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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 "sncat_ca.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 CA)

        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 word of the program's

        allocated memory space.  This is so because, in several cases, strncat

        will fetch ahead one word.  Disallowing the fetch ahead would impose

        a severe performance penalty.

        This program handles five cases:

        1) both arguments start on a word boundary

        2) neither are word aligned, but they are offset by the same amount

        3) source is word aligned, destination is not

        4) destination is word aligned, source is not

        5) neither is word aligned, and they are offset by differing amounts

        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  original dest ptr;  not modified, so that it may be returned.

        g1  src ptr;  shift count

        g2  max_bytes

        g3  src ptr (word aligned)

        g4  dest ptr (word aligned)

        g5  0xff  --  byte extraction mask

        Little endian:

                g6  lsw of double word for extraction of 4 bytes

                g7  msw of double word for extraction of 4 bytes

        Big endian:

                g6  msw of double word for extraction of 4 bytes

                g7  lsw of double word for extraction of 4 bytes

        g13 return address

        g14 byte extracted.

*/

#if __i960_BIG_ENDIAN__

#define MSW g6

#define LSW g7

#else

#define LSW g6

#define MSW g7

#endif

        .globl  _strncat

        .globl  __strncat

        .leafproc       _strncat, __strncat

        .align  2

_strncat:

#ifndef __PIC

        lda     Lrett,g14

#else

        lda     Lrett-(.+8)(ip),g14

#endif

__strncat:

        notand  g0,3,g4         # extract word addr of start of dest

         lda    (g14),g13       # preserve return address

        cmpibge.f 0,g2,Lexit_code # Lexit if number of bytes to move is <= zero.

        and     g0,3,LSW        # extract byte offset of dest

         ld     (g4),MSW        # fetch word containing at least first byte

        shlo    3,LSW,g14       # get shift count for making mask for first word

        subi    1,0,LSW         # mask initially all ones

#if __i960_BIG_ENDIAN__

        shro    g14,LSW,LSW     # get mask for bytes needed from first word

#else

        shlo    g14,LSW,LSW     # get mask for bytes needed from first word

#endif

        notor   MSW,LSW,MSW     # set unneeded bytes to all ones

         lda    0xff,g5         # byte extraction mask

Lsearch_for_word_with_null:

        scanbyte 0,MSW          # check for null byte

         lda    4(g4),g4        # post-increment dest word pointer

        mov     MSW,LSW         # keep a copy of current word

         ld     (g4),MSW        # fetch next word of dest

         bno.t  Lsearch_for_word_with_null      # branch if null not found yet

#if __i960_BIG_ENDIAN__

        shro    24,LSW,g14      # extract byte

#else

        and     g5,LSW,g14      # extract byte

#endif

        cmpo    0,g14           # branch if null is first byte of word

        subo    4,g4,g4         # move dest word ptr to word with null

        notand  g1,3,g3         # extract word addr of start of src

         bne.t  Lsearch_for_null

Lcase_14:

        cmpo    g1,g3           # check alignment of source

         ld     (g3),LSW        # fetch first word of source

        shlo    3,g1,g14        # compute shift count

         lda    4(g3),g3        # post-increment src addr

         bne.f  Lcase_4         # branch if source is unaligned

Lcase_1:

Lcase_1_wloop:                  # word copying loop

        cmpi    g2,4            # check for fewer than four bytes to move

         lda    (LSW),g1        # keep a copy of the src word

         bl.f   Lcase_1_cloop   # branch if fewer than four bytes to copy

        scanbyte 0,g1           # check for null byte in src word

         ld     (g3),LSW        # pre-fetch next word of src

        addo    4,g3,g3         # post-increment src addr

         bo.f   Lcase_1_cloop   # branch if word contains null byte

        subi    4,g2,g2         # decrease max_byte count by the 4 bytes moved

         st     g1,(g4)         # store word in dest string

        addo    4,g4,g4         # post-increment dest addr

         b      Lcase_1_wloop

Lcase_3_cloop:

Lcase_1_cloop:                  # character copying loop (max_bytes <= 3)

        cmpdeci 0,g2,g2         # is max_bytes exhausted?

#if __i960_BIG_ENDIAN__

        rotate  8,g1,g1         # move next byte into position for extraction

#endif

        and     g5,g1,g14       # extract next char

        be.f    Lstore_null     # if max_bytes is exhausted, store null and quit

        cmpo    0,g14           # check for null byte

         stob   g14,(g4)        # store the byte in dest

#if ! __i960_BIG_ENDIAN__

        shro    8,g1,g1         # move next byte into position for extraction

#endif

         lda    1(g4),g4        # post-increment dest byte addr

         bne.t  Lcase_1_cloop   # branch if null not reached

        bx      (g13)           # Lexit (g14 == 0)

Lstore_null:

        mov     0,g14           # store null, and set g14 to zero

        stob    g14,(g4)

        bx      (g13)

Lsearch_for_null:

