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

        dest_addr = strcpy (dest_addr, src_addr)

        copy the null terminated string pointed to by src_addr to 
        the string space pointed to by dest_addr.  Return the original
        dest_addr.

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

        Strategy:

        Fetch the source string and store the destination string by words
        until the null byte is encountered.  When the word with the null
        byte is reached, store it by bytes up through the null byte only.

        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.  This is supported by the intuition that most source and
        destination strings will be word aligned to begin with.


        procedure strcat

        dest_addr = strcat (dest_addr, src_addr)

        Appends the string pointed to by src_addr to the string pointed
        to by dest_addr.  The first character of the source string is
        copied to the location initially occupied by the trailing null
        byte of the destination string.  Thereafter, characters are copied
        from the source to the destination up thru the null byte that
        trails the source string.

        See the strcpy routine, above, for its caveats, as they apply here too.

        Strategy:

        Skip to the end (null byte) of the destination string, and then drop
        into the strcpy code.

        Tactics:

        Skipping to the null byte is Ldone by reading the destination string
        in long-words and scanbyte'ing them, then examining the bytes of the 
        word that contains the null byte, until the address of the null byte is
        known.  Then we drop into the strcpy routine.  It is probable (approx.
        three out of four times) that the destination string as strcpy sees
        it will NOT be word aligned (i.e. that the null byte won't be the
        last byte of a word).  But it is not worth the complication to that
        routine to force word aligned memory accesses to be gaurenteed.
*/
        .globl _strcpy, _strcat
        .globl __strcpy, __strcat
        .leafproc _strcpy,__strcpy
        .leafproc _strcat,__strcat
        .align    2
_strcat:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strcat:
        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,g5         # back up the byte pointer
Lsearch_for_null.a:
        and     g4,g3,g6        # extract byte
        cmpo    0,g6            # is it null?
        addo    1,g5,g5         # bump src byte ptr
        shro    8,g4,g4         # shift word to position next byte
        bne     Lsearch_for_null.a
        b       Lend_of_dest_found

_strcpy:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strcpy:
        mov     g0, g5
Lend_of_dest_found:
        ld      (g1), g2        # fetch first word of source 
        mov     g14,g6          # preserve return address
        lda     0xff, g3        # byte extraction mask = 0xff;
Lwloop:                         # word copying loop
        addo    4, g1, g1       # post-increment source ptr
        scanbyte 0, g2          # does source word contain null byte?
        mov     g2, g4          # save a copy of the source word
        be      Lcloop          # branch if null present
        ld      (g1), g2        # pre-fetch next word of source
        st      g4, (g5)        # store current word
        addo    4, g5, g5       # post-increment dest ptr
        b       Lwloop

Lcloop:                         # character copying loop
        and     g3, g4, g14     # extract next char
        shro    8, g4, g4       # position word for next byte extraction
        cmpo    0, g14          # is it null?
        stob    g14, (g5)       # store the byte
        addo    1, g5, g5       # post-increment dest ptr
        bne     Lcloop          # quit if null encountered

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