📄 strncpy.s
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/* * .seg "data" * .asciz "@(#)strncpy.s 1.1 92/07/30" * Copyright (c) 1989 by Sun Microsystems, Inc. */#include <sun4/asm_linkage.h> .seg "text" .align 4#define DEST %i0#define SRC %i1#define CNT %i2#define DESTSV %i5#define ADDMSK %l0#define ANDMSK %l1#define MSKB0 %l2#define MSKB1 %l3#define MSKB2 %l4#define SL %o0#define SR %o1#define MSKB3 0xff/* * strncpy(s1, s2) * Copy string s2 to s1, truncating or null-padding to always copy n bytes * return s1. */ ENTRY(strncpy) save %sp, -SA(WINDOWSIZE), %sp ! get a new window cmp CNT, 8 ! do a byte at a time for small n ble pad_trunc mov DEST, DESTSV ! save return value andcc SRC, 3, %i3 ! is src word aligned bz aldest cmp %i3, 2 ! is src half-word aligned be s2algn cmp %i3, 3 ! src is byte aligned ldub [SRC], %i3 ! move 1 or 3 bytes to align it inc SRC dec CNT stb %i3, [DEST] ! move a byte to align src be s3algn tst %i3s1algn: bnz s2algn ! now go align dest inc 1, DEST b,a pad_nulls2algn: lduh [SRC], %i3 ! know src is 2 byte alinged inc 2, SRC dec 2, CNT srl %i3, 8, %i4 tst %i4 stb %i4, [DEST] bnz,a 1f stb %i3, [DEST + 1] inc CNT ! back count up, only one transferred inc DEST b,a pad_null1: andcc %i3, MSKB3, %i3 bnz aldest inc 2, DEST b,a pad_nulls3algn: bnz aldest inc 1, DEST b,a pad_nullaldest: /* * In all the destination alignment cases: * CNT >= 4 upon entry. The idea is to copy a word at a time * until we hit a NULL, or the CNT becomes less than 4 in which * case we call pad_trunc in order to finish off the copying * a byte at a time or padding the destination with 0's */ set 0x7efefeff, ADDMSK ! masks to test for terminating null set 0x81010100, ANDMSK sethi %hi(0xff000000), MSKB0 sethi %hi(0x00ff0000), MSKB1 /* * source address is now aligned * We are guarenteed that there are at least 4 bytes left in * the count since we compare for n <= 8 at the entry */ andcc DEST, 3, %i3 ! is destination word aligned? bz w4str srl MSKB1, 8, MSKB2 ! generate 0x0000ff00 mask cmp %i3, 2 ! is destination halfword aligned? be w2str cmp %i3, 3 ! worst case, dest is byte alingedw1str: ld [SRC], %i3 ! read a word inc 4, SRC ! point to next one be w3str /* * Destination is byte aligned upon entry. We have to move 3 bytes * in order to align the destination. */ andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero /* First byte was null */ stb %g0, [DEST] inc DEST dec CNT b pad_null ! finish up dec 3,SRC1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero /* Second byte was null, dest is byte aligned */ dec 2, CNT srl %i3, 24, %o3 stb %o3, [DEST] stb %g0, [DEST + 1] inc 2, DEST b pad_null dec 2, SRC ! delay slot1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero /* Third byte was null, dest is byte aligned */ srl %i3, 8, %o3 sth %o3, [DEST + 1] ! store bytes 1, 2 srl %i3, 24, %o3 stb %o3, [DEST] ! store byte 0 dec 3, CNT inc 3, DEST b pad_null dec SRC1: bz 1f /* Fourth byte is NOT null, move 3 bytes to align dest */ srl %i3, 24, %o3 ! move three bytes to align dest stb %o3, [DEST] ! store byte 0 srl %i3, 8, %o3 sth %o3, [DEST + 1] ! store bytes 1, 2 inc 3, DEST ! destination now aligned dec 3, CNT b 7f mov %i3, %o31: /* Fourth byte was null, dest is byte aligned */ srl %i3, 24, %o3 stb %o3, [DEST] ! store byte 0 srl %i3, 8, %o3 sth %o3, [DEST + 1] ! store byte 1, 2 stb %g0, [DEST + 3] ! store byte 3 inc 4, DEST ! destination now aligned b pad_null dec 4, CNT ! Moved 4 bytes /* Top of loop */2: inc 4, DEST7: deccc 4, CNT ! check if CNT < 4 bge 1f sll %o3, 24, %o2 ! delay slot, save remaining byte /* Time to bail out */ dec SRC ! reset src ptr b pad_trunc inc 4, CNT ! delay slot, original value1: ld [SRC], %o3 ! read a word inc 4, SRC ! point to next one srl %o3, 8, %i3 or %i3, %o2, %i3 add %i3, ADDMSK, %l5 ! check for a zero byte