/******************************************************************************* * * 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 "sncat_ca.s" #ifdef __PIC .pic #endif #ifdef __PID .pid #endif /* * (c) copyright 1988,1993 Intel Corp., all rights reserved */ /* procedure strncat (optimized assembler version for the CA) dest_addr = strncat (dest_addr, src_addr, max_bytes) append the null terminated string pointed to by src_addr to the null terminated string pointed to by dest_addr. Return the original dest_addr. If the source string is longer than max_bytes, then append only max_bytes bytes, and tack on a null byte on the end 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 word of the program's allocated memory space. This is so because, in several cases, strncat will fetch ahead one word. Disallowing the fetch ahead would impose a severe performance penalty. This program handles five cases: 1) both arguments start on a word boundary 2) neither are word aligned, but they are offset by the same amount 3) source is word aligned, destination is not 4) destination is word aligned, source is not 5) neither is word aligned, and they are offset by differing amounts At the time of this writing, only g0 thru g7 and g13 are available for use in this leafproc; other registers would have to be saved and restored. These nine registers, plus tricky use of g14 are sufficient to implement the routine. The registers are used as follows: g0 original dest ptr; not modified, so that it may be returned. g1 src ptr; shift count g2 max_bytes g3 src ptr (word aligned) g4 dest ptr (word aligned) g5 0xff -- byte extraction mask Little endian: g6 lsw of double word for extraction of 4 bytes g7 msw of double word for extraction of 4 bytes Big endian: g6 msw of double word for extraction of 4 bytes g7 lsw of double word for extraction of 4 bytes g13 return address g14 byte extracted. */ #if __i960_BIG_ENDIAN__ #define MSW g6 #define LSW g7 #else #define LSW g6 #define MSW g7 #endif .globl _strncat .globl __strncat .leafproc _strncat, __strncat .align 2 _strncat: #ifndef __PIC lda Lrett,g14 #else lda Lrett-(.+8)(ip),g14 #endif __strncat: notand g0,3,g4 # extract word addr of start of dest lda (g14),g13 # preserve return address cmpibge.f 0,g2,Lexit_code # Lexit if number of bytes to move is <= zero. and g0,3,LSW # extract byte offset of dest ld (g4),MSW # fetch word containing at least first byte shlo 3,LSW,g14 # get shift count for making mask for first word subi 1,0,LSW # mask initially all ones #if __i960_BIG_ENDIAN__ shro g14,LSW,LSW # get mask for bytes needed from first word #else shlo g14,LSW,LSW # get mask for bytes needed from first word #endif notor MSW,LSW,MSW # set unneeded bytes to all ones lda 0xff,g5 # byte extraction mask Lsearch_for_word_with_null: scanbyte 0,MSW # check for null byte lda 4(g4),g4 # post-increment dest word pointer mov MSW,LSW # keep a copy of current word ld (g4),MSW # fetch next word of dest bno.t Lsearch_for_word_with_null # branch if null not found yet #if __i960_BIG_ENDIAN__ shro 24,LSW,g14 # extract byte #else and g5,LSW,g14 # extract byte #endif cmpo 0,g14 # branch if null is first byte of word subo 4,g4,g4 # move dest word ptr to word with null notand g1,3,g3 # extract word addr of start of src bne.t Lsearch_for_null Lcase_14: cmpo g1,g3 # check alignment of source ld (g3),LSW # fetch first word of source shlo 3,g1,g14 # compute shift count lda 4(g3),g3 # post-increment src addr bne.f Lcase_4 # branch if source is unaligned Lcase_1: Lcase_1_wloop: # word copying loop cmpi g2,4 # check for fewer than four bytes to move lda (LSW),g1 # keep a copy of the src word bl.f Lcase_1_cloop # branch if fewer than four bytes to copy scanbyte 0,g1 # check for null byte in src word ld (g3),LSW # pre-fetch next word of src addo 4,g3,g3 # post-increment src addr bo.f Lcase_1_cloop # branch if word contains null byte subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved st g1,(g4) # store word in dest string addo 4,g4,g4 # post-increment dest addr b Lcase_1_wloop Lcase_3_cloop: Lcase_1_cloop: # character copying loop (max_bytes <= 3) cmpdeci 0,g2,g2 # is max_bytes exhausted? #if __i960_BIG_ENDIAN__ rotate 8,g1,g1 # move next byte into position for extraction #endif and g5,g1,g14 # extract next char be.f Lstore_null # if max_bytes is exhausted, store null and quit cmpo 0,g14 # check for null byte stob g14,(g4) # store the byte in dest #if ! __i960_BIG_ENDIAN__ shro 8,g1,g1 # move next byte into position for extraction #endif lda 1(g4),g4 # post-increment dest byte addr bne.t Lcase_1_cloop # branch if null not reached bx (g13) # Lexit (g14 == 0) Lstore_null: mov 0,g14 # store null, and set g14 to zero stob g14,(g4) bx (g13) Lsearch_for_null: #if __i960_BIG_ENDIAN__ shlo 8,LSW,LSW # check next byte shro 24,LSW,g14 #else shlo 8,g5,g5 # move mask up to next byte and g5,LSW,g14 # extract byte #endif lda 1(g4),g4 # move dest byte ptr to next byte cmpobne.t 0,g14,Lsearch_for_null # branch if null is not yet found Lcase_235: cmpo g1,g3 # check alignment of src ld (g3),LSW # pre-fetch word with start of src and 3,g1,g1 # compute shift count lda 0xff,g5 # load mask for byte extraction shlo 3,g1,g14 lda 4(g3),g3 # post-increment src word counter be.t Lcase_3 # branch if src is word aligned and g4,3,MSW # extract byte offset for dest string cmpo MSW,g1 # < indicates first word of dest has more bytes /* than first word of source. */ ld (g3),MSW # fetch second word of src #if __i960_BIG_ENDIAN__ subo g14,0,g14 # adjust shift count for big endian #endif eshro g14,g6,g5 # extract four bytes #if __i960_BIG_ENDIAN__ bge.f 1f #else bg.f 1f #endif mov MSW,LSW lda 4(g3),g3 # move src word addr to second word boundary 1: mov g5,MSW lda 0xff,g5 b Lcase_25 Lcase_3: # src is word aligned; dest is not mov LSW,MSW # make copy of first word of src lda 32,g14 # initialize shift count to zero (mod 32) Lcase_25: Lcase_3_cloop_at_start: # character copying loop for start of dest str cmpdeci 0,g2,g2 # is max_bytes exhausted? #if __i960_BIG_ENDIAN__ shro 24,MSW,g5 # extract next char #else and g5,MSW,g5 # extract next char #endif be.f Lstore_null # Lexit if max_bytes is exhausted cmpo 0,g5 # check for null byte stob g5,(g4) # store the byte in dest addo 1,g4,g4 # post-increment dest ptr lda 0xff,g5 # re-initialize byte extraction mask notand g4,3,g1 # extract word address be.t Lexit_code # Lexit if null byte reached cmpo g1,g4 # have we reached word boundary in dest yet? #if __i960_BIG_ENDIAN__ lda -8(g14),g14 # augment the shift counter rotate 8,MSW,MSW # move next byte into position for extraction #else lda 8(g14),g14 # augment the shift counter shro 8,MSW,MSW # move next byte into position for extraction #endif bne.t Lcase_3_cloop_at_start # branch if reached word boundary? #if __i960_BIG_ENDIAN__ cmpo 0,g14 ld (g3),MSW # fetch msw of operand for double shift bne Lcase_3_wloop # branch if src is still unaligned. Lcase_3_wloop2: cmpi g2,4 # less than four bytes to move? mov LSW,g1 # extract 4 bytes of src lda 4(g3),g3 # post-increment src word addr bl.f Lcase_3_cloop # branch if < four bytes left to move scanbyte 0,g1 # check for null byte mov MSW,LSW # move msw to lsw ld (g3),MSW # pre-fetch msw of operand for double shift bo.f Lcase_3_cloop # branch if word contains null byte subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved st g1,(g4) # store 4 bytes to dest addo 4,g4,g4 # post-increment dest ptr b Lcase_3_wloop2 Lcase_4: subo g14,0,g14 # adjust shift count for big endian #else Lcase_4: #endif ld (g3),MSW # fetch msw of operand for double shift Lcase_3_wloop: cmpi g2,4 # less than four bytes to move? eshro g14,g6,g1 # extract 4 bytes of src lda 4(g3),g3 # post-increment src word addr bl.f Lcase_3_cloop # branch if < four bytes left to move scanbyte 0,g1 # check for null byte mov MSW,LSW # move msw to lsw ld (g3),MSW # pre-fetch msw of operand for double shift bo.f Lcase_3_cloop # branch if word contains null byte subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved st g1,(g4) # store 4 bytes to dest addo 4,g4,g4 # post-increment dest ptr b Lcase_3_wloop Lexit_code: mov 0,g14 # conform to register conventions bx (g13) # g0 = addr of dest; g14 = 0 Lrett: ret /* end of strncat */