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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.CONVERSIONS --
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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.Conversions is
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33 use Interfaces;
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34
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35 -- Convert from UTF-8/UTF-16BE/LE to UTF-8/UTF-16BE/LE
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36
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37 function Convert
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38 (Item : UTF_String;
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39 Input_Scheme : Encoding_Scheme;
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40 Output_Scheme : Encoding_Scheme;
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41 Output_BOM : Boolean := False) return UTF_String
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42 is
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43 begin
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44 -- Nothing to do if identical schemes, but for UTF_8 we need to
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45 -- handle overlong encodings, so need to do the full conversion.
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46
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47 if Input_Scheme = Output_Scheme
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48 and then Input_Scheme /= UTF_8
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49 then
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50 return Item;
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51
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52 -- For remaining cases, one or other of the operands is UTF-16BE/LE
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53 -- encoded, or we have the UTF-8 to UTF-8 case where we must handle
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54 -- overlong encodings. In all cases, go through UTF-16 intermediate.
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55
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56 else
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57 return Convert (UTF_16_Wide_String'(Convert (Item, Input_Scheme)),
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58 Output_Scheme, Output_BOM);
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59 end if;
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60 end Convert;
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61
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62 -- Convert from UTF-8/UTF-16BE/LE to UTF-16
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63
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64 function Convert
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65 (Item : UTF_String;
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66 Input_Scheme : Encoding_Scheme;
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67 Output_BOM : Boolean := False) return UTF_16_Wide_String
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68 is
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69 begin
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70 if Input_Scheme = UTF_8 then
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71 return Convert (Item, Output_BOM);
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72 else
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73 return To_UTF_16 (Item, Input_Scheme, Output_BOM);
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74 end if;
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75 end Convert;
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76
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77 -- Convert from UTF-8 to UTF-16
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78
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79 function Convert
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80 (Item : UTF_8_String;
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81 Output_BOM : Boolean := False) return UTF_16_Wide_String
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82 is
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83 Result : UTF_16_Wide_String (1 .. Item'Length + 1);
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84 -- Maximum length of result, including possible BOM
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85
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86 Len : Natural := 0;
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87 -- Number of characters stored so far in Result
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88
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89 Iptr : Natural;
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90 -- Next character to process in Item
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91
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92 C : Unsigned_8;
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93 -- Input UTF-8 code
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94
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95 R : Unsigned_16;
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96 -- Output UTF-16 code
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97
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98 procedure Get_Continuation;
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99 -- Reads a continuation byte of the form 10xxxxxx, shifts R left by 6
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100 -- bits, and or's in the xxxxxx to the low order 6 bits. On return Ptr
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101 -- is incremented. Raises exception if continuation byte does not exist
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102 -- or is invalid.
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103
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104 ----------------------
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105 -- Get_Continuation --
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106 ----------------------
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107
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108 procedure Get_Continuation is
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109 begin
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110 if Iptr > Item'Last then
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111 Raise_Encoding_Error (Iptr - 1);
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112
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113 else
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114 C := To_Unsigned_8 (Item (Iptr));
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115 Iptr := Iptr + 1;
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116
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117 if C < 2#10_000000# or else C > 2#10_111111# then
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118 Raise_Encoding_Error (Iptr - 1);
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119
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120 else
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121 R :=
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122 Shift_Left (R, 6) or Unsigned_16 (C and 2#00_111111#);
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123 end if;
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124 end if;
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125 end Get_Continuation;
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126
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127 -- Start of processing for Convert
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128
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129 begin
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130 -- Output BOM if required
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131
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132 if Output_BOM then
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133 Len := Len + 1;
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134 Result (Len) := BOM_16 (1);
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135 end if;
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136
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137 -- Skip OK BOM
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138
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139 Iptr := Item'First;
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140
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141 if Item'Length >= 3 and then Item (Iptr .. Iptr + 2) = BOM_8 then
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142 Iptr := Iptr + 3;
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143
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144 -- Error if bad BOM
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145
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146 elsif Item'Length >= 2
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147 and then (Item (Iptr .. Iptr + 1) = BOM_16BE
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148 or else
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149 Item (Iptr .. Iptr + 1) = BOM_16LE)
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150 then
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151 Raise_Encoding_Error (Iptr);
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152
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153 -- No BOM present
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154
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155 else
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156 Iptr := Item'First;
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157 end if;
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158
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159 while Iptr <= Item'Last loop
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160 C := To_Unsigned_8 (Item (Iptr));
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161 Iptr := Iptr + 1;
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162
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163 -- Codes in the range 16#00# .. 16#7F#
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164 -- UTF-8: 0xxxxxxx
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165 -- UTF-16: 00000000_0xxxxxxx
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166
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167 if C <= 16#7F# then
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168 Len := Len + 1;
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169 Result (Len) := Wide_Character'Val (C);
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170
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171 -- No initial code can be of the form 10xxxxxx. Such codes are used
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172 -- only for continuations.
