Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
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 | |
18 | strncat: | |
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 | ||
63 | 0: 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 | |
72 | 2: zap $1, $24, $1 | |
73 | stq_u $1, 0($16) | |
74 | ret | |
75 | ||
76 | 1: /* 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 |