Misc/abrash-black-book
Watch
1
0
Fork
You've already forked abrash-black-book
 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Use backtick code blocks for syntax highlighting

Browse source
This commit is contained in:
James Gregory 2013-12-31 11:38:48 +11:00
commit f658bfbb40
203 changed files with 26546 additions and 25801 deletions
Download patch file Download diff file Expand all files Collapse all files

96
16-08.md
View file

@ -12,20 +12,21 @@ pages: 316-319
**Listing 16.7 L16-7.ASM**
ScanLoop:
lodsw ;get the next 2 bytes (AL = first, AH = 2nd)
xlat ;look up first's char/not status
xor dl,al ;see if there's a new char/not status
add di,dx ;we add 1 for each char/not transition
mov dl,al
mov al,ah ;look at the second byte
xlat ;look up its char/not status
xor dl,al ;see if there's a new char/not status
add di,dx ;we add 1 for each char/not transition
mov dl,al
dec dx
jnz ScanLoop
```nasm
ScanLoop:
lodsw ;get the next 2 bytes (AL = first, AH = 2nd)
xlat ;look up first's char/not status
xor dl,al ;see if there's a new char/not status
add di,dx ;we add 1 for each char/not transition
mov dl,al
mov al,ah ;look at the second byte
xlat ;look up its char/not status
xor dl,al ;see if there's a new char/not status
add di,dx ;we add 1 for each char/not transition
mov dl,al
dec dx
jnz ScanLoop
```
John later divides the transition count by two to get the word count.
(Food for thought: It's also possible to use **CMP** and **ADC** to
@ -66,39 +67,40 @@ report a "location counter overflow" warning; ignore it.)
**LISTING 16.8 MAKETAB.C**
// MAKETAB.C — Build QSCAN3.INC for QSCAN3.ASM
#include <stdio.h>
#include <ctype.h>
#define ChType( c ) (((c) & 0x7f) == ‘\'' || isalnum((c) & 0x7f))
int NoCarry[ 4 ] = { 0, 0x80, 1, 0x80 };
int Carry[ 4 ] = { 1, 0x81, 1, 0x80 };
void main( void )
{
int ahChar, alChar, i;
FILE *t = fopen( "QSCAN3.INC", "wt" );
printf( "Building table. Please wait..." );
for( ahChar = 0; ahChar < 128; ahChar++ )
{
for( alChar = 0; alChar < 256; alChar++ )
{
i = ChType( alChar ) * 2 + ChType( ahChar );
if( alChar % 8 == 0 ) fprintf( t, "\ndb %02Xh", NoCarry[ i ] );
else fprintf( t, ",%02Xh", NoCarry[ i ] );
fprintf( t, ",%02Xh", Carry[ i ] );
}
}
fclose( t );
}
```c
// MAKETAB.C — Build QSCAN3.INC for QSCAN3.ASM
#include <stdio.h>
#include <ctype.h>
#define ChType( c ) (((c) & 0x7f) == ‘\'' || isalnum((c) & 0x7f))
int NoCarry[ 4 ] = { 0, 0x80, 1, 0x80 };
int Carry[ 4 ] = { 1, 0x81, 1, 0x80 };
void main( void )
{
int ahChar, alChar, i;
FILE *t = fopen( "QSCAN3.INC", "wt" );
printf( "Building table. Please wait..." );
for( ahChar = 0; ahChar < 128; ahChar++ )
{
for( alChar = 0; alChar < 256; alChar++ )
{
i = ChType( alChar ) * 2 + ChType( ahChar );
if( alChar % 8 == 0 ) fprintf( t, "\ndb %02Xh", NoCarry[ i ] );
else fprintf( t, ",%02Xh", NoCarry[ i ] );
fprintf( t, ",%02Xh", Carry[ i ] );
}
}
fclose( t );
}
```
David's approach is simplicity itself, although his implementation
arguably is not. Consider any three sequential bytes in the buffer.