strcat.s revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (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.
*/
.ident "%Z%%M% %I% %E% SMI"
.file "%M%"
/
/ strcat(s1, s2)
/
/ Concatenates s2 on the end of s1. s1's space must be large enough.
/ Returns s1.
/
/ Fast assembly language version of the following C-program strcat
/ which represents the `standard' for the C-library.
/
/ char *
/ strcat(char *s1, const char *s2)
/ {
/ char *os1 = s1;
/
/ while (*s1++)
/ ;
/ --s1;
/ while (*s1++ = *s2++)
/ ;
/ return (os1);
/ }
/
/ In this assembly language version, the following expression is used
/ to check if a 32-bit word data contains a null byte or not:
/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080
/ If the above expression geneates a value other than 0x80808080,
/ that means the 32-bit word data contains a null byte.
/
#include "SYS.h"
ENTRY(strcat)
pushl %edi / save register variable
/ find a null byte in destination string
movl 8(%esp), %edi / %edi = destination string address
testl $3, %edi / if %edi not word aligned
jnz .L1 / goto .L1
.align 4
.L2:
movl (%edi), %edx / move 1 word from (%edi) to %edx
movl $0x7f7f7f7f, %ecx
andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f
addl $4, %edi / next word
addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f
orl %edx, %ecx / %ecx |= %edx
andl $0x80808080, %ecx / %ecx &= 0x80808080
cmpl $0x80808080, %ecx / if no null byte in this word
je .L2 / goto .L2
subl $4, %edi / post-incremented
.L1:
cmpb $0, (%edi) / if a byte in (%edi) is null
je .L3 / goto .L3
incl %edi / next byte
testl $3, %edi / if %edi not word aligned
jnz .L1 / goto .L1
jmp .L2 / goto .L2 (%edi word aligned)
.align 4
.L3:
/ %edi points to a null byte in destination string
movl 12(%esp), %eax / %eax = source string address
testl $3, %eax / if %eax not word aligned
jnz .L4 / goto .L4
.align 4
.L5:
movl (%eax), %edx / move 1 word from (%eax) to %edx
movl $0x7f7f7f7f, %ecx
andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f
addl $4, %eax / next word
addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f
orl %edx, %ecx / %ecx |= %edx
andl $0x80808080, %ecx / %ecx &= 0x80808080
cmpl $0x80808080, %ecx / if null byte in this word
jne .L7 / goto .L7
movl %edx, (%edi) / copy this word to (%edi)
addl $4, %edi / next word
jmp .L5 / goto .L5
.L7:
subl $4, %eax / post-incremented
.align 4
.L4:
movb (%eax), %dl / %dl = a byte in (%eax)
cmpb $0, %dl / compare %dl with a null byte
movb %dl, (%edi) / copy %dl to (%edi)
je .L6 / if %dl is a null, goto .L6
incl %eax / next byte
incl %edi / next byte
testl $3, %eax / if %eax not word aligned
jnz .L4 / goto .L4
jmp .L5 / goto .L5 (%eax word aligned)
.align 4
.L6:
movl 8(%esp), %eax / return the destination address
popl %edi / restore register variable
ret
SET_SIZE(strcat)