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96 lines
2.1 KiB
96 lines
2.1 KiB
page ,132
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title memchr - search memory for a given character
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;***
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;memchr.asm - search block of memory for a given character
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;
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; Copyright (c) 1985-1991, Microsoft Corporation. All rights reserved.
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;
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;Purpose:
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; defines memchr() - search memory until a character is
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; found or a limit is reached.
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;
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;Revision History:
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; 05-16-84 RN initial version
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; 07-20-87 SKS rewritten for speed
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; 05-17-88 SJM Add model-independent (large model) ifdef
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; 08-04-88 SJM convert to cruntime/ add 32-bit support
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; 08-23-88 JCR 386 cleanup
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; 10-25-88 JCR General cleanup for 386-only code
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; 03-23-90 GJF Changed to _stdcall. Also, fixed the copyright.
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; 05-10-91 GJF Back to _cdecl, sigh...
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;
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;*******************************************************************************
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.xlist
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include cruntime.inc
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.list
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page
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;***
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;char *memchr(buf, chr, cnt) - search memory for given character.
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;
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;Purpose:
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; Searched at buf for the given character, stopping when chr is
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; first found or cnt bytes have been searched through.
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;
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; Algorithm:
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; char *
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; memchr (buf, chr, cnt)
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; char *buf;
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; int chr;
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; unsigned cnt;
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; {
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; while (cnt && *buf++ != c)
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; cnt--;
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; return(cnt ? --buf : NULL);
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; }
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;
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;Entry:
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; char *buf - memory buffer to be searched
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; char chr - character to search for
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; unsigned cnt - max number of bytes to search
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;
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;Exit:
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; returns pointer to first occurence of chr in buf
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; returns NULL if chr not found in the first cnt bytes
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;
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;Uses:
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;
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;Exceptions:
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;
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;*******************************************************************************
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CODESEG
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public memchr
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memchr proc \
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buf:ptr, \
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chr:byte, \
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cnt:IWORD
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xor eax,eax ; return NULL if cnt == 0
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mov ecx,(cnt) ; cx = count
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jecxz short empty
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push edi ; Preserve DI
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mov edi,buf ; di = buffer
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mov al,chr ; al = search char
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repne scasb ; scan for byte
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mov eax,0 ; assume not found (ax=NULL)
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jne short done ; not found -- return NULL
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lea eax,[edi-1] ; found - return address of matching byte
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done:
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pop edi ; Restore DI
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empty:
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ifdef _STDCALL_
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ret DPSIZE + 2*ISIZE ; _stdcall return
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else
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ret ; _cdecl return
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endif
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memchr endp
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end
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