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|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- ADA.STRINGS.UTF_ENCODING.CONVERSIONS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2010-2014, 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.Conversions is
use Interfaces;
-- Convert from UTF-8/UTF-16BE/LE to UTF-8/UTF-16BE/LE
function Convert
(Item : UTF_String;
Input_Scheme : Encoding_Scheme;
Output_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_String
is
begin
-- Nothing to do if identical schemes, but for UTF_8 we need to
-- handle overlong encodings, so need to do the full conversion.
if Input_Scheme = Output_Scheme
and then Input_Scheme /= UTF_8
then
return Item;
-- For remaining cases, one or other of the operands is UTF-16BE/LE
-- encoded, or we have the UTF-8 to UTF-8 case where we must handle
-- overlong encodings. In all cases, go through UTF-16 intermediate.
else
return Convert (UTF_16_Wide_String'(Convert (Item, Input_Scheme)),
Output_Scheme, Output_BOM);
end if;
end Convert;
-- Convert from UTF-8/UTF-16BE/LE to UTF-16
function Convert
(Item : UTF_String;
Input_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_16_Wide_String
is
begin
if Input_Scheme = UTF_8 then
return Convert (Item, Output_BOM);
else
return To_UTF_16 (Item, Input_Scheme, Output_BOM);
end if;
end Convert;
-- Convert from UTF-8 to UTF-16
function Convert
(Item : UTF_8_String;
Output_BOM : Boolean := False) return UTF_16_Wide_String
is
Result : UTF_16_Wide_String (1 .. Item'Length + 1);
-- Maximum length of result, including possible BOM
Len : Natural := 0;
-- Number of characters stored so far in Result
Iptr : Natural;
-- Next character to process in Item
C : Unsigned_8;
-- Input UTF-8 code
R : Unsigned_16;
-- Output UTF-16 code
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 < 2#10_000000# or else C > 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 Convert
begin
-- Output BOM if required
if Output_BOM then
Len := Len + 1;
Result (Len) := BOM_16 (1);
end if;
-- Skip OK BOM
Iptr := Item'First;
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);
-- No BOM present
else
Iptr := Item'First;
end if;
while Iptr <= Item'Last loop
C := To_Unsigned_8 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#00# .. 16#7F#
-- UTF-8: 0xxxxxxx
-- UTF-16: 00000000_0xxxxxxx
if C <= 16#7F# then
Len := Len + 1;
Result (Len) := Wide_Character'Val (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#
-- UTF-8: 110yyyxx 10xxxxxx
-- UTF-16: 00000yyy_xxxxxxxx
elsif C <= 2#110_11111# then
R := Unsigned_16 (C and 2#000_11111#);
Get_Continuation;
Len := Len + 1;
Result (Len) := Wide_Character'Val (R);
-- Codes in the range 16#800# .. 16#D7FF or 16#DF01# .. 16#FFFF#
-- UTF-8: 1110yyyy 10yyyyxx 10xxxxxx
-- UTF-16: yyyyyyyy_xxxxxxxx
elsif C <= 2#1110_1111# then
R := Unsigned_16 (C and 2#0000_1111#);
Get_Continuation;
Get_Continuation;
Len := Len + 1;
Result (Len) := Wide_Character'Val (R);
-- Make sure that we don't have a result in the forbidden range
-- reserved for UTF-16 surrogate characters.
if R in 16#D800# .. 16#DF00# then
Raise_Encoding_Error (Iptr - 3);
end if;
-- Codes in the range 16#10000# .. 16#10FFFF#
-- UTF-8: 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
-- UTF-16: 110110zz_zzyyyyyy 110111yy_xxxxxxxx
-- Note: zzzz in the output is input zzzzz - 1
elsif C <= 2#11110_111# then
R := Unsigned_16 (C and 2#00000_111#);
Get_Continuation;
-- R now has zzzzzyyyy
-- At this stage, we check for the case where we have an overlong
-- encoding, and the encoded value in fact lies in the single word
-- range (16#800# .. 16#D7FF or 16#DF01# .. 16#FFFF#). This means
-- that the result fits in a single result word.