#if __i960_BIG_ENDIAN__

        shlo    8,LSW,LSW       # check next byte

        shro    24,LSW,g14

#else

        shlo    8,g5,g5         # move mask up to next byte

        and     g5,LSW,g14      # extract byte

#endif

         lda    1(g4),g4        # move dest byte ptr to next byte

        cmpobne.t 0,g14,Lsearch_for_null        # branch if null is not yet found

Lcase_235:

        cmpo    g1,g3           # check alignment of src

         ld     (g3),LSW        # pre-fetch word with start of src

        and     3,g1,g1         # compute shift count

         lda    0xff,g5         # load mask for byte extraction

        shlo    3,g1,g14

         lda    4(g3),g3        # post-increment src word counter

         be.t   Lcase_3         # branch if src is word aligned

        and     g4,3,MSW        # extract byte offset for dest string

        cmpo    MSW,g1          # < indicates first word of dest has more bytes

                                /* than first word of source. */

         ld     (g3),MSW        # fetch second word of src

#if __i960_BIG_ENDIAN__

        subo    g14,0,g14       # adjust shift count for big endian

#endif

        eshro   g14,g6,g5       # extract four bytes

#if __i960_BIG_ENDIAN__

         bge.f  1f

#else

         bg.f   1f

#endif

        mov     MSW,LSW

         lda    4(g3),g3        # move src word addr to second word boundary

1:

        mov     g5,MSW

         lda    0xff,g5

         b      Lcase_25

Lcase_3:                                # src is word aligned; dest is not

        mov     LSW,MSW         # make copy of first word of src

         lda    32,g14          # initialize shift count to zero (mod 32)

Lcase_25:

Lcase_3_cloop_at_start:         # character copying loop for start of dest str

        cmpdeci 0,g2,g2         # is max_bytes exhausted?

#if __i960_BIG_ENDIAN__

        shro    24,MSW,g5       # extract next char

#else

        and     g5,MSW,g5       # extract next char

#endif

         be.f   Lstore_null     # Lexit if max_bytes is exhausted

        cmpo    0,g5            # check for null byte

         stob   g5,(g4)         # store the byte in dest

        addo    1,g4,g4         # post-increment dest ptr

         lda    0xff,g5         # re-initialize byte extraction mask

        notand  g4,3,g1         # extract word address

         be.t   Lexit_code      # Lexit if null byte reached

        cmpo    g1,g4           # have we reached word boundary in dest yet?

#if __i960_BIG_ENDIAN__

         lda    -8(g14),g14     # augment the shift counter

        rotate  8,MSW,MSW       # move next byte into position for extraction

#else

         lda    8(g14),g14      # augment the shift counter

        shro    8,MSW,MSW       # move next byte into position for extraction

#endif

         bne.t  Lcase_3_cloop_at_start  # branch if reached word boundary?

#if __i960_BIG_ENDIAN__

        cmpo    0,g14

         ld     (g3),MSW        # fetch msw of operand for double shift

        bne     Lcase_3_wloop   # branch if src is still unaligned.

Lcase_3_wloop2:

        cmpi    g2,4            # less than four bytes to move?

        mov     LSW,g1          # extract 4 bytes of src

         lda    4(g3),g3        # post-increment src word addr

         bl.f   Lcase_3_cloop   # branch if < four bytes left to move

        scanbyte 0,g1           # check for null byte

        mov     MSW,LSW         # move msw to lsw

         ld     (g3),MSW        # pre-fetch msw of operand for double shift

         bo.f   Lcase_3_cloop   # branch if word contains null byte

        subi    4,g2,g2         # decrease max_byte count by the 4 bytes moved

         st     g1,(g4)         # store 4 bytes to dest

        addo    4,g4,g4         # post-increment dest ptr

         b      Lcase_3_wloop2

Lcase_4:

        subo    g14,0,g14       # adjust shift count for big endian

#else

Lcase_4:

#endif

        ld      (g3),MSW        # fetch msw of operand for double shift

Lcase_3_wloop:

        cmpi    g2,4            # less than four bytes to move?

        eshro   g14,g6,g1       # extract 4 bytes of src

         lda    4(g3),g3        # post-increment src word addr

         bl.f   Lcase_3_cloop   # branch if < four bytes left to move

        scanbyte 0,g1           # check for null byte

        mov     MSW,LSW         # move msw to lsw

         ld     (g3),MSW        # pre-fetch msw of operand for double shift

         bo.f   Lcase_3_cloop   # branch if word contains null byte

        subi    4,g2,g2         # decrease max_byte count by the 4 bytes moved

         st     g1,(g4)         # store 4 bytes to dest

        addo    4,g4,g4         # post-increment dest ptr

         b      Lcase_3_wloop

Lexit_code:

        mov     0,g14           # conform to register conventions

        bx      (g13)           # g0 = addr of dest;  g14 = 0

Lrett:

        ret

/* end of strncat */