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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * arch/alpha/lib/strncat.S
3 * Contributed by Richard Henderson (rth@tamu.edu)
4 *
5 * Append no more than COUNT characters from the null-terminated string SRC
6 * to the null-terminated string DST. Always null-terminate the new DST.
7 *
8 * This differs slightly from the semantics in libc in that we never write
9 * past count, whereas libc may write to count+1. This follows the generic
10 * implementation in lib/string.c and is, IMHO, more sensible.
11 */
12
13 .text
14
15 .align 3
16 .globl strncat
17 .ent strncat
18strncat:
19 .frame $30, 0, $26
20 .prologue 0
21
22 mov $16, $0 # set up return value
23 beq $18, $zerocount
24
25 /* Find the end of the string. */
26
27 ldq_u $1, 0($16) # load first quadword ($16 may be misaligned)
28 lda $2, -1($31)
29 insqh $2, $16, $2
30 andnot $16, 7, $16
31 or $2, $1, $1
32 cmpbge $31, $1, $2 # bits set iff byte == 0
33 bne $2, $found
34
35$loop: ldq $1, 8($16)
36 addq $16, 8, $16
37 cmpbge $31, $1, $2
38 beq $2, $loop
39
40$found: negq $2, $3 # clear all but least set bit
41 and $2, $3, $2
42
43 and $2, 0xf0, $3 # binary search for that set bit
44 and $2, 0xcc, $4
45 and $2, 0xaa, $5
46 cmovne $3, 4, $3
47 cmovne $4, 2, $4
48 cmovne $5, 1, $5
49 addq $3, $4, $3
50 addq $16, $5, $16
51 addq $16, $3, $16
52
53 /* Now do the append. */
54
55 bsr $23, __stxncpy
56
57 /* Worry about the null termination. */
58
59 zapnot $1, $27, $2 # was last byte a null?
60 bne $2, 0f
61 ret
62
630: cmplt $27, $24, $2 # did we fill the buffer completely?
64 or $2, $18, $2
65 bne $2, 2f
66
67 and $24, 0x80, $2 # no zero next byte
68 bne $2, 1f
69
70 /* Here there are bytes left in the current word. Clear one. */
71 addq $24, $24, $24 # end-of-count bit <<= 1
722: zap $1, $24, $1
73 stq_u $1, 0($16)
74 ret
75
761: /* Here we must read the next DST word and clear the first byte. */
77 ldq_u $1, 8($16)
78 zap $1, 1, $1
79 stq_u $1, 8($16)
80
81$zerocount:
82 ret
83
84 .end strncat