minix/lib/libc/arch/i386/string/_strnlen.S

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/* _strnlen() Author: Kees J. Bot */
/* 1 Jan 1994 */
/* size_t _strnlen(const char *s, size_t ecx) */
/* Return the length of a string. */
/* */
#include <machine/asm.h>
ENTRY(_strnlen)
push %ebp
movl %esp, %ebp
push %edi
movl 8(%ebp), %edi /* edi = string */
xorb %al, %al /* Look for a zero byte */
movl %ecx, %edx /* Save maximum count */
cmpb $1, %cl /* 'Z' bit must be clear if ecx = 0 */
cld
repne scasb /* Look for zero */
jne no0
incl %ecx /* Don't count zero byte */
no0:
movl %edx, %eax
subl %ecx, %eax /* Compute bytes scanned */
pop %edi
pop %ebp
ret