/*
   * 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