You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
184 lines
5.6 KiB
184 lines
5.6 KiB
page ,132
|
|
title strstr - search for one string inside another
|
|
;***
|
|
;strstr.asm - search for one string inside another
|
|
;
|
|
; Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
|
|
;
|
|
;Purpose:
|
|
; defines strstr() - search for one string inside another
|
|
;
|
|
;Revision History:
|
|
; 02-02-88 SKS Rewritten from scratch. Now works correctly with
|
|
; strings > 32 KB in length. Also smaller and faster.
|
|
; 03-01-88 SKS Ensure that ES = DS right away (Small/Medium models)
|
|
; 05-18-88 SJM Add model-independent (large model) ifdef
|
|
; 08-04-88 SJM convert to cruntime/ add 32-bit support
|
|
; 08-18-88 PHG Corrected return value when src is empty string
|
|
; to conform with ANSI.
|
|
; 08-23-88 JCR Minor 386 cleanup
|
|
; 10-26-88 JCR General cleanup for 386-only code
|
|
; 03-26-90 GJF Changed to _stdcall. Also, fixed the copyright.
|
|
; 05-10-91 GJF Back to _cdecl, sigh...
|
|
; 12-19-94 GJF Revised to improve performance a bit.
|
|
; 12-04-95 GJF Much faster version from Intel.
|
|
; 06-12-01 PML inc->add 1, dec->sub 1 for Pentium 4 perf (vs7#267015)
|
|
;
|
|
;*******************************************************************************
|
|
|
|
.xlist
|
|
include cruntime.inc
|
|
.list
|
|
|
|
page
|
|
;***
|
|
;char *strstr(str1, str2) - search for str2 in str1
|
|
;
|
|
;Purpose:
|
|
; finds the first occurrence of str2 in str1
|
|
;
|
|
;Entry:
|
|
; char *str1 - string to search in
|
|
; char *str2 - string to search for
|
|
;
|
|
;Exit:
|
|
; returns a pointer to the first occurrence of string2 in
|
|
; string1, or NULL if string2 does not occur in string1
|
|
;
|
|
;Uses:
|
|
;
|
|
;Exceptions:
|
|
;
|
|
;*******************************************************************************
|
|
|
|
|
|
__from_strstr_to_strchr proto
|
|
|
|
CODESEG
|
|
|
|
public strstr
|
|
|
|
strstr proc
|
|
|
|
mov ecx,[esp + 8] ; str2 (the string to be searched for)
|
|
|
|
push edi ; Preserve edi, ebx and esi
|
|
push ebx
|
|
push esi
|
|
|
|
mov dl,[ecx] ; dl contains first char from str2
|
|
|
|
mov edi,[esp + 10h] ; str1 (the string to be searched)
|
|
|
|
test dl,dl ; is str2 empty?
|
|
jz empty_str2
|
|
|
|
mov dh,[ecx + 1] ; second char from str2
|
|
test dh,dh ; is str2 a one-character string?
|
|
jz strchr_call ; if so, go use strchr code
|
|
|
|
; length of str2 is now known to be > 1 (used later)
|
|
; dl contains first char from str2
|
|
; dh contains second char from str2
|
|
; edi holds str1
|
|
|
|
findnext:
|
|
mov esi,edi ; esi = edi = pointers to somewhere in str1
|
|
mov ecx,[esp + 14h] ; str2
|
|
|
|
;use edi instead of esi to eliminate AGI
|
|
mov al,[edi] ; al is next char from str1
|
|
|
|
add esi,1 ; increment pointer into str1
|
|
|
|
cmp al,dl
|
|
je first_char_found
|
|
|
|
test al,al ; end of str1?
|
|
jz not_found ; yes, and no match has been found
|
|
|
|
loop_start:
|
|
mov al,[esi] ; put next char from str1 into al
|
|
add esi,1 ; increment pointer in str1
|
|
in_loop:
|
|
cmp al,dl
|
|
je first_char_found
|
|
|
|
test al,al ; end of str1?
|
|
jnz loop_start ; no, go get another char from str1
|
|
|
|
not_found:
|
|
pop esi
|
|
pop ebx
|
|
pop edi
|
|
xor eax,eax
|
|
ret
|
|
|
|
; recall that dh contains the second char from str2
|
|
|
|
first_char_found:
|
|
mov al,[esi] ; put next char from str1 into al
|
|
add esi,1
|
|
|
|
cmp al,dh ; compare second chars
|
|
jnz in_loop ; no match, continue search
|
|
|
|
two_first_chars_equal:
|
|
lea edi,[esi - 1] ; store position of last read char in str1
|
|
|
|
compare_loop:
|
|
mov ah,[ecx + 2] ; put next char from str2 into ah
|
|
test ah,ah ; end of str2?
|
|
jz match ; if so, then a match has been found
|
|
|
|
mov al,[esi] ; get next char from str1
|
|
add esi,2 ; bump pointer into str1 by 2
|
|
|
|
cmp al,ah ; are chars from str1 and str2 equal?
|
|
jne findnext ; no
|
|
|
|
; do one more iteration
|
|
|
|
mov al,[ecx + 3] ; put the next char from str2 into al
|
|
test al,al ; end of str2
|
|
jz match ; if so, then a match has been found
|
|
|
|
mov ah,[esi - 1] ; get next char from str1
|
|
add ecx,2 ; bump pointer in str1 by 2
|
|
cmp al,ah ; are chars from str1 and str2 equal?
|
|
je compare_loop
|
|
|
|
; no match. test some more chars (to improve execution time for bad strings).
|
|
|
|
jmp findnext
|
|
|
|
; str2 string contains only one character so it's like the strchr functioin
|
|
|
|
strchr_call:
|
|
xor eax,eax
|
|
pop esi
|
|
pop ebx
|
|
pop edi
|
|
mov al,dl
|
|
jmp __from_strstr_to_strchr
|
|
|
|
;
|
|
;
|
|
; Match! Return (ebx - 1)
|
|
;
|
|
match:
|
|
lea eax,[edi - 1]
|
|
pop esi
|
|
pop ebx
|
|
pop edi
|
|
ret
|
|
|
|
empty_str2: ; empty target string, return src (ANSI mandated)
|
|
mov eax,edi
|
|
pop esi
|
|
pop ebx
|
|
pop edi
|
|
ret
|
|
|
|
strstr endp
|
|
end
|