arch/alpha/lib/strncpy.S

   1 /*
   2  * arch/alpha/lib/strncpy.S
   3  * Contributed by Richard Henderson (rth@tamu.edu)
   4  *
   5  * Copy no more than COUNT bytes of the null-terminated string from
   6  * SRC to DST.  If SRC does not cover all of COUNT, the balance is
   7  * zeroed.
   8  *
   9  * Or, rather, if the kernel cared about that weird ANSI quirk.  This
  10  * version has cropped that bit o' nastiness as well as assuming that
  11  * __stxncpy is in range of a branch.
  12  */
  13
  14         .set noat
  15         .set noreorder
  16
  17         .text
  18
  19         .align 4
  20         .globl strncpy
  21         .ent strncpy
  22 strncpy:
  23         .frame $30, 0, $26
  24         .prologue 0
  25
  26         mov     $16, $0         # set return value now
  27         beq     $18, $zerolen
  28         unop
  29         bsr     $23, __stxncpy  # do the work of the copy
  30
  31         unop
  32         bne     $18, $multiword # do we have full words left?
  33         subq    $24, 1, $3      # nope
  34         subq    $27, 1, $4
  35
  36         or      $3, $24, $3     # clear the bits between the last
  37         or      $4, $27, $4     # written byte and the last byte in COUNT
  38         andnot  $4, $3, $4
  39         zap     $1, $4, $1
  40
  41         stq_u   $1, 0($16)
  42         ret
  43
  44         .align  4
  45 $multiword:
  46         subq    $24, 1, $2      # clear the final bits in the prev word
  47         or      $2, $24, $2
  48         zapnot  $1, $2, $1
  49         subq    $18, 1, $18
  50
  51         stq_u   $1, 0($16)
  52         addq    $16, 8, $16
  53         unop
  54         beq     $18, 1f
  55
  56         nop
  57         unop
  58         nop
  59         blbc    $18, 0f
  60
  61         stq_u   $31, 0($16)     # zero one word
  62         subq    $18, 1, $18
  63         addq    $16, 8, $16
  64         beq     $18, 1f
  65
  66 0:      stq_u   $31, 0($16)     # zero two words
  67         subq    $18, 2, $18
  68         stq_u   $31, 8($16)
  69         addq    $16, 16, $16
  70         bne     $18, 0b
  71
  72 1:      ldq_u   $1, 0($16)      # clear the leading bits in the final word
  73         subq    $27, 1, $2
  74         or      $2, $27, $2
  75
  76         zap     $1, $2, $1
  77         stq_u   $1, 0($16)
  78 $zerolen:
  79         ret
  80
  81         .end    strncpy