers,
+                        malloc.h for Microsoft compilers */
+
+#define BLOCK_SIZE  0x4000   /* we&rsquo;ll process the file in 16K blocks */
+
+/* Searches the specified number of sequences in the specified
+   buffer for matches to SearchString of SearchStringLength. Note
+   that the calling code should already have shortened SearchLength
+   if necessary to compensate for the distance from the end of the
+   buffer to the last possible start of a matching sequence in the
+   buffer.
+*/
+
+int SearchForString(unsigned char *Buffer, int SearchLength,
+   unsigned char *SearchString, int SearchStringLength)
+{
+   unsigned char *PotentialMatch;
+
+   /* Search so long as there are potential-match locations
+      remaining */
+   while ( SearchLength ) {
+     /* See if the first character of SearchString can be found */
+     if ( (PotentialMatch =
+           memchr(Buffer, *SearchString, SearchLength)) == NULL ) {
+        break;   /* No matches in this buffer */
+     }
+      /* The first character matches; see if the rest of the string
+         also matches */
+      if ( SearchStringLength == 1 ) {
+         return(1);  /* That one matching character was the whole
+                        search string, so we&rsquo;ve got a match */
+      }
+      else {
+         /* Check whether the remaining characters match */
+         if ( !memcmp(PotentialMatch + 1, SearchString + 1,
+               SearchStringLength - 1) ) {
+            return(1);  /* We&rsquo;ve got a match */
+         }
+      }
+      /* The string doesn&rsquo;t match; keep going by pointing past the
+         potential match location we just rejected */
+      SearchLength -= PotentialMatch - Buffer + 1;
+      Buffer = PotentialMatch + 1;
+   }
+
+   return(0);  /* No match found */
+}
+
+main(int argc, char *argv[]) {
+   int Done;               /* Indicates whether search is done */
+   int Handle;             /* Handle of file being searched */
+   int WorkingLength;      /* Length of current block */
+   int SearchStringLength; /* Length of string to search for */
+   int BlockSearchLength;  /* Length to search in current block */
+   int Found;              /* Indicates final search completion
+                              status */
+   int NextLoadCount;      /* # of bytes to read into next block,
+                              accounting for bytes copied from the
+                              last block */
+   unsigned char *WorkingBlock; /* Block storage buffer */
+   unsigned char *SearchString; /* Pointer to the string to search for */
+   unsigned char *NextLoadPtr;  /* Offset at which to start loading
+                                   the next block, accounting for
+                                   bytes copied from the last block */
+
+   /* Check for the proper number of arguments */
+   if ( argc != 3 ) {
+      printf(&ldquo;usage: search filename search-string\n&rdquo;);
+      exit(1);
+   }
+
+   /* Try to open the file to be searched */
+   if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
+      printf(&ldquo;Can&rsquo;t open file: %s\n&rdquo;, argv[1]);
+      exit(1);
+   }
+   /* Calculate the length of text to search for */
+   SearchString = argv[2];
+   SearchStringLength = strlen(SearchString);
+   /* Try to get memory in which to buffer the data */
+   if ( (WorkingBlock = malloc(BLOCK_SIZE)) == NULL ) {
+      printf(&ldquo;Can&rsquo;t get enough memory\n&rdquo;);
+      exit(1);
+   }
+
+   /* Load the first block at the start of the buffer, and try to
+      fill the entire buffer */
+   NextLoadPtr = WorkingBlock;
+   NextLoadCount = BLOCK_SIZE;
+   Done = 0;      /* Not done with search yet */
+   Found = 0;     /* Assume we won&rsquo;t find a match */
+   /* Search the file in BLOCK_SIZE chunks */
+   do {
+      /* Read in however many bytes are needed to fill out the block
+         (accounting for bytes copied over from the last block), or
+         the rest of the bytes in the file, whichever is less */
+      if ( (WorkingLength = read(Handle, NextLoadPtr,
+            NextLoadCount)) == -1 ) {
+         printf(&ldquo;Error reading file %s\n&rdquo;, argv[1]);
+         exit(1);
+      }
+      /* If we didn&rsquo;t read all the bytes we requested, we&rsquo;re done
+         after this block, whether we find a match or not */
+      if ( WorkingLength != NextLoadCount ) {
+         Done = 1;
+      }
+
+      /* Account for any bytes we copied from the end of the last
+         block in the total length of this block */
+      WorkingLength += NextLoadPtr - WorkingBlock;
+      /* Calculate the number of bytes in this block that could
+         possibly be the start of a matching sequence that lies
+         entirely in this block (sequences that run off the end of
+         the block will be transferred to the next block and found
+         when that block is searched)
+      */
+      if ( (BlockSearchLength =
+               WorkingLength - SearchStringLength + 1) &lt;= 0 ) {
+            Done = 1;  /* Too few characters in this block for
+                          there to be any possible matches, so this
+                          is the final block and we&rsquo;re done without
+                          finding a match
+                       */
+      }
+      else {
+         /* Search this block */
+         if ( SearchForString(WorkingBlock, BlockSearchLength,
+               SearchString, SearchStringLength) ) {
+            Found = 1;     /* We&rsquo;ve found a match */
+            Done = 1;
+         }
+         else {
+            /* Copy any bytes from the end of the block that start
+               potentially-matching sequences that would run off
+               the end of the block over to the next block */
+            if ( SearchStringLength &gt; 1 ) {
+               memcpy(WorkingBlock,
+                  WorkingBlock+BLOCK_SIZE - SearchStringLength + 1,
+                  SearchStringLength - 1);
+            }
+            /* Set up to load the next bytes from the file after the
+               bytes copied from the end of the current block */
+            NextLoadPtr = WorkingBlock + SearchStringLength - 1;
+            NextLoadCount = BLOCK_SIZE - SearchStringLength + 1;
+         }
+      }
+   } while ( !Done );
+
+   /* Report the results */
+   if ( Found ) {
+      printf(&ldquo;String found\n&rdquo;);
+   } else {
+      printf(&ldquo;String not found\n&rdquo;);
+   }
+   exit(Found);   /* Return the found/not found status as the
+                     DOS errorlevel */
+}
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="05-02.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="05-04.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+  <hr width="90%" size="1" noshade="noshade" />
+
+  <div align="center">
+    Graphics Programming Black Book &copy; 2001 Michael Abrash
+  </div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
+  <!-- reference_subfoot = footer -->
+  <!-- reference_footer = subfoot -->
+  <!-- BEGIN SUB FOOTER -->
+  <!-- END FOOTER -->
+</body>
+</html>

09-04.html

@@ -1,202 +1,199 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: Hints My Readers Gave Me</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=09//-->
-<!--PAGES=178-180//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="09-03.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="09-05.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P><B>LISTING 9.2 L9-2.ASM</B></P>
-<!-- CODE //-->
-<PRE>
-; Searches a text buffer for a text string. Uses REPNZ SCASB to scan
-; the buffer for locations that match a specified character of the
-; searched-for string, then uses REPZ CMPS to check fully only those
-; locations that REPNZ SCASB has identified as potential matches.
-;
-; C small model-callable as:
-;    unsigned char * FindString(unsigned char * Buffer,
-;     unsigned int BufferLength, unsigned char * SearchString,
-;     unsigned int SearchStringLength,
-;     unsigned int ScanCharOffset);
-;
-; Returns a pointer to the first match for SearchString in Buffer,or
-; a NULL pointer if no match is found. Buffer should not start at
-; offset 0 in the data segment to avoid confusing a match at 0 with
-; no match found.
-Parms  struc
-                        dw      2 dup(?)      ;pushed BP/return address
-Buffer                  dw      ?             ;pointer to buffer to search
-BufferLength            dw      ?             ;length of buffer to search
-SearchString            dw      ?             ;pointer to string for which to search
-SearchStringLength      dw      ?             ;length of string for which to search
-ScanCharOffset          dw      ?             ;offset in string of character for
-                                              ; which to scan
-Parmsends
-      .model      small
-      .code
-      public _FindString
-_FindStringprocnear
-      push     bp      ;preserve caller&rsquo;s stack frame
-      mov      bp,sp   ;point to our stack frame
-      push     si      ;preserve caller&rsquo;s register variables
-      push     di
-      cld              ;make string instructions increment pointers
-      mov      si,[bp+SearchString]       ;pointer to string to search for
-      mov      cx,[bp+SearchStringLength] ;length of string
-      jcxz     FindStringNotFound         ;no match if string is 0 length
-      mov      dx,[bp+BufferLength]       ;length of buffer
-      sub      dx,cx                      ;difference between buffer and search
-                                          ; lengths
-      jc        FindStringNotFound ;no match if search string is
-                    ; longer than buffer
-      inc       dx  ; difference between buffer and search string
-                    ; lengths, plus 1 (# of possible string start
-                    ; locations to check in the buffer)
-      mov       di,ds
-      mov       es,di
-      mov       di,[bp+Buffer]         ;point ES:DI to buffer to search thru
-      mov       bx,[bp+ScanCharOffset] ;offset in string of character
-                                       ; on which to scan
-      add       di,bx         ;point ES:DI to first buffer byte to scan
-      mov       al,[si+bx]    ;put the scan character in AL
-      inc       bx            ;set BX to the offset back to the start of the
-                              ; potential full match after a scan match,
-                              ; accounting for the 1-byte overrun of
-                              ; REPNZ SCASB
-FindStringLoop:
-      mov       cx,dx              ;put remaining buffer search length in CX
-      repnz     scasb              ;scan for the scan byte
-      jnz       FindStringNotFound ;not found, so there&rsquo;s no match
-                                   ;found, so we have a potential match-check the
-                                   ; rest of this candidate location
-      push       di                ;remember the address of the next byte to scan
-      mov        dx,cx             ;set aside the remaining length to search in
-                                   ; the buffer
-      sub        di,bx             ;point back to the potential start of the
-                                   ; match in the buffer
-      mov        si,[bp+SearchString]       ;point to the start of the string
-      mov        cx,[bp+SearchStringLength] ;string length
-      shr        cx,1                       ;convert to word for faster search
-      jnc        FindStringWord             ;do word search if no odd byte
-      cmpsb                                 ;compare the odd byte
-      jnz        FindStringNoMatch          ;odd byte doesn&rsquo;t match, so we
-                                            ; haven&rsquo;t found the search string here
-FindStringWord:
-      jcxz       FindStringFound        ;if the string is only 1 byte long,
-                                        ; we&rsquo;ve found a match
-      repz       cmpsw                  ;check the rest of the string a word at a time
-      jz         FindStringFound        ;it&rsquo;s a match
-FindStringNoMatch:
-      pop        di                     ;get back pointer to the next byte to scan
-      and        dx,dx                  ;is there anything left to check?
-      jnz        FindStringLoop         ;yes-check next byte
-FindStringNotFound:
-      sub        ax,ax                  ;return a NULL pointer indicating that the
-      jmp        FindStringDone         ; string was not found
-FindStringFound:
-      pop         ax         ;point to the buffer location at which the
-      sub         ax,bx      ; string was found (earlier we pushed the
-                             ; address of the byte after the scan match)
-FindStringDone:
-      pop         di         ;restore caller&rsquo;s register variables
-      pop         si
-      pop         bp         ;restore caller&rsquo;s stack frame
-      ret
-_FindStringendp
-      end
-</PRE>
-<!-- END CODE //-->
-<P><B>LISTING 9.3 L9-3.C</B></P>
-<!-- CODE //-->
-<PRE>
-/* Program to exercise buffer-search routines in Listings 9.1 &amp; 9.2 */
-#include &lt;stdio.h&gt;
-#include &lt;string.h&gt;
-
-#define DISPLAY_LENGTH  40
-extern unsigned char * FindString(unsigned char *, unsigned int,
-      unsigned char *, unsigned int, unsigned int);
-void main(void);
-static unsigned char TestBuffer[] = &ldquo;When, in the course of human \
-events, it becomes necessary for one people to dissolve the \
-political bands which have connected them with another, and to \
-assume among the powers of the earth the separate and equal station \
-to which the laws of nature and of nature&rsquo;s God entitle them...&rdquo;;
-void main() {
-   static unsigned char TestString[] = &ldquo;equal&rdquo;;
-   unsigned char TempBuffer[DISPLAY_LENGTH+1];
-   unsigned char *MatchPtr;
-   /* Search for TestString and report the results */
-   if ((MatchPtr = FindString(TestBuffer,
-         (unsigned int) strlen(TestBuffer), TestString,
-         (unsigned int) strlen(TestString), 1)) == NULL) {
-      /* TestString wasn&rsquo;t found */
-      printf(&ldquo;\&rdquo;%s\&ldquo; not found\n&rdquo;, TestString);
-   } else {
-      /* TestString was found. Zero-terminate TempBuffer; strncpy
-         won&rsquo;t do it if DISPLAY_LENGTH characters are copied */
-      TempBuffer[DISPLAY_LENGTH] = 0;
-      printf(&ldquo;\&rdquo;%s\&ldquo; found. Next %d characters at match:\n\&rdquo;%s\&ldquo;\n&rdquo;,
-            TestString, DISPLAY_LENGTH,
-            strncpy(TempBuffer, MatchPtr, DISPLAY_LENGTH));
-   }
-}
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="09-03.html">Previous</A></TD>
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-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: Hints My Readers Gave Me</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=09//-->
+  <!--PAGES=178-180//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="09-03.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="09-05.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p><b>LISTING 9.2 L9-2.ASM</b></p><!-- CODE //-->
+  <pre>
+; Searches a text buffer for a text string. Uses REPNZ SCASB to scan
+; the buffer for locations that match a specified character of the
+; searched-for string, then uses REPZ CMPS to check fully only those
+; locations that REPNZ SCASB has identified as potential matches.