if R <= 2#1111# then
Get_Continuation;
Get_Continuation;
-- Make sure we are not in the forbidden surrogate range
if R in 16#D800# .. 16#DF00# then
Raise_Encoding_Error (Iptr - 3);
end if;
-- Otherwise output a single UTF-16 value
Len := Len + 1;
Result (Len) := Wide_Character'Val (R);
-- Here for normal case (code value > 16#FFFF and zzzzz non-zero)
else
-- Subtract 1 from input zzzzz value to get output zzzz value
R := R - 2#0000_1_0000#;
-- R now has zzzzyyyy (zzzz minus one for the output)
Get_Continuation;
-- R now has zzzzyy_yyyyyyxx
Len := Len + 1;
Result (Len) :=
Wide_Character'Val
(2#110110_00_0000_0000# or Shift_Right (R, 4));
R := R and 2#1111#;
Get_Continuation;
Len := Len + 1;
Result (Len) :=
Wide_Character'Val (2#110111_00_0000_0000# or R);
end if;
-- Any other code is an error
else
Raise_Encoding_Error (Iptr - 1);
end if;
end loop;
return Result (1 .. Len);
end Convert;
-- Convert from UTF-16 to UTF-8/UTF-16-BE/LE
function Convert
(Item : UTF_16_Wide_String;
Output_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_String
is
begin
if Output_Scheme = UTF_8 then
return Convert (Item, Output_BOM);
else
return From_UTF_16 (Item, Output_Scheme, Output_BOM);
end if;
end Convert;
-- Convert from UTF-16 to UTF-8
function Convert
(Item : UTF_16_Wide_String;
Output_BOM : Boolean := False) return UTF_8_String
is
Result : UTF_8_String (1 .. 3 * Item'Length + 3);
-- Worst case is 3 output codes for each input code + BOM space
Len : Natural;
-- Number of result codes stored
Iptr : Natural;
-- Pointer to next input character
C1, C2 : Unsigned_16;
zzzzz : Unsigned_16;
yyyyyyyy : Unsigned_16;
xxxxxxxx : Unsigned_16;
-- Components of double length case
begin
Iptr := Item'First;
-- Skip BOM at start of input
if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then
Iptr := Iptr + 1;
end if;
-- Generate output BOM if required
if Output_BOM then
Result (1 .. 3) := BOM_8;
Len := 3;
else
Len := 0;
end if;
-- Loop through input
while Iptr <= Item'Last loop
C1 := To_Unsigned_16 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#0000# - 16#007F#
-- UTF-16: 000000000xxxxxxx
-- UTF-8: 0xxxxxxx
if C1 <= 16#007F# then
Result (Len + 1) := Character'Val (C1);
Len := Len + 1;
-- Codes in the range 16#80# - 16#7FF#
-- UTF-16: 00000yyyxxxxxxxx
-- UTF-8: 110yyyxx 10xxxxxx
elsif C1 <= 16#07FF# then
Result (Len + 1) :=
Character'Val
(2#110_00000# or Shift_Right (C1, 6));
Result (Len + 2) :=
Character'Val
(2#10_000000# or (C1 and 2#00_111111#));
Len := Len + 2;
-- Codes in the range 16#800# - 16#D7FF# or 16#E000# - 16#FFFF#
-- UTF-16: yyyyyyyyxxxxxxxx
-- UTF-8: 1110yyyy 10yyyyxx 10xxxxxx
elsif C1 <= 16#D7FF# or else C1 >= 16#E000# then
Result (Len + 1) :=
Character'Val
(2#1110_0000# or Shift_Right (C1, 12));
Result (Len + 2) :=
Character'Val
(2#10_000000# or (Shift_Right (C1, 6) and 2#00_111111#));
Result (Len + 3) :=
Character'Val
(2#10_000000# or (C1 and 2#00_111111#));
Len := Len + 3;
-- Codes in the range 16#10000# - 16#10FFFF#
-- UTF-16: 110110zzzzyyyyyy 110111yyxxxxxxxx
-- UTF-8: 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
-- Note: zzzzz in the output is input zzzz + 1
elsif C1 <= 2#110110_11_11111111# then
if Iptr > Item'Last then
Raise_Encoding_Error (Iptr - 1);
else
C2 := To_Unsigned_16 (Item (Iptr));
Iptr := Iptr + 1;
end if;
if (C2 and 2#111111_00_00000000#) /= 2#110111_00_00000000# then
Raise_Encoding_Error (Iptr - 1);
end if;
zzzzz := (Shift_Right (C1, 6) and 2#1111#) + 1;
yyyyyyyy := ((Shift_Left (C1, 2) and 2#111111_00#)
or
(Shift_Right (C2, 8) and 2#000000_11#));
xxxxxxxx := C2 and 2#11111111#;
Result (Len + 1) :=
Character'Val
(2#11110_000# or (Shift_Right (zzzzz, 2)));
Result (Len + 2) :=
Character'Val
(2#10_000000# or Shift_Left (zzzzz and 2#11#, 4)
or Shift_Right (yyyyyyyy, 4));
Result (Len + 3) :=
Character'Val
(2#10_000000# or Shift_Left (yyyyyyyy and 2#1111#, 4)
or Shift_Right (xxxxxxxx, 6));
Result (Len + 4) :=
Character'Val
(2#10_000000# or (xxxxxxxx and 2#00_111111#));
Len := Len + 4;
-- Error if input in 16#DC00# - 16#DFFF# (2nd surrogate with no 1st)
else
Raise_Encoding_Error (Iptr - 2);
end if;
end loop;
return Result (1 .. Len);
end Convert;
end Ada.Strings.UTF_Encoding.Conversions;
|
