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Diffstat (limited to 'private/crt32/string/i386/memcmp.asm')
| -rw-r--r-- | private/crt32/string/i386/memcmp.asm | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/private/crt32/string/i386/memcmp.asm b/private/crt32/string/i386/memcmp.asm new file mode 100644 index 000000000..cd419fd2e --- /dev/null +++ b/private/crt32/string/i386/memcmp.asm @@ -0,0 +1,101 @@ + page ,132 + title memcmp - compare to blocks of memory +;*** +;memcmp.asm - compare two blocks of memory +; +; Copyright (c) 1985-1991, Microsoft Corporation. All rights reserved. +; +;Purpose: +; defines memcmp() - compare two memory blocks lexically and +; find their order. +; +;Revision History: +; 05-16-83 RN initial version +; 07-20-87 SKS rewritten for speed +; 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 386 cleanup +; 10-25-88 JCR General cleanup for 386-only code +; 03-23-90 GJF Changed to _stdcall. Also, fixed the copyright. +; 05-10-91 GJF Back to _cdecl, sigh... +; +;******************************************************************************* + + .xlist + include cruntime.inc + .list + +page +;*** +;int memcmp(buf1, buf2, count) - compare memory for lexical order +; +;Purpose: +; Compares count bytes of memory starting at buf1 and buf2 +; and find if equal or which one is first in lexical order. +; +; Algorithm: +; int +; memcmp (buf1, buf2, count) +; char *buf1, *buf2; +; unsigned count; +; { +; if (!count) +; return(0); +; while (--count && *buf1 == *buf2) +; { +; buf1++; +; buf2++; +; } +; return(*buf1 - *buf2); +; } +; +;Entry: +; char *buf1, *buf2 - pointers to memory sections to compare +; unsigned count - length of sections to compare +; +;Exit: +; returns -1 if buf1 < buf2 +; returns 0 if buf1 == buf2 +; returns +1 if buf1 > buf2 +; +;Uses: +; +;Exceptions: +; +;******************************************************************************* + + CODESEG + + public memcmp +memcmp proc \ + uses edi esi, \ + buf1:ptr byte, \ + buf2:ptr byte, \ + count:IWORD + + mov esi,buf1 ; si = buf1 + mov edi,buf2 ; di = buf2 + +; +; choose ds:si=buf1 and es:di=buf2 so that the CARRY flag +; gets the right way by the REP CMPSB instruction below. +; + xor eax,eax + mov ecx,count + jecxz short done + + repe cmpsb ; compare while equal, at most "count" bytes + je short done ; buf1 == buf2? (AX = 0) + ; buf1 < buf2 buf1 > buf2 + sbb eax,eax ; AX=-1, CY=1 AX=0, CY=0 + sbb eax,-1 ; AX=-1 AX=1 +done: + +ifdef _STDCALL_ + ret 2*DPSIZE + ISIZE ; _stdcall return +else + ret ; _cdecl return +endif + +memcmp endp + end |