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 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 85