+;
+; C small model-callable as:
+;    unsigned char * FindString(unsigned char * Buffer,
+;     unsigned int BufferLength, unsigned char * SearchString,
+;     unsigned int SearchStringLength,
+;     unsigned int ScanCharOffset);
+;
+; Returns a pointer to the first match for SearchString in Buffer,or
+; a NULL pointer if no match is found. Buffer should not start at
+; offset 0 in the data segment to avoid confusing a match at 0 with
+; no match found.
+Parms  struc
+                        dw      2 dup(?)      ;pushed BP/return address
+Buffer                  dw      ?             ;pointer to buffer to search
+BufferLength            dw      ?             ;length of buffer to search
+SearchString            dw      ?             ;pointer to string for which to search
+SearchStringLength      dw      ?             ;length of string for which to search
+ScanCharOffset          dw      ?             ;offset in string of character for
+                                              ; which to scan
+Parmsends
+      .model      small
+      .code
+      public _FindString
+_FindStringprocnear
+      push     bp      ;preserve caller&rsquo;s stack frame
+      mov      bp,sp   ;point to our stack frame
+      push     si      ;preserve caller&rsquo;s register variables
+      push     di
+      cld              ;make string instructions increment pointers
+      mov      si,[bp+SearchString]       ;pointer to string to search for
+      mov      cx,[bp+SearchStringLength] ;length of string
+      jcxz     FindStringNotFound         ;no match if string is 0 length
+      mov      dx,[bp+BufferLength]       ;length of buffer
+      sub      dx,cx                      ;difference between buffer and search
+                                          ; lengths
+      jc        FindStringNotFound ;no match if search string is
+                    ; longer than buffer
+      inc       dx  ; difference between buffer and search string
+                    ; lengths, plus 1 (# of possible string start
+                    ; locations to check in the buffer)
+      mov       di,ds
+      mov       es,di
+      mov       di,[bp+Buffer]         ;point ES:DI to buffer to search thru
+      mov       bx,[bp+ScanCharOffset] ;offset in string of character
+                                       ; on which to scan
+      add       di,bx         ;point ES:DI to first buffer byte to scan
+      mov       al,[si+bx]    ;put the scan character in AL
+      inc       bx            ;set BX to the offset back to the start of the
+                              ; potential full match after a scan match,
+                              ; accounting for the 1-byte overrun of
+                              ; REPNZ SCASB
+FindStringLoop:
+      mov       cx,dx              ;put remaining buffer search length in CX
+      repnz     scasb              ;scan for the scan byte
+      jnz       FindStringNotFound ;not found, so there&rsquo;s no match
+                                   ;found, so we have a potential match-check the
+                                   ; rest of this candidate location
+      push       di                ;remember the address of the next byte to scan
+      mov        dx,cx             ;set aside the remaining length to search in
+                                   ; the buffer
+      sub        di,bx             ;point back to the potential start of the
+                                   ; match in the buffer
+      mov        si,[bp+SearchString]       ;point to the start of the string
+      mov        cx,[bp+SearchStringLength] ;string length
+      shr        cx,1                       ;convert to word for faster search
+      jnc        FindStringWord             ;do word search if no odd byte
+      cmpsb                                 ;compare the odd byte
+      jnz        FindStringNoMatch          ;odd byte doesn&rsquo;t match, so we
+                                            ; haven&rsquo;t found the search string here
+FindStringWord:
+      jcxz       FindStringFound        ;if the string is only 1 byte long,
+                                        ; we&rsquo;ve found a match
+      repz       cmpsw                  ;check the rest of the string a word at a time
+      jz         FindStringFound        ;it&rsquo;s a match
+FindStringNoMatch:
+      pop        di                     ;get back pointer to the next byte to scan
+      and        dx,dx                  ;is there anything left to check?
+      jnz        FindStringLoop         ;yes-check next byte
+FindStringNotFound:
+      sub        ax,ax                  ;return a NULL pointer indicating that the
+      jmp        FindStringDone         ; string was not found
+FindStringFound:
+      pop         ax         ;point to the buffer location at which the
+      sub         ax,bx      ; string was found (earlier we pushed the
+                             ; address of the byte after the scan match)
+FindStringDone:
+      pop         di         ;restore caller&rsquo;s register variables
+      pop         si
+      pop         bp         ;restore caller&rsquo;s stack frame
+      ret
+_FindStringendp
+      end
+</pre><!-- END CODE //-->
+
+  <p><b>LISTING 9.3 L9-3.C</b></p><!-- CODE //-->
+  <pre>
+/* Program to exercise buffer-search routines in Listings 9.1 &amp; 9.2 */
+#include &lt;stdio.h&gt;
+#include &lt;string.h&gt;
+
+#define DISPLAY_LENGTH  40
+extern unsigned char * FindString(unsigned char *, unsigned int,
+      unsigned char *, unsigned int, unsigned int);
+void main(void);
+static unsigned char TestBuffer[] = &ldquo;When, in the course of human \
+events, it becomes necessary for one people to dissolve the \
+political bands which have connected them with another, and to \
+assume among the powers of the earth the separate and equal station \
+to which the laws of nature and of nature&rsquo;s God entitle them...&rdquo;;
+void main() {
+   static unsigned char TestString[] = &ldquo;equal&rdquo;;
+   unsigned char TempBuffer[DISPLAY_LENGTH+1];
+   unsigned char *MatchPtr;
+   /* Search for TestString and report the results */
+   if ((MatchPtr = FindString(TestBuffer,
+         (unsigned int) strlen(TestBuffer), TestString,
+         (unsigned int) strlen(TestString), 1)) == NULL) {
+      /* TestString wasn&rsquo;t found */
+      printf(&ldquo;\&rdquo;%s\&ldquo; not found\n&rdquo;, TestString);
+   } else {
+      /* TestString was found. Zero-terminate TempBuffer; strncpy
+         won&rsquo;t do it if DISPLAY_LENGTH characters are copied */
+      TempBuffer[DISPLAY_LENGTH] = 0;
+      printf(&ldquo;\&rdquo;%s\&ldquo; found. Next %d characters at match:\n\&rdquo;%s\&ldquo;\n&rdquo;,
+            TestString, DISPLAY_LENGTH,
+            strncpy(TempBuffer, MatchPtr, DISPLAY_LENGTH));
+   }
+}
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="09-03.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="09-05.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+  <hr width="90%" size="1" noshade="noshade" />
+
+  <div align="center">
+    Graphics Programming Black Book &copy; 2001 Michael Abrash
+  </div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
+  <!-- reference_subfoot = footer -->
+  <!-- reference_footer = subfoot -->
+  <!-- BEGIN SUB FOOTER -->
+  <!-- END FOOTER -->
+</body>
+</html>

14-05.html

@@ -1,229 +1,227 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: Boyer-Moore String Searching</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=14//-->
-<!--PAGES=271-274//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="14-04.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="14-06.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P><B>LISTING 14.3 L14-3.ASM</B></P>
-<!-- CODE //-->
-<PRE>
-; Searches a buffer for a specified pattern. In case of a mismatch,
-; uses the value of the mismatched byte to skip across as many
-; potential match locations as possible (partial Boyer-Moore).
-; Returns start offset of first match searching forward, or NULL if
-; no match is found.
-; Tested with TASM.
-; C near-callable as:
-;       unsigned char * FindString(unsigned char * BufferPtr,
-;          unsigned int BufferLength, unsigned char * PatternPtr,
-;          unsigned int PatternLength);
-
-parms   struc
-        dw      2 dup(?)   ;pushed BP &amp; return address
-BufferPtr dw    ?          ;pointer to buffer to be searched
-BufferLength dw ?          ;# of bytes in buffer to be searched
-PatternPtr dw   ?          ;pointer to pattern for which to search
-PatternLength dw ?         ;length of pattern for which to search
-parms   ends
-
-        .model small
-        .code
-        public _FindString
-_FindString     proc    near
-        cld
-        push    bp         ;preserve caller&rsquo;s stack frame
-        mov     bp,sp      ;point to our stack frame
-        push    si         ;preserve caller&rsquo;s register variables
-        push    di
-        sub     sp,256*2   ;allocate space for SkipTable
-; Create the table of distances by which to skip ahead on mismatches
-; for every possible byte value. First, initialize all skips to the
-; pattern length; this is the skip distance for bytes that don&rsquo;t
-; appear in the pattern.
-        mov     ax,[bp+PatternLength]
-        and     ax,ax      ;return an instant match if the pattern is
-        jz      InstantMatch ;0-length
-        mov     di,ds
-        mov     es,di      ;ES=DS=SS
-        mov     di,sp      ;point to SkipBuffer
-        mov     cx,256
-        rep     stosw
-        dec     ax                      ;from now on, we only need
-        mov     [bp+PatternLength],ax   ; PatternLength - 1
-; Point to last (rightmost) byte of first potential pattern match
-; location in buffer.
-        add     [bp+BufferPtr],ax
-; Reject if buffer is too small, and set the count of the number of
-; potential pattern match locations in the buffer.
-        sub     [bp+BufferLength],ax
-        jbe     NoMatch
-; Set the skip values for the bytes that do appear in the pattern to
-; the distance from the byte location to the end of the pattern.
-; When there are multiple instances of the same byte, the rightmost
-; instance&rsquo;s skip value is used. Note that the rightmost byte of the
-; pattern isn&rsquo;t entered in the skip table; if we get that value for
-; a mismatch, we know for sure that the right end of the pattern has
-; already passed the mismatch location, so this is not a relevant byte
-; for skipping purposes.
-        mov     si,[bp+PatternPtr] ;point to start of pattern
-        and     ax,ax              ;are there any skips to set?
-        jz      SetSkipDone        ;no
-        mov     di,sp              ;point to SkipBuffer
-SetSkipLoop:
-        sub     bx,bx      ;prepare for word addressing off byte value
-        mov     bl,[si]    ;get the next pattern byte
-        inc     si         ;advance the pattern pointer
-        shl     bx,1       ;prepare for word lookup
-        mov     [di+bx],ax ;set the skip value when this byte value is
-                           ; the mismatch value in the buffer
-        dec     ax
-        jnz     SetSkipLoop
-SetSkipDone:
-        mov     dl,[si]            ;DL=rightmost pattern byte from now on
-        dec     si                 ;point to next-to-rightmost byte of pattern
-        mov     [bp+PatternPtr],si ; from now on
-; Search the buffer.
-        std                        ;for backward REPZ CMPSB
-        mov     di,[bp+BufferPtr]  ;point to first search location
-        mov     cx,[bp+BufferLength]   ;# of match locations to check
-SearchLoop:
-        mov     si,sp                  ;point SI to SkipTable
-; Skip through until there&rsquo;s a match for the rightmost pattern byte.
-QuickSearchLoop:
-        mov     bl,[di]         ;rightmost buffer byte at this location
-        cmp     dl,bl           ;does it match the rightmost pattern byte?
