2N/A * The contents of this file are subject to the terms of the 2N/A * Common Development and Distribution License (the "License"). 2N/A * You may not use this file except in compliance with the License. 2N/A * See the License for the specific language governing permissions 2N/A * and limitations under the License. 2N/A * When distributing Covered Code, include this CDDL HEADER in each 2N/A * If applicable, add the following below this CDDL HEADER, with the 2N/A * fields enclosed by brackets "[]" replaced with your own identifying 2N/A * information: Portions Copyright [yyyy] [name of copyright owner] 2N/A * Copyright 2005 Sun Microsystems, Inc. All rights reserved. 2N/A * Use is subject to license terms. 2N/A/ strlen(const char *s) 2N/A/ const char *s0 = s + 1; 2N/A/ while (*s++ != '\0
') 2N/A/ In this assembly language version, the following expression is used 2N/A/ to check if a 32-bit word data contains a null byte or not: 2N/A/ (((A & 0x7f7f7f7f) + 0x7f7f7f7f) | A) & 0x80808080 2N/A/ If the above expression geneates a value other than 0x80808080, 2N/A/ that means the 32-bit word data contains a null byte. 2N/A mov 4(%esp), %edx / src in %edx 2N/A mov %edx, %eax / cpy src to %eax 2N/A and $3, %edx / is src aligned? 2N/A / work byte-wise until aligned 2N/A cmpb $0, (%eax) / is *src == 0 ? 2N/A inc %eax / increment src 2N/A cmp $3, %edx / if aligned, jump to word-wise check 2N/A mov (%eax), %ecx / load wrd 2N/A add $4, %eax / increment src by 4 (bytes in word) 2N/A lea -0x01010101(%ecx), %edx / (wrd - 0x01010101) 2N/A and $0x80808080, %ecx / ~wrd & 0x80808080 2N/A and %edx, %ecx / (wrd - 0x01010101) & ~wrd & 0x80808080 2N/A jz countbytes / if zero, no null byte found -- cont 2N/A bsfl %ecx, %ecx / find first set bit (null byte) 2N/A shr $3, %ecx / switch bit position to byte posn 2N/A lea -4(%eax, %ecx, 1), %eax / undo pre-increment and count bytes 2N/A sub 4(%esp), %eax / return (src - old_src)