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/*******************************************************************************

 *

 * 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 */