-        jz      FullCompare     ;yes, so keep going
-        sub     bh,bh           ;convert to a word
-        add     bx,bx           ;prepare for look-up in SkipTable
-        mov     ax,[si+bx]      ;get skip value from skip table for this
-                                ; mismatch value
-        add     di,ax           ;BufferPtr += Skip;
-        sub     cx,ax           ;BufferLength -= Skip;
-        ja      QuickSearchLoop ;continue if any buffer left
-        jmp     short NoMatch
-; Return a pointer to the start of the buffer (for 0-length pattern).
-        align   2
-InstantMatch:
-        mov     ax,[bp+BufferPtr]
-        jmp     short Done
-; Compare the pattern and the buffer location, searching from high
-; memory toward low (right to left).
-        align   2
-FullCompare:
-        mov     [bp+BufferPtr],di       ;save the current state of
-        mov     [bp+BufferLength],cx    ; the search
-        mov     cx,[bp+PatternLength]   ;# of bytes yet to compare
-        jcxz    Match                   ;done if only one character
-        mov     si,[bp+PatternPtr]      ;point to next-to-rightmost bytes
-        dec     di                      ; of buffer location and pattern
-        repz    cmpsb                   ;compare the rest of the pattern
-        jz      Match                   ;that&rsquo;s it; we&rsquo;ve found a match
-; It&rsquo;s a mismatch; let&rsquo;s see what we can learn from it.
-        inc     di      ;compensate for 1-byte overrun of REPZ CMPSB;
-                        ; point to mismatch location in buffer
-; # of bytes that did match.
-        mov     si,[bp+BufferPtr]
-        sub     si,di
-; If, based on the mismatch character, we can&rsquo;t even skip ahead as far
-; as where we started this particular comparison, then just advance by
-; 1 to the next potential match; otherwise, skip ahead from this
-; comparison location by the skip distance for the mismatch character,
-; less the distance covered by the partial match.
-        sub     bx,bx     ;prepare for word addressing off byte value
-        mov     bl,[di]   ;get the value of the mismatch byte in buffer
-        add     bx,bx     ;prepare for word look-up
-        add     bx,sp     ;SP points to SkipTable
-        mov     cx,[bx]   ;get the skip value for this mismatch
-        mov     ax,1      ;assume we&rsquo;ll just advance to the next
-                          ; potential match location
-        sub     cx,si     ;is the skip far enough to be worth taking?
-        jna     MoveAhead ;no, go with the default advance of 1
-        mov     ax,cx     ;yes; this is the distance to skip ahead from
-                          ; the last potential match location checked
-MoveAhead:
-; Skip ahead and perform the next comparison, if there&rsquo;s any buffer
-; left to check.
-        mov     di,[bp+BufferPtr]
-        add     di,ax                   ;BufferPtr += Skip;
-        mov     cx,[bp+BufferLength]
-        sub     cx,ax                   ;BufferLength -= Skip;
-        ja      SearchLoop              ;continue if any buffer left
-; Return a NULL pointer for no match.
-        align   2
-NoMatch:
-        sub     ax,ax
-        jmp     short Done
-; Return start of match in buffer (BufferPtr - (PatternLength - 1)).
-        align   2
-Match:
-        mov     ax,[bp+BufferPtr]
-        sub     ax,[bp+PatternLength]
-Done:
-        cld              ;restore default direction flag
-        add     sp,256*2 ;deallocate space for SkipTable
-        pop     di       ;restore caller&rsquo;s register variables
-        pop     si
-        pop     bp       ;restore caller&rsquo;s stack frame
-        ret
-_FindString     endp
-        end
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="14-04.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="14-06.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-
-<hr width="90%" size="1" noshade>
-<div align="center">
-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
-<!-- all of the reference materials (books) have the footer and subfoot reveresed -->
-<!-- reference_subfoot = footer -->
-<!-- reference_footer = subfoot -->
-
-<!-- BEGIN SUB FOOTER -->
-</BODY>
-</HTML>
-
-<!-- END FOOTER -->
-
-
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: Boyer-Moore String Searching</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=14//-->
+  <!--PAGES=271-274//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="14-04.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="14-06.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p><b>LISTING 14.3 L14-3.ASM</b></p><!-- CODE //-->
+  <pre>
+; Searches a buffer for a specified pattern. In case of a mismatch,
+; uses the value of the mismatched byte to skip across as many
+; potential match locations as possible (partial Boyer-Moore).
+; Returns start offset of first match searching forward, or NULL if
+; no match is found.
+; Tested with TASM.
+; C near-callable as:
+;       unsigned char * FindString(unsigned char * BufferPtr,
+;          unsigned int BufferLength, unsigned char * PatternPtr,
+;          unsigned int PatternLength);
+
+parms   struc
+        dw      2 dup(?)   ;pushed BP &amp; return address
+BufferPtr dw    ?          ;pointer to buffer to be searched
+BufferLength dw ?          ;# of bytes in buffer to be searched
+PatternPtr dw   ?          ;pointer to pattern for which to search
+PatternLength dw ?         ;length of pattern for which to search
+parms   ends
+
+        .model small
+        .code
+        public _FindString
+_FindString     proc    near
+        cld
+        push    bp         ;preserve caller&rsquo;s stack frame
+        mov     bp,sp      ;point to our stack frame
+        push    si         ;preserve caller&rsquo;s register variables
+        push    di
+        sub     sp,256*2   ;allocate space for SkipTable
+; Create the table of distances by which to skip ahead on mismatches
+; for every possible byte value. First, initialize all skips to the
+; pattern length; this is the skip distance for bytes that don&rsquo;t
+; appear in the pattern.
+        mov     ax,[bp+PatternLength]
+        and     ax,ax      ;return an instant match if the pattern is
+        jz      InstantMatch ;0-length
+        mov     di,ds
+        mov     es,di      ;ES=DS=SS
+        mov     di,sp      ;point to SkipBuffer
+        mov     cx,256
+        rep     stosw
+        dec     ax                      ;from now on, we only need
+        mov     [bp+PatternLength],ax   ; PatternLength - 1
+; Point to last (rightmost) byte of first potential pattern match
+; location in buffer.
+        add     [bp+BufferPtr],ax
+; Reject if buffer is too small, and set the count of the number of
+; potential pattern match locations in the buffer.
+        sub     [bp+BufferLength],ax
+        jbe     NoMatch
+; Set the skip values for the bytes that do appear in the pattern to
+; the distance from the byte location to the end of the pattern.
+; When there are multiple instances of the same byte, the rightmost
+; instance&rsquo;s skip value is used. Note that the rightmost byte of the
+; pattern isn&rsquo;t entered in the skip table; if we get that value for
+; a mismatch, we know for sure that the right end of the pattern has
+; already passed the mismatch location, so this is not a relevant byte
+; for skipping purposes.
+        mov     si,[bp+PatternPtr] ;point to start of pattern
+        and     ax,ax              ;are there any skips to set?
+        jz      SetSkipDone        ;no
+        mov     di,sp              ;point to SkipBuffer
+SetSkipLoop:
+        sub     bx,bx      ;prepare for word addressing off byte value
+        mov     bl,[si]    ;get the next pattern byte
+        inc     si         ;advance the pattern pointer
+        shl     bx,1       ;prepare for word lookup
+        mov     [di+bx],ax ;set the skip value when this byte value is
+                           ; the mismatch value in the buffer
+        dec     ax
+        jnz     SetSkipLoop
+SetSkipDone:
+        mov     dl,[si]            ;DL=rightmost pattern byte from now on
+        dec     si                 ;point to next-to-rightmost byte of pattern
+        mov     [bp+PatternPtr],si ; from now on
+; Search the buffer.
+        std                        ;for backward REPZ CMPSB
+        mov     di,[bp+BufferPtr]  ;point to first search location
+        mov     cx,[bp+BufferLength]   ;# of match locations to check
+SearchLoop:
+        mov     si,sp                  ;point SI to SkipTable
+; Skip through until there&rsquo;s a match for the rightmost pattern byte.
+QuickSearchLoop:
+        mov     bl,[di]         ;rightmost buffer byte at this location
+        cmp     dl,bl           ;does it match the rightmost pattern byte?
+        jz      FullCompare     ;yes, so keep going
+        sub     bh,bh           ;convert to a word
+        add     bx,bx           ;prepare for look-up in SkipTable
+        mov     ax,[si+bx]      ;get skip value from skip table for this
+                                ; mismatch value
+        add     di,ax           ;BufferPtr += Skip;
+        sub     cx,ax           ;BufferLength -= Skip;
+        ja      QuickSearchLoop ;continue if any buffer left
+        jmp     short NoMatch
+; Return a pointer to the start of the buffer (for 0-length pattern).
+        align   2
+InstantMatch:
+        mov     ax,[bp+BufferPtr]
+        jmp     short Done
+; Compare the pattern and the buffer location, searching from high
+; memory toward low (right to left).
+        align   2
+FullCompare:
+        mov     [bp+BufferPtr],di       ;save the current state of
+        mov     [bp+BufferLength],cx    ; the search
+        mov     cx,[bp+PatternLength]   ;# of bytes yet to compare
+        jcxz    Match                   ;done if only one character
+        mov     si,[bp+PatternPtr]      ;point to next-to-rightmost bytes
+        dec     di                      ; of buffer location and pattern
+        repz    cmpsb                   ;compare the rest of the pattern
+        jz      Match                   ;that&rsquo;s it; we&rsquo;ve found a match
+; It&rsquo;s a mismatch; let&rsquo;s see what we can learn from it.
+        inc     di      ;compensate for 1-byte overrun of REPZ CMPSB;
+                        ; point to mismatch location in buffer
+; # of bytes that did match.
+        mov     si,[bp+BufferPtr]
+        sub     si,di
+; If, based on the mismatch character, we can&rsquo;t even skip ahead as far
+; as where we started this particular comparison, then just advance by
+; 1 to the next potential match; otherwise, skip ahead from this
+; comparison location by the skip distance for the mismatch character,
+; less the distance covered by the partial match.
+        sub     bx,bx     ;prepare for word addressing off byte value
+        mov     bl,[di]   ;get the value of the mismatch byte in buffer
+        add     bx,bx     ;prepare for word look-up
+        add     bx,sp     ;SP points to SkipTable
+        mov     cx,[bx]   ;get the skip value for this mismatch
+        mov     ax,1      ;assume we&rsquo;ll just advance to the next
+                          ; potential match location
+        sub     cx,si     ;is the skip far enough to be worth taking?
+        jna     MoveAhead ;no, go with the default advance of 1
+        mov     ax,cx     ;yes; this is the distance to skip ahead from
+                          ; the last potential match location checked
+MoveAhead:
+; Skip ahead and perform the next comparison, if there&rsquo;s any buffer
+; left to check.
+        mov     di,[bp+BufferPtr]
+        add     di,ax                   ;BufferPtr += Skip;
+        mov     cx,[bp+BufferLength]
+        sub     cx,ax                   ;BufferLength -= Skip;
+        ja      SearchLoop              ;continue if any buffer left
+; Return a NULL pointer for no match.
+        align   2
+NoMatch:
+        sub     ax,ax
+        jmp     short Done
+; Return start of match in buffer (BufferPtr - (PatternLength - 1)).
