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

        dest_addr = strncpy (dest_addr, src_addr, max_bytes)

        copy the null terminated string pointed to by src_addr to the 
        string pointed to by dest_addr.  Return the original dest_addr.
        If the source string is shorter than max_bytes, then null-pad 
        the destination string.  If it is longer than max_bytes, the 
        copy stops at max_bytes bytes (and no terminating null appears 
        in the destination string).

        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 strncpy fetches
        ahead.  Disallowing the fetch ahead would impose a severe performance 
        penalty.

        Strategy:

        Fetch and store the strings by words and go to a character move loop 
        as soon as a null byte is encountered.  If max_bytes is exhausted
        first, then terminate after moving only max_bytes (with the last
        0, 1, 2, or 3 bytes moved as single bytes, not as a word).
        Otherwise, the character move loop moves the last bytes or the
        source string, and then null-pads the destination string until
        max_bytes is exhausted.

        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 and convoluted body that would be necessary to assure 
        alignment.  

        2) When the null byte is encountered in a source word, null out the
        higher-numbered bytes in that word, store the word in the destination,
        and go to the word null-padder, which may eventually go to the byte
        null-padder.
*/

        .globl _strncpy
        .globl __strncpy
        .leafproc _strncpy,__strncpy
        .align    2
_strncpy:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strncpy:      
        mov     g14, g13
        cmpibge 0,g2,Lexit      # quit early if max_bytes <= 0
        ld      (g1), g7        # fetch the first word of the source
        mov     g0, g5
        lda     0xff, g3        # byte extraction mask
        addo    g1, g2, g6
        addo    g2, g5, g2
Lwloop:                         # word copying loop
        addo    4, g1, g1       # post-increment source ptr
        cmpo    g6, g1          # max_bytes < 4 ?
        mov     g7, g4          # keep a copy of source word
        bl      Lcloop.a                # if less than four bytes to go, go to char loop
        scanbyte 0, g4          # null byte found?
        ld      (g1), g7        # pre-fetch next word of the source
        be      Lcloop.c                # go to char loop if null encountered
        st      g4, (g5)        # store current word
        addo    4, g5, g5       # post-increment destination ptr
        b       Lwloop

Lcloop.a:                       # character copying loop (max_bytes < 3)
        and     g3, g4, g14     # extract byte
Lcloop.b:
        cmpo    g2, g5          # max_bytes <= 0 ?
        shro    8, g4, g4       # position word to extract next byte
        be      Lexit           # exit if max_bytes exhausted
        cmpo    0, g14          # is it null?
        stob    g14, (g5)       # store it
        addo    1, g5, g5       # post-increment dest ptr
        bne     Lcloop.a                # branch if we are NOT null padding
        b       Lcloop.b                # branch if we are null padding

Lexit:
        mov     0, g14
        bx      (g13)           # g0 = dest string address; g14 = 0
Lrett:  
        ret

Lcloop.c:                       # character copying loop
        and     g3, g4, g14     # extract byte
        cmpo    0, g14          # is it null?
        mov     g3, g7          # save mask
        shlo    8, g3, g3       # shift mask to next byte position
        bne     Lcloop.c                # loop until null found
        subo    1, g7, g3       # mask to null pad after null byte
        and     g3, g4, g4      # null-out stuff after null byte
        st      g4, (g5)        # store last part of src and first of null-pad
        subo    8,g2,g6         # adjust max_byte counter

Lzwloop:
        cmpo    g5, g6          # max_bytes < 4 ?
        addo    4, g5, g5       
        bg      Lcloop.b                # if so, goto character loop
        st      g14, (g5)       # store four null bytes
        b       Lzwloop

/* end of strncpy */