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178 lines
6.3 KiB
ArmAsm
178 lines
6.3 KiB
ArmAsm
/*******************************************************************************
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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 "strcpy.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 strcpy (optimized assembler version for the 80960K series)
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procedure strcat (optimized assembler version for the 80960K series)
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dest_addr = strcpy (dest_addr, src_addr)
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copy the null terminated string pointed to by src_addr to
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the string space pointed to by dest_addr. Return the original
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dest_addr.
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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 strcpy 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 the source string and store the destination string by words
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until the null byte is encountered. When the word with the null
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byte is reached, store it by bytes up through the null byte only.
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Tactics:
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1) Do NOT try to fetch and store the words in a word aligned manner
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because, in my judgement, the performance degradation experienced due
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to 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. This is supported by the intuition that most source and
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destination strings will be word aligned to begin with.
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procedure strcat
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dest_addr = strcat (dest_addr, src_addr)
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Appends the string pointed to by src_addr to the string pointed
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to by dest_addr. The first character of the source string is
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copied to the location initially occupied by the trailing null
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byte of the destination string. Thereafter, characters are copied
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from the source to the destination up thru the null byte that
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trails the source string.
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See the strcpy routine, above, for its caveats, as they apply here too.
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Strategy:
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Skip to the end (null byte) of the destination string, and then drop
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into the strcpy code.
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Tactics:
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Skipping to the null byte is Ldone by reading the destination string
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in long-words and scanbyte'ing them, then examining the bytes of the
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word that contains the null byte, until the address of the null byte is
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known. Then we drop into the strcpy routine. It is probable (approx.
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three out of four times) that the destination string as strcpy sees
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it will NOT be word aligned (i.e. that the null byte won't be the
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last byte of a word). But it is not worth the complication to that
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routine to force word aligned memory accesses to be gaurenteed.
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*/
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.globl _strcpy, _strcat
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.globl __strcpy, __strcat
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.leafproc _strcpy,__strcpy
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.leafproc _strcat,__strcat
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.align 2
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_strcat:
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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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__strcat:
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mov g14,g13 # preserve return address
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ldl (g0),g4 # fetch first two words
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addo 8,g0,g2 # post-increment src word pointer
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lda 0xff,g3 # byte extraction mask
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Lsearch_for_word_with_null_byte:
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scanbyte 0,g4 # check for null byte
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mov g5,g7 # copy second word
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bo.f Lsearch_for_null # branch if null found
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scanbyte 0,g7 # check for null byte
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ldl (g2),g4 # fetch next pair of word of src
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addo 8,g2,g2 # post-increment src word pointer
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bno Lsearch_for_word_with_null_byte # branch if null not found yet
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subo 4,g2,g2 # back up the byte pointer
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mov g7,g4 # move word with null to search word
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Lsearch_for_null:
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subo 9,g2,g5 # back up the byte pointer
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Lsearch_for_null.a:
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and g4,g3,g6 # extract byte
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cmpo 0,g6 # is it null?
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addo 1,g5,g5 # bump src byte ptr
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shro 8,g4,g4 # shift word to position next byte
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bne Lsearch_for_null.a
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b Lend_of_dest_found
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_strcpy:
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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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__strcpy:
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mov g0, g5
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Lend_of_dest_found:
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ld (g1), g2 # fetch first word of source
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mov g14,g6 # preserve return address
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lda 0xff, g3 # byte extraction mask = 0xff;
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Lwloop: # word copying loop
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addo 4, g1, g1 # post-increment source ptr
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scanbyte 0, g2 # does source word contain null byte?
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mov g2, g4 # save a copy of the source word
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be Lcloop # branch if null present
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ld (g1), g2 # pre-fetch next word of source
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st g4, (g5) # store current word
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addo 4, g5, g5 # post-increment dest ptr
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b Lwloop
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Lcloop: # character copying loop
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and g3, g4, g14 # extract next char
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shro 8, g4, g4 # position word for next byte extraction
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cmpo 0, g14 # is it null?
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stob g14, (g5) # store the byte
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addo 1, g5, g5 # post-increment dest ptr
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bne Lcloop # quit if null encountered
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bx (g6) # g0 = dest string address; g14 = 0
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Lrett:
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ret
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