+        align   2
+Match:
+        mov     ax,[bp+BufferPtr]
+        sub     ax,[bp+PatternLength]
+Done:
+        cld              ;restore default direction flag
+        add     sp,256*2 ;deallocate space for SkipTable
+        pop     di       ;restore caller&rsquo;s register variables
+        pop     si
+        pop     bp       ;restore caller&rsquo;s stack frame
+        ret
+_FindString     endp
+        end
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="14-04.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="14-06.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+  <hr width="90%" size="1" noshade="noshade" />
+
+  <div align="center">
+    Graphics Programming Black Book &copy; 2001 Michael Abrash
+  </div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
+  <!-- reference_subfoot = footer -->
+  <!-- reference_footer = subfoot -->
+  <!-- BEGIN SUB FOOTER -->
+  <!-- END FOOTER -->
+</body>
+</html>

16-05.html

@@ -1,307 +1,373 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: There Ain't No Such Thing as the Fastest Code</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=16//-->
-<!--PAGES=308-311//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="16-04.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="16-06.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P>Table 16.2 has two times for each entry listed: the first value is the overall counting time, including time spent in the main program, disk I/O, and everything else; the second value is the time actually spent counting words, the time spent in <B>ScanBuffer</B> . The first value is the time perceived by the user, but the second value best reflects the quality of the optimization in each entry, since the rest of the overall execution time is fixed.</P>
-<TABLE WIDTH="85%"><TR>
-<TD COLSPAN="3"><HR>
-<TR>
-<TD VALIGN="TOP" ALIGN="LFFT">
-<TH ALIGN="CENTER" COLSPAN="2">Word-Counting Time
-<TR>
-<TH WIDTH="35%" ALIGN="LEFT" VALIGN="TOP">Name
-<TH WIDTH="25%" ALIGN="LEFT" VALIGN="TOP">Overall time
-<TH WIDTH="25%" ALIGN="LEFT" VALIGN="TOP">(ScanBuffer only)
-<TR>
-<TD COLSPAN="3"><HR>
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">David Stafford Listing 16.5       <TD ALIGN="LEFT" VALIGN="TOP">0.61 seconds
-<TD ALIGN="LEFT" VALIGN="TOP">0.33 seconds
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Dave Methvin
-<TD ALIGN="LEFT" VALIGN="TOP">0.66
-<TD ALIGN="LEFT" VALIGN="TOP">0.39
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Mick Brown
-<TD ALIGN="LEFT" VALIGN="TOP">0.70
-<TD ALIGN="LEFT" VALIGN="TOP">0.41
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Wendell Neubert
-<TD ALIGN="LEFT" VALIGN="TOP">0.92
-<TD ALIGN="LEFT" VALIGN="TOP">0.65
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP"><B>For Comparison:</B> 
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Michael Abrash
-<TD ALIGN="LEFT" VALIGN="TOP">1.73
-<TD ALIGN="LEFT" VALIGN="TOP">1.44
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">assembly code
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Listing 16.1
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Michael Abrash
-<TD ALIGN="LEFT" VALIGN="TOP">4.70
-<TD ALIGN="LEFT" VALIGN="TOP">4.43
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">C code
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP">Listing 16.4
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TD ALIGN="LEFT" VALIGN="TOP">
-<TR>
-<TD ALIGN="LEFT" VALIGN="TOP" COLSPAN="3"><SMALL><B>Note:</B> All times measured on a 20 MHz cached 386 DX.</SMALL>
-<TR>
-<TH ALIGN="LEFT" VALIGN="TOP" COLSPAN="3">Table 16.2  The top four word-counting entries.
-<TR>
-<TD COLSPAN="3"><HR>
-</TABLE>
-<P><B>LISTING 16.5  QSCAN3.ASM</B></P>
-<!-- CODE //-->
-<PRE>
- ;  QSCAN3.ASM
- ;  David Stafford
- 
- 
-         COMMENT $
-  
-How it works
-&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;
-The idea is to go through the buffer fetching each letter-pair (words
-rather than bytes).  The carry flag indicates whether we are
-currently in a (text) word or not.  The letter-pair fetched from the
-buffer is converted to a 16-bit address by shifting it left one bit
-(losing the high bit of the second character) and putting the carry
-flag in the low bit.  The high bit of the count register is set to
-1.  Then the count register is added to the byte found at the given
-address in a large (64K, naturally) table.  The byte at the given
-address will contain a 1 in the high bit if the last character of the
-letter-pair is a word-letter (alphanumeric or apostrophe).  This  will
-set the carry flag since the high bit of the count register is also a
-1. The low bit of the byte found at the given address will be one if
-the second character of the previous letter-pair was a word-letter
-and the first character of this letter-pair is not a word-letter. It
-will also be 1 if the first character of this letter-pair is a
-word-letter but the second character is not.  This process is
-repeated.  Finally, the carry flag is saved to indicate the final
-in-a-word/not-in-a-word status.  The count register is masked to
-remove the high bit and the count of words remains in the count
-register.
- Sound complicated?  You&rsquo;re right!  But it&rsquo;s fast!
-  
-The beauty of this method is that no jumps are required, the
-operations are fast, it requires only one table and the process can
-be repeated (unrolled) many times.  QSCAN3 can read 256 bytes without
-jumping.
- 
-         COMMEND $
-                 .model small
-                 .code
-  
- Test1           macro   x,y             ;9 or 10 bytes
- Addr&amp;x:         mov     di,[bp+y]       ;3 or 4 bytes
-                 adc     di,di
-                 or      ax,si
-                 add     al,[di]
-                 endm
-  
- Test2           macro   x,y              ;7 or 8 bytes
- Addr&amp;x:         mov     di,[bp+y]        ;3 or 4 bytes
-                 adc     di,di
-                 add     ah,[di]
-                 endm
-  
- Scan            =       128           ;scan 256 bytes at a time 
- Buffer          =       4             ;parms
- BufferLength    =       6
- CharFlag        =       8
- WordCount       =       10
-  
-                 public _ScanBuffer
- _ScanBuffer     proc near
-                 push    bp
-                 mov     bp,sp
-                 push    si
-                 push    di
-  
-                 xor     cx,cx
-                 mov     si,[bp+Buffer]       ;si = text buffer
-                 mov     ax,[bp+BufferLength] ;dx = length in bytes
-                 shr     ax,1                 ;dx = length in words
-                 jnz     NormalBuf
- OneByteBuf:
-                 mov     ax,seg WordTable
-                 mov     es,ax
-  
-                 mov     di,[bp+CharFlag]
-                 mov     bh,[di]             ;bh = old CharFlag
-                 mov     bl,[si]             ;bl = character
-                 add     bh,&lsquo;A&rsquo;-1            ;make bh into character
-                 add     bx,bx               ;prepare to index
-                 mov     al,es:[bx]
-                 cbw                         ;get hi bit in ah (then bh)
-                 shr     al,1                ;get low bit
-                 adc     cx,cx               ;cx = 0 or 1
-                 xchg    ax,bx
-                 jmp     CleanUp
- NormalBuf:
-                 push    bp                  ;(1)
-                 pushf                       ;(2)
-  
-                 cwd                         ;dx = 0
-                 mov     cl,Scan
-                 div     cx
-                 or      dx,dx               ;remainder?
-                 jz      StartAtTheTop       ;nope, do the whole banana 
-                 sub     cx,dx
-                 sub     si,cx               ;adjust buf pointer
-                 sub     si,cx
-                 inc     ax                  ;adjust for partial read
- 
- StartAtTheTop:  mov     bx,dx               ;get index for start...
-                 shl     bx,1
-                 mov     di,LoopEntry[bx]    ;...address in di
-                 xchg    dx,ax               ;dx is the loop counter
-                 xor     cx,cx               ;total word count
-                 mov     bx,[bp+CharFlag]
-                 mov     bl,[bx]             ;bl = old CharFlag
-                 mov     bp,seg WordTable
-                 mov     ds,bp
-                 mov     bp,si               ;scan buffer with bp
-                 mov     si,8080h            ;hi bits
-                 mov     ax,si               ;init local word counter
-                 shr     bl,1                ;carry = old CharFlag
-                 jmp     di
-  
-                 align   2
- Top:            add     bx,bx               ;restore carry
- n               =       0
-                 rept    Scan/2
-                 Test1   %n,%n*2
-                 Test2   %n+1,%n*2+2
- n               =       n+2
-                 endm
- EndCount:
-                 sbb     bx,bx             ;save carry
-  if             Scan ge 128               ;because al+ah may equal 128!
-                 or      ax,si
-                 add     al,ah
-                 mov     ah,0
- else
-                 add     al,ah
-                 and     ax,7fh            ;mask
- endif
-                 add     cx,ax             ;update word count
-                 mov     ax,si
-                 add     bp,Scan*2
-                 dec     dx                ;any left?
-                 jng     Quit
-                 jmp     Top
-  
- Quit:           popf                      ;(2) even or odd buffer?
-                 jnc     ItsEven 
-                 clc
-                 Test1   Odd,-1
-                 sbb     bx,bx             ;save carry
-                 shr     ax,1
-                 adc     cx,0
- ItsEven:
-                 push    ss                ;restore ds
-                 pop     ds
-                 pop     bp                ;(1)
- CleanUp:
-                 mov     si,[bp+WordCount]
-                 add     [si],cx
-                 adc     word ptr [si+2],0
-                 and     bh,1              ;save only the carry flag
-                 mov     si,[bp+CharFlag]
-                 mov     [si],bh
-                 pop     di
-                 pop     si
-                 pop     bp
-                 ret
- _ScanBuffer     endp
-  
-                 .data
- Address         macro   X
-                 dw      Addr&amp;X
-                 endm
-  
- LoopEntry       label word
- n               =       Scan
-                 REPT Scan
-                 Address %n MOD Scan
- n               =       n - 1
-                 ENDM
-  
-                 .fardata WordTable
- include         qscan3.inc                ;built by MAKETAB
-                 end
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="16-04.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="16-06.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-
-<hr width="90%" size="1" noshade>
-<div align="center">
-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
-<!-- all of the reference materials (books) have the footer and subfoot reveresed -->
-<!-- reference_subfoot = footer -->
-<!-- reference_footer = subfoot -->
-
-<!-- BEGIN SUB FOOTER -->
-</BODY>
-</HTML>
-
-<!-- END FOOTER -->
-
-
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: There Ain't No Such Thing as the Fastest Code</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=16//-->
+  <!--PAGES=308-311//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="16-04.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="16-06.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p>Table 16.2 has two times for each entry listed: the first value is the overall counting time, including time spent in the main program, disk I/O, and everything else; the second value is the time actually spent counting words, the time spent in <b>ScanBuffer</b> . The first value is the time perceived by the user, but the second value best reflects the quality of the optimization in each entry, since the rest of the overall execution time is fixed.</p>
+
+  <table width="85%">
+    <tr>
+      <td colspan="3">
+        <hr />
+      </td>
+    </tr>
+
+    <tr>
+      <td valign="top" align="lfft"></td>
+
+      <th align="center" colspan="2">Word-Counting Time</th>
+    </tr>
+
+    <tr>
+      <th width="35%" align="left" valign="top">Name</th>
+
+      <th width="25%" align="left" valign="top">Overall time</th>
+
+      <th width="25%" align="left" valign="top">(ScanBuffer only)</th>
+    </tr>
+
+    <tr>
+      <td colspan="3">
+        <hr />
+      </td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">David Stafford Listing 16.5</td>
+
+      <td align="left" valign="top">0.61 seconds</td>
+
+      <td align="left" valign="top">0.33 seconds</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Dave Methvin</td>
+
+      <td align="left" valign="top">0.66</td>
+
+      <td align="left" valign="top">0.39</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Mick Brown</td>
+
+      <td align="left" valign="top">0.70</td>
+
+      <td align="left" valign="top">0.41</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Wendell Neubert</td>
+
+      <td align="left" valign="top">0.92</td>
+
+      <td align="left" valign="top">0.65</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top"><b>For Comparison:</b></td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Michael Abrash</td>
+
+      <td align="left" valign="top">1.73</td>
+
+      <td align="left" valign="top">1.44</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">assembly code</td>
+
+      <td align="left" valign="top"></td>
+
+      <td align="left" valign="top"></td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Listing 16.1</td>
+
+      <td align="left" valign="top"></td>
+
+      <td align="left" valign="top"></td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Michael Abrash</td>
+
+      <td align="left" valign="top">4.70</td>
+
+      <td align="left" valign="top">4.43</td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">C code</td>
+
+      <td align="left" valign="top"></td>
+
+      <td align="left" valign="top"></td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top">Listing 16.4</td>
+
+      <td align="left" valign="top"></td>
+
+      <td align="left" valign="top"></td>
+    </tr>
+
+    <tr>
+      <td align="left" valign="top" colspan="3"><small><b>Note:</b> All times measured on a 20 MHz cached 386 DX.</small></td>
+    </tr>
+
+    <tr>
+      <th align="left" valign="top" colspan="3">Table 16.2 The top four word-counting entries.</th>
+    </tr>
+
+    <tr>
+      <td colspan="3">
+        <hr />
+      </td>
+    </tr>
+  </table>
+
+  <p><b>LISTING 16.5 QSCAN3.ASM</b></p><!-- CODE //-->
+  <pre>
+ ;  QSCAN3.ASM
+ ;  David Stafford
+ 
+ 
+         COMMENT $
+  
+How it works
+&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;
+The idea is to go through the buffer fetching each letter-pair (words
+rather than bytes).  The carry flag indicates whether we are
+currently in a (text) word or not.  The letter-pair fetched from the
+buffer is converted to a 16-bit address by shifting it left one bit
+(losing the high bit of the second character) and putting the carry
+flag in the low bit.  The high bit of the count register is set to
+1.  Then the count register is added to the byte found at the given
+address in a large (64K, naturally) table.  The byte at the given
+address will contain a 1 in the high bit if the last character of the
+letter-pair is a word-letter (alphanumeric or apostrophe).  This  will
+set the carry flag since the high bit of the count register is also a
+1. The low bit of the byte found at the given address will be one if
+the second character of the previous letter-pair was a word-letter
+and the first character of this letter-pair is not a word-letter. It
+will also be 1 if the first character of this letter-pair is a
+word-letter but the second character is not.  This process is
+repeated.  Finally, the carry flag is saved to indicate the final
+in-a-word/not-in-a-word status.  The count register is masked to
+remove the high bit and the count of words remains in the count
+register.
