1*5d9d9091SRichard Lowe/* 2*5d9d9091SRichard Lowe * CDDL HEADER START 3*5d9d9091SRichard Lowe * 4*5d9d9091SRichard Lowe * The contents of this file are subject to the terms of the 5*5d9d9091SRichard Lowe * Common Development and Distribution License (the "License"). 6*5d9d9091SRichard Lowe * You may not use this file except in compliance with the License. 7*5d9d9091SRichard Lowe * 8*5d9d9091SRichard Lowe * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9*5d9d9091SRichard Lowe * or http://www.opensolaris.org/os/licensing. 10*5d9d9091SRichard Lowe * See the License for the specific language governing permissions 11*5d9d9091SRichard Lowe * and limitations under the License. 12*5d9d9091SRichard Lowe * 13*5d9d9091SRichard Lowe * When distributing Covered Code, include this CDDL HEADER in each 14*5d9d9091SRichard Lowe * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15*5d9d9091SRichard Lowe * If applicable, add the following below this CDDL HEADER, with the 16*5d9d9091SRichard Lowe * fields enclosed by brackets "[]" replaced with your own identifying 17*5d9d9091SRichard Lowe * information: Portions Copyright [yyyy] [name of copyright owner] 18*5d9d9091SRichard Lowe * 19*5d9d9091SRichard Lowe * CDDL HEADER END 20*5d9d9091SRichard Lowe */ 21*5d9d9091SRichard Lowe/* 22*5d9d9091SRichard Lowe * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 23*5d9d9091SRichard Lowe * Use is subject to license terms. 24*5d9d9091SRichard Lowe */ 25*5d9d9091SRichard Lowe 26*5d9d9091SRichard Lowe .file "strncat.s" 27*5d9d9091SRichard Lowe 28*5d9d9091SRichard Lowe/ 29*5d9d9091SRichard Lowe/ strncat(s1, s2, n) 30*5d9d9091SRichard Lowe/ 31*5d9d9091SRichard Lowe/ Concatenates s2 on the end of s1. s1's space must be large enough. 32*5d9d9091SRichard Lowe/ At most n characters are moved. 33*5d9d9091SRichard Lowe/ Returns s1. 34*5d9d9091SRichard Lowe/ 35*5d9d9091SRichard Lowe/ Fast assembly language version of the following C-program strncat 36*5d9d9091SRichard Lowe/ which represents the `standard' for the C-library. 37*5d9d9091SRichard Lowe/ 38*5d9d9091SRichard Lowe/ char * 39*5d9d9091SRichard Lowe/ strncat(char *s1, const char *s2, size_t n) 40*5d9d9091SRichard Lowe/ { 41*5d9d9091SRichard Lowe/ char *os1 = s1; 42*5d9d9091SRichard Lowe/ 43*5d9d9091SRichard Lowe/ n++; 44*5d9d9091SRichard Lowe/ while (*s1++) 45*5d9d9091SRichard Lowe/ ; 46*5d9d9091SRichard Lowe/ --s1; 47*5d9d9091SRichard Lowe/ while (*s1++ = *s2++) 48*5d9d9091SRichard Lowe/ if (--n == 0) { 49*5d9d9091SRichard Lowe/ s1[-1] = '\0'; 50*5d9d9091SRichard Lowe/ break; 51*5d9d9091SRichard Lowe/ } 52*5d9d9091SRichard Lowe/ return (os1); 53*5d9d9091SRichard Lowe/ } 54*5d9d9091SRichard Lowe/ 55*5d9d9091SRichard Lowe/ In this assembly language version, the following expression is used 56*5d9d9091SRichard Lowe/ to check if a 32-bit word data contains a null byte or not: 57*5d9d9091SRichard Lowe/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 58*5d9d9091SRichard Lowe/ If the above expression geneates a value other than 0x80808080, 59*5d9d9091SRichard Lowe/ that means the 32-bit word data contains a null byte. 60*5d9d9091SRichard Lowe/ 61*5d9d9091SRichard Lowe 62*5d9d9091SRichard Lowe#include "SYS.h" 63*5d9d9091SRichard Lowe 64*5d9d9091SRichard Lowe ENTRY(strncat) 65*5d9d9091SRichard Lowe pushl %edi / save register variables 66*5d9d9091SRichard Lowe pushl %esi 67*5d9d9091SRichard Lowe movl 12(%esp), %edi / %edi = destination string address 68*5d9d9091SRichard Lowe testl $3, %edi / if %edi not word aligned 69*5d9d9091SRichard Lowe jnz .L1 / goto .L1 70*5d9d9091SRichard Lowe .align 4 71*5d9d9091SRichard Lowe.L2: 72*5d9d9091SRichard Lowe movl (%edi), %edx / move 1 word from (%edi) to %edx 73*5d9d9091SRichard Lowe movl $0x7f7f7f7f, %ecx 74*5d9d9091SRichard Lowe andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 75*5d9d9091SRichard Lowe addl $4, %edi / next word 76*5d9d9091SRichard Lowe addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 77*5d9d9091SRichard Lowe orl %edx, %ecx / %ecx |= %edx 78*5d9d9091SRichard Lowe andl $0x80808080, %ecx / %ecx &= 