Misc/abrash-black-book
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This commit is contained in:
James Gregory 2013-12-30 18:34:31 +11:00
commit 18011c595a
352 changed files with 6040 additions and 6040 deletions
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26
14-05.md
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@ -28,14 +28,14 @@
public _FindString
_FindString proc near
cld
push bp ;preserve caller’s stack frame
push bp ;preserve caller's stack frame
mov bp,sp ;point to our stack frame
push si ;preserve caller’s register variables
push si ;preserve caller'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’t
; pattern length; this is the skip distance for bytes that don't
; appear in the pattern.
mov ax,[bp+PatternLength]
and ax,ax ;return an instant match if the pattern is
@ -57,8 +57,8 @@
; 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’s skip value is used. Note that the rightmost byte of the
; pattern isn’t entered in the skip table; if we get that value for
; instance's skip value is used. Note that the rightmost byte of the
; pattern isn'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.
@ -85,7 +85,7 @@
mov cx,[bp+BufferLength] ;# of match locations to check
SearchLoop:
mov si,sp ;point SI to SkipTable
; Skip through until there’s a match for the rightmost pattern byte.
; Skip through until there'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?
@ -114,14 +114,14 @@
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’s it; we’ve found a match
; It’s a mismatch; let’s see what we can learn from it.
jz Match ;that's it; we've found a match
; It's a mismatch; let'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’t even skip ahead as far
; If, based on the mismatch character, we can'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,
@ -131,14 +131,14 @@
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’ll just advance to the next
mov ax,1 ;assume we'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’s any buffer
; Skip ahead and perform the next comparison, if there's any buffer
; left to check.
mov di,[bp+BufferPtr]
add di,ax ;BufferPtr += Skip;
@ -158,9 +158,9 @@
Done:
cld ;restore default direction flag
add sp,256*2 ;deallocate space for SkipTable
pop di ;restore caller’s register variables
pop di ;restore caller's register variables
pop si
pop bp ;restore caller’s stack frame
pop bp ;restore caller's stack frame
ret
_FindString endp
end