+ Sound complicated?  You&rsquo;re right!  But it&rsquo;s fast!
+  
+The beauty of this method is that no jumps are required, the
+operations are fast, it requires only one table and the process can
+be repeated (unrolled) many times.  QSCAN3 can read 256 bytes without
+jumping.
+ 
+         COMMEND $
+                 .model small
+                 .code
+  
+ Test1           macro   x,y             ;9 or 10 bytes
+ Addr&amp;x:         mov     di,[bp+y]       ;3 or 4 bytes
+                 adc     di,di
+                 or      ax,si
+                 add     al,[di]
+                 endm
+  
+ Test2           macro   x,y              ;7 or 8 bytes
+ Addr&amp;x:         mov     di,[bp+y]        ;3 or 4 bytes
+                 adc     di,di
+                 add     ah,[di]
+                 endm
+  
+ Scan            =       128           ;scan 256 bytes at a time 
+ Buffer          =       4             ;parms
+ BufferLength    =       6
+ CharFlag        =       8
+ WordCount       =       10
+  
+                 public _ScanBuffer
+ _ScanBuffer     proc near
+                 push    bp
+                 mov     bp,sp
+                 push    si
+                 push    di
+  
+                 xor     cx,cx
+                 mov     si,[bp+Buffer]       ;si = text buffer
+                 mov     ax,[bp+BufferLength] ;dx = length in bytes
+                 shr     ax,1                 ;dx = length in words
+                 jnz     NormalBuf
+ OneByteBuf:
+                 mov     ax,seg WordTable
+                 mov     es,ax
+  
+                 mov     di,[bp+CharFlag]
+                 mov     bh,[di]             ;bh = old CharFlag
+                 mov     bl,[si]             ;bl = character
+                 add     bh,&lsquo;A&rsquo;-1            ;make bh into character
+                 add     bx,bx               ;prepare to index
+                 mov     al,es:[bx]
+                 cbw                         ;get hi bit in ah (then bh)
+                 shr     al,1                ;get low bit
+                 adc     cx,cx               ;cx = 0 or 1
+                 xchg    ax,bx
+                 jmp     CleanUp
+ NormalBuf:
+                 push    bp                  ;(1)
+                 pushf                       ;(2)
+  
+                 cwd                         ;dx = 0
+                 mov     cl,Scan
+                 div     cx
+                 or      dx,dx               ;remainder?
+                 jz      StartAtTheTop       ;nope, do the whole banana 
+                 sub     cx,dx
+                 sub     si,cx               ;adjust buf pointer
+                 sub     si,cx
+                 inc     ax                  ;adjust for partial read
+ 
+ StartAtTheTop:  mov     bx,dx               ;get index for start...
+                 shl     bx,1
+                 mov     di,LoopEntry[bx]    ;...address in di
+                 xchg    dx,ax               ;dx is the loop counter
+                 xor     cx,cx               ;total word count
+                 mov     bx,[bp+CharFlag]
+                 mov     bl,[bx]             ;bl = old CharFlag
+                 mov     bp,seg WordTable
+                 mov     ds,bp
+                 mov     bp,si               ;scan buffer with bp
+                 mov     si,8080h            ;hi bits
+                 mov     ax,si               ;init local word counter
+                 shr     bl,1                ;carry = old CharFlag
+                 jmp     di
+  
+                 align   2
+ Top:            add     bx,bx               ;restore carry
+ n               =       0
+                 rept    Scan/2
+                 Test1   %n,%n*2
+                 Test2   %n+1,%n*2+2
+ n               =       n+2
+                 endm
+ EndCount:
+                 sbb     bx,bx             ;save carry
+  if             Scan ge 128               ;because al+ah may equal 128!
+                 or      ax,si
+                 add     al,ah
+                 mov     ah,0
+ else
+                 add     al,ah
+                 and     ax,7fh            ;mask
+ endif
+                 add     cx,ax             ;update word count
+                 mov     ax,si
+                 add     bp,Scan*2
+                 dec     dx                ;any left?
+                 jng     Quit
+                 jmp     Top
+  
+ Quit:           popf                      ;(2) even or odd buffer?
+                 jnc     ItsEven 
+                 clc
+                 Test1   Odd,-1
+                 sbb     bx,bx             ;save carry
+                 shr     ax,1
+                 adc     cx,0
+ ItsEven:
+                 push    ss                ;restore ds
+                 pop     ds
+                 pop     bp                ;(1)
+ CleanUp:
+                 mov     si,[bp+WordCount]
+                 add     [si],cx
+                 adc     word ptr [si+2],0
+                 and     bh,1              ;save only the carry flag
+                 mov     si,[bp+CharFlag]
+                 mov     [si],bh
+                 pop     di
+                 pop     si
+                 pop     bp
+                 ret
+ _ScanBuffer     endp
+  
+                 .data
+ Address         macro   X
+                 dw      Addr&amp;X
+                 endm
+  
+ LoopEntry       label word
+ n               =       Scan
+                 REPT Scan
+                 Address %n MOD Scan
+ n               =       n - 1
+                 ENDM
+  
+                 .fardata WordTable
+ include         qscan3.inc                ;built by MAKETAB
+                 end
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="16-04.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="16-06.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+  <hr width="90%" size="1" noshade="noshade" />
+
+  <div align="center">
+    Graphics Programming Black Book &copy; 2001 Michael Abrash
+  </div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
+  <!-- reference_subfoot = footer -->
+  <!-- reference_footer = subfoot -->
+  <!-- BEGIN SUB FOOTER -->
+  <!-- END FOOTER -->
+</body>
+</html>

17-02.html

@@ -1,324 +1,321 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: The Game of Life</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=17//-->
-<!--PAGES=325-329//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="17-01.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="17-03.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P><B>LISTING 17.1 L17-1.CPP</B></P>
-<!-- CODE //-->
-<PRE>
-/* C++ Game of Life implementation for any mode for which mode set
-   and draw pixel functions can be provided.
-   Tested with Borland C++ in the small model. */
-#include &lt;stdlib.h&gt;
-#include &lt;stdio.h&gt;
-#include &lt;iostream.h&gt;
-#include &lt;conio.h&gt;
-#include &lt;time.h&gt;
-#include &lt;dos.h&gt;
-#include &lt;bios.h&gt;
-#include &lt;mem.h&gt;
-
-#define ON_COLOR  15       // on-cell pixel color
-#define OFF_COLOR 0        // off-cell pixel color
-#define MSG_LINE  10       // row for text messages
-#define GENERATION_LINE 12 // row for generation # display
-#define LIMIT_18_HZ  1     // set 1 for maximum frame rate = 18Hz
-#define WRAP_EDGES   1     // set to 0 to disable wrapping around
-                           // at cell map edges
-class cellmap {
-private:
-   unsigned char *cells;
-   unsigned int width;
-   unsigned int width_in_bytes;
-   unsigned int height;
-   unsigned int length_in_bytes;
-public:
-   cellmap(unsigned int h, unsigned int v);
-   ~cellmap(void);
-   void copy_cells(cellmap &amp;sourcemap);
-   void set_cell(unsigned int x, unsigned int y);
-   void clear_cell(unsigned int x, unsigned int y);
-   int cell_state(int x, int y);
-   void next_generation(cellmap&amp; dest_map);
-};
-
-extern void enter_display_mode(void);
-extern void exit_display_mode(void);
-extern void draw_pixel(unsigned int X, unsigned int Y,
-   unsigned int Color);
-extern void show_text(int x, int y, char *text);
-
-/* Controls the size of the cell map. Must be within the capabilities
-   of the display mode, and must be limited to leave room for text
-   display at right. */
-unsigned int cellmap_width = 96;
-unsigned int cellmap_height = 96;
-/* Width &amp; height in pixels of each cell as displayed on screen. */
-unsigned int magnifier = 2;
-
-void main()
-{
-   unsigned int init_length, x, y, seed;
-   unsigned long generation = 0;
-   char gen_text[80];
-   long bios_time, start_bios_time;
-
-   cellmap current_map(cellmap_height, cellmap_width);
-   cellmap next_map(cellmap_height, cellmap_width);
-
-   // Get the seed; seed randomly if 0 entered
-   cout &lt;&lt; &ldquo;Seed (0 for random seed): &rdquo;;
-   cin &gt;&gt; seed;
-   if (seed == 0) seed = (unsigned) time(NULL);
-
-   // Randomly initialize the initial cell map
-   cout &lt;&lt; &ldquo;Initializing...&rdquo;;
-   srand(seed);
-   init_length = (cellmap_height * cellmap_width) / 2;
-   do {
-      x = random(cellmap_width);
-      y = random(cellmap_height);
-      next_map.set_cell(x, y);
-   } while (&mdash;init_length);
-   current_map.copy_cells(next_map); // put init map in current_map
-
-   enter_display_mode();
-
-   // Keep recalculating and redisplaying generations until a key
-   // is pressed
-   show_text(0, MSG_LINE, &ldquo;Generation: &rdquo;);
-   start_bios_time = _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
-   do {
-      generation++;
-      sprintf(gen_text, &ldquo;%10lu&rdquo;, generation);
-      show_text(1, GENERATION_LINE, gen_text);
-      // Recalculate and draw the next generation
-      current_map.next_generation(next_map);
-      // Make current_map current again
-      current_map.copy_cells(next_map);
-#if LIMIT_18_HZ
-      // Limit to a maximum of 18.2 frames per second,for visibility
-      do {
-         _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
-      } while (start_bios_time == bios_time);
-      start_bios_time = bios_time;
-#endif
-   } while (!kbhit());
-   getch();    // clear keypress
-   exit_display_mode();
-   cout &lt;&lt; &ldquo;Total generations: &rdquo; &lt;&lt; generation &lt;&lt; &ldquo;\nSeed: &rdquo; &lt;&lt;
-         seed &lt;&lt; &ldquo;\n&rdquo;;
-}
-
-/* cellmap constructor. */
-cellmap::cellmap(unsigned int h, unsigned int w)
-{
-   width = w;
-   width_in_bytes = (w + 7) / 8;
-   height = h;
-   length_in_bytes = width_in_bytes * h;
-   cells = new unsigned char[length_in_bytes];  // cell storage
-   memset(cells, 0, length_in_bytes);  // clear all cells, to start
-}
-
-/* cellmap destructor. */
-cellmap::~cellmap(void)
-{
-   delete[] cells;
-}
-
-/* Copies one cellmap&rsquo;s cells to another cellmap. Both cellmaps are
-   assumed to be the same size.  */
-void cellmap::copy_cells(cellmap &amp;sourcemap)
-{
-   memcpy(cells, sourcemap.cells, length_in_bytes);
-}
-
-/* Turns cell on. */
-void cellmap::set_cell(unsigned int x, unsigned int y)
-{
-   unsigned char *cell_ptr =
-         cells + (y * width_in_bytes) + (x / 8);
-
-   *(cell_ptr) |= 0x80 &gt;&gt; (x &amp; 0x07);
-}
-
-/* Turns cell off. */
-void cellmap::clear_cell(unsigned int x, unsigned int y)
-{
-   unsigned char *cell_ptr =
-         cells + (y * width_in_bytes) + (x / 8);
-
-   *(cell_ptr) &amp;= ~(0x80 &gt;&gt; (x &amp; 0x07));
-}
-
-/* Returns cell state (1=on or 0=off), optionally wrapping at the
-   borders around to the opposite edge. */
-int cellmap::cell_state(int x, int y)
-{
-   unsigned char *cell_ptr;
-
-#if WRAP_EDGES
-   while (x &lt; 0) x += width;     // wrap, if necessary
-   while (x &gt;= width) x -= width;
-   while (y &lt; 0) y += height;
-   while (y &gt;= height) y -= height;
-#else
-   if ((x &lt; 0) || (x &gt;= width) || (y &lt; 0) || (y &gt;= height))
-      return 0;   // return 0 for off edges if no wrapping
-#endif
-   cell_ptr = cells + (y * width_in_bytes) + (x / 8);
-   return (*cell_ptr &amp; (0x80 &gt;&gt; (x &amp; 0x07))) ? 1 : 0;
-}
-
-/* Calculates the next generation of a cellmap and stores it in
-   next_map. */
-void cellmap::next_generation(cellmap&amp; next_map)
-{
-   unsigned int x, y, neighbor_count;
-
-   for (y=0; y&lt;height; y++) {
-      for (x=0; x&lt;width; x++) {
-         // Figure out how many neighbors this cell has
-         neighbor_count = cell_state(x-1, y-1) + cell_state(x, y-1) +
-               cell_state(x+1, y-1) + cell_state(x-1, y) +
-               cell_state(x+1, y) + cell_state(x-1, y+1) +
-               cell_state(x, y+1) + cell_state(x+1, y+1);
-         if (cell_state(x, y) == 1) {
-            // The cell is on; does it stay on?
