10Sstevel@tonic-gate/* 20Sstevel@tonic-gate * CDDL HEADER START 30Sstevel@tonic-gate * 40Sstevel@tonic-gate * The contents of this file are subject to the terms of the 5*7298SMark.J.Nelson@Sun.COM * Common Development and Distribution License (the "License"). 6*7298SMark.J.Nelson@Sun.COM * You may not use this file except in compliance with the License. 70Sstevel@tonic-gate * 80Sstevel@tonic-gate * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 90Sstevel@tonic-gate * or http://www.opensolaris.org/os/licensing. 100Sstevel@tonic-gate * See the License for the specific language governing permissions 110Sstevel@tonic-gate * and limitations under the License. 120Sstevel@tonic-gate * 130Sstevel@tonic-gate * When distributing Covered Code, include this CDDL HEADER in each 140Sstevel@tonic-gate * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 150Sstevel@tonic-gate * If applicable, add the following below this CDDL HEADER, with the 160Sstevel@tonic-gate * fields enclosed by brackets "[]" replaced with your own identifying 170Sstevel@tonic-gate * information: Portions Copyright [yyyy] [name of copyright owner] 180Sstevel@tonic-gate * 190Sstevel@tonic-gate * CDDL HEADER END 200Sstevel@tonic-gate */ 210Sstevel@tonic-gate/* 220Sstevel@tonic-gate * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 230Sstevel@tonic-gate * Use is subject to license terms. 240Sstevel@tonic-gate */ 250Sstevel@tonic-gate 26*7298SMark.J.Nelson@Sun.COM .file "strncpy.s" 270Sstevel@tonic-gate 280Sstevel@tonic-gate/ 290Sstevel@tonic-gate/ strncpy(s1, s2, n) 300Sstevel@tonic-gate/ 310Sstevel@tonic-gate/ Copies s2 to s1, truncating or null-padding to always copy n bytes 320Sstevel@tonic-gate/ Returns s1 330Sstevel@tonic-gate/ 340Sstevel@tonic-gate/ Fast assembly language version of the following C-program strncpy 350Sstevel@tonic-gate/ which represents the `standard' for the C-library. 360Sstevel@tonic-gate/ 370Sstevel@tonic-gate/ char * 380Sstevel@tonic-gate/ strncpy(char *s1, const char *s2, size_t n) 390Sstevel@tonic-gate/ { 400Sstevel@tonic-gate/ char *os1 = s1; 410Sstevel@tonic-gate/ 420Sstevel@tonic-gate/ n++; 430Sstevel@tonic-gate/ while ((--n != 0) && ((*s1++ = *s2++) != '\0')) 440Sstevel@tonic-gate/ ; 450Sstevel@tonic-gate/ if (n != 0) 460Sstevel@tonic-gate/ while (--n != 0) 470Sstevel@tonic-gate/ *s1++ = '\0'; 480Sstevel@tonic-gate/ return (os1); 490Sstevel@tonic-gate/ } 500Sstevel@tonic-gate/ 510Sstevel@tonic-gate/ In this assembly language version, the following expression is used 520Sstevel@tonic-gate/ to check if a 32-bit word data contains a null byte or not: 530Sstevel@tonic-gate/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 540Sstevel@tonic-gate/ If the above expression geneates a value other than 0x80808080, 550Sstevel@tonic-gate/ that means the 32-bit word data contains a null byte. 560Sstevel@tonic-gate/ 570Sstevel@tonic-gate 580Sstevel@tonic-gate/ Assume relatively long strings and small numbers of nulls at end. 590Sstevel@tonic-gate 600Sstevel@tonic-gate#include "SYS.h" 610Sstevel@tonic-gate 620Sstevel@tonic-gate ENTRY(strncpy) 630Sstevel@tonic-gate pushl %edi / save register variables 640Sstevel@tonic-gate pushl %esi 650Sstevel@tonic-gate 660Sstevel@tonic-gate movl 16(%esp), %eax / %eax = source string address 670Sstevel@tonic-gate movl 12(%esp), %edi / %edi = destination string address 680Sstevel@tonic-gate movl 20(%esp), %esi / %esi = number of bytes 690Sstevel@tonic-gate 700Sstevel@tonic-gate testl $3, %eax / if %eax not word aligned 710Sstevel@tonic-gate jnz .L1 / goto .L1 720Sstevel@tonic-gate.L8: 730Sstevel@tonic-gate cmpl $4, %esi / if number of bytes < 4 740Sstevel@tonic-gate jb .L4 / goto .L4 750Sstevel@tonic-gate .align 4 760Sstevel@tonic-gate.L2: 770Sstevel@tonic-gate movl (%eax), %edx / move 1 word from (%eax) to %edx 780Sstevel@tonic-gate movl $0x7f7f7f7f, %ecx 790Sstevel@tonic-gate andl %edx, %ecx / %ecx = %edx & 0x7f7f7f7f 800Sstevel@tonic-gate addl $4, %eax / next word 810Sstevel@tonic-gate addl $0x7f7f7f7f, %ecx / %ecx += 0x7f7f7f7f 820Sstevel@tonic-gate orl %edx, %ecx / %ecx |= %edx 830Sstevel@tonic-gate andl $0x80808080, %ecx / %ecx &= 0x80808080 840Sstevel@tonic-gate cmpl $0x80808080, %ecx / if null byte in this word 850Sstevel@tonic-gate jne .L3 / goto .L3 860Sstevel@tonic-gate movl %edx, (%edi) / copy this word to (%edi) 870Sstevel@tonic-gate subl $4, %esi / decrement number of bytes by 4 880Sstevel@tonic-gate addl $4, %edi / next word 890Sstevel@tonic-gate cmpl $4, %esi / if number of bytes >= 4 900Sstevel@tonic-gate jae .L2 / goto .L2 910Sstevel@tonic-gate jmp .L4 / goto .L4 920Sstevel@tonic-gate.L3: 930Sstevel@tonic-gate subl $4, %eax / post-incremented 940Sstevel@tonic-gate .align 4 950Sstevel@tonic-gate.L4: 960Sstevel@tonic-gate / (number of bytes < 4) or (a null byte found in the word) 970Sstevel@tonic-gate cmpl $0, %esi / if number of bytes == 0 980Sstevel@tonic-gate je .L7 / goto .L7 (finished) 990Sstevel@tonic-gate movb (%eax), %dl / %dl = a byte in (%eax) 1000Sstevel@tonic-gate decl %esi / decrement number of bytes by 1 1010Sstevel@tonic-gate movb %dl, (%edi) / copy %dl to (%edi) 1020Sstevel@tonic-gate incl %eax / next byte 1030Sstevel@tonic-gate incl %edi / next byte 1040Sstevel@tonic-gate cmpb $0, %dl / compare %dl with a null byte 1050Sstevel@tonic-gate je .L5 / if %dl is a null, goto .L5 1060Sstevel@tonic-gate jmp .L4 / goto .L4 1070Sstevel@tonic-gate .align 4 1080Sstevel@tonic-gate.L1: 1090Sstevel@tonic-gate / %eax not aligned 1100Sstevel@tonic-gate cmpl $0, %esi / if number of bytes == 0 1110Sstevel@tonic-gate je .L7 / goto .L7 (finished) 1120Sstevel@tonic-gate movb (%eax), %dl / %dl = a byte in (%eax) 1130Sstevel@tonic-gate decl %esi / decrement number of bytes by 1 1140Sstevel@tonic-gate movb %dl, (%edi) / copy %dl to (%edi) 1150Sstevel@tonic-gate incl %edi / next byte 1160Sstevel@tonic-gate incl %eax / next byte 1170Sstevel@tonic-gate cmpb $0, %dl / compare %dl with a null byte 1180Sstevel@tonic-gate je .L5 / if %dl is a null, goto .L5 1190Sstevel@tonic-gate testl $3, %eax / if %eax word aligned 1200Sstevel@tonic-gate jz .L8 / goto .L8 1210Sstevel@tonic-gate jmp .L1 / goto .L1 (not word aligned) 1220Sstevel@tonic-gate .align 4 1230Sstevel@tonic-gate.L5: 1240Sstevel@tonic-gate movl %esi, %ecx / %ecx = length to copy null bytes 1250Sstevel@tonic-gate xorl %eax, %eax / clear %eax 1260Sstevel@tonic-gate shrl $2, %ecx / %ecx = words to copy null bytes 1270Sstevel@tonic-gate rep ; sstol / rep;sstol is optimal 1280Sstevel@tonic-gate andl $3, %esi / %esi = leftover bytes 1290Sstevel@tonic-gate.L6: 1300Sstevel@tonic-gate cmpl $0, %esi / if number of bytes == 0 1310Sstevel@tonic-gate jz .L7 / goto .L7 (finished) 1320Sstevel@tonic-gate movb $0, (%edi) / move a null byte to (%edi) 1330Sstevel@tonic-gate decl %esi / decrement number of bytes by 1 1340Sstevel@tonic-gate incl %edi / next byte 1350Sstevel@tonic-gate jmp .L6 / goto .L6 1360Sstevel@tonic-gate .align 4 1370Sstevel@tonic-gate.L7: 1380Sstevel@tonic-gate movl 12(%esp), %eax / return the destination address 1390Sstevel@tonic-gate popl %esi / restore register variables 1400Sstevel@tonic-gate popl %edi 1410Sstevel@tonic-gate ret 1420Sstevel@tonic-gate SET_SIZE(strncpy) 143