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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 /*
     22  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 	.file	"memchr.s"
     27 
     28 /
     29 / memchr(sptr, c1, n)
     30 /
     31 / Returns the pointer in sptr at which the character c1 appears;
     32 / or NULL if not found in chars; doesn't stop at \0.
     33 /
     34 / Fast assembly language version of the following C-program memchr
     35 / which represents the `standard' for the C-library.
     36 /
     37 /	void *
     38 /	memchr(const void *sptr, int c1, size_t n)
     39 /	{
     40 /		if (n != 0) {
     41 /			unsigned char	c = (unsigned char)c1;
     42 /			const unsigned char	*sp = sptr;
     43 /
     44 /			do {
     45 /				if (*sp++ == c)
     46 /					return ((void *)--sp);
     47 /			} while (--n != 0);
     48 /		}
     49 /		return (NULL);
     50 /	}
     51 /
     52 
     53 #include "SYS.h"
     54 
     55 	.globl	memchr
     56 	.align	4
     57 
     58 	ENTRY(memchr)
     59 	pushl	%edi		/ save register variable
     60 	movl	8(%esp), %eax	/ %eax = string address
     61 	movl	12(%esp), %ecx	/ %cl = byte that is sought
     62 	movl	16(%esp), %edi	/ %edi = number of bytes
     63 	cmpl	$4, %edi	/ if number of bytes < 4
     64 	jb	.L1		/ goto .L1
     65 	testl	$3, %eax	/ if %eax not word aligned
     66 	jnz	.L2		/ goto .L2
     67 	.align	4
     68 .L3:
     69 	movl	(%eax), %edx	/ move 1 word from (%eax) to %edx
     70 	cmpb	%dl, %cl	/ if the first byte is %cl
     71 	je	.L4		/ goto .L4 (found)
     72 	cmpb	%dh, %cl	/ if the second byte is %cl
     73 	je	.L5		/ goto .L5 (found)
     74 	shrl	$16, %edx	/ right shift 16-bit
     75 	cmpb	%dl, %cl	/ if the third byte is %cl
     76 	je	.L6		/ goto .L6 (found)
     77 	cmpb	%dh, %cl	/ if the fourth is %cl
     78 	je	.L7		/ goto .L7 (found)
     79 	subl	$4, %edi	/ decrement number of bytes by 4
     80 	addl	$4, %eax	/ next word
     81 	cmpl	$4, %edi	/ if number of bytes >= 4
     82 	jae	.L3		/ goto .L3
     83 .L1:
     84 	cmpl	$0, %edi	/ if number of bytes == 0
     85 	jz	.L8		/ goto .L8 (not found)
     86 	cmpb	(%eax), %cl	/ if a byte in (%eax) is %cl
     87 	je	.L4		/ goto .L4 (found)
     88 	decl	%edi		/ decrement number of bytes by 1
     89 	incl	%eax		/ next byte
     90 	jmp	.L1		/ goto .L1
     91 	.align	4
     92 .L8:
     93 	xorl	%eax, %eax	/ not found
     94 	popl	%edi		/ restore register
     95 	ret			/ return (0)
     96 	.align	4
     97 .L2:
     98 	cmpl	$0, %edi	/ if number of bytes == 0
     99 	jz	.L8		/ goto .L8 (not found)
    100 	cmpb	(%eax), %cl	/ if a byte in (%eax) is %cl
    101 	je	.L4		/ goto .L4 (found)
    102 	incl	%eax		/ next byte
    103 	decl	%edi		/ decrement number of bytes by 1
    104 	testl	$3, %eax	/ if %eax not word aligned
    105 	jnz	.L2		/ goto .L2
    106 	cmpl	$4, %edi	/ if number of bytes >= 4
    107 	jae	.L3		/ goto .L3 (word aligned)
    108 	jmp	.L1		/ goto .L1
    109 	.align	4
    110 .L7:
    111 	/ found at the fourth byte
    112 	incl	%eax
    113 .L6:
    114 	/ found at the third byte
    115 	incl	%eax
    116 .L5:
    117 	/ found at the second byte
    118 	incl	%eax
    119 .L4:
    120 	/ found at the first byte
    121 	popl	%edi		/ restore register variable
    122 	ret
    123 	SET_SIZE(memchr)
    124