xor %l5, %i3, %l5 and %l5, ANDMSK, %l5 cmp %l5, ANDMSK be,a 2b ! if no zero byte in word, loop st %i3, [DEST] andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero stb %g0, [DEST] ! first byte was zero inc DEST inc 3, CNT ! Only moved 1 byte b pad_null ! may have to do some padding dec 3, SRC ! delay slot1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero /* Second byte was 0, aligned dest */ srl %i3, 16, %o3 sth %o3, [DEST] ! store bytes 0, 1 inc 2, DEST inc 2, CNT b pad_null dec 2, SRC1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero /* Third byte was 0, aligned dest */ srl %i3, 16, %o3 sth %o3, [DEST] ! store bytes 0, 1 stb %g0, [DEST + 2] ! store byte 3 inc 3, DEST inc 1, CNT b pad_null dec SRC1: st %i3, [DEST] ! it is safe to write the word now bnz 7b ! if not zero, go read another word inc 4, DEST ! else finished b,a pad_null ! 4th byte was 0/* * Destination is byte aligned upon entry. We have to move 1 byte * in order to align the destination. */w3str: bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero /* First byte was null */ stb %g0, [DEST] inc DEST dec CNT b pad_null ! finish up dec 3,SRC1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero /* 2nd byte was null, dest is byte aligned */ dec 2, CNT srl %i3, 24, %o3 stb %o3, [DEST] stb %g0, [DEST + 1] inc 2, DEST b pad_null dec 2, SRC ! delay slot1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero /* Third byte was null, dest is byte aligned */ srl %i3, 8, %o3 sth %o3, [DEST + 1] ! store bytes 1, 2 srl %i3, 24, %o3 stb %o3, [DEST] ! store byte 0 dec 3, CNT inc 3, DEST b pad_null dec SRC1: bz 1f srl %i3, 24, %o3 ! move three bytes to align dest /* Fourth byte is NOT null, move 1 byte to align dest */ stb %o3, [DEST] ! store byte 0 inc DEST ! destination now aligned dec CNT b 8f mov %i3, %o31: /* Fourth byte was null, dest is byte aligned */ stb %o3, [DEST] ! store byte 0 srl %i3, 8, %o3 sth %o3, [DEST + 1] ! store byte 1, 2 stb %g0, [DEST + 3] ! store byte 3 inc 4, DEST b pad_null dec 4, CNT ! Moved 4 bytes /* Top of loop */2: inc 4, DEST8: deccc 4, CNT ! check if CNT < 4 bge 1f sll %o3, 8, %o2 ! delay slot, save remaining byte /* Time to bail out */ dec 3, SRC ! reset src ptr b pad_trunc inc 4, CNT ! delay slot, original value1: ld [SRC], %o3 ! read a word inc 4, SRC ! point to next one srl %o3, 24, %i3 or %i3, %o2, %i3 add %i3, ADDMSK, %l5 ! check for a zero byte xor %l5, %i3, %l5 and %l5, ANDMSK, %l5 cmp %l5, ANDMSK be,a 2b ! if no zero byte in word, loop st %i3, [DEST] andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero /* First byte was zero */ stb %g0, [DEST] inc DEST inc 3, CNT ! Only moved 1 byte b pad_null ! may have to do some padding dec 3, SRC ! delay slot1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero /* Second byte was 0, aligned dest */ srl %i3, 16, %o3 sth %o3, [DEST] ! store bytes 0, 1 inc 2, DEST inc 2, CNT b pad_null dec 2, SRC1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero /* Third byte was 0, aligned dest */ srl %i3, 16, %o3 sth %o3, [DEST] ! store bytes 0, 1 stb %g0, [DEST + 2] ! store byte 3 inc 3, DEST inc 1, CNT b pad_null dec SRC1: st %i3, [DEST] ! it is safe to write the word now bnz 8b ! if not zero, go read another word inc 4, DEST ! else finished b,a pad_null/* * * Destination is halfword aligned */w2str: ld [SRC], %i3 ! read a word inc 4, SRC ! point to next one andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero stb %g0, [DEST] inc DEST dec CNT b pad_null ! may have to do some padding dec 3, SRC ! delay slot1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero srl %i3, 16, %i4 ! second byte of word was 0 sth %i4, [DEST] ! store 2 bytes inc 2, DEST ! new DEST ptr dec 2, CNT ! b pad_null ! may have to do some padding dec 2, SRC ! delay slot1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero