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, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22/* 23 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 .ident "%Z%%M% %I% %E% SMI" 28 29 .file "%M%" 30 31/ 32/ strcat(s1, s2) 33/ 34/ Concatenates s2 on the end of s1. s1's space must be large enough. 35/ Returns s1. 36/ 37/ Fast assembly language version of the following C-program strcat 38/ which represents the `standard' for the C-library. 39/ 40/ char * 41/ strcat(char *s1, const char *s2) 42/ { 43/ char *os1 = s1; 44/ 45/ while (*s1++) 46/ ; 47/ --s1; 48/ while (*s1++ = *s2++) 49/ ; 50/ return (os1); 51/ } 52/ 53/ In this assembly language version, the following expression is used 54/ to check if a 32-bit word data contains a null byte or not: 55/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 56/ If the above expression geneates a value other than 0x80808080, 57/ that means the 32-bit word data contains a null byte. 58/ 59 60#include "SYS.h" 61 62 ENTRY(strcat) 63 pushl %edi / save register variable 64 / find a null byte in destination string 65 movl 8(%esp), %edi / %edi = destination string address 66 testl $3, %edi / if %edi not word aligned 67 jnz .L1 / goto .L1 68 .align 4 69.L2: 70 movl (%edi), %edx / move 1 word from (%edi) to %edx 71 movl $0x7f7f7f7f, %ecx 72 andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 73 addl $4, %edi / next word 74 addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 75 orl %edx, %ecx / %ecx |= %edx 76 andl $0x80808080, %ecx / %ecx &= 0x80808080 77 cmpl $0x80808080, %ecx / if no null byte in this word 78 je .L2 / goto .L2 79 subl $4, %edi / post-incremented 80.L1: 81 cmpb $0, (%edi) / if a byte in (%edi) is null 82 je .L3 / goto .L3 83 incl %edi / next byte 84 testl $3, %edi / if %edi not word aligned 85 jnz .L1 / goto .L1 86 jmp .L2 / goto .L2 (%edi word aligned) 87 .align 4 88.L3: 89 / %edi points to a null byte in destination string 90 movl 12(%esp), %eax / %eax = source string address 91 testl $3, %eax / if %eax not word aligned 92 jnz .L4 / goto .L4 93 .align 4 94.L5: 95 movl (%eax), %edx / move 1 word from (%eax) to %edx 96 movl $0x7f7f7f7f, %ecx 97 andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 98 addl $4, %eax / next word 99 addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 100 orl %edx, %ecx / %ecx |= %edx 101 andl $0x80808080, %ecx / %ecx &= 0x80808080 102 cmpl $0x80808080, %ecx / if null byte in this word 103 jne .L7 / goto .L7 104 movl %edx, (%edi) / copy this word to (%edi) 105 addl $4, %edi / next word 106 jmp .L5 / goto .L5 107.L7: 108 subl $4, %eax / post-incremented 109 .align 4 110.L4: 111 movb (%eax), %dl / %dl = a byte in (%eax) 112 cmpb $0, %dl / compare %dl with a null byte 113 movb %dl, (%edi) / copy %dl to (%edi) 114 je .L6 / if %dl is a null, goto .L6 115 incl %eax / next byte 116 incl %edi / next byte 117 testl $3, %eax / if %eax not word aligned 118 jnz .L4 / goto .L4 119 jmp .L5 / goto .L5 (%eax word aligned) 120 .align 4 121.L6: 122 movl 8(%esp), %eax / return the destination address 123 popl %edi / restore register variable 124 ret 125 SET_SIZE(strcat) 126