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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- ADA.STRINGS.UTF_ENCODING.STRINGS --
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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) 2010-2018, 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 package body Ada.Strings.UTF_Encoding.Strings is
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33 use Interfaces;
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34
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35 ------------
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36 -- Decode --
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37 ------------
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38
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39 -- Decode UTF-8/UTF-16BE/UTF-16LE input to String
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40
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41 function Decode
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42 (Item : UTF_String;
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43 Input_Scheme : Encoding_Scheme) return String
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44 is
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45 begin
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46 if Input_Scheme = UTF_8 then
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47 return Decode (Item);
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48 else
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49 return Decode (To_UTF_16 (Item, Input_Scheme));
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50 end if;
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51 end Decode;
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52
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53 -- Decode UTF-8 input to String
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54
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55 function Decode (Item : UTF_8_String) return String is
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56 Result : String (1 .. Item'Length);
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57 -- Result string (worst case is same length as input)
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58
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59 Len : Natural := 0;
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60 -- Length of result stored so far
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61
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62 Iptr : Natural;
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63 -- Input Item pointer
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64
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65 C : Unsigned_8;
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66 R : Unsigned_16;
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67
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68 procedure Get_Continuation;
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69 -- Reads a continuation byte of the form 10xxxxxx, shifts R left
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70 -- by 6 bits, and or's in the xxxxxx to the low order 6 bits. On
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71 -- return Ptr is incremented. Raises exception if continuation
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72 -- byte does not exist or is invalid.
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73
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74 ----------------------
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75 -- Get_Continuation --
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76 ----------------------
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77
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78 procedure Get_Continuation is
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79 begin
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80 if Iptr > Item'Last then
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81 Raise_Encoding_Error (Iptr - 1);
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82
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83 else
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84 C := To_Unsigned_8 (Item (Iptr));
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85 Iptr := Iptr + 1;
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86
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87 if C not in 2#10_000000# .. 2#10_111111# then
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88 Raise_Encoding_Error (Iptr - 1);
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89 else
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90 R := Shift_Left (R, 6) or Unsigned_16 (C and 2#00_111111#);
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91 end if;
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92 end if;
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93 end Get_Continuation;
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94
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95 -- Start of processing for Decode
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96
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97 begin
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98 Iptr := Item'First;
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99
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100 -- Skip BOM at start
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101
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102 if Item'Length >= 3
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103 and then Item (Iptr .. Iptr + 2) = BOM_8
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104 then
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105 Iptr := Iptr + 3;
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106
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107 -- Error if bad BOM
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108
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109 elsif Item'Length >= 2
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110 and then (Item (Iptr .. Iptr + 1) = BOM_16BE
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111 or else
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112 Item (Iptr .. Iptr + 1) = BOM_16LE)
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113 then
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114 Raise_Encoding_Error (Iptr);
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115 end if;
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116
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117 while Iptr <= Item'Last loop
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118 C := To_Unsigned_8 (Item (Iptr));
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119 Iptr := Iptr + 1;
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120
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121 -- Codes in the range 16#00# - 16#7F# are represented as
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122 -- 0xxxxxxx
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123
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124 if C <= 16#7F# then
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125 R := Unsigned_16 (C);
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126
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127 -- No initial code can be of the form 10xxxxxx. Such codes are used
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128 -- only for continuations.
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129
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130 elsif C <= 2#10_111111# then
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131 Raise_Encoding_Error (Iptr - 1);
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132
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133 -- Codes in the range 16#80# - 16#7FF# are represented as
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134 -- 110yyyxx 10xxxxxx
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135
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136 elsif C <= 2#110_11111# then
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137 R := Unsigned_16 (C and 2#000_11111#);
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138 Get_Continuation;
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139
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140 -- Codes in the range 16#800# - 16#FFFF# are represented as
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141 -- 1110yyyy 10yyyyxx 10xxxxxx
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142
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143 -- Such codes are out of range for type Character
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144
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145 -- Codes in the range 16#10000# - 16#10FFFF# are represented as
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146 -- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
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147
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148 -- Such codes are out of range for Wide_String output
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149
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150 -- Thus all remaining cases raise Encoding_Error
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151
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152 else
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153 Raise_Encoding_Error (Iptr - 1);
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154 end if;
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155
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156 Len := Len + 1;
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157
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158 -- The value may still be out of range of Standard.Character. We make
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159 -- the check explicit because the library is typically compiled with
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160 -- range checks disabled.