-            if ((neighbor_count != 2) &amp;&amp; (neighbor_count != 3)) {
-               next_map.clear_cell(x, y);    // turn it off
-               draw_pixel(x, y, OFF_COLOR);
-            }
-         } else {
-            // The cell is off; does it turn on?
-            if (neighbor_count == 3) {
-               next_map.set_cell(x, y);      // turn it on
-               draw_pixel(x, y, ON_COLOR);
-            }
-         }
-      }
-   }
-}
-</PRE>
-<!-- END CODE //-->
-<P><B>LISTING 17.2 L17-2.CPP</B></P>
-<!-- CODE //-->
-<PRE>
-/* VGA mode 13h functions for Game of Life.
-   Tested with Borland C++. */
-#include &lt;stdio.h&gt;
-#include &lt;conio.h&gt;
-#include &lt;dos.h&gt;
-
-#define TEXT_X_OFFSET   27
-#define SCREEN_WIDTH_IN_BYTES 320
-
-/* Width &amp; height in pixels of each cell. */
-extern unsigned int magnifier;
-
-/* Mode 13h draw pixel function. Pixels are of width &amp; height
-   specified by magnifier. */
-void draw_pixel(unsigned int x, unsigned int y, unsigned int color)
-{
-#define SCREEN_SEGMENT  0xA000
-   unsigned char far *screen_ptr;
-   int i, j;
-
-   FP_SEG(screen_ptr) = SCREEN_SEGMENT;
-   FP_OFF(screen_ptr) =
-         y * magnifier * SCREEN_WIDTH_IN_BYTES + x * magnifier;
-   for (i=0; i&lt;magnifier; i++) {
-      for (j=0; j&lt;magnifier; j++) {
-         *(screen_ptr+j) = color;
-      }
-      screen_ptr += SCREEN_WIDTH_IN_BYTES;
-   }
-}
-
-/* Mode 13h mode-set function. */
-void enter_display_mode()
-{
-   union REGS regset;
-
-   regset.x.ax = 0x0013;
-   int86(0x10, &amp;regset, &amp;regset);
-}
-
-/* Text mode mode-set function. */
-void exit_display_mode()
-{
-   union REGS regset;
-
-   regset.x.ax = 0x0003;
-   int86(0x10, &amp;regset, &amp;regset);
-}
-
-/* Text display function. Offsets text to non-graphics area of
-   screen. */
-void show_text(int x, int y, char *text)
-{
-   gotoxy(TEXT_X_OFFSET + x, y);
-   puts(text);
-}
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="17-01.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="17-03.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-
-<hr width="90%" size="1" noshade>
-<div align="center">
-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
-<!-- all of the reference materials (books) have the footer and subfoot reveresed -->
-<!-- reference_subfoot = footer -->
-<!-- reference_footer = subfoot -->
-
-<!-- BEGIN SUB FOOTER -->
-</BODY>
-</HTML>
-
-<!-- END FOOTER -->
-
-
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: The Game of Life</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=17//-->
+  <!--PAGES=325-329//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="17-01.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="17-03.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p><b>LISTING 17.1 L17-1.CPP</b></p><!-- CODE //-->
+  <pre>
+/* C++ Game of Life implementation for any mode for which mode set
+   and draw pixel functions can be provided.
+   Tested with Borland C++ in the small model. */
+#include &lt;stdlib.h&gt;
+#include &lt;stdio.h&gt;
+#include &lt;iostream.h&gt;
+#include &lt;conio.h&gt;
+#include &lt;time.h&gt;
+#include &lt;dos.h&gt;
+#include &lt;bios.h&gt;
+#include &lt;mem.h&gt;
+
+#define ON_COLOR  15       // on-cell pixel color
+#define OFF_COLOR 0        // off-cell pixel color
+#define MSG_LINE  10       // row for text messages
+#define GENERATION_LINE 12 // row for generation # display
+#define LIMIT_18_HZ  1     // set 1 for maximum frame rate = 18Hz
+#define WRAP_EDGES   1     // set to 0 to disable wrapping around
+                           // at cell map edges
+class cellmap {
+private:
+   unsigned char *cells;
+   unsigned int width;
+   unsigned int width_in_bytes;
+   unsigned int height;
+   unsigned int length_in_bytes;
+public:
+   cellmap(unsigned int h, unsigned int v);
+   ~cellmap(void);
+   void copy_cells(cellmap &amp;sourcemap);
+   void set_cell(unsigned int x, unsigned int y);
+   void clear_cell(unsigned int x, unsigned int y);
+   int cell_state(int x, int y);
+   void next_generation(cellmap&amp; dest_map);
+};
+
+extern void enter_display_mode(void);
+extern void exit_display_mode(void);
+extern void draw_pixel(unsigned int X, unsigned int Y,
+   unsigned int Color);
+extern void show_text(int x, int y, char *text);
+
+/* Controls the size of the cell map. Must be within the capabilities
+   of the display mode, and must be limited to leave room for text
+   display at right. */
+unsigned int cellmap_width = 96;
+unsigned int cellmap_height = 96;
+/* Width &amp; height in pixels of each cell as displayed on screen. */
+unsigned int magnifier = 2;
+
+void main()
+{
+   unsigned int init_length, x, y, seed;
+   unsigned long generation = 0;
+   char gen_text[80];
+   long bios_time, start_bios_time;
+
+   cellmap current_map(cellmap_height, cellmap_width);
+   cellmap next_map(cellmap_height, cellmap_width);
+
+   // Get the seed; seed randomly if 0 entered
+   cout &lt;&lt; &ldquo;Seed (0 for random seed): &rdquo;;
+   cin &gt;&gt; seed;
+   if (seed == 0) seed = (unsigned) time(NULL);
+
+   // Randomly initialize the initial cell map
+   cout &lt;&lt; &ldquo;Initializing...&rdquo;;
+   srand(seed);
+   init_length = (cellmap_height * cellmap_width) / 2;
+   do {
+      x = random(cellmap_width);
+      y = random(cellmap_height);
+      next_map.set_cell(x, y);
+   } while (&mdash;init_length);
+   current_map.copy_cells(next_map); // put init map in current_map
+
+   enter_display_mode();
+
+   // Keep recalculating and redisplaying generations until a key
+   // is pressed
+   show_text(0, MSG_LINE, &ldquo;Generation: &rdquo;);
+   start_bios_time = _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
+   do {
+      generation++;
+      sprintf(gen_text, &ldquo;%10lu&rdquo;, generation);
+      show_text(1, GENERATION_LINE, gen_text);
+      // Recalculate and draw the next generation
+      current_map.next_generation(next_map);
+      // Make current_map current again
+      current_map.copy_cells(next_map);
+#if LIMIT_18_HZ
+      // Limit to a maximum of 18.2 frames per second,for visibility
+      do {
+         _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
+      } while (start_bios_time == bios_time);
+      start_bios_time = bios_time;
+#endif
+   } while (!kbhit());
+   getch();    // clear keypress
+   exit_display_mode();
+   cout &lt;&lt; &ldquo;Total generations: &rdquo; &lt;&lt; generation &lt;&lt; &ldquo;\nSeed: &rdquo; &lt;&lt;
+         seed &lt;&lt; &ldquo;\n&rdquo;;
+}
+
+/* cellmap constructor. */
+cellmap::cellmap(unsigned int h, unsigned int w)
+{
+   width = w;
+   width_in_bytes = (w + 7) / 8;
+   height = h;
+   length_in_bytes = width_in_bytes * h;
+   cells = new unsigned char[length_in_bytes];  // cell storage
+   memset(cells, 0, length_in_bytes);  // clear all cells, to start
+}
+
+/* cellmap destructor. */
+cellmap::~cellmap(void)
+{
+   delete[] cells;
+}
+
+/* Copies one cellmap&rsquo;s cells to another cellmap. Both cellmaps are
+   assumed to be the same size.  */
+void cellmap::copy_cells(cellmap &amp;sourcemap)
+{
+   memcpy(cells, sourcemap.cells, length_in_bytes);
+}
+
+/* Turns cell on. */
+void cellmap::set_cell(unsigned int x, unsigned int y)
+{
+   unsigned char *cell_ptr =
+         cells + (y * width_in_bytes) + (x / 8);
+
+   *(cell_ptr) |= 0x80 &gt;&gt; (x &amp; 0x07);
+}
+
+/* Turns cell off. */
+void cellmap::clear_cell(unsigned int x, unsigned int y)
+{
+   unsigned char *cell_ptr =
+         cells + (y * width_in_bytes) + (x / 8);
+
+   *(cell_ptr) &amp;= ~(0x80 &gt;&gt; (x &amp; 0x07));
+}
+
+/* Returns cell state (1=on or 0=off), optionally wrapping at the
+   borders around to the opposite edge. */
+int cellmap::cell_state(int x, int y)
+{
+   unsigned char *cell_ptr;
+
+#if WRAP_EDGES
+   while (x &lt; 0) x += width;     // wrap, if necessary
+   while (x &gt;= width) x -= width;
+   while (y &lt; 0) y += height;
+   while (y &gt;= height) y -= height;
+#else
+   if ((x &lt; 0) || (x &gt;= width) || (y &lt; 0) || (y &gt;= height))
+      return 0;   // return 0 for off edges if no wrapping
+#endif
+   cell_ptr = cells + (y * width_in_bytes) + (x / 8);
+   return (*cell_ptr &amp; (0x80 &gt;&gt; (x &amp; 0x07))) ? 1 : 0;
+}
+
+/* Calculates the next generation of a cellmap and stores it in
+   next_map. */
+void cellmap::next_generation(cellmap&amp; next_map)
+{
+   unsigned int x, y, neighbor_count;
+
+   for (y=0; y&lt;height; y++) {
+      for (x=0; x&lt;width; x++) {
+         // Figure out how many neighbors this cell has
+         neighbor_count = cell_state(x-1, y-1) + cell_state(x, y-1) +
+               cell_state(x+1, y-1) + cell_state(x-1, y) +
+               cell_state(x+1, y) + cell_state(x-1, y+1) +
+               cell_state(x, y+1) + cell_state(x+1, y+1);
+         if (cell_state(x, y) == 1) {
+            // The cell is on; does it stay on?
+            if ((neighbor_count != 2) &amp;&amp; (neighbor_count != 3)) {
+               next_map.clear_cell(x, y);    // turn it off
+               draw_pixel(x, y, OFF_COLOR);
+            }
+         } else {
+            // The cell is off; does it turn on?
+            if (neighbor_count == 3) {
+               next_map.set_cell(x, y);      // turn it on
+               draw_pixel(x, y, ON_COLOR);
+            }
+         }
+      }
+   }
+}
+</pre><!-- END CODE //-->
+
+  <p><b>LISTING 17.2 L17-2.CPP</b></p><!-- CODE //-->
+  <pre>
+/* VGA mode 13h functions for Game of Life.
