1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME COMPONENTS -- 4-- -- 5-- ADA.STRINGS.UTF_ENCODING.STRINGS -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 2010-2013, 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 32package body Ada.Strings.UTF_Encoding.Strings is 33 use Interfaces; 34 35 ------------ 36 -- Decode -- 37 ------------ 38 39 -- Decode UTF-8/UTF-16BE/UTF-16LE input to String 40 41 function Decode 42 (Item : UTF_String; 43 Input_Scheme : Encoding_Scheme) return String 44 is 45 begin 46 if Input_Scheme = UTF_8 then 47 return Decode (Item); 48 else 49 return Decode (To_UTF_16 (Item, Input_Scheme)); 50 end if; 51 end Decode; 52 53 -- Decode UTF-8 input to String 54 55 function Decode (Item : UTF_8_String) return String is 56 Result : String (1 .. Item'Length); 57 -- Result string (worst case is same length as input) 58 59 Len : Natural := 0; 60 -- Length of result stored so far 61 62 Iptr : Natural; 63 -- Input Item pointer 64 65 C : Unsigned_8; 66 R : Unsigned_16; 67 68 procedure Get_Continuation; 69 -- Reads a continuation byte of the form 10xxxxxx, shifts R left 70 -- by 6 bits, and or's in the xxxxxx to the low order 6 bits. On 71 -- return Ptr is incremented. Raises exception if continuation 72 -- byte does not exist or is invalid. 73 74 ---------------------- 75 -- Get_Continuation -- 76 ---------------------- 77 78 procedure Get_Continuation is 79 begin 80 if Iptr > Item'Last then 81 Raise_Encoding_Error (Iptr - 1); 82 83 else 84 C := To_Unsigned_8 (Item (Iptr)); 85 Iptr := Iptr + 1; 86 87 if C not in 2#10_000000# .. 2#10_111111# then 88 Raise_Encoding_Error (Iptr - 1); 89 else 90 R := Shift_Left (R, 6) or Unsigned_16 (C and 2#00_111111#); 91 end if; 92 end if; 93 end Get_Continuation; 94 95 -- Start of processing for Decode 96 97 begin 98 Iptr := Item'First; 99 100 -- Skip BOM at start 101 102 if Item'Length >= 3 103 and then Item (Iptr .. Iptr + 2) = BOM_8 104 then 105 Iptr := Iptr + 3; 106 107 -- Error if bad BOM 108 109 elsif Item'Length >= 2 110 and then (Item (Iptr .. Iptr + 1) = BOM_16BE 111 or else 112 Item (Iptr .. Iptr + 1) = BOM_16LE) 113 then 114 Raise_Encoding_Error (Iptr); 115 end if; 116 117 while Iptr <= Item'Last loop 118 C := To_Unsigned_8 (Item (Iptr)); 119 Iptr := Iptr + 1; 120 121 -- Codes in the range 16#00# - 16#7F# are represented as 122 -- 0xxxxxxx 123 124 if C <= 16#7F# then 125 R := Unsigned_16 (C); 126 127 -- No initial code can be of the form 10xxxxxx. Such codes are used 128 -- only for continuations. 129 130 elsif C <= 2#10_111111# then 131 Raise_Encoding_Error (Iptr - 1); 132 133 -- Codes in the range 16#80# - 16#7FF# are represented as 134 -- 110yyyxx 10xxxxxx 135 136 elsif C <= 2#110_11111# then 137 R := Unsigned_16 (C and 2#000_11111#); 138 Get_Continuation; 139 140 -- Codes in the range 16#800# - 16#FFFF# are represented as 141 -- 1110yyyy 10yyyyxx 10xxxxxx 142 143 -- Such codes are out of range for type Character 144 145 -- Codes in the range 16#10000# - 16#10FFFF# are represented as 146 -- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx 147 148 -- Such codes are out of range for Wide_String output 149 150 -- Thus all remaining cases raise Encoding_Error 151 152 else 153 Raise_Encoding_Error (Iptr - 1); 154 end if; 155 156 Len := Len + 1; 157 158 -- The value may still be out of range of Standard.Character. We make 159 -- the check explicit because the library is typically compiled with 160 -- range checks disabled. 