|
|
page ,132 title memccpy - copy bytes until character found;***;memccpy.asm - copy bytes until a character is found;; Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.;;Purpose:; defines _memccpy() - copies bytes until a specifed character; is found, or a maximum number of characters have been copied.;;Revision History:; 05-16-84 RN initial version; 05-17-88 SJM Add model-independent (large model) ifdef; 08-04-88 SJM convert to cruntime/ add 32-bit support; 08-23-88 JCR Minor 386 adjustments; 10-25-88 JCR General cleanup for 386-only code; 03-23-90 GJF Changed to _stdcall. Also, fixed the copyright.; 01-17-91 GJF ANSI naming.; 05-10-91 GJF Back to _cdecl, sigh...; 10-27-92 SKS Avoid using a MASM keyword ("C") as a parameter name; 01-19-95 GJF Faster version courtesy of Intel Israel.; 01-24-95 GJF Added FPO directive.; 06-12-01 PML inc->add 1, dec->sub 1 for Pentium 4 perf (vs7#267015);;*******************************************************************************
.xlist include cruntime.inc .list
page;***;char *_memccpy(dest, src, _c, count) - copy bytes until character found;;Purpose:; Copies bytes from src to dest until count bytes have been; copied, or up to and including the character _c, whichever; comes first.;; Algorithm:; char *; _memccpy (dest, src, _c, count); char *dest, *src, _c;; unsigned int count;; {; while (count && (*dest++ = *src++) != _c); count--;;; return(count ? dest : NULL);; };;Entry:; char *dest - pointer to memory to receive copy; char *src - source of bytes; char _c - character to stop copy at; int count - max number of bytes to copy;;Exit:; returns pointer to byte immediately after _c in dest;; returns NULL if _c was never found;;Uses:;;Exceptions:;;*******************************************************************************
CODESEG
public _memccpy_memccpy proc
.FPO ( 0, 4, 0, 0, 0, 0 )
mov ecx,[esp + 10h] ; ecx = max byte count push ebx ; save ebx test ecx,ecx ; if it's nothing to move jz ret_zero_len ; restore ebx, and return NULL mov bh,[esp + 10h] ; bh = byte to look for push esi ; save esi test ecx,1 ; test if counter is odd or even mov eax,[esp + 0ch] ; eax = dest , don't affect flags mov esi,[esp + 10h] ; esi = source , don't affect flags ; nop jz lupe2 ; if counter is even, do double loop ; else do one iteration, and drop into double loop mov bl,[esi] ; get first byte into bl add esi,1 ; kick src (esi points to src) mov [eax],bl ; store it in dest add eax,1 ; kick dest cmp bl,bh ; see if we just moved the byte je short toend sub ecx,1 ; decrement counter jz retnull ; drop into double loop if nonzero lupe2: mov bl,[esi] ; get first byte into bl add esi,2 ; kick esi (src) cmp bl,bh ; check if we just moved the byte (from bl) je toend_mov_inc ; store bl & exit mov [eax],bl ; store first byte from bl mov bl,[esi - 1] ; get second byte into bl mov [eax + 1],bl ; store second byte from bl add eax,2 ; kick eax (dest) cmp bl,bh ; see if we just moved the byte je short toend ; end of string sub ecx,2 ; modify counter, and if nonzero continue jnz lupe2 ; else drop out & return NULL retnull: pop esiret_zero_len: xor eax,eax ; null pointer pop ebx ret ; _cdecl return toend_mov_inc: mov [eax],bl ; store first byte from bl add eax,1 ; eax points right after the value toend: pop esi pop ebx ret ; _cdecl return _memccpy endp
end
|
