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|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- ADA.STRINGS.UTF_ENCODING.WIDE_WIDE_STRINGS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2010-2022, 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.Wide_Wide_Strings is
use Interfaces;
------------
-- Decode --
------------
-- Decode UTF-8/UTF-16BE/UTF-16LE input to Wide_Wide_String
function Decode
(Item : UTF_String;
Input_Scheme : Encoding_Scheme) return Wide_Wide_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 Wide_Wide_String
function Decode (Item : UTF_8_String) return Wide_Wide_String is
Result : Wide_Wide_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 string pointer
C : Unsigned_8;
R : Unsigned_32;
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_32 (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;
-- Loop through input characters
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_32 (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_32 (C and 2#000_11111#);
Get_Continuation;
-- Codes in the range 16#800# - 16#FFFF# are represented as
-- 1110yyyy 10yyyyxx 10xxxxxx
elsif C <= 2#1110_1111# then
R := Unsigned_32 (C and 2#0000_1111#);
Get_Continuation;
Get_Continuation;
-- Codes in the range 16#10000# - 16#10FFFF# are represented as
-- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
elsif C <= 2#11110_111# then
R := Unsigned_32 (C and 2#00000_111#);
Get_Continuation;
Get_Continuation;
Get_Continuation;
-- Any other code is an error
else
Raise_Encoding_Error (Iptr - 1);
end if;
Len := Len + 1;
Result (Len) := Wide_Wide_Character'Val (R);
end loop;
return Result (1 .. Len);
end Decode;
-- Decode UTF-16 input to Wide_Wide_String
function Decode (Item : UTF_16_Wide_String) return Wide_Wide_String is
Result : Wide_Wide_String (1 .. Item'Length);
-- Result cannot be longer than the input string
Len : Natural := 0;
-- Length of result
Iptr : Natural;
-- Pointer to next element in Item
C : Unsigned_16;
R : Unsigned_32;
begin
-- Skip UTF-16 BOM at start
Iptr := Item'First;
if Iptr <= Item'Last 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#D7FF# or 16#E000#..16#FFFD#
-- represent their own value.
if C <= 16#D7FF# or else C in 16#E000# .. 16#FFFD# then
Len := Len + 1;
Result (Len) := Wide_Wide_Character'Val (C);
-- Codes in the range 16#D800#..16#DBFF# represent the first of the
-- two surrogates used to encode the range 16#01_000#..16#10_FFFF".
-- The first surrogate provides 10 high order bits of the result.
elsif C <= 16#DBFF# then
R := Shift_Left ((Unsigned_32 (C) - 16#D800#), 10);
-- Error if at end of string
if Iptr > Item'Last then
Raise_Encoding_Error (Iptr - 1);
-- Otherwise next character must be valid low order surrogate
-- which provides the low 10 order bits of the result.
else
C := To_Unsigned_16 (Item (Iptr));
Iptr := Iptr + 1;
if C not in 16#DC00# .. 16#DFFF# then
Raise_Encoding_Error (Iptr - 1);
else
R := R or (Unsigned_32 (C) mod 2 ** 10);
-- The final adjustment is to add 16#01_0000 to get the
-- result back in the required 21 bit range.