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161
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162 if R > Character'Pos (Character'Last) then
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163 Raise_Encoding_Error (Iptr - 1);
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164 end if;
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165
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166 Result (Len) := Character'Val (R);
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167 end loop;
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168
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169 return Result (1 .. Len);
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170 end Decode;
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171
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172 -- Decode UTF-16 input to String
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173
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174 function Decode (Item : UTF_16_Wide_String) return String is
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175 Result : String (1 .. Item'Length);
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176 -- Result is same length as input (possibly minus 1 if BOM present)
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177
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178 Len : Natural := 0;
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179 -- Length of result
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180
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181 Iptr : Natural;
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182 -- Index of next Item element
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183
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184 C : Unsigned_16;
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185
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186 begin
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187 -- Skip UTF-16 BOM at start
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188
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189 Iptr := Item'First;
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190
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191 if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then
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192 Iptr := Iptr + 1;
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193 end if;
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194
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195 -- Loop through input characters
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196
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197 while Iptr <= Item'Last loop
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198 C := To_Unsigned_16 (Item (Iptr));
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199 Iptr := Iptr + 1;
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200
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201 -- Codes in the range 16#0000#..16#00FF# represent their own value
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202
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203 if C <= 16#00FF# then
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204 Len := Len + 1;
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205 Result (Len) := Character'Val (C);
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206
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207 -- All other codes are invalid, either they are invalid UTF-16
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208 -- encoding sequences, or they represent values that are out of
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209 -- range for type Character.
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210
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211 else
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212 Raise_Encoding_Error (Iptr - 1);
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213 end if;
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214 end loop;
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215
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216 return Result (1 .. Len);
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217 end Decode;
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218
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219 ------------
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220 -- Encode --
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221 ------------
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222
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223 -- Encode String in UTF-8, UTF-16BE or UTF-16LE
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224
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225 function Encode
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226 (Item : String;
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227 Output_Scheme : Encoding_Scheme;
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228 Output_BOM : Boolean := False) return UTF_String
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229 is
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230 begin
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231 -- Case of UTF_8
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232
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233 if Output_Scheme = UTF_8 then
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234 return Encode (Item, Output_BOM);
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235
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236 -- Case of UTF_16LE or UTF_16BE, use UTF-16 intermediary
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237
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238 else
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239 return From_UTF_16 (UTF_16_Wide_String'(Encode (Item)),
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240 Output_Scheme, Output_BOM);
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241 end if;
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242 end Encode;
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243
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244 -- Encode String in UTF-8
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245
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246 function Encode
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247 (Item : String;
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248 Output_BOM : Boolean := False) return UTF_8_String
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249 is
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250 Result : UTF_8_String (1 .. 3 * Item'Length + 3);
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251 -- Worst case is three bytes per input byte + space for BOM
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252
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253 Len : Natural;
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254 -- Number of output codes stored in Result
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255
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256 C : Unsigned_8;
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257 -- Single input character
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258
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259 procedure Store (C : Unsigned_8);
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260 pragma Inline (Store);
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261 -- Store one output code, C is in the range 0 .. 255
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262
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263 -----------
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264 -- Store --
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265 -----------
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266
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267 procedure Store (C : Unsigned_8) is
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268 begin
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269 Len := Len + 1;
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270 Result (Len) := Character'Val (C);
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271 end Store;
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272
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273 -- Start of processing for UTF8_Encode
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274
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275 begin
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276 -- Output BOM if required
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277
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278 if Output_BOM then
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279 Result (1 .. 3) := BOM_8;
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280 Len := 3;
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281 else
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282 Len := 0;
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283 end if;
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284
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285 -- Loop through characters of input
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286
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287 for J in Item'Range loop
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288 C := To_Unsigned_8 (Item (J));
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289
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290 -- Codes in the range 16#00# - 16#7F# are represented as
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291 -- 0xxxxxxx
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292
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293 if C <= 16#7F# then
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294 Store (C);
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295
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296 -- Codes in the range 16#80# - 16#7FF# are represented as
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297 -- 110yyyxx 10xxxxxx
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298
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299 -- For type character of course, the limit is 16#FF# in any case
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300
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301 else
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302 Store (2#110_00000# or Shift_Right (C, 6));
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303 Store (2#10_000000# or (C and 2#00_111111#));
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304 end if;
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305 end loop;
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306
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307 return Result (1 .. Len);
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308 end Encode;
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309
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310 -- Encode String in UTF-16
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311
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312 function Encode
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313 (Item : String;
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314 Output_BOM : Boolean := False) return UTF_16_Wide_String
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315 is
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316 Result : UTF_16_Wide_String
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317 (1 .. Item'Length + Boolean'Pos (Output_BOM));
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318 -- Output is same length as input + possible BOM
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319
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320 Len : Integer;
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321 -- Length of output string
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322
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323 C : Unsigned_8;
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324
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325 begin
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326 -- Output BOM if required
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327
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328 if Output_BOM then
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329 Result (1) := BOM_16 (1);
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330 Len := 1;
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331 else
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332 Len := 0;
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333 end if;
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334
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335 -- Loop through input characters encoding them
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336
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337 for Iptr in Item'Range loop
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338 C := To_Unsigned_8 (Item (Iptr));
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339
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340 -- Codes in the range 16#0000#..16#00FF# are output unchanged. This
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341 -- includes all possible cases of Character values.
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342
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343 Len := Len + 1;
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344 Result (Len) := Wide_Character'Val (C);
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345 end loop;
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346
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347 return Result;
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348 end Encode;
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349
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350 end Ada.Strings.UTF_Encoding.Strings;
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