95 lines
2.3 KiB
NASM
95 lines
2.3 KiB
NASM
page ,132
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title strchr - search string for given character
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;***
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;strchr.asm - search a string 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 strchr() - search a string for a character
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;
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;Revision History:
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; 10-27-83 RN initial version
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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 *strchr(string, c) - search a string for a character
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;
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;Purpose:
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; Searches a string for a given character, which may be the
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; null character '\0'.
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;
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; Algorithm:
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; char *
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; strchr (string, ch)
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; char *string, ch;
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; {
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; while (*string && *string != ch)
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; string++;
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; if (*string == ch)
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; return(string);
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; return((char *)0);
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; }
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;
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;Entry:
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; char *string - string to search in
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; char c - character to search for
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;
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;Exit:
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; returns pointer to the first occurence of c in string
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; returns NULL if c does not occur in string
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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 strchr
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strchr proc \
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uses edi, \
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string:ptr char, \
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chr:byte
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mov edi,[string] ; edi = string
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push edi ; save string pointer
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xor eax,eax ; null byte to search for
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mov ecx, -1
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repne scasb ; find string length by scanning for null
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not ecx ; cx = length of string
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mov al,[chr] ; al=byte to search for
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pop edi ; restore saved string pointer
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repne scasb ; find that byte (if it exists)!
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; edi points one past byte which stopped scan
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dec edi ; edi points to byte which stopped scan
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cmp [edi],al ; take one last look to be sure
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je short retdi ; return edi if it matches
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xor edi,edi ; no match, so return NULL
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retdi:
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mov eax,edi ; ret value: pointer to matching byte
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ifdef _STDCALL_
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ret DPSIZE + ISIZE ; _stdcall return
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else
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ret ; _cdecl return
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endif
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strchr endp
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end
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