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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME LIBRARY COMPONENTS --
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4 -- --
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5 -- S Y S T E M . S T R I N G _ C O M P A R E --
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6 -- --
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7 -- B o d y --
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8 -- --
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131
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9 -- Copyright (C) 2002-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 pragma Compiler_Unit_Warning;
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33
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34 with Ada.Unchecked_Conversion;
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35
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36 package body System.String_Compare is
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37
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38 type Word is mod 2 ** 32;
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39 -- Used to process operands by words
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40
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41 type Big_Words is array (Natural) of Word;
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42 type Big_Words_Ptr is access Big_Words;
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43 for Big_Words_Ptr'Storage_Size use 0;
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44 -- Array type used to access by words
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45
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46 type Byte is mod 2 ** 8;
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47 -- Used to process operands by bytes
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48
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49 type Big_Bytes is array (Natural) of Byte;
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50 type Big_Bytes_Ptr is access Big_Bytes;
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51 for Big_Bytes_Ptr'Storage_Size use 0;
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52 -- Array type used to access by bytes
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53
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54 function To_Big_Words is new
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55 Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
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56
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57 function To_Big_Bytes is new
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58 Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
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59
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60 -----------------
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61 -- Str_Compare --
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62 -----------------
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63
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64 function Str_Compare
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65 (Left : System.Address;
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66 Right : System.Address;
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67 Left_Len : Natural;
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68 Right_Len : Natural) return Integer
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69 is
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70 Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
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71
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72 begin
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73 -- If operands are non-aligned, or length is too short, go by bytes
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74
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75 if (((Left or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
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76 return Str_Compare_Bytes (Left, Right, Left_Len, Right_Len);
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77 end if;
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78
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79 -- Here we can go by words
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80
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81 declare
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82 LeftP : constant Big_Words_Ptr := To_Big_Words (Left);
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83 RightP : constant Big_Words_Ptr := To_Big_Words (Right);
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84 Clen4 : constant Natural := Compare_Len / 4 - 1;
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85 Clen4F : constant Natural := Clen4 * 4;
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86
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87 begin
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88 for J in 0 .. Clen4 loop
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89 if LeftP (J) /= RightP (J) then
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90 return Str_Compare_Bytes
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91 (Left + Address (4 * J),
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92 Right + Address (4 * J),
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93 4, 4);
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94 end if;
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95 end loop;
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96
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97 return Str_Compare_Bytes
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98 (Left + Address (Clen4F),
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99 Right + Address (Clen4F),
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100 Left_Len - Clen4F,
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101 Right_Len - Clen4F);
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102 end;
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103 end Str_Compare;
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104
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105 -----------------------
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106 -- Str_Compare_Bytes --
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107 -----------------------
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108
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109 function Str_Compare_Bytes
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110 (Left : System.Address;
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111 Right : System.Address;
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112 Left_Len : Natural;
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113 Right_Len : Natural) return Integer
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114 is
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115 Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
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116
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117 LeftP : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
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118 RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
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119
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120 begin
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121 for J in 0 .. Compare_Len - 1 loop
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122 if LeftP (J) /= RightP (J) then
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123 if LeftP (J) > RightP (J) then
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124 return +1;
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125 else
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126 return -1;
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127 end if;
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128 end if;
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129 end loop;
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130
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131 if Left_Len = Right_Len then
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132 return 0;
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133 elsif Left_Len > Right_Len then
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134 return +1;
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135 else
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136 return -1;
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137 end if;
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138 end Str_Compare_Bytes;
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139
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140 end System.String_Compare;
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