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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 */
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