0x80808080 79*5d9d9091SRichard Lowe cmpl $0x80808080, %ecx / if no null byte in this word 80*5d9d9091SRichard Lowe je .L2 / goto .L2 81*5d9d9091SRichard Lowe subl $4, %edi / post-incremented 82*5d9d9091SRichard Lowe.L1: 83*5d9d9091SRichard Lowe cmpb $0, (%edi) / if a byte in (%edi) is null 84*5d9d9091SRichard Lowe je .L3 / goto .L3 85*5d9d9091SRichard Lowe incl %edi / next byte 86*5d9d9091SRichard Lowe testl $3, %edi / if %edi not word aligned 87*5d9d9091SRichard Lowe jnz .L1 / goto .L1 88*5d9d9091SRichard Lowe jmp .L2 / goto .L2 (%edi word aligned) 89*5d9d9091SRichard Lowe .align 4 90*5d9d9091SRichard Lowe.L3: 91*5d9d9091SRichard Lowe / %edi points to a null byte in destination string 92*5d9d9091SRichard Lowe movl 16(%esp), %eax / %eax = source string address 93*5d9d9091SRichard Lowe movl 20(%esp), %esi / %esi = number of bytes 94*5d9d9091SRichard Lowe 95*5d9d9091SRichard Lowe testl $3, %eax / if %eax not word aligned 96*5d9d9091SRichard Lowe jnz .L4 / goto .L4 97*5d9d9091SRichard Lowe cmpl $4, %esi / if number of bytes < 4 98*5d9d9091SRichard Lowe jb .L7 / goto .L7 99*5d9d9091SRichard Lowe .align 4 100*5d9d9091SRichard Lowe.L5: 101*5d9d9091SRichard Lowe movl (%eax), %edx / move 1 word from (%eax) to %edx 102*5d9d9091SRichard Lowe movl $0x7f7f7f7f, %ecx 103*5d9d9091SRichard Lowe andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 104*5d9d9091SRichard Lowe addl $4, %eax / next word 105*5d9d9091SRichard Lowe addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 106*5d9d9091SRichard Lowe orl %edx, %ecx / %ecx |= %edx 107*5d9d9091SRichard Lowe andl $0x80808080, %ecx / %ecx &= 0x80808080 108*5d9d9091SRichard Lowe cmpl $0x80808080, %ecx / if null byte in this word 109*5d9d9091SRichard Lowe jne .L6 / goto .L6 110*5d9d9091SRichard Lowe movl %edx, (%edi) / copy this word to (%edi) 111*5d9d9091SRichard Lowe subl $4, %esi / decrement number of bytes by 4 112*5d9d9091SRichard Lowe addl $4, %edi / next word 113*5d9d9091SRichard Lowe cmpl $4, %esi / if number of bytes >= 4 114*5d9d9091SRichard Lowe jae .L5 / goto .L5 115*5d9d9091SRichard Lowe jmp .L7 / goto .L7 116*5d9d9091SRichard Lowe.L6: 117*5d9d9091SRichard Lowe subl $4, %eax / post-incremented 118*5d9d9091SRichard Lowe .align 4 119*5d9d9091SRichard Lowe.L7: 120*5d9d9091SRichard Lowe / number of bytes < 4 or a null byte found in the word 121*5d9d9091SRichard Lowe cmpl $0, %esi / if number of bytes == 0 122*5d9d9091SRichard Lowe jz .L8 / goto .L8 (finished) 123*5d9d9091SRichard Lowe movb (%eax), %dl / %dl = a byte in (%eax) 124*5d9d9091SRichard Lowe decl %esi / decrement number of bytes by 1 125*5d9d9091SRichard Lowe movb %dl, (%edi) / copy %dl to (%edi) 126*5d9d9091SRichard Lowe incl %eax / next byte 127*5d9d9091SRichard Lowe incl %edi / next byte 128*5d9d9091SRichard Lowe cmpb $0, %dl / compare %dl with a null byte 129*5d9d9091SRichard Lowe je .L9 / if %dl is a null, goto .L9 130*5d9d9091SRichard Lowe jmp .L7 / goto .L7 131*5d9d9091SRichard Lowe .align 4 132*5d9d9091SRichard Lowe 133*5d9d9091SRichard Lowe.L4: 134*5d9d9091SRichard Lowe / %eax not aligned 135*5d9d9091SRichard Lowe cmpl $0, %esi / if number of bytes == 0 136*5d9d9091SRichard Lowe jz .L8 / goto .L8 (finished) 137*5d9d9091SRichard Lowe movb (%eax), %dl / %dl = a byte in (%eax) 138*5d9d9091SRichard Lowe decl %esi / decrement number of bytes by 1 139*5d9d9091SRichard Lowe movb %dl, (%edi) / copy %dl to (%edi) 140*5d9d9091SRichard Lowe incl %edi / next byte 141*5d9d9091SRichard Lowe incl %eax / next byte 142*5d9d9091SRichard Lowe cmpb $0, %dl / compare %dl with a null byte 143*5d9d9091SRichard Lowe je .L9 / if %dl is a null, goto .L9 144*5d9d9091SRichard Lowe jmp .L4 / goto .L4 145*5d9d9091SRichard Lowe .align 4 146*5d9d9091SRichard Lowe.L8: 147*5d9d9091SRichard Lowe movb $0, (%edi) / null termination 148*5d9d9091SRichard Lowe.L9: 149*5d9d9091SRichard Lowe movl 12(%esp), %eax / return the destination address 150*5d9d9091SRichard Lowe popl %esi / restore register variables 151*5d9d9091SRichard Lowe popl %edi 152*5d9d9091SRichard Lowe ret 153*5d9d9091SRichard Lowe SET_SIZE(strncat) 154