memchr.s

一个操作系统,用C语言实现开发的,我在一个浙江大学的操作系统实验网站找到.大家学习以下

# Kernel Library
# memchr

.include "f_asm.inc"

.equ PTR,	DES
.equ CHR,	SRC

.text

.global _memchr

_memchr:
	ENTER
		pushl %esi
						
		movl LEN(%ebp), %ecx
		movb CHR(%ebp), %dl
		movl PTR(%ebp), %esi
		
		cld
next:				
		lodsb
		cmpb %dl, %al
		loopnz next
		jnz none

		movl %esi, %eax
		decl %eax
		jmp done
none:
		xorl %eax, %eax		
done:
		popl %esi

	LEAVE
		ret