strrchr.s

minux的源代码,一个非常小的操作系统

!	strrchr()					Author: Kees J. Bot
!								2 Jan 1994
.sect .text; .sect .rom; .sect .data; .sect .bss

! char *strrchr(const char *s, int c)
!	Look for the last occurrence a character in a string.
!
.sect .text
.define _strrchr
	.align	16
_strrchr:
	push	ebp
	mov	ebp, esp
	push	edi
	mov	edi, 8(ebp)	! edi = string
	mov	ecx, -1
	xorb	al, al
	cld
	repne
	scasb			! Look for the end of the string
	not	ecx		! -1 - ecx = Length of the string + null
	dec	edi		! Put edi back on the zero byte
	movb	al, 12(ebp)	! The character to look for
	std			! Downwards search
	repne
	scasb
	cld			! Direction bit back to default
	jne	failure
	lea	eax, 1(edi)	! Found it
	pop	edi
	pop	ebp
	ret
failure:xor	eax, eax	! Not there
	pop	edi
	pop	ebp
	ret