+   Tested with Borland C++. */
+#include &lt;stdio.h&gt;
+#include &lt;conio.h&gt;
+#include &lt;dos.h&gt;
+
+#define TEXT_X_OFFSET   27
+#define SCREEN_WIDTH_IN_BYTES 320
+
+/* Width &amp; height in pixels of each cell. */
+extern unsigned int magnifier;
+
+/* Mode 13h draw pixel function. Pixels are of width &amp; height
+   specified by magnifier. */
+void draw_pixel(unsigned int x, unsigned int y, unsigned int color)
+{
+#define SCREEN_SEGMENT  0xA000
+   unsigned char far *screen_ptr;
+   int i, j;
+
+   FP_SEG(screen_ptr) = SCREEN_SEGMENT;
+   FP_OFF(screen_ptr) =
+         y * magnifier * SCREEN_WIDTH_IN_BYTES + x * magnifier;
+   for (i=0; i&lt;magnifier; i++) {
+      for (j=0; j&lt;magnifier; j++) {
+         *(screen_ptr+j) = color;
+      }
+      screen_ptr += SCREEN_WIDTH_IN_BYTES;
+   }
+}
+
+/* Mode 13h mode-set function. */
+void enter_display_mode()
+{
+   union REGS regset;
+
+   regset.x.ax = 0x0013;
+   int86(0x10, &amp;regset, &amp;regset);
+}
+
+/* Text mode mode-set function. */
+void exit_display_mode()
+{
+   union REGS regset;
+
+   regset.x.ax = 0x0003;
+   int86(0x10, &amp;regset, &amp;regset);
+}
+
+/* Text display function. Offsets text to non-graphics area of
+   screen. */
+void show_text(int x, int y, char *text)
+{
+   gotoxy(TEXT_X_OFFSET + x, y);
+   puts(text);
+}
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="17-01.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="17-03.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+  <hr width="90%" size="1" noshade="noshade" />
+
+  <div align="center">
+    Graphics Programming Black Book &copy; 2001 Michael Abrash
+  </div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
+  <!-- reference_subfoot = footer -->
+  <!-- reference_footer = subfoot -->
+  <!-- BEGIN SUB FOOTER -->
+  <!-- END FOOTER -->
+</body>
+</html>

17-07.html

@@ -1,342 +1,340 @@
-<HTML>
-<HEAD>
-<META name=vsisbn content="1576101746">
-<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
-<META name=vsauthor content="Michael Abrash">
-<META name=vspublisher content="The Coriolis Group">
-<META name=vspubdate content="07/01/97">
-<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
-
-
-
-
-
-
-<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: The Game of Life</TITLE>
-
-<!-- HEADER -->
-<!-- Empty Reference Subhead -->
-
-<!--ISBN=1576101746//-->
-<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
-<!--AUTHOR=Michael Abrash//-->
-<!--PUBLISHER=The Coriolis Group, Inc.//-->
-<!--CHAPTER=17//-->
-<!--PAGES=340-345//-->
-<!--UNASSIGNED1//-->
-<!--UNASSIGNED2//--></HEAD><body>
-
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="17-06.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="17-08.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-<P><BR></P>
-<P><B>LISTING 17.5 L17-5.CPP</B></P>
-<!-- CODE //-->
-<PRE>
-/* C++ Game of Life implementation for any mode for which mode set
-   and draw pixel functions can be provided. The cellmap stores the
-   neighbor count for each cell as well as the state of each cell;
-   this allows very fast next-state determination. Edges always wrap
-   in this implementation.
-   Tested with Borland C++. To run, link with Listing 17.2
-   in the large model. */
-#include &lt;stdlib.h&gt;
-#include &lt;stdio.h&gt;
-#include &lt;iostream.h&gt;
-#include &lt;conio.h&gt;
-#include &lt;time.h&gt;
-#include &lt;dos.h&gt;
-#include &lt;bios.h&gt;
-#include &lt;mem.h&gt;
-
-#define ON_COLOR  15       // on-cell pixel color
-#define OFF_COLOR 0        // off-cell pixel color
-#define MSG_LINE  10       // row for text messages
-#define GENERATION_LINE 12 // row for generation # display
-#define LIMIT_18_HZ  0     // set 1 to to maximum frame rate = 18Hz
-
-class cellmap {
-private:
-   unsigned char *cells;
-   unsigned char *temp_cells;
-   unsigned int width;
-   unsigned int height;
-   unsigned int length_in_bytes;
-public:
-   cellmap(unsigned int h, unsigned int v);
-   ~cellmap(void);
-   void set_cell(unsigned int x, unsigned int y);
-   void clear_cell(unsigned int x, unsigned int y);
-   int cell_state(int x, int y);
-   int count_neighbors(int x, int y);
-   void next_generation(void);
-   void init(void);
-};
-
-extern void enter_display_mode(void);
-extern void exit_display_mode(void);
-extern void draw_pixel(unsigned int X, unsigned int Y,
-   unsigned int Color);
-extern void show_text(int x, int y, char *text);
-
-/* Controls the size of the cell map. Must be within the capabilities
-   of the display mode, and must be limited to leave room for text
-   display at right. */
-unsigned int cellmap_width = 96;
-unsigned int cellmap_height = 96;
-
-/* Width &amp; height in pixels of each cell. */
-unsigned int magnifier = 2;
-
-/* Randomizing seed */
-unsigned int seed;
-
-void main()
-{
-   unsigned long generation = 0;
-   char gen_text[80];
-   long bios_time, start_bios_time;
-
-   cellmap current_map(cellmap_height, cellmap_width);
-
-   current_map.init();  // randomly initialize cell map
-
-   enter_display_mode();
-
-   // Keep recalculating and redisplaying generations until any key
-   // is pressed
-   show_text(0, MSG_LINE, &ldquo;Generation: &rdquo;);
-   start_bios_time = _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
-   do {
-      generation++;
-      sprintf(gen_text, &ldquo;%10lu&rdquo;, generation);
-      show_text(1, GENERATION_LINE, gen_text);
-      // Recalculate and draw the next generation
-      current_map.next_generation();
-#if LIMIT_18_HZ
-      // Limit to a maximum of 18.2 frames per second, for visibility
-      do {
-         _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
-      } while (start_bios_time == bios_time);
-      start_bios_time = bios_time;
-#endif
-   } while (!kbhit());
-
-   getch();    // clear keypress
-   exit_display_mode();
-   cout &lt;&lt; &ldquo;Total generations: &rdquo; &lt;&lt; generation &lt;&lt; &ldquo;\nSeed: &rdquo; &lt;&lt;
-         seed &lt;&lt; &ldquo;\n&rdquo;;
-}
-
-/* cellmap constructor. */
-cellmap::cellmap(unsigned int h, unsigned int w)
-{
-   width = w;
-   height = h;
-   length_in_bytes = w * h;
-   cells = new unsigned char[length_in_bytes];  // cell storage
-   temp_cells = new unsigned char[length_in_bytes]; // temp cell storage
-   if ( (cells == NULL) || (temp_cells == NULL) ) {
-      printf(&ldquo;Out of memory\n&rdquo;);
-      exit(1);
-   }
-   memset(cells, 0, length_in_bytes);  // clear all cells, to start
-}
-
-/* cellmap destructor. */
-cellmap::~cellmap(void)
-{
-   delete[] cells;
-   delete[] temp_cells;
-}
-
-/* Turns an off-cell on, incrementing the on-neighbor count for the
-   eight neighboring cells. */
-void cellmap::set_cell(unsigned int x, unsigned int y)
-{
-   unsigned int w = width, h = height;
-   int xoleft, xoright, yoabove, yobelow;
-   unsigned char *cell_ptr = cells + (y * w) + x;
-
-   // Calculate the offsets to the eight neighboring cells,
-   // accounting for wrapping around at the edges of the cell map
-   if (x == 0)
-      xoleft = w - 1;
-   else
-      xoleft = -1;
-   if (y == 0)
-      yoabove = length_in_bytes - w;
-   else
-      yoabove = -w;
-   if (x == (w - 1))
-      xoright = -(w - 1);
-   else
-      xoright = 1;
-   if (y == (h - 1))
-      yobelow = -(length_in_bytes - w);
-   else
-      yobelow = w;
-
-   *(cell_ptr) |= 0x01;
-   *(cell_ptr + yoabove + xoleft) += 2;
-   *(cell_ptr + yoabove) += 2;
-   *(cell_ptr + yoabove + xoright) += 2;
-   *(cell_ptr + xoleft) += 2;
-   *(cell_ptr + xoright) += 2;
-   *(cell_ptr + yobelow + xoleft) += 2;
-   *(cell_ptr + yobelow) += 2;
-   *(cell_ptr + yobelow + xoright) += 2;
-}
-
-/* Turns an on-cell off, decrementing the on-neighbor count for the
-   eight neighboring cells. */
-void cellmap::clear_cell(unsigned int x, unsigned int y)
-{
-   unsigned int w = width, h = height;
-   int xoleft, xoright, yoabove, yobelow;
-   unsigned char *cell_ptr = cells + (y * w) + x;
-
-   // Calculate the offsets to the eight neighboring cells,
-   // accounting for wrapping around at the edges of the cell map
-   if (x == 0)
-      xoleft = w - 1;
-   else
-      xoleft = -1;
-   if (y == 0)
-      yoabove = length_in_bytes - w;
-   else
-      yoabove = -w;
-   if (x == (w - 1))
-      xoright = -(w - 1);
-   else
-      xoright = 1;
-   if (y == (h - 1))
-      yobelow = -(length_in_bytes - w);
-   else
-      yobelow = w;
-
-   *(cell_ptr) &amp;= ~0x01;
-   *(cell_ptr + yoabove + xoleft) -= 2;
-   *(cell_ptr + yoabove ) -= 2;
-   *(cell_ptr + yoabove + xoright) -= 2;
-   *(cell_ptr + xoleft) -= 2;
-   *(cell_ptr + xoright) -= 2;
-   *(cell_ptr + yobelow + xoleft) -= 2;
-   *(cell_ptr + yobelow) -= 2;
-   *(cell_ptr + yobelow + xoright) -= 2;
-}
-
-/* Returns cell state (1=on or 0=off). */
-int cellmap::cell_state(int x, int y)
-{
-   unsigned char *cell_ptr;
-
-   cell_ptr = cells + (y * width) + x;
-   return *cell_ptr &amp; 0x01;
-}
-
-/* Calculates and displays the next generation of current_map */
-void cellmap::next_generation()
-{
-   unsigned int x, y, count;
-   unsigned int h = height, w = width;
-   unsigned char *cell_ptr, *row_cell_ptr;
-
-   // Copy to temp map, so we can have an unaltered version from
-   // which to work
-   memcpy(temp_cells, cells, length_in_bytes);
-
-   // Process all cells in the current cell map
-   cell_ptr = temp_cells;     // first cell in cell map
-   for (y=0; y&lt;h; y++) {      // repeat for each row of cells
-   // Process all cells in the current row of the cell map
-      x = 0;
-      do {        // repeat for each cell in row
-                  // Zip quickly through as many off-cells with no
-                  // neighbors as possible
-         while (*cell_ptr == 0) {
-            cell_ptr++; // advance to the next cell
-            if (++x &gt;= w) goto RowDone;
-         }
-         // Found a cell that&rsquo;s either on or has on-neighbors,
-         // so see if its state needs to be changed
-         count = *cell_ptr &gt;&gt; 1; // # of neighboring on-cells
-         if (*cell_ptr &amp; 0x01) {
-            // Cell is on; turn it off if it doesn&rsquo;t have
-            // 2 or 3 neighbors
-            if ((count != 2) &amp;&amp; (count != 3)) {
-               clear_cell(x, y);
-               draw_pixel(x, y, OFF_COLOR);
-            }
-         } else {
-            // Cell is off; turn it on if it has exactly 3 neighbors
-            if (count == 3) {
-               set_cell(x, y);
-               draw_pixel(x, y, ON_COLOR);
-            }
-         }
-         // Advance to the next cell
-         cell_ptr++; // advance to the next cell byte
-      } while (++x &lt; w);
-RowDone:
-   }
-}
-
-/* Randomly initializes the cellmap to about 50% on-pixels. */
-void cellmap::init()
-{
-   unsigned int x, y, init_length;
-
-   // Get the seed; seed randomly if 0 entered
-   cout &lt;&lt; &ldquo;Seed (0 for random seed): &rdquo;;
-   cin &gt;&gt; seed;
-   if (seed == 0) seed = (unsigned) time(NULL);
-
-   // Randomly initialize the initial cell map to 50% on-pixels
-   // (actually generally fewer, because some coordinates will be
-   // randomly selected more than once)
-   cout &lt;&lt; &ldquo;Initializing...&rdquo;;
-   srand(seed);
-   init_length = (height * width) / 2;
-   do {
-      x = random(width);
-      y = random(height);
-      if (cell_state(x, y) == 0) {
-         set_cell(x, y);
-      }
-   } while (&mdash;init_length);
-}
-</PRE>
-<!-- END CODE //-->
-<P><BR></P>
-<CENTER>
-<TABLE BORDER>
-<TR>
-<TD><A HREF="17-06.html">Previous</A></TD>
-<TD><A HREF="index.html">Table of Contents</A></TD>
-<TD><A HREF="17-08.html">Next</A></TD>
-</TR>
-</TABLE>
-</CENTER>
-
-<hr width="90%" size="1" noshade>
-<div align="center">
-Graphics Programming Black Book &copy; 2001 Michael Abrash
-</div>
-<!-- all of the reference materials (books) have the footer and subfoot reveresed -->
-<!-- reference_subfoot = footer -->
-<!-- reference_footer = subfoot -->
-
-<!-- BEGIN SUB FOOTER -->
-</BODY>
-</HTML>
-
-<!-- END FOOTER -->
-
-
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+  <meta name="vsisbn" content="1576101746" />
+  <meta name="vstitle" content="Michael Abrash's Graphics Programming Black Book, Special Edition" />
+  <meta name="vsauthor" content="Michael Abrash" />
+  <meta name="vspublisher" content="The Coriolis Group" />
+  <meta name="vspubdate" content="07/01/97" />
+  <meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
+
+  <title>Michael Abrash's Graphics Programming Black Book Special Edition: The Game of Life</title><!-- HEADER -->
+  <!-- Empty Reference Subhead -->
+  <!--ISBN=1576101746//-->
+  <!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
+  <!--AUTHOR=Michael Abrash//-->
+  <!--PUBLISHER=The Coriolis Group, Inc.//-->
+  <!--CHAPTER=17//-->
+  <!--PAGES=340-345//-->
+  <!--UNASSIGNED1//-->
+  <!--UNASSIGNED2//-->
+</head>
+
+<body>
+  <center>
+    <table border="1">
+      <tr>
+        <td><a href="17-06.html">Previous</a></td>
+
+        <td><a href="index.html">Table of Contents</a></td>
+
+        <td><a href="17-08.html">Next</a></td>
+      </tr>
+    </table>
+  </center>
+
+  <p><br /></p>
+
+  <p><b>LISTING 17.5 L17-5.CPP</b></p><!-- CODE //-->
+  <pre>
+/* C++ Game of Life implementation for any mode for which mode set
+   and draw pixel functions can be provided. The cellmap stores the
+   neighbor count for each cell as well as the state of each cell;
+   this allows very fast next-state determination. Edges always wrap
+   in this implementation.
