windows-server-2003/base/crts/crtw32/string/i386/strnset.asm

	page	,132
	title	strnset - set first n characters to one char.
;***
;strnset.asm - set first n characters to single character
;
;	Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
;
;Purpose:
;	defines _strnset() - sets at most the first n characters of a string
;	to a given character.
;
;Revision History:
;	11-18-83  RN	initial version
;	05-18-88  SJM	Add model-independent (large model) ifdef
;	05-23-88  WAJ	If count = strlen(string)+1 then strlen+1 bytes were set.
;	08-04-88  SJM	convert to cruntime/ add 32-bit support
;	08-23-88  JCR	386 cleanup
;	10-26-88  JCR	General cleanup for 386-only code
;	03-23-90  GJF	Changed to _stdcall. Also, fixed the copyright.
;	01-18-91  GJF	ANSI naming.
;	05-10-91  GJF	Back to _cdecl, sigh...
;       06-12-01  PML   inc->add 1, dec->sub 1 for Pentium 4 perf (vs7#267015)
;
;*******************************************************************************

	.xlist
	include cruntime.inc
	.list

page
;***
;char *_strnset(string, val, count) - set at most count characters to val
;
;Purpose:
;	Sets the first count characters of string the character value.
;	If the length of string is less than count, the length of
;	string is used in place of n.
;
;	Algorithm:
;	char *
;	_strnset (string, val, count)
;	      char *string,val;
;	      unsigned int count;
;	      {
;	      char *start = string;
;
;	      while (count-- && *string)
;		      *string++ = val;
;	      return(start);
;	      }
;
;Entry:
;	char *string - string to set characters in
;	char val - character to fill with
;	unsigned count - count of characters to fill
;
;Exit:
;	returns string, now filled with count copies of val.
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************

	CODESEG

	public	_strnset
_strnset proc \
	uses edi ebx, \
	string:ptr byte, \
	val:byte, \
	count:IWORD


	mov	edi,[string]	; di = string
	mov	edx,edi 	; dx=string addr; save return value
	mov	ebx,[count]	; cx = max chars to set
	xor	eax,eax 	; null byte
	mov	ecx,ebx
	jecxz	short done	; zero length specified

repne	scasb			; find null byte & count bytes in cx
	jne	short nonull	; null not found
	add	ecx,1		; don't want the null

nonull:
	sub	ebx,ecx 	; bx=strlen (not null)
	mov	ecx,ebx 	; cx=strlen (not null)

	mov	edi,edx 	; restore string pointer
	mov	al,val		; byte value
rep	stosb			; fill 'er up

done:
	mov	eax,edx 	; return value: string addr

ifdef	_STDCALL_
	ret	DPSIZE + 2*ISIZE ; _stdcall return
else
	ret			; _cdecl return
endif

_strnset endp
	end