290 lines
10 KiB
ArmAsm
290 lines
10 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 "sncpy_ca.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 CA)
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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
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the string space pointed to by dest_addr. Return the original
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dest_addr. If the source string is shorter than max_bytes,
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then null-pad 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 word of the program's
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allocated memory space. This is so because, in several cases, strcpy
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will fetch ahead one word. Disallowing the fetch ahead would impose
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a severe performance penalty.
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This program handles five cases:
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1) both arguments start on a word boundary
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2) neither are word aligned, but they are offset by the same amount
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3) source is word aligned, destination is not
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4) destination is word aligned, source is not
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5) neither is word aligned, and they are offset by differing amounts
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At the time of this writing, only g0 thru g7 and g13 are available
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for use in this leafproc; other registers would have to be saved and
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restored. These nine registers, plus tricky use of g14 are sufficient
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to implement the routine. The registers are used as follows:
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g0 original dest ptr; not modified, so that it may be returned.
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g1 src ptr; shift count
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g2 max_bytes
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g3 src ptr (word aligned)
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g4 dest ptr (word aligned)
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g5 0xff -- byte extraction mask
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Little endian:
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g6 lsw of double word for extraction of 4 bytes
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g7 msw of double word for extraction of 4 bytes
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Big endian:
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g6 msw of double word for extraction of 4 bytes
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g7 lsw of double word for extraction of 4 bytes
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g13 return address
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g14 byte extracted.
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*/
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#if __i960_BIG_ENDIAN__
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#define MSW g6
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#define LSW g7
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#else
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#define LSW g6
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#define MSW g7
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#endif
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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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notand g1,3,g3 # extract word addr of start of src
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lda (g14),g13 # preserve return address
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cmpibge.f 0,g2,Lexit_code # Lexit if number of bytes to move is <= zero.
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cmpo g3,g1 # check alignment of src
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ld (g3),LSW # fetch word containing at least first byte
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notand g0,3,g4 # extract word addr of start of dest
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lda 4(g3),g3 # advance src word addr
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bne.f Lcase_245 # branch if src is NOT word aligned
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Lcase_13:
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cmpo g0,g4 # check alignment of dest
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lda 0xff,g5 # load mask for byte extraction
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subo 4,g4,g4 # store is pre-incrementing; back up dest addr
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bne.f Lcase_3 # branch if dest not word aligned
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Lcase_1: # src and dest are word aligned
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Lcase_1_wloop: # word copying loop
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cmpi g2,4 # check for fewer than four bytes to move
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lda (LSW),g1 # keep a copy of the src word
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addo 4,g4,g4 # pre-increment dest addr
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bl.f Lcase_1_cloop.a # branch if fewer than four bytes to copy
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scanbyte 0,g1 # check for null byte in src word
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ld (g3),LSW # pre-fetch next word of src
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subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
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bo.f Lcase_1_cloop.c # branch if word contains null byte
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addo 4,g3,g3 # post-increment src addr
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st g1,(g4) # store word in dest string
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b Lcase_1_wloop
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Lcase_3_cloop.a:
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Lcase_1_cloop.a: # character copying loop (max_bytes <= 3)
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#if __i960_BIG_ENDIAN__
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rotate 8,g1,g1 # move next byte into position for extraction
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#endif
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and g5,g1,g14 # extract next char
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Lcase_1_cloop.b:
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cmpdeci 0,g2,g2 # is max_bytes exhausted?
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be.f Lexit_code # Lexit if max_bytes is exhausted
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cmpo 0,g14 # check for null byte
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stob g14,(g4) # store the byte in dest
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#if ! __i960_BIG_ENDIAN__
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shro 8,g1,g1 # move next byte into position for extraction
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#endif
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lda 1(g4),g4 # post-increment dest byte addr
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bne.t Lcase_1_cloop.a # branch if null not reached
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b Lcase_1_cloop.b
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Lexit_code:
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mov 0,g14 # conform to register conventions
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bx (g13) # g0 = addr of dest; g14 = 0
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Lrett:
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ret
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Lcase_1_cloop.c:
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Lcase_3_cloop.c:
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#if __i960_BIG_ENDIAN__
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rotate 24,g5,g5 # move mask into position for testing next byte
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#endif
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and g5,g1,g14 # extract next char
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cmpo 0,g14 # check for null byte
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#if ! __i960_BIG_ENDIAN__
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lda (g5),LSW # keep a copy of the current mask
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shlo 8,g5,g5 # move mask into position for testing next byte
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#endif
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bne.t Lcase_1_cloop.c # branch if null not reached
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#if __i960_BIG_ENDIAN__
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subo 1,g5,g5 # null pad.
