gcc/ada/s-casi16.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                    GNAT RUN-TIME LIBRARY COMPONENTS                      --
   4 --                                                                          --
   5 --       S Y S T E M . C O M P A R E _ A R R A Y _ S I G N E D _ 1 6        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2002-2009, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with System.Address_Operations; use System.Address_Operations;
  33
  34 with Ada.Unchecked_Conversion;
  35
  36 package body System.Compare_Array_Signed_16 is
  37
  38    type Word is mod 2 ** 32;
  39    --  Used to process operands by words
  40
  41    type Half is range -(2 ** 15) .. (2 ** 15) - 1;
  42    for Half'Size use 16;
  43    --  Used to process operands by half words
  44
  45    type Uhalf is new Half;
  46    for Uhalf'Alignment use 1;
  47    --  Used to process operands when unaligned
  48
  49    type WP is access Word;
  50    type HP is access Half;
  51    type UP is access Uhalf;
  52
  53    function W is new Ada.Unchecked_Conversion (Address, WP);
  54    function H is new Ada.Unchecked_Conversion (Address, HP);
  55    function U is new Ada.Unchecked_Conversion (Address, UP);
  56
  57    -----------------------
  58    -- Compare_Array_S16 --
  59    -----------------------
  60
  61    function Compare_Array_S16
  62      (Left      : System.Address;
  63       Right     : System.Address;
  64       Left_Len  : Natural;
  65       Right_Len : Natural) return Integer
  66    is
  67       Clen : Natural := Natural'Min (Left_Len, Right_Len);
  68       --  Number of elements left to compare
  69
  70       L : Address := Left;
  71       R : Address := Right;
  72       --  Pointers to next elements to compare
  73
  74    begin
  75       --  Go by words if possible
  76
  77       if ModA (OrA (Left, Right), 4) = 0 then
  78          while Clen > 1
  79            and then W (L).all = W (R).all
  80          loop
  81             Clen := Clen - 2;
  82             L := AddA (L, 4);
  83             R := AddA (R, 4);
  84          end loop;
  85       end if;
  86
  87       --  Case of going by aligned half words
  88
  89       if ModA (OrA (Left, Right), 2) = 0 then
  90          while Clen /= 0 loop
  91             if H (L).all /= H (R).all then
  92                if H (L).all > H (R).all then
  93                   return +1;
  94                else
  95                   return -1;
  96                end if;
  97             end if;
  98
  99             Clen := Clen - 1;
 100             L := AddA (L, 2);
 101             R := AddA (R, 2);
 102          end loop;
 103
 104       --  Case of going by unaligned half words
 105
 106       else
 107          while Clen /= 0 loop
 108             if U (L).all /= U (R).all then
 109                if U (L).all > U (R).all then
 110                   return +1;
 111                else
 112                   return -1;
 113                end if;
 114             end if;
 115
 116             Clen := Clen - 1;
 117             L := AddA (L, 2);
 118             R := AddA (R, 2);
 119          end loop;
 120       end if;
 121
 122       --  Here if common section equal, result decided by lengths
 123
 124       if Left_Len = Right_Len then
 125          return 0;
 126       elsif Left_Len > Right_Len then
 127          return +1;
 128       else
 129          return -1;
 130       end if;
 131    end Compare_Array_S16;
 132
 133 end System.Compare_Array_Signed_16;