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/*

 * 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