srl %i3, 16, %i4 ! third byte of word was the term 0 sth %i4, [DEST] stb %g0, [DEST + 2] inc 3, DEST dec 3, CNT ! only really did 3 bytes b pad_null ! may have to do some padding dec 3, SRC1: bnz 1f srl %i3, 16, %o3 sth %o3, [DEST] ! Last byte was 0 sth %i3, [DEST + 2] inc 4, DEST b pad_null dec 4, CNT1: sth %o3, [DEST] inc 2, DEST ! DEST is now word aligned dec 2, CNT b 9f mov %i3, %o3 /* Top of loop */loop2: inc 4, DEST9: deccc 4, CNT ! check if CNT < 4 bge,a 1f sll %o3, 16, %o2 ! delay slot, save rest dec 2, SRC ! reset src ptr b pad_trunc inc 4, CNT ! delay slot, original value1: ld [SRC], %o3 ! read a word inc 4, SRC ! point to next one srl %o3, 16, %i3 or %i3, %o2, %i3 add %i3, ADDMSK, %l5 ! check for a zero byte xor %l5, %i3, %l5 and %l5, ANDMSK, %l5 cmp %l5, ANDMSK be,a loop2 ! if no zero byte in word, loop st %i3, [DEST] andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero /* First byte zero */ stb %g0, [DEST] ! store byte inc DEST inc 3, CNT ! only really did 1 byte b pad_null ! may have to do some padding dec 3, SRC1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero srl %i3, 16, %i4 ! second byte of word was 0 sth %i4, [DEST] ! store 2 bytes inc 2, DEST inc 2, CNT ! only really did 2 bytes b pad_null dec 2, SRC ! delay slot, reset src ptr1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero srl %i3, 16, %i4 ! third byte of word was 0 sth %i4, [DEST] stb %g0, [DEST + 2] inc 3, DEST inc CNT ! only really did 3 bytes b pad_null dec 1, SRC ! delay slot, reset src ptr1: st %i3, [DEST] ! it is safe to write the word now bnz 9b ! if not zero, go read another word inc 4, DEST ! else fall through b,a pad_null/* * Both src and destination fields are word aligned. * CNT >= 4 upon entry. The idea is to copy a word at a time * until we hit a NULL, or the CNT becomes less than 4 in which * case we call pad_trunc in order to finish off the copying * a byte at a time or padding the destination with 0's */2: inc 4, DESTw4str: deccc 4, CNT ble,a pad_trunc ! if less than 4 bytes left go 1 by 1 inc 4, CNT ! delay slot, original value ld [SRC], %i3 ! read a word inc 4, SRC ! point to next one add %i3, ADDMSK, %l5 ! check for a zero byte xor %l5, %i3, %l5 and %l5, ANDMSK, %l5 cmp %l5, ANDMSK be,a 2b ! if no zero byte in word, loop st %i3, [DEST] andcc %i3, MSKB0, %g0 ! check if first byte was zero bnz 1f andcc %i3, MSKB1, %g0 ! check if second byte was zero stb %g0, [DEST] ! store byte inc DEST inc 3, CNT ! only really did 1 byte b pad_null ! may have to do some padding dec 3, SRC1: bnz 1f andcc %i3, MSKB2, %g0 ! check if third byte was zero srl %i3, 16, %i4 ! second byte of word was the term 0 sth %i4, [DEST] inc 2, DEST inc 2, CNT ! only really did 2 bytes b pad_null dec 2, SRC1: bnz 1f andcc %i3, MSKB3, %g0 ! check if last byte is zero srl %i3, 16, %i4 ! third byte of word was the term 0 sth %i4, [DEST] stb %g0, [DEST + 2] inc 3, DEST inc CNT ! only really did 3 bytes b pad_null dec SRC1: st %i3, [DEST] ! it is safe to write the word now bnz w4str ! if not zero, go read another word inc 4, DEST ! else pad the rest b,a pad_nulldone: ret ! last byte of word was the terminating zero restore DESTSV, %g0, %o0/* * Copy a byte at a time until we: * 1) Exhaust the CNT (may cause truncation) * 2) Hit a null in the src, at which point we pad the destination * with nulls until the CNT is done. */pad_trunc: deccc CNT bneg,a 2f ! all done now. May have truncated ret ! delay slot ldub [SRC], %i3 ! get byte inc SRC stb %i3, [DEST] ! store result tst %i3 ! check for zero bnz pad_trunc inc DEST ! delay slot /* null pad the rest */pad_null: deccc CNT bneg,a 2f ! all done now. ret ! delay slot stb %g0, [DEST] b pad_null inc DEST ! delay slot2: restore DESTSV, %g0, %o0⌨️ 快捷键说明
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