kolibrios-fun/drivers/ddk/string/_strncmp.S

/*	strncmp()					Author: Kees J. Bot */
/*								1 Jan 1994 */

/* int strncmp(const char *s1, const char *s2, size_t ecx) */
/*	Compare two strings. */
/* */
#include "asm.h"

ENTRY(_strncmp)
	push	%ebp
	movl	%esp, %ebp
	push	%esi
	push	%edi
	testl	%ecx, %ecx	/* Max length is zero? */
	je	done
	movl	8(%ebp), %esi	/* esi = string s1 */
	movl	12(%ebp), %edi	/* edi = string s2 */
	cld
compare:
	cmpsb	/* Compare two bytes */
	jne	done
	cmpb	$0, -1(%esi)	/* End of string? */
	je	done
	decl	%ecx	/* Length limit reached? */
	jne	compare
done:
	seta	%al	/* al = (s1 > s2) */
	setb	%ah	/* ah = (s1 < s2) */
	subb	%ah, %al
	movsbl	%al, %eax	/* eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1 */
	pop	%edi
	pop	%esi
	pop	%ebp
	ret