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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 "strncat.s"
#ifdef  __PIC
        .pic
#endif
#ifdef  __PID
        .pid
#endif
/*
 * (c) copyright 1988,1993 Intel Corp., all rights reserved
 */
/*
        procedure strncat  (optimized assembler version for the 80960K Series)

        dest_addr = strncat (dest_addr, src_addr, max_bytes)

        append the null terminated string pointed to by src_addr to the null 
        terminated string pointed to by dest_addr.  Return the original
        dest_addr.  If the source string is longer than max_bytes, then 
        append only max_bytes bytes, and tack on a null byte on the end.

        This routine will fail if the source and destination string
        overlap (in particular, if the end of the source is overlapped
        by the beginning of the destination).  The behavior is undefined.
        This is acceptable according to the draft C standard.

        Undefined behavior will also 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 strncat fetches
        ahead.  Disallowing the fetch ahead would impose a severe performance 
        penalty.

        Strategy:

        First, skip to the null byte in the destination string.  Then
        fetch the source string by words and store them by words to the
        destination string, until there are fewer than three bytes left
        to copy.  Then, using the last word of the source (the one that
        contains the remaining 0, 1, 2, or 3 bytes to be copied), store
        a byte at a time until Ldone.  

        If, before exhausting the max_byte count, the null byte is encountered
        in the source string, then just copy up thru the null byte.

        Tactics:

        1) Do NOT try to fetch and store 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 and convoluted body that would be necessary to assure 
        alignment.  
*/

        .globl _strncat
        .globl __strncat
        .leafproc _strncat,__strncat
        .align    2
_strncat:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strncat:
        mov     g14,g6
        cmpibge 0, g2, Lno_operation    # Lexit early if max_bytes <= 0
        mov     g0, g5
Lskip_word_loop:
        ld      (g5), g7        # fetch word of dest string
        addo    4, g5, g5       # post-increment dest ptr
        scanbyte 0, g7          # does it contain null byte?
        bno     Lskip_word_loop # if not, loop
        subo    5, g5, g5       # adjust dest ptr 
        lda     0xff, g3        # byte extraction mask = 0xff;
Lskip_byte_loop:
        and     g7, g3, g14     # extract byte of last word of dest string
        cmpo    0, g14          # is it null?
        addo    1, g5, g5       # adjust dest ptr
        shro    8, g7, g7       # position next byte for extraction
        bne     Lskip_byte_loop # loop if null not found yet

        ld      (g1), g7        # fetch first word of source string
Lwloop:                         # word copying loop
        cmpo    4, g2           # max_bytes < 4 ?
        addo    4, g1, g1       # post-increment source ptr
        bge     Lcloop.a                # branch if less than 4 bytes to move
        scanbyte 0, g7          # is null byte reached yet?
        mov     g7, g4          # keep a copy of the source word
        be      Lcloop          # branch if null byte reached
        ld      (g1), g7        # pre-fetch next word of source
        subo    4, g2, g2       # reduce max_byte counter
        st      g4, (g5)        # store current word
        addo    4, g5, g5       # post-increment destination ptr
        b       Lwloop

Lcloop.b:
        addo    1, g5, g5       # post-increment destination ptr
        shro    8, g7, g7       # position next byte for extraction
Lcloop:                         # character copying loop  (max_byte > 3)
        and     g3, g7, g4      # extract character
        cmpo    0, g4           # is it null?
        stob    g4, (g5)        # store it
        bne     Lcloop.b                # loop if null not encountered yet

        bx      (g6)            # g0 = dest string address; g14 = 0
Lrett:  
        ret

Lcloop.c:
        addo    1, g5, g5       # post-increment destination ptr
        shro    8, g7, g7       # position next byte for extraction
Lcloop.a:                       # character copying loop  (max_byte <= 3)
        cmpdeco 0,g2,g2         # max_byte == 0?
        and     g3, g7, g4      # extract character
        be      Ldone           # store null and Lexit if max_byte exhausted
        cmpo    0, g4           # is it null?
        stob    g4, (g5)        # store it
        bne     Lcloop.c                # loop if null not encountered yet

Ldone:  stob    g14, (g5)       # store trailing null
        bx      (g6)            # g0 = dest string address; g14 = 0

Lno_operation: mov 0, g14       # conform to register conventions
        bx      (g6)

/* end of strncat */