strncpy.s revision 2
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * CDDL HEADER START
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a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * CDDL HEADER END
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * Use is subject to license terms.
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * strncpy(s1, s2)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * Copy string s2 to s1, truncating or null-padding to always copy n bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * Fast assembler language version of the following C-program for strncpy
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * which represents the `standard' for the C-library.
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * strncpy(char *s1, const char *s2, size_t n)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * char *os1 = s1;
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * while ((--n != 0) && ((*s1++ = *s2++) != '\0'))
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * while (--n != 0)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * *s1++ = '\0';
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering * return (os1);
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering ! strncpy works similarly to strcpy, except that n bytes of s2
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! are copied to s1. If a null character is reached in s2 yet more
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! bytes remain to be copied, strncpy will copy null bytes into
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! This implementation works by first aligning the src ptr and
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! performing small copies until it is aligned. Then, the string
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering ! is copied based upon destination alignment. (byte, half-word,
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering nop ! pad to align loop on 16-byte boundary
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o4, 8, %o4 ! bytes until src aligned
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering tst %o1 ! end of src reached (null byte) ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bz,a %ncc, .bytepad ! yes, at least one byte to pad here
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o2, %g4, %o3 ! need single dest pointer for fill
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bnz,a %ncc, .alignsrc ! no, copy another byte
6c12b52e19640747e96f89d85422941a23dc6b29Lennart Poettering sethi %hi(0x01010101), %o4 ! Alan Mycroft's magic1
6c12b52e19640747e96f89d85422941a23dc6b29Lennart Poettering add %o2, %g4, %g5 ! dst
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering or %o4, %lo(0x01010101),%o4! finish loading magic1
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering and %g5, 3, %g1 ! dst<1:0> to examine offset
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sllx %o4, 32, %o1 ! spread magic1
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering cmp %g1, 1 ! dst offset of 1 or 5
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering or %o4, %o1, %o4 ! to all 64 bits
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o2, 8, %o2 ! adjust for dest pre-incr in cpy loops
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering be,pn %ncc, .storebyte1241 ! store 1, 2, 4, 1 bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering be,pn %ncc, .storebyte1421 ! store 1, 4, 2, 1 bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering be,pn %ncc, .storehalfword ! yup, store half-word wise
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bnz,pn %ncc, .storeword2 ! yup, store word wise
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %g4, 8, %g4 ! n += 8, src += 8, dst += 8
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering bcs,pn %ncc,.lastword ! if counter wraps, last word
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering andn %o5, %o1, %g1 ! ~dword & 0x8080808080808080
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o1, %o4, %g5 ! dword - 0x0101010101010101
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering andcc %g5, %g1, %g0 ! ((dword - 0x0101010101010101) & ~dword & 0x8080808080808080)
79008bddf679a5e0900369950eb346c9fa687107Lennart Poettering bz,a,pt %ncc, .storedword ! no zero byte if magic expression == 0
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering stx %o1, [%o2 + %g4] ! store word to dst (address pre-incremented)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! n has not expired, but src is at the end. we need to push out the
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! remaining src bytes and then start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o2, %g4, %o3 ! pointer to dest string
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
598459cebac7cc93089769a992e7b03287f77e12Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %g4, 16, %g0 ! number of pad bytes < 16 ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bcs,pn %ncc, .bytepad ! yes, do simple byte wise fill
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %o3, 7, %o4 ! dst offset relative to dword boundary
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bz,pn %ncc, .fillaligned ! dst already dword aligned
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! here there is a least one more byte to zero out: otherwise we would
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o4, 8, %o4 ! bytes to align dst to dword boundary
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %o4, 1, %o4 ! any more byte needed to align
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bnz,pt %ncc, .makealigned ! yup, pad another byte
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! here we know that there at least another 8 bytes to pad, since
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! we don't get here unless there were >= 16 bytes to pad to begin
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! with, and we have padded at most 7 bytes suring dst aligning
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering add %g4, 7, %o2 ! round up to next dword boundary
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering and %o2, -8, %o4 ! pointer to next dword boundary
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering and %o2, 8, %o2 ! dword count odd ? 8 : 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stx %g0, [%o3] ! store first dword
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %o4, %o2, %o4 ! dword count == 1 ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %g4, %o2, %g4 ! if dword count odd, n -= 8
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bz,pt %ncc, .bytepad ! if dword count == 1, pad leftover bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o3, %o2, %o3 ! bump dst if dword count odd
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %o4, 16, %o4 ! count -= 16
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stx %g0, [%o3] ! dst[n] = 0
82a2b6bb5e4e5d294f09af778c48974a7857afb6Lennart Poettering stx %g0, [%o3 + 8] ! dst[n+8] = 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o3, 16, %o3 ! dst += 16
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bcc,pt %ncc, .filldword ! fill dwords until count == 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %g4, 16, %g4 ! n -= 16
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bz,pn %ncc, .done ! if n == 0, we are done
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering and %g4, 1, %o2 ! byte count odd ? 1 : 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g0, [%o3] ! store first byte
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering addcc %g4, %o2, %g4 ! byte count == 1 ?
