source: trunk/libs/newlib/src/newlib/libc/machine/i960/strncpy.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: 5.5 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 "strncpy.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 strncpy  (optimized assembler version for the 80960K Series)
43
44        dest_addr = strncpy (dest_addr, src_addr, max_bytes)
45
46        copy the null terminated string pointed to by src_addr to the
47        string pointed to by dest_addr.  Return the original dest_addr.
48        If the source string is shorter than max_bytes, then null-pad
49        the destination string.  If it is longer than max_bytes, the
50        copy stops at max_bytes bytes (and no terminating null appears
51        in the destination string).
52
53        This routine will fail if the source and destination string
54        overlap (in particular, if the end of the source is overlapped
55        by the beginning of the destination).  The behavior is undefined.
56        This is acceptable according to the draft C standard.
57
58        Undefined behavior will also occur if the end of the source string
59        (i.e. the terminating null byte) is in the last two words of the
60        program's allocated memory space.  This is so because strncpy fetches
61        ahead.  Disallowing the fetch ahead would impose a severe performance
62        penalty.
63
64        Strategy:
65
66        Fetch and store the strings by words and go to a character move loop
67        as soon as a null byte is encountered.  If max_bytes is exhausted
68        first, then terminate after moving only max_bytes (with the last
69        0, 1, 2, or 3 bytes moved as single bytes, not as a word).
70        Otherwise, the character move loop moves the last bytes or the
71        source string, and then null-pads the destination string until
72        max_bytes is exhausted.
73
74        Tactics:
75
76        1) Do NOT try to fetch the words in a word aligned manner because,
77        in my judgement, the performance degradation experienced due to
78        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        2) When the null byte is encountered in a source word, null out the
83        higher-numbered bytes in that word, store the word in the destination,
84        and go to the word null-padder, which may eventually go to the byte
85        null-padder.
86*/
87
88        .globl _strncpy
89        .globl __strncpy
90        .leafproc _strncpy,__strncpy
91        .align    2
92_strncpy:
93#ifndef __PIC
94        lda     Lrett,g14
95#else
96        lda     Lrett-(.+8)(ip),g14
97#endif
98__strncpy:     
99        mov     g14, g13
100        cmpibge 0,g2,Lexit      # quit early if max_bytes <= 0
101        ld      (g1), g7        # fetch the first word of the source
102        mov     g0, g5
103        lda     0xff, g3        # byte extraction mask
104        addo    g1, g2, g6
105        addo    g2, g5, g2
106Lwloop:                         # word copying loop
107        addo    4, g1, g1       # post-increment source ptr
108        cmpo    g6, g1          # max_bytes < 4 ?
109        mov     g7, g4          # keep a copy of source word
110        bl      Lcloop.a                # if less than four bytes to go, go to char loop
111        scanbyte 0, g4          # null byte found?
112        ld      (g1), g7        # pre-fetch next word of the source
113        be      Lcloop.c                # go to char loop if null encountered
114        st      g4, (g5)        # store current word
115        addo    4, g5, g5       # post-increment destination ptr
116        b       Lwloop
117
118Lcloop.a:                       # character copying loop (max_bytes < 3)
119        and     g3, g4, g14     # extract byte
120Lcloop.b:
121        cmpo    g2, g5          # max_bytes <= 0 ?
122        shro    8, g4, g4       # position word to extract next byte
123        be      Lexit           # exit if max_bytes exhausted
124        cmpo    0, g14          # is it null?
125        stob    g14, (g5)       # store it
126        addo    1, g5, g5       # post-increment dest ptr
127        bne     Lcloop.a                # branch if we are NOT null padding
128        b       Lcloop.b                # branch if we are null padding
129
130Lexit:
131        mov     0, g14
132        bx      (g13)           # g0 = dest string address; g14 = 0
133Lrett: 
134        ret
135
136Lcloop.c:                       # character copying loop
137        and     g3, g4, g14     # extract byte
138        cmpo    0, g14          # is it null?
139        mov     g3, g7          # save mask
140        shlo    8, g3, g3       # shift mask to next byte position
141        bne     Lcloop.c                # loop until null found
142        subo    1, g7, g3       # mask to null pad after null byte
143        and     g3, g4, g4      # null-out stuff after null byte
144        st      g4, (g5)        # store last part of src and first of null-pad
145        subo    8,g2,g6         # adjust max_byte counter
146
147Lzwloop:
148        cmpo    g5, g6          # max_bytes < 4 ?
149        addo    4, g5, g5       
150        bg      Lcloop.b                # if so, goto character loop
151        st      g14, (g5)       # store four null bytes
152        b       Lzwloop
153
154/* end of strncpy */
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