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kolibrios/drivers/ddk/string/strchr.S

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/* strchr() Author: Kees J. Bot */
/* 1 Jan 1994 */
/* char *strchr(const char *s, int c) */
/* Look for a character in a string. */
/* */
#include "asm.h"
ENTRY(strchr)
push %ebp
movl %esp, %ebp
push %edi
cld
movl 8(%ebp), %edi /* edi = string */
movl $16, %edx /* Look at small chunks of the string */
next:
shll $1, %edx /* Chunks become bigger each time */
movl %edx, %ecx
xorb %al, %al /* Look for the zero at the end */
repne scasb
pushf /* Remember the flags */
subl %edx, %ecx
negl %ecx /* Some or all of the chunk */
subl %ecx, %edi /* Step back */
movb 12(%ebp), %al /* The character to look for */
repne scasb
je found
popf /* Did we find the end of string earlier? */
jne next /* No, try again */
xorl %eax, %eax /* Return NULL */
pop %edi
pop %ebp
ret
found:
pop %eax /* Get rid of those flags */
leal -1(%edi), %eax /* Address of byte found */
pop %edi
pop %ebp
ret