161 162 if R > Character'Pos (Character'Last) then 163 Raise_Encoding_Error (Iptr - 1); 164 end if; 165 166 Result (Len) := Character'Val (R); 167 end loop; 168 169 return Result (1 .. Len); 170 end Decode; 171 172 -- Decode UTF-16 input to String 173 174 function Decode (Item : UTF_16_Wide_String) return String is 175 Result : String (1 .. Item'Length); 176 -- Result is same length as input (possibly minus 1 if BOM present) 177 178 Len : Natural := 0; 179 -- Length of result 180 181 Iptr : Natural; 182 -- Index of next Item element 183 184 C : Unsigned_16; 185 186 begin 187 -- Skip UTF-16 BOM at start 188 189 Iptr := Item'First; 190 191 if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then 192 Iptr := Iptr + 1; 193 end if; 194 195 -- Loop through input characters 196 197 while Iptr <= Item'Last loop 198 C := To_Unsigned_16 (Item (Iptr)); 199 Iptr := Iptr + 1; 200 201 -- Codes in the range 16#0000#..16#00FF# represent their own value 202 203 if C <= 16#00FF# then 204 Len := Len + 1; 205 Result (Len) := Character'Val (C); 206 207 -- All other codes are invalid, either they are invalid UTF-16 208 -- encoding sequences, or they represent values that are out of 209 -- range for type Character. 210 211 else 212 Raise_Encoding_Error (Iptr - 1); 213 end if; 214 end loop; 215 216 return Result (1 .. Len); 217 end Decode; 218 219 ------------ 220 -- Encode -- 221 ------------ 222 223 -- Encode String in UTF-8, UTF-16BE or UTF-16LE 224 225 function Encode 226 (Item : String; 227 Output_Scheme : Encoding_Scheme; 228 Output_BOM : Boolean := False) return UTF_String 229 is 230 begin 231 -- Case of UTF_8 232 233 if Output_Scheme = UTF_8 then 234 return Encode (Item, Output_BOM); 235 236 -- Case of UTF_16LE or UTF_16BE, use UTF-16 intermediary 237 238 else 239 return From_UTF_16 (UTF_16_Wide_String'(Encode (Item)), 240 Output_Scheme, Output_BOM); 241 end if; 242 end Encode; 243 244 -- Encode String in UTF-8 245 246 function Encode 247 (Item : String; 248 Output_BOM : Boolean := False) return UTF_8_String 249 is 250 Result : UTF_8_String (1 .. 3 * Item'Length + 3); 251 -- Worst case is three bytes per input byte + space for BOM 252 253 Len : Natural; 254 -- Number of output codes stored in Result 255 256 C : Unsigned_8; 257 -- Single input character 258 259 procedure Store (C : Unsigned_8); 260 pragma Inline (Store); 261 -- Store one output code, C is in the range 0 .. 255 262 263 ----------- 264 -- Store -- 265 ----------- 266 267 procedure Store (C : Unsigned_8) is 268 begin 269 Len := Len + 1; 270 Result (Len) := Character'Val (C); 271 end Store; 272 273 -- Start of processing for UTF8_Encode 274 275 begin 276 -- Output BOM if required 277 278 if Output_BOM then 279 Result (1 .. 3) := BOM_8; 280 Len := 3; 281 else 282 Len := 0; 283 end if; 284 285 -- Loop through characters of input 286 287 for J in Item'Range loop 288 C := To_Unsigned_8 (Item (J)); 289 290 -- Codes in the range 16#00# - 16#7F# are represented as 291 -- 0xxxxxxx 292 293 if C <= 16#7F# then 294 Store (C); 295 296 -- Codes in the range 16#80# - 16#7FF# are represented as 297 -- 110yyyxx 10xxxxxx 298 299 -- For type character of course, the limit is 16#FF# in any case 300 301 else 302 Store (2#110_00000# or Shift_Right (C, 6)); 303 Store (2#10_000000# or (C and 2#00_111111#)); 304 end if; 305 end loop; 306 307 return Result (1 .. Len); 308 end Encode; 309 310 -- Encode String in UTF-16 311 312 function Encode 313 (Item : String; 314 Output_BOM : Boolean := False) return UTF_16_Wide_String 315 is 316 Result : UTF_16_Wide_String 317 (1 .. Item'Length + Boolean'Pos (Output_BOM)); 318 -- Output is same length as input + possible BOM 319 320 Len : Integer; 321 -- Length of output string 322 323 C : Unsigned_8; 324 325 begin 326 -- Output BOM if required 327 328 if Output_BOM then 329 Result (1) := BOM_16 (1); 330 Len := 1; 331 else 332 Len := 0; 333 end if; 334 335 -- Loop through input characters encoding them 336 337 for Iptr in Item'Range loop 338 C := To_Unsigned_8 (Item (Iptr)); 339 340 -- Codes in the range 16#0000#..16#00FF# are output unchanged. This 341 -- includes all possible cases of Character values. 342 343 Len := Len + 1; 344 Result (Len) := Wide_Character'Val (C); 345 end loop; 346 347 return Result; 348 end Encode; 349 350end Ada.Strings.UTF_Encoding.Strings; 351