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173
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174 elsif C <= 2#10_111111# then
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175 Raise_Encoding_Error (Iptr - 1);
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176
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177 -- Codes in the range 16#80# .. 16#7FF#
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178 -- UTF-8: 110yyyxx 10xxxxxx
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179 -- UTF-16: 00000yyy_xxxxxxxx
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180
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181 elsif C <= 2#110_11111# then
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182 R := Unsigned_16 (C and 2#000_11111#);
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183 Get_Continuation;
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184 Len := Len + 1;
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185 Result (Len) := Wide_Character'Val (R);
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186
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187 -- Codes in the range 16#800# .. 16#D7FF or 16#DF01# .. 16#FFFF#
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188 -- UTF-8: 1110yyyy 10yyyyxx 10xxxxxx
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189 -- UTF-16: yyyyyyyy_xxxxxxxx
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190
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191 elsif C <= 2#1110_1111# then
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192 R := Unsigned_16 (C and 2#0000_1111#);
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193 Get_Continuation;
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194 Get_Continuation;
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195 Len := Len + 1;
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196 Result (Len) := Wide_Character'Val (R);
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197
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198 -- Make sure that we don't have a result in the forbidden range
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199 -- reserved for UTF-16 surrogate characters.
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200
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201 if R in 16#D800# .. 16#DF00# then
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202 Raise_Encoding_Error (Iptr - 3);
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203 end if;
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204
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205 -- Codes in the range 16#10000# .. 16#10FFFF#
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206 -- UTF-8: 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
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207 -- UTF-16: 110110zz_zzyyyyyy 110111yy_xxxxxxxx
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208 -- Note: zzzz in the output is input zzzzz - 1
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209
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210 elsif C <= 2#11110_111# then
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211 R := Unsigned_16 (C and 2#00000_111#);
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212 Get_Continuation;
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213
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214 -- R now has zzzzzyyyy
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215
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216 -- At this stage, we check for the case where we have an overlong
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217 -- encoding, and the encoded value in fact lies in the single word
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218 -- range (16#800# .. 16#D7FF or 16#DF01# .. 16#FFFF#). This means
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219 -- that the result fits in a single result word.
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220
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221 if R <= 2#1111# then
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222 Get_Continuation;
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223 Get_Continuation;
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224
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225 -- Make sure we are not in the forbidden surrogate range
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226
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227 if R in 16#D800# .. 16#DF00# then
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228 Raise_Encoding_Error (Iptr - 3);
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229 end if;
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230
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231 -- Otherwise output a single UTF-16 value
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232
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233 Len := Len + 1;
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234 Result (Len) := Wide_Character'Val (R);
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235
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236 -- Here for normal case (code value > 16#FFFF and zzzzz non-zero)
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237
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238 else
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239 -- Subtract 1 from input zzzzz value to get output zzzz value
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240
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241 R := R - 2#0000_1_0000#;
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242
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243 -- R now has zzzzyyyy (zzzz minus one for the output)
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244
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245 Get_Continuation;
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246
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247 -- R now has zzzzyy_yyyyyyxx
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248
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249 Len := Len + 1;
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250 Result (Len) :=
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251 Wide_Character'Val
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252 (2#110110_00_0000_0000# or Shift_Right (R, 4));
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253
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254 R := R and 2#1111#;
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255 Get_Continuation;
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256 Len := Len + 1;
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257 Result (Len) :=
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258 Wide_Character'Val (2#110111_00_0000_0000# or R);
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259 end if;
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260
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261 -- Any other code is an error
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262
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263 else
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264 Raise_Encoding_Error (Iptr - 1);
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265 end if;
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266 end loop;
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267
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268 return Result (1 .. Len);
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269 end Convert;
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270
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271 -- Convert from UTF-16 to UTF-8/UTF-16-BE/LE
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272
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273 function Convert
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274 (Item : UTF_16_Wide_String;
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275 Output_Scheme : Encoding_Scheme;
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276 Output_BOM : Boolean := False) return UTF_String
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277 is
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278 begin
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279 if Output_Scheme = UTF_8 then
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280 return Convert (Item, Output_BOM);
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281 else
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282 return From_UTF_16 (Item, Output_Scheme, Output_BOM);
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283 end if;
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284 end Convert;
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285
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286 -- Convert from UTF-16 to UTF-8
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287
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288 function Convert
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289 (Item : UTF_16_Wide_String;
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290 Output_BOM : Boolean := False) return UTF_8_String
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291 is
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292 Result : UTF_8_String (1 .. 3 * Item'Length + 3);
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293 -- Worst case is 3 output codes for each input code + BOM space
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294
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295 Len : Natural;