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering bz,pt %ncc, .done ! yup, we are done
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o3, %o2, %o3 ! bump pointer if odd
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering addcc %g4, 2, %g4 ! n -= 2
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g0, [%o3] ! dst[n] = 0
718db96199eb307751264e4163555662c9a389faLennart Poettering stb %g0, [%o3 + 1] ! dst[n+1] = 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bnz,pt %ncc, .fillbyte ! fill until n == 0
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o3, 2, %o3 ! dst += 2
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering nop ! pad to align loops below
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering nop ! pad to align loops below
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! this is the last word. It may contain null bytes. store bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ! until n == 0. if null byte encountered, continue
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %g4, 8, %g4 ! undo counter pre-increment
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering add %o2, 8, %o2 ! adjust dst for counter un-bumping
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 56, %g1 ! first byte
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g1, [%o2 + %g4] ! store it
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering inccc %g4 ! n--
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 40, %g1 ! third byte
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g1, [%o2 + %g4] ! store it
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering inccc %g4 ! n--
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 24, %g1 ! fifth byte
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g1, [%o2 + %g4] ! store it
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering inccc %g4 ! n--
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 8, %g1 ! seventh byte
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stb %g1, [%o2 + %g4] ! store it
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering inccc %g4 ! n--
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g1, 0xff, %g0 ! end of src reached ?
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering movz %ncc, %g0, %o1 ! if so, start padding with null bytes
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering ba .done ! here n must be zero, we are done
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering bcs,pn %ncc,.lastword ! if counter wraps, last word
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andn %o5, %o1, %g1 ! ~x & 0x8080808080808080
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o1, %o4, %g5 ! x - 0x0101010101010101
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g5, %g1, %g0 ! ((x - 0x0101010101010101) & ~x & 0x8080808080808080)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bnz,pn %ncc, .zerobyte ! end of src found, may need to pad
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering add %o2, %g4, %g5 ! dst (in pointer form)
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 56, %g1 ! %g1<7:0> = first byte; word aligned now
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 24, %g1 ! %g1<31:0> = bytes 2, 3, 4, 5
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stw %g1, [%g5 + 1] ! store bytes 2, 3, 4, 5
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 8, %g1 ! %g1<15:0> = bytes 6, 7
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering bcs,pn %ncc,.lastword ! if counter wraps, last word
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andn %o5, %o1, %g1 ! ~x & 0x8080808080808080
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering sub %o1, %o4, %g5 ! x - 0x0101010101010101
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering andcc %g5, %g1, %g0 ! ((x - 0x0101010101010101) & ~x & 0x8080808080808080)
718db96199eb307751264e4163555662c9a389faLennart Poettering bnz,pn %ncc, .zerobyte ! x has zero byte, handle end cases
8e2af478402414f060bbc16e1b4bbe7de1779c13Lennart Poettering add %o2, %g4, %g5 ! dst (in pointer form)
8e2af478402414f060bbc16e1b4bbe7de1779c13Lennart Poettering srlx %o1, 56, %g1 ! %g1<7:0> = first byte; half-word aligned now
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering srlx %o1, 40, %g1 ! %g1<15:0> = bytes 2, 3
4ad490007b70e6ac18d3cb04fa2ed92eba1451faLennart Poettering srlx %o1, 8, %g1 ! %g1<31:0> = bytes 4, 5, 6, 7
a016b9228f338cb9b380ce7e00826ef462767d98Lennart Poettering stw %g1, [%g5 + 3] ! store bytes 4, 5, 6, 7