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andnot g5,g1,g1 # last bytes to copy, and null pad rest of word
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#else
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subo 1,LSW,g5 # mask to get last bytes to copy, and null pad
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and g5,g1,g1 # last bytes to copy, and null pad rest of word
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#endif
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st g1,(g4)
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Lcase_1_zwloop: # zero word loop
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cmpi g2,4 # check for fewer than four bytes to move
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addo 4,g4,g4 # pre-increment dest addr
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bl.f Lcase_1_cloop.b # branch if fewer than four bytes to copy
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subo 4,g2,g2 # decrease max_byte count by the 4 bytes moved
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st g14,(g4) # store word in dest string
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b Lcase_1_zwloop
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Lcase_3: # src is word aligned; dest is not
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addo 8,g4,g4 # move dest word ptr to first word boundary
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lda (g0),g1 # copy dest byte ptr
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mov LSW,MSW # make copy of first word of src
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lda 32,g14 # initialize shift count to zero (mod 32)
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Lcase_25:
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Lcase_3_cloop_at_start: # character copying loop for start of dest str
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cmpdeci 0,g2,g2 # is max_bytes exhausted?
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#if __i960_BIG_ENDIAN__
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shro 24,MSW,g5 # extract next char
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#else
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and g5,MSW,g5 # extract next char
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#endif
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be.f Lexit_code # Lexit if max_bytes is exhausted
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cmpo 0,g5 # check for null byte
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stob g5,(g1) # store the byte in dest
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addo 1,g1,g1 # post-increment dest ptr
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lda 0xff,g5 # re-initialize byte extraction mask
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bne.t 1f # drop thru if null byte reached (to pad)
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movl 0,g6 # blank out remainder of input buffer
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1:
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cmpo g1,g4 # have we reached word boundary in dest yet?
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#if __i960_BIG_ENDIAN__
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lda -8(g14),g14 # augment the shift counter
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rotate 8,MSW,MSW # move next byte into position for extraction
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#else
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lda 8(g14),g14 # augment the shift counter
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shro 8,MSW,MSW # move next byte into position for extraction
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#endif
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bne.t Lcase_3_cloop_at_start # branch if reached word boundary?
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ld (g3),MSW # fetch msw of operand for double shift
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Lcase_4:
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#if __i960_BIG_ENDIAN__
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cmpobne 0,g14,Lcase_3_wloop # branch if src is still unaligned.
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Lcase_3_wloop2:
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cmpi g2,4 # less than four bytes to move?
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lda (LSW),g1 # extract 4 bytes of src
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lda 4(g3),g3 # post-increment src word addr
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bl.f Lcase_3_cloop.a # branch if < four bytes left to move
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scanbyte 0,g1 # check for null byte
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lda (MSW),LSW # move msw to lsw
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subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
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ld (g3),MSW # pre-fetch msw of operand for double shift
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bo.f Lcase_3_cloop.c # branch if word contains null byte
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st g1,(g4) # store 4 bytes to dest
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addo 4,g4,g4 # post-increment dest ptr
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b Lcase_3_wloop2
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#endif
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Lcase_3_wloop:
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cmpi g2,4 # less than four bytes to move?
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eshro g14,g6,g1 # extract 4 bytes of src
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lda 4(g3),g3 # post-increment src word addr
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bl.f Lcase_3_cloop.a # branch if < four bytes left to move
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scanbyte 0,g1 # check for null byte
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lda (MSW),LSW # move msw to lsw
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subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
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ld (g3),MSW # pre-fetch msw of operand for double shift
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bo.f Lcase_3_cloop.c # branch if word contains null byte
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st g1,(g4) # store 4 bytes to dest
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addo 4,g4,g4 # post-increment dest ptr
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b Lcase_3_wloop
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Lcase_245:
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cmpo g0,g4 # check alignment of dest
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ld (g3),MSW # pre-fetch second half
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and 3,g1,g1 # compute shift count
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lda 0xff,g5 # load mask for byte extraction
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#if __i960_BIG_ENDIAN__
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subo g1,4,g14 # adjust shift count for big endian.
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shlo 3,g14,g14
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#else
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shlo 3,g1,g14
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#endif
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be.t Lcase_4 # branch if dest is word aligned
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or g4,g1,g1 # is src earlier in word, later, or sync w/ dst
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cmpo g0,g1 # < indicates first word of dest has more bytes
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/* than first word of source. */
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lda 4(g4),g4 # move dest word addr to first word boundary
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eshro g14,g6,g5 # extract four bytes
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lda (g0),g1
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bg.f 1f
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mov MSW,LSW
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lda 4(g3),g3 # move src word addr to second word boundary
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1:
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mov g5,MSW
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lda 0xff,g5
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b Lcase_25
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/* end of strncpy */
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