File : s-caun16.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 _ U N 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 -- --
19 -- --
20 -- --
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_Unsigned_16 is
37
38 type Word is mod 2 ** 32;
39 -- Used to process operands by words
40
41 type Half is mod 2 ** 16;
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_U16 --
59 -----------------------
60
61 function Compare_Array_U16
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_U16;
132
133 end System.Compare_Array_Unsigned_16;