/*
* arch/alpha/lib/strncat.S
* Contributed by Richard Henderson (rth@tamu.edu)
*
* Append no more than COUNT characters from the null-terminated string SRC
* to the null-terminated string DST. Always null-terminate the new DST.
*
* This differs slightly from the semantics in libc in that we never write
* past count, whereas libc may write to count+1. This follows the generic
* implementation in lib/string.c and is, IMHO, more sensible.
*/
.text
.align 3
.globl strncat
.ent strncat
strncat:
.frame $30, 0, $26
.prologue 0
mov $16, $0 # set up return value
beq $18, $zerocount
/* Find the end of the string. */
ldq_u $1, 0($16) # load first quadword ($16 may be misaligned)
lda $2, -1($31)
insqh $2, $16, $2
andnot $16, 7, $16
or $2, $1, $1
cmpbge $31, $1, $2 # bits set iff byte == 0
bne $2, $found
$loop: ldq $1, 8($16)
addq $16, 8, $16
cmpbge $31, $1, $2
beq $2, $loop
$found: negq $2, $3 # clear all but least set bit
and $2, $3, $2
and $2, 0xf0, $3 # binary search for that set bit
and $2, 0xcc, $4
and $2, 0xaa, $5
cmovne $3, 4, $3
cmovne $4, 2, $4
cmovne $5, 1, $5
addq $3, $4, $3
addq $16, $5, $16
addq $16, $3, $16
/* Now do the append. */
bsr $23, __stxncpy
/* Worry about the null termination. */
zapnot $1, $27, $2 # was last byte a null?
bne $2, 0f
ret
0: cmplt $27, $24, $2 # did we fill the buffer completely?
or $2, $18, $2
bne $2, 2f
and $24, 0x80, $2 # no zero next byte
bne $2, 1f
/* Here there are bytes left in the current word. Clear one. */
addq $24, $24, $24 # end-of-count bit <<= 1
2: zap $1, $24, $1
stq_u $1, 0($16)
ret
1: /* Here we must read the next DST word and clear the first byte. */
ldq_u $1, 8($16)
zap $1, 1, $1
stq_u $1, 8($16)
$zerocount:
ret
.end strncat
