| /******************************************************************************* |
| * |
| * Copyright (c) 1993 Intel Corporation |
| * |
| * Intel hereby grants you permission to copy, modify, and distribute this |
| * software and its documentation. Intel grants this permission provided |
| * that the above copyright notice appears in all copies and that both the |
| * copyright notice and this permission notice appear in supporting |
| * documentation. In addition, Intel grants this permission provided that |
| * you prominently mark as "not part of the original" any modifications |
| * made to this software or documentation, and that the name of Intel |
| * Corporation not be used in advertising or publicity pertaining to |
| * distribution of the software or the documentation without specific, |
| * written prior permission. |
| * |
| * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR |
| * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY |
| * OR FITNESS FOR A PARTICULAR PURPOSE. Intel makes no guarantee or |
| * representations regarding the use of, or the results of the use of, |
| * the software and documentation in terms of correctness, accuracy, |
| * reliability, currentness, or otherwise; and you rely on the software, |
| * documentation and results solely at your own risk. |
| * |
| * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS, |
| * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES |
| * OF ANY KIND. IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM |
| * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER. |
| * |
| ******************************************************************************/ |
| |
| .file "strlen.s" |
| #ifdef __PIC |
| .pic |
| #endif |
| #ifdef __PID |
| .pid |
| #endif |
| |
| /* |
| * (c) copyright 1988,1993 Intel Corp., all rights reserved |
| */ |
| |
| /* |
| procedure strlen (optimized assembler version for the 80960K series) |
| |
| src_addr = strlen (src_addr) |
| |
| return the number of bytes that precede the null byte in the |
| string pointed to by src_addr. |
| |
| Undefined behavior will occur if the end of the source string (i.e. |
| the terminating null byte) is in the last four words of the program's |
| allocated memory space. This is so because strlen fetches ahead |
| several words. Disallowing the fetch ahead would impose a severe |
| performance penalty. |
| |
| Strategy: |
| |
| Fetch the source array by long-words and scanbyte the words for the |
| null byte until found. Examine the word in which the null byte is |
| found, to determine its actual position, and return the length. |
| |
| Tactics: |
| |
| 1) Do NOT try to fetch the words in a word aligned manner because, |
| in my judgement, the performance degradation experienced due to |
| non-aligned accesses does NOT outweigh the time and complexity added |
| by the preamble that would be necessary to assure alignment. This |
| is supported by the intuition that many source strings will be word |
| aligned to begin with. |
| */ |
| |
| .globl _strlen |
| .globl __strlen |
| .leafproc _strlen, __strlen |
| .align 2 |
| _strlen: |
| #ifndef __PIC |
| lda Lrett,g14 |
| #else |
| lda Lrett-(.+8)(ip),g14 |
| #endif |
| __strlen: |
| |
| mov g14,g13 # preserve return address |
| ldl (g0),g4 # fetch first two words |
| addo 8,g0,g2 # post-increment src word pointer |
| lda 0xff,g3 # byte extraction mask |
| |
| |
| Lsearch_for_word_with_null_byte: |
| scanbyte 0,g4 # check for null byte |
| mov g5,g7 # copy second word |
| bo.f Lsearch_for_null # branch if null found |
| scanbyte 0,g7 # check for null byte |
| ldl (g2),g4 # fetch next pair of word of src |
| addo 8,g2,g2 # post-increment src word pointer |
| bno Lsearch_for_word_with_null_byte # branch if null not found yet |
| |
| subo 4,g2,g2 # back up the byte pointer |
| mov g7,g4 # move word with null to search word |
| Lsearch_for_null: |
| subo 9,g2,g2 # back up the byte pointer |
| Lsearch_for_null.a: |
| and g4,g3,g14 # extract byte |
| cmpo 0,g14 # is it null? |
| addo 1,g2,g2 # bump src byte ptr |
| shro 8,g4,g4 # shift word to position next byte |
| bne Lsearch_for_null.a |
| |
| Lexit_code: |
| subo g0,g2,g0 # calculate string length |
| bx (g13) # g0 = addr of src; g14 = 0 |
| Lrett: |
| ret |
| |
| /* end of strlen */ |