/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

        .file   "memchr.s"

/
/ memchr(sptr, c1, n)
/
/ Returns the pointer in sptr at which the character c1 appears;
/ or NULL if not found in chars; doesn't stop at \0.
/
/ Fast assembly language version of the following C-program memchr
/ which represents the `standard' for the C-library.
/
/       void *
/       memchr(const void *sptr, int c1, size_t n)
/       {
/               if (n != 0) {
/                       unsigned char   c = (unsigned char)c1;
/                       const unsigned char     *sp = sptr;
/
/                       do {
/                               if (*sp++ == c)
/                                       return ((void *)--sp);
/                       } while (--n != 0);
/               }
/               return (NULL);
/       }
/

#include "SYS.h"

        .globl  memchr
        .align  4

        ENTRY(memchr)
        pushl   %edi            / save register variable
        movl    8(%esp), %eax   / %eax = string address
        movl    12(%esp), %ecx  / %cl = byte that is sought
        movl    16(%esp), %edi  / %edi = number of bytes
        cmpl    $4, %edi        / if number of bytes < 4
        jb      .L1             / goto .L1
        testl   $3, %eax        / if %eax not word aligned
        jnz     .L2             / goto .L2
        .align  4
.L3:
        movl    (%eax), %edx    / move 1 word from (%eax) to %edx
        cmpb    %dl, %cl        / if the first byte is %cl
        je      .L4             / goto .L4 (found)
        cmpb    %dh, %cl        / if the second byte is %cl
        je      .L5             / goto .L5 (found)
        shrl    $16, %edx       / right shift 16-bit
        cmpb    %dl, %cl        / if the third byte is %cl
        je      .L6             / goto .L6 (found)
        cmpb    %dh, %cl        / if the fourth is %cl
        je      .L7             / goto .L7 (found)
        subl    $4, %edi        / decrement number of bytes by 4
        addl    $4, %eax        / next word
        cmpl    $4, %edi        / if number of bytes >= 4
        jae     .L3             / goto .L3
.L1:
        cmpl    $0, %edi        / if number of bytes == 0
        jz      .L8             / goto .L8 (not found)
        cmpb    (%eax), %cl     / if a byte in (%eax) is %cl
        je      .L4             / goto .L4 (found)
        decl    %edi            / decrement number of bytes by 1
        incl    %eax            / next byte
        jmp     .L1             / goto .L1
        .align  4
.L8:
        xorl    %eax, %eax      / not found
        popl    %edi            / restore register
        ret                     / return (0)
        .align  4
.L2:
        cmpl    $0, %edi        / if number of bytes == 0
        jz      .L8             / goto .L8 (not found)
        cmpb    (%eax), %cl     / if a byte in (%eax) is %cl
        je      .L4             / goto .L4 (found)
        incl    %eax            / next byte
        decl    %edi            / decrement number of bytes by 1
        testl   $3, %eax        / if %eax not word aligned
        jnz     .L2             / goto .L2
        cmpl    $4, %edi        / if number of bytes >= 4
        jae     .L3             / goto .L3 (word aligned)
        jmp     .L1             / goto .L1
        .align  4
.L7:
        / found at the fourth byte
        incl    %eax
.L6:
        / found at the third byte
        incl    %eax
.L5:
        / found at the second byte
        incl    %eax
.L4:
        / found at the first byte
        popl    %edi            / restore register variable
        ret
        SET_SIZE(memchr)