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 "strncpy.s" 27*5d9d9091SRichard Lowe 28*5d9d9091SRichard Lowe/ 29*5d9d9091SRichard Lowe/ strncpy(s1, s2, n) 30*5d9d9091SRichard Lowe/ 31*5d9d9091SRichard Lowe/ Copies s2 to s1, truncating or null-padding to always copy n bytes 32*5d9d9091SRichard Lowe/ Returns s1 33*5d9d9091SRichard Lowe/ 34*5d9d9091SRichard Lowe/ Fast assembly language version of the following C-program strncpy 35*5d9d9091SRichard Lowe/ which represents the `standard' for the C-library. 36*5d9d9091SRichard Lowe/ 37*5d9d9091SRichard Lowe/ char * 38*5d9d9091SRichard Lowe/ strncpy(char *s1, const char *s2, size_t n) 39*5d9d9091SRichard Lowe/ { 40*5d9d9091SRichard Lowe/ char *os1 = s1; 41*5d9d9091SRichard Lowe/ 42*5d9d9091SRichard Lowe/ n++; 43*5d9d9091SRichard Lowe/ while ((--n != 0) && ((*s1++ = *s2++) != '\0')) 44*5d9d9091SRichard Lowe/ ; 45*5d9d9091SRichard Lowe/ if (n != 0) 46*5d9d9091SRichard Lowe/ while (--n != 0) 47*5d9d9091SRichard Lowe/ *s1++ = '\0'; 48*5d9d9091SRichard Lowe/ return (os1); 49*5d9d9091SRichard Lowe/ } 50*5d9d9091SRichard Lowe/ 51*5d9d9091SRichard Lowe/ In this assembly language version, the following expression is used 52*5d9d9091SRichard Lowe/ to check if a 32-bit word data contains a null byte or not: 53*5d9d9091SRichard Lowe/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 54*5d9d9091SRichard Lowe/ If the above expression geneates a value other than 0x80808080, 55*5d9d9091SRichard Lowe/ that means the 32-bit word data contains a null byte. 56*5d9d9091SRichard Lowe/ 57*5d9d9091SRichard Lowe 58*5d9d9091SRichard Lowe/ Assume relatively long strings and small numbers of nulls at end. 59*5d9d9091SRichard Lowe 60*5d9d9091SRichard Lowe#include "SYS.h" 61*5d9d9091SRichard Lowe 62*5d9d9091SRichard Lowe ENTRY(strncpy) 63*5d9d9091SRichard Lowe pushl %edi / save register variables 64*5d9d9091SRichard Lowe pushl %esi 65*5d9d9091SRichard Lowe 66*5d9d9091SRichard Lowe movl 16(%esp), %eax / %eax = source string address 67*5d9d9091SRichard Lowe movl 12(%esp), %edi / %edi = destination string address 68*5d9d9091SRichard Lowe movl 20(%esp), %esi / %esi = number of bytes 69*5d9d9091SRichard Lowe 70*5d9d9091SRichard Lowe testl $3, %eax / if %eax not word aligned 71*5d9d9091SRichard Lowe jnz .L1 / goto .L1 72*5d9d9091SRichard Lowe.L8: 73*5d9d9091SRichard Lowe cmpl $4, %esi / if number of bytes < 4 74*5d9d9091SRichard Lowe jb .L4 / goto .L4 75*5d9d9091SRichard Lowe .align 4 76*5d9d9091SRichard Lowe.L2: 77*5d9d9091SRichard Lowe movl (%eax), %edx / move 1 word from (%eax) to %edx 78*5d9d9091SRichard Lowe movl $0x7f7f7f7f, %ecx 79*5d9d9091SRichard Lowe andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 80*5d9d9091SRichard Lowe addl $4, %eax / next word 81*5d9d9091SRichard Lowe addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 82*5d9d9091SRichard Lowe orl %edx, %ecx / %ecx |= %edx 83*5d9d9091SRichard Lowe andl $0x80808080, %ecx / %ecx &= 0x80808080 84*5d9d9091SRichard Lowe cmpl $0x80808080, %ecx / if null byte in this word 85*5d9d9091SRichard Lowe jne .L3 / goto .L3 86*5d9d9091SRichard Lowe