R := R + 16#01_0000#;
Len := Len + 1;
Result (Len) := Wide_Wide_Character'Val (R);
end if;
end if;
-- Remaining codes are invalid
else
Raise_Encoding_Error (Iptr - 1);
end if;
end loop;
return Result (1 .. Len);
end Decode;
------------
-- Encode --
------------
-- Encode Wide_Wide_String in UTF-8, UTF-16BE or UTF-16LE
function Encode
(Item : Wide_Wide_String;
Output_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_String
is
begin
if Output_Scheme = UTF_8 then
return Encode (Item, Output_BOM);
else
return From_UTF_16 (Encode (Item), Output_Scheme, Output_BOM);
end if;
end Encode;
-- Encode Wide_Wide_String in UTF-8
function Encode
(Item : Wide_Wide_String;
Output_BOM : Boolean := False) return UTF_8_String
is
Result : String (1 .. 4 * Item'Length + 3);
-- Worst case is four bytes per input byte + space for BOM
Len : Natural;
-- Number of output codes stored in Result
C : Unsigned_32;
-- Single input character
procedure Store (C : Unsigned_32);
pragma Inline (Store);
-- Store one output code (input is in range 0 .. 255)
-----------
-- Store --
-----------
procedure Store (C : Unsigned_32) is
begin
Len := Len + 1;
Result (Len) := Character'Val (C);
end Store;
-- Start of processing for 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 Iptr in Item'Range loop
C := To_Unsigned_32 (Item (Iptr));
-- 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
elsif C <= 16#7FF# then
Store (2#110_00000# or Shift_Right (C, 6));
Store (2#10_000000# or (C and 2#00_111111#));
-- Codes in the range 16#800#..16#D7FF# or 16#E000#..16#FFFD# are
-- represented as
-- 1110yyyy 10yyyyxx 10xxxxxx
elsif C <= 16#D7FF# or else C in 16#E000# .. 16#FFFD# then
Store (2#1110_0000# or Shift_Right (C, 12));
Store (2#10_000000# or
Shift_Right (C and 2#111111_000000#, 6));
Store (2#10_000000# or (C and 2#00_111111#));
-- Codes in the range 16#10000# - 16#10FFFF# are represented as
-- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
elsif C in 16#1_0000# .. 16#10_FFFF# then
Store (2#11110_000# or
Shift_Right (C, 18));
Store (2#10_000000# or
Shift_Right (C and 2#111111_000000_000000#, 12));
Store (2#10_000000# or
Shift_Right (C and 2#111111_000000#, 6));
Store (2#10_000000# or
(C and 2#00_111111#));
-- All other codes are invalid
else
Raise_Encoding_Error (Iptr);
end if;
end loop;
return Result (1 .. Len);
end Encode;
-- Encode Wide_Wide_String in UTF-16
function Encode
(Item : Wide_Wide_String;
Output_BOM : Boolean := False) return UTF_16_Wide_String
is
Result : UTF_16_Wide_String (1 .. 2 * Item'Length + 1);
-- Worst case is each input character generates two output characters
-- plus one for possible BOM.
Len : Integer;
-- Length of output string
C : Unsigned_32;
begin
-- Output BOM if needed
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_32 (Item (Iptr));
-- Codes in the range 16#00_0000#..16#00_D7FF# or 16#E000#..16#FFFD#
-- are output unchanged
if C <= 16#00_D7FF# or else C in 16#E000# .. 16#FFFD# then
Len := Len + 1;
Result (Len) := Wide_Character'Val (C);
-- Codes in the range 16#01_0000#..16#10_FFFF# are output using two
-- surrogate characters. First 16#1_0000# is subtracted from the code
-- point to give a 20-bit value. This is then split into two separate
-- 10-bit values each of which is represented as a surrogate with the
-- most significant half placed in the first surrogate. The ranges of
-- values used for the two surrogates are 16#D800#-16#DBFF# for the
-- first, most significant surrogate and 16#DC00#-16#DFFF# for the
-- second, least significant surrogate.
elsif C in 16#1_0000# .. 16#10_FFFF# then
C := C - 16#1_0000#;
Len := Len + 1;
Result (Len) := Wide_Character'Val (16#D800# + C / 2 ** 10);
Len := Len + 1;
Result (Len) := Wide_Character'Val (16#DC00# + C mod 2 ** 10);
-- All other codes are invalid
else
Raise_Encoding_Error (Iptr);
end if;
end loop;
return Result (1 .. Len);
end Encode;
end Ada.Strings.UTF_Encoding.Wide_Wide_Strings;
|
