------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- ADA.STRINGS.UTF_ENCODING.STRINGS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2010-2023, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
package body Ada.Strings.UTF_Encoding.Strings is
use Interfaces;
------------
-- Decode --
------------
-- Decode UTF-8/UTF-16BE/UTF-16LE input to String
function Decode
(Item : UTF_String;
Input_Scheme : Encoding_Scheme) return String
is
begin
if Input_Scheme = UTF_8 then
return Decode (Item);
else
return Decode (To_UTF_16 (Item, Input_Scheme));
end if;
end Decode;
-- Decode UTF-8 input to String
function Decode (Item : UTF_8_String) return String is
Result : String (1 .. Item'Length);
-- Result string (worst case is same length as input)
Len : Natural := 0;
-- Length of result stored so far
Iptr : Natural;
-- Input Item pointer
C : Unsigned_8;
R : Unsigned_16;
procedure Get_Continuation;
-- Reads a continuation byte of the form 10xxxxxx, shifts R left
-- by 6 bits, and or's in the xxxxxx to the low order 6 bits. On
-- return Ptr is incremented. Raises exception if continuation
-- byte does not exist or is invalid.
----------------------
-- Get_Continuation --
----------------------
procedure Get_Continuation is
begin
if Iptr > Item'Last then
Raise_Encoding_Error (Iptr - 1);
else
C := To_Unsigned_8 (Item (Iptr));
Iptr := Iptr + 1;
if C not in 2#10_000000# .. 2#10_111111# then
Raise_Encoding_Error (Iptr - 1);
else
R := Shift_Left (R, 6) or Unsigned_16 (C and 2#00_111111#);
end if;
end if;
end Get_Continuation;
-- Start of processing for Decode
begin
Iptr := Item'First;
-- Skip BOM at start
if Item'Length >= 3
and then Item (Iptr .. Iptr + 2) = BOM_8
then
Iptr := Iptr + 3;
-- Error if bad BOM
elsif Item'Length >= 2
and then (Item (Iptr .. Iptr + 1) = BOM_16BE
or else
Item (Iptr .. Iptr + 1) = BOM_16LE)
then
Raise_Encoding_Error (Iptr);
end if;
while Iptr <= Item'Last loop
C := To_Unsigned_8 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#00# - 16#7F# are represented as
-- 0xxxxxxx
if C <= 16#7F# then
R := Unsigned_16 (C);
-- No initial code can be of the form 10xxxxxx. Such codes are used
-- only for continuations.
elsif C <= 2#10_111111# then
Raise_Encoding_Error (Iptr - 1);
-- Codes in the range 16#80# - 16#7FF# are represented as
-- 110yyyxx 10xxxxxx
elsif C <= 2#110_11111# then
R := Unsigned_16 (C and 2#000_11111#);
Get_Continuation;
-- Codes in the range 16#800# - 16#FFFF# are represented as
-- 1110yyyy 10yyyyxx 10xxxxxx
-- Such codes are out of range for type Character
-- Codes in the range 16#10000# - 16#10FFFF# are represented as
-- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
-- Such codes are out of range for Wide_String output
-- Thus all remaining cases raise Encoding_Error
else
Raise_Encoding_Error (Iptr - 1);
end if;
Len := Len + 1;
-- The value may still be out of range of Standard.Character. We make
-- the check explicit because the library is typically compiled with
-- range checks disabled.
if R > Character'Pos (Character'Last) then
Raise_Encoding_Error (Iptr - 1);
end if;
Result (Len) := Character'Val (R);
end loop;
return Result (1 .. Len);
end Decode;
-- Decode UTF-16 input to String
function Decode (Item : UTF_16_Wide_String) return String is
Result : String (1 .. Item'Length);
-- Result is same length as input (possibly minus 1 if BOM present)
Len : Natural := 0;
-- Length of result
Iptr : Natural;
-- Index of next Item element
C : Unsigned_16;
begin
-- Skip UTF-16 BOM at start
Iptr := Item'First;
if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then
Iptr := Iptr + 1;
end if;
-- Loop through input characters
while Iptr <= Item'Last loop
C := To_Unsigned_16 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#0000#..16#00FF# represent their own value
if C <= 16#00FF# then
Len := Len + 1;
Result (Len) := Character'Val (C);
-- All other codes are invalid, either they are invalid UTF-16
-- encoding sequences, or they represent values that are out of
-- range for type Character.
else
Raise_Encoding_Error (Iptr - 1);
end if;
end loop;
return Result (1 .. Len);
end Decode;
------------
-- Encode --
------------
-- Encode String in UTF-8, UTF-16BE or UTF-16LE
function Encode
(Item : String;
Output_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_String
is
begin
-- Case of UTF_8
if Output_Scheme = UTF_8 then
return Encode (Item, Output_BOM);
-- Case of UTF_16LE or UTF_16BE, use UTF-16 intermediary
else
return From_UTF_16 (UTF_16_Wide_String'(Encode (Item)),
Output_Scheme, Output_BOM);
end if;
end Encode;
-- Encode String in UTF-8
function Encode
(Item : String;
Output_BOM : Boolean := False) return UTF_8_String
is
Result : UTF_8_String (1 .. 3 * Item'Length + 3);
-- Worst case is three bytes per input byte + space for BOM
Len : Natural;
-- Number of output codes stored in Result
C : Unsigned_8;
-- Single input character
procedure Store (C : Unsigned_8);
pragma Inline (Store);
-- Store one output code, C is in the range 0 .. 255
-----------
-- Store --
-----------
procedure Store (C : Unsigned_8) is
begin
Len := Len + 1;
Result (Len) := Character'Val (C);
end Store;
-- Start of processing for UTF8_Encode
begin
-- Output BOM if required
if Output_BOM then
Result (1 .. 3) := BOM_8;
Len := 3;
else
Len := 0;
end if;
-- Loop through characters of input
for J in Item'Range loop
C := To_Unsigned_8 (Item (J));
-- Codes in the range 16#00# - 16#7F# are represented as
-- 0xxxxxxx
if C <= 16#7F# then
Store (C);
-- Codes in the range 16#80# - 16#7FF# are represented as
-- 110yyyxx 10xxxxxx
-- For type character of course, the limit is 16#FF# in any case
else
Store (2#110_00000# or Shift_Right (C, 6));
Store (2#10_000000# or (C and 2#00_111111#));
end if;
end loop;
return Result (1 .. Len);
end Encode;
-- Encode String in UTF-16
function Encode
(Item : String;
Output_BOM : Boolean := False) return UTF_16_Wide_String
is
Result : UTF_16_Wide_String
(1 .. Item'Length + Boolean'Pos (Output_BOM));
-- Output is same length as input + possible BOM
Len : Integer;
-- Length of output string
C : Unsigned_8;
begin
-- Output BOM if required
if Output_BOM then
Result (1) := BOM_16 (1);
Len := 1;
else
Len := 0;
end if;
-- Loop through input characters encoding them
for Iptr in Item'Range loop
C := To_Unsigned_8 (Item (Iptr));
-- Codes in the range 16#0000#..16#00FF# are output unchanged. This
-- includes all possible cases of Character values.
Len := Len + 1;
Result (Len) := Wide_Character'Val (C);
end loop;
return Result;
end Encode;
end Ada.Strings.UTF_Encoding.Strings;