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296 -- Number of result codes stored
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297
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298 Iptr : Natural;
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299 -- Pointer to next input character
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300
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301 C1, C2 : Unsigned_16;
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302
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303 zzzzz : Unsigned_16;
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304 yyyyyyyy : Unsigned_16;
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305 xxxxxxxx : Unsigned_16;
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306 -- Components of double length case
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307
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308 begin
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309 Iptr := Item'First;
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310
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311 -- Skip BOM at start of input
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312
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313 if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then
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314 Iptr := Iptr + 1;
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315 end if;
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316
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317 -- Generate output BOM if required
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318
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319 if Output_BOM then
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320 Result (1 .. 3) := BOM_8;
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321 Len := 3;
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322 else
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323 Len := 0;
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324 end if;
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325
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326 -- Loop through input
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327
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328 while Iptr <= Item'Last loop
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329 C1 := To_Unsigned_16 (Item (Iptr));
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330 Iptr := Iptr + 1;
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331
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332 -- Codes in the range 16#0000# - 16#007F#
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333 -- UTF-16: 000000000xxxxxxx
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334 -- UTF-8: 0xxxxxxx
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335
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336 if C1 <= 16#007F# then
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337 Result (Len + 1) := Character'Val (C1);
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338 Len := Len + 1;
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339
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340 -- Codes in the range 16#80# - 16#7FF#
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341 -- UTF-16: 00000yyyxxxxxxxx
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342 -- UTF-8: 110yyyxx 10xxxxxx
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343
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344 elsif C1 <= 16#07FF# then
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345 Result (Len + 1) :=
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346 Character'Val
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347 (2#110_00000# or Shift_Right (C1, 6));
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348 Result (Len + 2) :=
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349 Character'Val
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350 (2#10_000000# or (C1 and 2#00_111111#));
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351 Len := Len + 2;
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352
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353 -- Codes in the range 16#800# - 16#D7FF# or 16#E000# - 16#FFFF#
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354 -- UTF-16: yyyyyyyyxxxxxxxx
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355 -- UTF-8: 1110yyyy 10yyyyxx 10xxxxxx
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356
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357 elsif C1 <= 16#D7FF# or else C1 >= 16#E000# then
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358 Result (Len + 1) :=
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359 Character'Val
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360 (2#1110_0000# or Shift_Right (C1, 12));
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361 Result (Len + 2) :=
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362 Character'Val
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363 (2#10_000000# or (Shift_Right (C1, 6) and 2#00_111111#));
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364 Result (Len + 3) :=
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365 Character'Val
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366 (2#10_000000# or (C1 and 2#00_111111#));
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367 Len := Len + 3;
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368
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369 -- Codes in the range 16#10000# - 16#10FFFF#
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370 -- UTF-16: 110110zzzzyyyyyy 110111yyxxxxxxxx
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371 -- UTF-8: 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
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372 -- Note: zzzzz in the output is input zzzz + 1
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373
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374 elsif C1 <= 2#110110_11_11111111# then
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375 if Iptr > Item'Last then
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376 Raise_Encoding_Error (Iptr - 1);
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377 else
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378 C2 := To_Unsigned_16 (Item (Iptr));
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379 Iptr := Iptr + 1;
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380 end if;
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381
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382 if (C2 and 2#111111_00_00000000#) /= 2#110111_00_00000000# then
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383 Raise_Encoding_Error (Iptr - 1);
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384 end if;
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385
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386 zzzzz := (Shift_Right (C1, 6) and 2#1111#) + 1;
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387 yyyyyyyy := ((Shift_Left (C1, 2) and 2#111111_00#)
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388 or
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389 (Shift_Right (C2, 8) and 2#000000_11#));
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390 xxxxxxxx := C2 and 2#11111111#;
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391
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392 Result (Len + 1) :=
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393 Character'Val
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394 (2#11110_000# or (Shift_Right (zzzzz, 2)));
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395 Result (Len + 2) :=
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396 Character'Val
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397 (2#10_000000# or Shift_Left (zzzzz and 2#11#, 4)
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398 or Shift_Right (yyyyyyyy, 4));
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399 Result (Len + 3) :=
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400 Character'Val
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401 (2#10_000000# or Shift_Left (yyyyyyyy and 2#1111#, 4)
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402 or Shift_Right (xxxxxxxx, 6));
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403 Result (Len + 4) :=
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404 Character'Val
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405 (2#10_000000# or (xxxxxxxx and 2#00_111111#));
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406 Len := Len + 4;
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407
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408 -- Error if input in 16#DC00# - 16#DFFF# (2nd surrogate with no 1st)
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409
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410 else
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411 Raise_Encoding_Error (Iptr - 2);
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412 end if;
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413 end loop;
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414
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415 return Result (1 .. Len);
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416 end Convert;
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417
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418 end Ada.Strings.UTF_Encoding.Conversions;
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