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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 "strch_ca.s"
#ifdef  __PIC
        .pic
#endif
#ifdef  __PID
        .pid
#endif
/*
 * (c) copyright 1988,1993 Intel Corp., all rights reserved
 */

/*
        procedure strchr  (optimized assembler version for the CA)

        src_addr = strchr (src_addr, char)

        return a pointer to the first byte that contains the indicated
        byte in the source string.  Return null if the byte is not found.

        Undefined behavior will occur if the end of the source string (i.e. 
        the terminating null byte) is in the last two words of the program's
        allocated memory space.  This is so because, in several cases, strchr
        will fetch ahead.  Disallowing the fetch ahead would impose a severe 
        performance penalty.

        This program handles two cases:

        1) the argument starts on a word boundary
        2) the argument doesn't start on a word boundary

        At the time of this writing, only g0 thru g7 and g13 are available 
        for use in this leafproc;  other registers would have to be saved and
        restored.  These nine registers, plus tricky use of g14 are sufficient
        to implement the routine.  The registers are used as follows:

        g0  src ptr;  upon return it is a pointer to the matching byte, or null
        g1  char to seek
        g2  mask to avoid unimportant bytes in first word
        g3  char to seek, broadcast to all four bytes 
        g4  word of the source string
        g5  copy of the word
        g6  extracted character
        g7  byte extraction mask
        g13 return address
        g14 
*/

        .globl  _strchr
        .globl  __strchr
        .leafproc       _strchr, __strchr
        .align  2
_strchr:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strchr:

        lda     0xff,g7         # byte extraction mask
        and     g1,g7,g1        # make char an 8-bit ordinal
        shlo    8,g1,g2         # broadcast the char to four bytes
        or      g1,g2,g2
        shlo    16,g2,g4
        cmpo    g1,g7           # is char being sought 0xff?
        or      g4,g2,g3
         lda    (g14),g13       # preserve return address
        notand  g0,3,g5         # extract word addr of start of src
         lda    0,g14           # conform to register linkage standard
        and     g0,3,g6         # extract byte offset of src
         ld     (g5),g4         # fetch word containing at least first byte
        shlo    3,g6,g6         # get shift count for making mask for first word
         lda    4(g5),g0        # post-increment src word pointer
        subi    1,0,g5          # mask initially all ones
#if __i960_BIG_ENDIAN__
        shro    g6,g5,g5        # get mask for bytes needed from first word
#else
        shlo    g6,g5,g5        # get mask for bytes needed from first word
#endif
        notor   g4,g5,g4        # set unneeded bytes to all ones
         be.f   Lsearch_for_0xff        # branch if seeking 0xff

Lsearch_for_word_with_char_or_null:
        scanbyte g3,g4          # check for byte with char
         lda    (g4),g5         # copy word
        ld      (g0),g4         # fetch next word of src
         bo.f   Lsearch_for_char        # branch if null found 
        scanbyte 0,g5           # check for null byte
         lda    4(g0),g0        # post-increment src word pointer
        bno.t   Lsearch_for_word_with_char_or_null      # branch if not null

Lnot_found:
        mov     0,g0            # char not found.  Return null
Lexit_code:
        bx      (g13)           # g0 = addr of char in src (or null);  g14 = 0
Lrett:
        ret

Lsearch_for_char:
        subo    5,g0,g0         # back up the byte pointer
Lsearch_for_char.a:
#if __i960_BIG_ENDIAN__
        rotate  8,g5,g5         # shift word to position next byte
#endif
        and     g5,g7,g6        # extract byte
        cmpo    g1,g6           # is it char?
         lda    1(g0),g0        # bump src byte ptr
#if ! __i960_BIG_ENDIAN__
        shro    8,g5,g5         # shift word to position next byte
#endif
         be.f   Lexit_code
        cmpobne.t 0,g6,Lsearch_for_char.a       # quit if null comes before char
        b       Lnot_found

Lsearch_for_0xff:
        lda     0xf0f0f0f0,g2   # make first comparison mask for char=-1 case.
        or      g5,g2,g2
        and     g4,g2,g4        # make unimportant bytes of first word 0x0f
         b      Lsearch_for_word_with_char_or_null

/* end of strchr */