source: trunk/libs/newlib/src/newlib/libc/machine/i960/strncat.S @ 444

Last change on this file since 444 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
File size: 5.6 KB
Line 
1/*******************************************************************************
2 *
3 * Copyright (c) 1993 Intel Corporation
4 *
5 * Intel hereby grants you permission to copy, modify, and distribute this
6 * software and its documentation.  Intel grants this permission provided
7 * that the above copyright notice appears in all copies and that both the
8 * copyright notice and this permission notice appear in supporting
9 * documentation.  In addition, Intel grants this permission provided that
10 * you prominently mark as "not part of the original" any modifications
11 * made to this software or documentation, and that the name of Intel
12 * Corporation not be used in advertising or publicity pertaining to
13 * distribution of the software or the documentation without specific,
14 * written prior permission.
15 *
16 * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
17 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
18 * OR FITNESS FOR A PARTICULAR PURPOSE.  Intel makes no guarantee or
19 * representations regarding the use of, or the results of the use of,
20 * the software and documentation in terms of correctness, accuracy,
21 * reliability, currentness, or otherwise; and you rely on the software,
22 * documentation and results solely at your own risk.
23 *
24 * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
25 * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
26 * OF ANY KIND.  IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
27 * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
28 *
29 ******************************************************************************/
30
31        .file "strncat.s"
32#ifdef  __PIC
33        .pic
34#endif
35#ifdef  __PID
36        .pid
37#endif
38/*
39 * (c) copyright 1988,1993 Intel Corp., all rights reserved
40 */
41/*
42        procedure strncat  (optimized assembler version for the 80960K Series)
43
44        dest_addr = strncat (dest_addr, src_addr, max_bytes)
45
46        append the null terminated string pointed to by src_addr to the null
47        terminated string pointed to by dest_addr.  Return the original
48        dest_addr.  If the source string is longer than max_bytes, then
49        append only max_bytes bytes, and tack on a null byte on the end.
50
51        This routine will fail if the source and destination string
52        overlap (in particular, if the end of the source is overlapped
53        by the beginning of the destination).  The behavior is undefined.
54        This is acceptable according to the draft C standard.
55
56        Undefined behavior will also occur if the end of the source string
57        (i.e. the terminating null byte) is in the last two words of the
58        program's allocated memory space.  This is so because strncat fetches
59        ahead.  Disallowing the fetch ahead would impose a severe performance
60        penalty.
61
62        Strategy:
63
64        First, skip to the null byte in the destination string.  Then
65        fetch the source string by words and store them by words to the
66        destination string, until there are fewer than three bytes left
67        to copy.  Then, using the last word of the source (the one that
68        contains the remaining 0, 1, 2, or 3 bytes to be copied), store
69        a byte at a time until Ldone. 
70
71        If, before exhausting the max_byte count, the null byte is encountered
72        in the source string, then just copy up thru the null byte.
73
74        Tactics:
75
76        1) Do NOT try to fetch and store the words in a word aligned manner
77        because, in my judgement, the performance degradation experienced due
78        to non-aligned accesses does NOT outweigh the time and complexity added
79        by the preamble and convoluted body that would be necessary to assure
80        alignment. 
81*/
82
83        .globl _strncat
84        .globl __strncat
85        .leafproc _strncat,__strncat
86        .align    2
87_strncat:
88#ifndef __PIC
89        lda     Lrett,g14
90#else
91        lda     Lrett-(.+8)(ip),g14
92#endif
93__strncat:
94        mov     g14,g6
95        cmpibge 0, g2, Lno_operation    # Lexit early if max_bytes <= 0
96        mov     g0, g5
97Lskip_word_loop:
98        ld      (g5), g7        # fetch word of dest string
99        addo    4, g5, g5       # post-increment dest ptr
100        scanbyte 0, g7          # does it contain null byte?
101        bno     Lskip_word_loop # if not, loop
102        subo    5, g5, g5       # adjust dest ptr
103        lda     0xff, g3        # byte extraction mask = 0xff;
104Lskip_byte_loop:
105        and     g7, g3, g14     # extract byte of last word of dest string
106        cmpo    0, g14          # is it null?
107        addo    1, g5, g5       # adjust dest ptr
108        shro    8, g7, g7       # position next byte for extraction
109        bne     Lskip_byte_loop # loop if null not found yet
110
111        ld      (g1), g7        # fetch first word of source string
112Lwloop:                         # word copying loop
113        cmpo    4, g2           # max_bytes < 4 ?
114        addo    4, g1, g1       # post-increment source ptr
115        bge     Lcloop.a                # branch if less than 4 bytes to move
116        scanbyte 0, g7          # is null byte reached yet?
117        mov     g7, g4          # keep a copy of the source word
118        be      Lcloop          # branch if null byte reached
119        ld      (g1), g7        # pre-fetch next word of source
120        subo    4, g2, g2       # reduce max_byte counter
121        st      g4, (g5)        # store current word
122        addo    4, g5, g5       # post-increment destination ptr
123        b       Lwloop
124
125Lcloop.b:
126        addo    1, g5, g5       # post-increment destination ptr
127        shro    8, g7, g7       # position next byte for extraction
128Lcloop:                         # character copying loop  (max_byte > 3)
129        and     g3, g7, g4      # extract character
130        cmpo    0, g4           # is it null?
131        stob    g4, (g5)        # store it
132        bne     Lcloop.b                # loop if null not encountered yet
133
134        bx      (g6)            # g0 = dest string address; g14 = 0
135Lrett: 
136        ret
137
138Lcloop.c:
139        addo    1, g5, g5       # post-increment destination ptr
140        shro    8, g7, g7       # position next byte for extraction
141Lcloop.a:                       # character copying loop  (max_byte <= 3)
142        cmpdeco 0,g2,g2         # max_byte == 0?
143        and     g3, g7, g4      # extract character
144        be      Ldone           # store null and Lexit if max_byte exhausted
145        cmpo    0, g4           # is it null?
146        stob    g4, (g5)        # store it
147        bne     Lcloop.c                # loop if null not encountered yet
148
149Ldone:  stob    g14, (g5)       # store trailing null
150        bx      (g6)            # g0 = dest string address; g14 = 0
151
152Lno_operation: mov 0, g14       # conform to register conventions
153        bx      (g6)
154
155/* end of strncat */
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