+   Tested with Borland C++. To run, link with Listing 17.2
+   in the large model. */
+#include &lt;stdlib.h&gt;
+#include &lt;stdio.h&gt;
+#include &lt;iostream.h&gt;
+#include &lt;conio.h&gt;
+#include &lt;time.h&gt;
+#include &lt;dos.h&gt;
+#include &lt;bios.h&gt;
+#include &lt;mem.h&gt;
+
+#define ON_COLOR  15       // on-cell pixel color
+#define OFF_COLOR 0        // off-cell pixel color
+#define MSG_LINE  10       // row for text messages
+#define GENERATION_LINE 12 // row for generation # display
+#define LIMIT_18_HZ  0     // set 1 to to maximum frame rate = 18Hz
+
+class cellmap {
+private:
+   unsigned char *cells;
+   unsigned char *temp_cells;
+   unsigned int width;
+   unsigned int height;
+   unsigned int length_in_bytes;
+public:
+   cellmap(unsigned int h, unsigned int v);
+   ~cellmap(void);
+   void set_cell(unsigned int x, unsigned int y);
+   void clear_cell(unsigned int x, unsigned int y);
+   int cell_state(int x, int y);
+   int count_neighbors(int x, int y);
+   void next_generation(void);
+   void init(void);
+};
+
+extern void enter_display_mode(void);
+extern void exit_display_mode(void);
+extern void draw_pixel(unsigned int X, unsigned int Y,
+   unsigned int Color);
+extern void show_text(int x, int y, char *text);
+
+/* Controls the size of the cell map. Must be within the capabilities
+   of the display mode, and must be limited to leave room for text
+   display at right. */
+unsigned int cellmap_width = 96;
+unsigned int cellmap_height = 96;
+
+/* Width &amp; height in pixels of each cell. */
+unsigned int magnifier = 2;
+
+/* Randomizing seed */
+unsigned int seed;
+
+void main()
+{
+   unsigned long generation = 0;
+   char gen_text[80];
+   long bios_time, start_bios_time;
+
+   cellmap current_map(cellmap_height, cellmap_width);
+
+   current_map.init();  // randomly initialize cell map
+
+   enter_display_mode();
+
+   // Keep recalculating and redisplaying generations until any key
+   // is pressed
+   show_text(0, MSG_LINE, &ldquo;Generation: &rdquo;);
+   start_bios_time = _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
+   do {
+      generation++;
+      sprintf(gen_text, &ldquo;%10lu&rdquo;, generation);
+      show_text(1, GENERATION_LINE, gen_text);
+      // Recalculate and draw the next generation
+      current_map.next_generation();
+#if LIMIT_18_HZ
+      // Limit to a maximum of 18.2 frames per second, for visibility
+      do {
+         _bios_timeofday(_TIME_GETCLOCK, &amp;bios_time);
+      } while (start_bios_time == bios_time);
+      start_bios_time = bios_time;
+#endif
+   } while (!kbhit());
+
+   getch();    // clear keypress
+   exit_display_mode();
+   cout &lt;&lt; &ldquo;Total generations: &rdquo; &lt;&lt; generation &lt;&lt; &ldquo;\nSeed: &rdquo; &lt;&lt;
+         seed &lt;&lt; &ldquo;\n&rdquo;;
+}
+
+/* cellmap constructor. */
+cellmap::cellmap(unsigned int h, unsigned int w)
+{
+   width = w;
+   height = h;
+   length_in_bytes = w * h;
+   cells = new unsigned char[length_in_bytes];  // cell storage
+   temp_cells = new unsigned char[length_in_bytes]; // temp cell storage
+   if ( (cells == NULL) || (temp_cells == NULL) ) {
+      printf(&ldquo;Out of memory\n&rdquo;);
+      exit(1);
+   }
+   memset(cells, 0, length_in_bytes);  // clear all cells, to start
+}
+
+/* cellmap destructor. */
+cellmap::~cellmap(void)
+{
+   delete[] cells;
+   delete[] temp_cells;
+}
+
+/* Turns an off-cell on, incrementing the on-neighbor count for the
+   eight neighboring cells. */
+void cellmap::set_cell(unsigned int x, unsigned int y)
+{
+   unsigned int w = width, h = height;
+   int xoleft, xoright, yoabove, yobelow;
+   unsigned char *cell_ptr = cells + (y * w) + x;
+
+   // Calculate the offsets to the eight neighboring cells,
+   // accounting for wrapping around at the edges of the cell map
+   if (x == 0)
+      xoleft = w - 1;
+   else
+      xoleft = -1;
+   if (y == 0)
+      yoabove = length_in_bytes - w;
+   else
+      yoabove = -w;
+   if (x == (w - 1))
+      xoright = -(w - 1);
+   else
+      xoright = 1;
+   if (y == (h - 1))
+      yobelow = -(length_in_bytes - w);
+   else
+      yobelow = w;
+
+   *(cell_ptr) |= 0x01;
+   *(cell_ptr + yoabove + xoleft) += 2;
+   *(cell_ptr + yoabove) += 2;
+   *(cell_ptr + yoabove + xoright) += 2;
+   *(cell_ptr + xoleft) += 2;
+   *(cell_ptr + xoright) += 2;
+   *(cell_ptr + yobelow + xoleft) += 2;
+   *(cell_ptr + yobelow) += 2;
+   *(cell_ptr + yobelow + xoright) += 2;
+}
+
+/* Turns an on-cell off, decrementing the on-neighbor count for the
+   eight neighboring cells. */
+void cellmap::clear_cell(unsigned int x, unsigned int y)
+{
+   unsigned int w = width, h = height;
+   int xoleft, xoright, yoabove, yobelow;
+   unsigned char *cell_ptr = cells + (y * w) + x;
+
+   // Calculate the offsets to the eight neighboring cells,
+   // accounting for wrapping around at the edges of the cell map
+   if (x == 0)
+      xoleft = w - 1;
+   else
+      xoleft = -1;
+   if (y == 0)
+      yoabove = length_in_bytes - w;
+   else
+      yoabove = -w;
+   if (x == (w - 1))
+      xoright = -(w - 1);
+   else
+      xoright = 1;
+   if (y == (h - 1))
+      yobelow = -(length_in_bytes - w);
+   else
+      yobelow = w;
+
+   *(cell_ptr) &amp;= ~0x01;
+   *(cell_ptr + yoabove + xoleft) -= 2;
+   *(cell_ptr + yoabove ) -= 2;
+   *(cell_ptr + yoabove + xoright) -= 2;
+   *(cell_ptr + xoleft) -= 2;
+   *(cell_ptr + xoright) -= 2;
+   *(cell_ptr + yobelow + xoleft) -= 2;
+   *(cell_ptr + yobelow) -= 2;
+   *(cell_ptr + yobelow + xoright) -= 2;
+}
+
+/* Returns cell state (1=on or 0=off). */
+int cellmap::cell_state(int x, int y)
+{
+   unsigned char *cell_ptr;
+
+   cell_ptr = cells + (y * width) + x;
+   return *cell_ptr &amp; 0x01;
+}
+
+/* Calculates and displays the next generation of current_map */
+void cellmap::next_generation()
+{
+   unsigned int x, y, count;
+   unsigned int h = height, w = width;
+   unsigned char *cell_ptr, *row_cell_ptr;
+
+   // Copy to temp map, so we can have an unaltered version from
+   // which to work
+   memcpy(temp_cells, cells, length_in_bytes);
+
+   // Process all cells in the current cell map
+   cell_ptr = temp_cells;     // first cell in cell map
+   for (y=0; y&lt;h; y++) {      // repeat for each row of cells
+   // Process all cells in the current row of the cell map
+      x = 0;
+      do {        // repeat for each cell in row
+                  // Zip quickly through as many off-cells with no
+                  // neighbors as possible
+         while (*cell_ptr == 0) {
+            cell_ptr++; // advance to the next cell
+            if (++x &gt;= w) goto RowDone;
+         }
+         // Found a cell that&rsquo;s either on or has on-neighbors,
+         // so see if its state needs to be changed
+         count = *cell_ptr &gt;&gt; 1; // # of neighboring on-cells
+         if (*cell_ptr &amp; 0x01) {
+            // Cell is on; turn it off if it doesn&rsquo;t have
+            // 2 or 3 neighbors
+            if ((count != 2) &amp;&amp; (count != 3)) {
+               clear_cell(x, y);
+               draw_pixel(x, y, OFF_COLOR);
+            }
+         } else {
+            // Cell is off; turn it on if it has exactly 3 neighbors
+            if (count == 3) {
+               set_cell(x, y);
+               draw_pixel(x, y, ON_COLOR);
+            }
+         }
+         // Advance to the next cell
+         cell_ptr++; // advance to the next cell byte
+      } while (++x &lt; w);
+RowDone:
+   }
+}
+
+/* Randomly initializes the cellmap to about 50% on-pixels. */
+void cellmap::init()
+{
+   unsigned int x, y, init_length;
+
+   // Get the seed; seed randomly if 0 entered
+   cout &lt;&lt; &ldquo;Seed (0 for random seed): &rdquo;;
+   cin &gt;&gt; seed;
+   if (seed == 0) seed = (unsigned) time(NULL);
+
+   // Randomly initialize the initial cell map to 50% on-pixels
+   // (actually generally fewer, because some coordinates will be
+   // randomly selected more than once)
+   cout &lt;&lt; &ldquo;Initializing...&rdquo;;
+   srand(seed);
+   init_length = (height * width) / 2;
+   do {
+      x = random(width);
+      y = random(height);
+      if (cell_state(x, y) == 0) {
+         set_cell(x, y);
+      }
+   } while (&mdash;init_length);
+}
+</pre><!-- END CODE //-->
+
+  <p><br /></p>
+
+  <center>
+    <table border="1">
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+
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+      </tr>
+    </table>
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+
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+    Graphics Programming Black Book &copy; 2001 Michael Abrash
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