movl %edx, (%edi) / copy this word to (%edi) 87*5d9d9091SRichard Lowe subl $4, %esi / decrement number of bytes by 4 88*5d9d9091SRichard Lowe addl $4, %edi / next word 89*5d9d9091SRichard Lowe cmpl $4, %esi / if number of bytes >= 4 90*5d9d9091SRichard Lowe jae .L2 / goto .L2 91*5d9d9091SRichard Lowe jmp .L4 / goto .L4 92*5d9d9091SRichard Lowe.L3: 93*5d9d9091SRichard Lowe subl $4, %eax / post-incremented 94*5d9d9091SRichard Lowe .align 4 95*5d9d9091SRichard Lowe.L4: 96*5d9d9091SRichard Lowe / (number of bytes < 4) or (a null byte found in the word) 97*5d9d9091SRichard Lowe cmpl $0, %esi / if number of bytes == 0 98*5d9d9091SRichard Lowe je .L7 / goto .L7 (finished) 99*5d9d9091SRichard Lowe movb (%eax), %dl / %dl = a byte in (%eax) 100*5d9d9091SRichard Lowe decl %esi / decrement number of bytes by 1 101*5d9d9091SRichard Lowe movb %dl, (%edi) / copy %dl to (%edi) 102*5d9d9091SRichard Lowe incl %eax / next byte 103*5d9d9091SRichard Lowe incl %edi / next byte 104*5d9d9091SRichard Lowe cmpb $0, %dl / compare %dl with a null byte 105*5d9d9091SRichard Lowe je .L5 / if %dl is a null, goto .L5 106*5d9d9091SRichard Lowe jmp .L4 / goto .L4 107*5d9d9091SRichard Lowe .align 4 108*5d9d9091SRichard Lowe.L1: 109*5d9d9091SRichard Lowe / %eax not aligned 110*5d9d9091SRichard Lowe cmpl $0, %esi / if number of bytes == 0 111*5d9d9091SRichard Lowe je .L7 / goto .L7 (finished) 112*5d9d9091SRichard Lowe movb (%eax), %dl / %dl = a byte in (%eax) 113*5d9d9091SRichard Lowe decl %esi / decrement number of bytes by 1 114*5d9d9091SRichard Lowe movb %dl, (%edi) / copy %dl to (%edi) 115*5d9d9091SRichard Lowe incl %edi / next byte 116*5d9d9091SRichard Lowe incl %eax / next byte 117*5d9d9091SRichard Lowe cmpb $0, %dl / compare %dl with a null byte 118*5d9d9091SRichard Lowe je .L5 / if %dl is a null, goto .L5 119*5d9d9091SRichard Lowe testl $3, %eax / if %eax word aligned 120*5d9d9091SRichard Lowe jz .L8 / goto .L8 121*5d9d9091SRichard Lowe jmp .L1 / goto .L1 (not word aligned) 122*5d9d9091SRichard Lowe .align 4 123*5d9d9091SRichard Lowe.L5: 124*5d9d9091SRichard Lowe movl %esi, %ecx / %ecx = length to copy null bytes 125*5d9d9091SRichard Lowe xorl %eax, %eax / clear %eax 126*5d9d9091SRichard Lowe shrl $2, %ecx / %ecx = words to copy null bytes 127*5d9d9091SRichard Lowe rep ; sstol / rep;sstol is optimal 128*5d9d9091SRichard Lowe andl $3, %esi / %esi = leftover bytes 129*5d9d9091SRichard Lowe.L6: 130*5d9d9091SRichard Lowe cmpl $0, %esi / if number of bytes == 0 131*5d9d9091SRichard Lowe jz .L7 / goto .L7 (finished) 132*5d9d9091SRichard Lowe movb $0, (%edi) / move a null byte to (%edi) 133*5d9d9091SRichard Lowe decl %esi / decrement number of bytes by 1 134*5d9d9091SRichard Lowe incl %edi / next byte 135*5d9d9091SRichard Lowe jmp .L6 / goto .L6 136*5d9d9091SRichard Lowe .align 4 137*5d9d9091SRichard Lowe.L7: 138*5d9d9091SRichard Lowe movl 12(%esp), %eax / return the destination address 139*5d9d9091SRichard Lowe popl %esi / restore register variables 140*5d9d9091SRichard Lowe popl %edi 141*5d9d9091SRichard Lowe ret 142*5d9d9091SRichard Lowe SET_SIZE(strncpy) 143