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jlechner |
/*******************************************************************************
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*
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* Copyright (c) 1993 Intel Corporation
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*
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* Intel hereby grants you permission to copy, modify, and distribute this
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* software and its documentation. Intel grants this permission provided
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* that the above copyright notice appears in all copies and that both the
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* copyright notice and this permission notice appear in supporting
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* documentation. In addition, Intel grants this permission provided that
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* you prominently mark as "not part of the original" any modifications
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* made to this software or documentation, and that the name of Intel
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* Corporation not be used in advertising or publicity pertaining to
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* distribution of the software or the documentation without specific,
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* written prior permission.
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*
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* Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
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* IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
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* OR FITNESS FOR A PARTICULAR PURPOSE. Intel makes no guarantee or
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* representations regarding the use of, or the results of the use of,
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* the software and documentation in terms of correctness, accuracy,
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* reliability, currentness, or otherwise; and you rely on the software,
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* documentation and results solely at your own risk.
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*
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* IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
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* LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
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* OF ANY KIND. IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
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* PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
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*
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******************************************************************************/
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.file "strncpy.s"
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#ifdef __PIC
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.pic
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#endif
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#ifdef __PID
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.pid
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#endif
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/*
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* (c) copyright 1988,1993 Intel Corp., all rights reserved
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*/
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/*
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procedure strncpy (optimized assembler version for the 80960K Series)
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dest_addr = strncpy (dest_addr, src_addr, max_bytes)
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copy the null terminated string pointed to by src_addr to the
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string pointed to by dest_addr. Return the original dest_addr.
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If the source string is shorter than max_bytes, then null-pad
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the destination string. If it is longer than max_bytes, the
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copy stops at max_bytes bytes (and no terminating null appears
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in the destination string).
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This routine will fail if the source and destination string
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overlap (in particular, if the end of the source is overlapped
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by the beginning of the destination). The behavior is undefined.
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This is acceptable according to the draft C standard.
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Undefined behavior will also occur if the end of the source string
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(i.e. the terminating null byte) is in the last two words of the
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program's allocated memory space. This is so because strncpy fetches
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ahead. Disallowing the fetch ahead would impose a severe performance
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penalty.
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Strategy:
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Fetch and store the strings by words and go to a character move loop
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as soon as a null byte is encountered. If max_bytes is exhausted
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first, then terminate after moving only max_bytes (with the last
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0, 1, 2, or 3 bytes moved as single bytes, not as a word).
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Otherwise, the character move loop moves the last bytes or the
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source string, and then null-pads the destination string until
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max_bytes is exhausted.
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Tactics:
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1) Do NOT try to fetch the words in a word aligned manner because,
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in my judgement, the performance degradation experienced due to
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non-aligned accesses does NOT outweigh the time and complexity added
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by the preamble and convoluted body that would be necessary to assure
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alignment.
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2) When the null byte is encountered in a source word, null out the
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higher-numbered bytes in that word, store the word in the destination,
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and go to the word null-padder, which may eventually go to the byte
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null-padder.
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*/
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.globl _strncpy
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.globl __strncpy
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.leafproc _strncpy,__strncpy
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.align 2
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_strncpy:
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#ifndef __PIC
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lda Lrett,g14
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#else
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lda Lrett-(.+8)(ip),g14
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#endif
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__strncpy:
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mov g14, g13
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cmpibge 0,g2,Lexit # quit early if max_bytes <= 0
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ld (g1), g7 # fetch the first word of the source
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mov g0, g5
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lda 0xff, g3 # byte extraction mask
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addo g1, g2, g6
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addo g2, g5, g2
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Lwloop: # word copying loop
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addo 4, g1, g1 # post-increment source ptr
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cmpo g6, g1 # max_bytes < 4 ?
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mov g7, g4 # keep a copy of source word
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bl Lcloop.a # if less than four bytes to go, go to char loop
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scanbyte 0, g4 # null byte found?
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ld (g1), g7 # pre-fetch next word of the source
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be Lcloop.c # go to char loop if null encountered
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st g4, (g5) # store current word
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addo 4, g5, g5 # post-increment destination ptr
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b Lwloop
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Lcloop.a: # character copying loop (max_bytes < 3)
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and g3, g4, g14 # extract byte
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Lcloop.b:
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cmpo g2, g5 # max_bytes <= 0 ?
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shro 8, g4, g4 # position word to extract next byte
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be Lexit # exit if max_bytes exhausted
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cmpo 0, g14 # is it null?
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stob g14, (g5) # store it
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addo 1, g5, g5 # post-increment dest ptr
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bne Lcloop.a # branch if we are NOT null padding
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b Lcloop.b # branch if we are null padding
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Lexit:
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mov 0, g14
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bx (g13) # g0 = dest string address; g14 = 0
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Lrett:
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ret
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Lcloop.c: # character copying loop
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and g3, g4, g14 # extract byte
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cmpo 0, g14 # is it null?
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mov g3, g7 # save mask
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shlo 8, g3, g3 # shift mask to next byte position
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bne Lcloop.c # loop until null found
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subo 1, g7, g3 # mask to null pad after null byte
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and g3, g4, g4 # null-out stuff after null byte
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st g4, (g5) # store last part of src and first of null-pad
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subo 8,g2,g6 # adjust max_byte counter
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Lzwloop:
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cmpo g5, g6 # max_bytes < 4 ?
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addo 4, g5, g5
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bg Lcloop.b # if so, goto character loop
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st g14, (g5) # store four null bytes
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b Lzwloop
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/* end of strncpy */
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