(*
    Copyright 2016, 2023 Anton Krotov

    This file is part of fb2read.

    fb2read is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    fb2read is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with fb2read. If not, see <http://www.gnu.org/licenses/>.
*)

MODULE Encoding;

IMPORT SYSTEM;


CONST
	TABLE_SIZE = 65536;


TYPE
	tUtf8* = ARRAY 4 OF CHAR;
	tCodePage* = ARRAY 256 OF RECORD code*, len*: INTEGER; utf8*: tUtf8 END;


VAR
	cp1250*, cp1251*, cp1252*, cp866*: tCodePage;

	table1251: ARRAY TABLE_SIZE OF BYTE;


PROCEDURE getUtf8Char* (VAR ptr, size: INTEGER): INTEGER;
VAR
	c: BYTE;
	n, k, code: INTEGER;
	end: BOOLEAN;
BEGIN
	code := 0;
	end := FALSE;
	REPEAT
		SYSTEM.GET(ptr, c);
		INC(ptr);
		DEC(size);
		CASE c OF
		|  0..127:
			code := c;
			end := TRUE

		|128..191:
			code := code * 64 + c MOD 64;
			DEC(n);
			end := n <= 0

		|192..255:
			k := LSL(c, 24);
			n := -2;
			REPEAT
				k := ROR(k, -1);
				INC(n)
			UNTIL k MOD 2 = 0;
			k := LSL(c, n + 25);
			code := LSR(k, n + 25)

		END
	UNTIL (size = 0) OR end
	RETURN code
END getUtf8Char;


PROCEDURE convert1251* (src, dst: INTEGER; len: INTEGER);
VAR
	val, size: INTEGER;
BEGIN
	WHILE len > 0 DO
		size := 0;
		val := getUtf8Char(src, size);
		IF (0 <= val) & (val < TABLE_SIZE) THEN
			SYSTEM.PUT8(dst, table1251[val])
		ELSE
			SYSTEM.PUT8(dst, ORD("?"))
		END;
		INC(dst);
		DEC(len)
	END
END convert1251;


PROCEDURE utf8* (code: INTEGER; VAR utf8char: tUtf8);
BEGIN
	utf8char[0] := 0X;
	IF code < 80H THEN
		utf8char[0] := CHR(code);
		utf8char[1] := 0X
	ELSIF code < 800H THEN
		utf8char[1] := CHR(code MOD 64 + 80H);
		utf8char[0] := CHR(code DIV 64 + 0C0H);
		utf8char[2] := 0X
	ELSIF code < 10000H THEN
		utf8char[2] := CHR(code MOD 64 + 80H);
		code := code DIV 64;
		utf8char[1] := CHR(code MOD 64 + 80H);
		utf8char[0] := CHR(code DIV 64 + 0E0H);
		utf8char[3] := 0X
	(*
	ELSIF code < 200000H THEN
	ELSIF code < 4000000H THEN
	ELSE *)
	END
END utf8;


PROCEDURE ucs2to1251 (code: INTEGER): BYTE;
VAR
	i: INTEGER;
BEGIN
	i := 255;
	WHILE (i >= 0) & (cp1251[i].code # code) DO
		DEC(i)
	END;
	IF i < 0 THEN
		i := ORD("?")
	END
	RETURN i
END ucs2to1251;


PROCEDURE initCP (VAR cp: tCodePage);
VAR
	i: INTEGER;
BEGIN
	FOR i := 0H TO 7FH DO
		cp[i].code := i
	END;
	FOR i := 0H TO 0FFH DO
		utf8(cp[i].code, cp[i].utf8);
		cp[i].len := LENGTH(cp[i].utf8)
	END
END initCP;


PROCEDURE init8 (VAR cp: tCodePage; VAR n: INTEGER; a, b, c, d, e, f, g, h: INTEGER);
BEGIN
	cp[n].code := a; INC(n);
	cp[n].code := b; INC(n);
	cp[n].code := c; INC(n);
	cp[n].code := d; INC(n);
	cp[n].code := e; INC(n);
	cp[n].code := f; INC(n);
	cp[n].code := g; INC(n);
	cp[n].code := h; INC(n);
END init8;


PROCEDURE init1250 (VAR cp: tCodePage);
VAR
	n: INTEGER;
BEGIN
	n := 80H;
	init8(cp, n, 20ACH,   20H, 201AH,   20H, 201EH, 2026H, 2020H, 2021H);
	init8(cp, n,   20H, 2030H, 0160H, 2039H, 015AH, 0164H, 017DH, 0179H);
	init8(cp, n,   20H, 2018H, 2019H, 201CH, 201DH, 2022H, 2013H, 2014H);
	init8(cp, n,   20H, 2122H, 0161H, 203AH, 015BH, 0165H, 017EH, 017AH);
	init8(cp, n, 00A0H, 02C7H, 02D8H, 0141H, 00A4H, 0104H, 00A6H, 00A7H);
	init8(cp, n, 00A8H, 00A9H, 015EH, 00ABH, 00ACH, 00ADH, 00AEH, 017BH);
	init8(cp, n, 00B0H, 00B1H, 02DBH, 0142H, 00B4H, 00B5H, 00B6H, 00B7H);
	init8(cp, n, 00B8H, 0105H, 015FH, 00BBH, 013DH, 02DDH, 013EH, 017CH);
	init8(cp, n, 0154H, 00C1H, 00C2H, 0102H, 00C4H, 0139H, 0106H, 00C7H);
	init8(cp, n, 010CH, 00C9H, 0118H, 00CBH, 011AH, 00CDH, 00CEH, 010EH);
	init8(cp, n, 0110H, 0143H, 0147H, 00D3H, 00D4H, 0150H, 00D6H, 00D7H);
	init8(cp, n, 0158H, 016EH, 00DAH, 0170H, 00DCH, 00DDH, 0162H, 00DFH);
	init8(cp, n, 0155H, 00E1H, 00E2H, 0103H, 00E4H, 013AH, 0107H, 00E7H);
	init8(cp, n, 010DH, 00E9H, 0119H, 00EBH, 011BH, 00EDH, 00EEH, 010FH);
	init8(cp, n, 0111H, 0144H, 0148H, 00F3H, 00F4H, 0151H, 00F6H, 00F7H);
	init8(cp, n, 0159H, 016FH, 00FAH, 0171H, 00FCH, 00FDH, 0163H, 02D9H);
	initCP(cp)
END init1250;


PROCEDURE init1251 (VAR cp: tCodePage);
VAR
	n, i: INTEGER;
BEGIN
	n := 80H;
	init8(cp, n, 0402H, 0403H, 201AH, 0453H, 201EH, 2026H, 2020H, 2021H);
	init8(cp, n, 20ACH, 2030H, 0409H, 2039H, 040AH, 040CH, 040BH, 040FH);
	init8(cp, n, 0452H, 2018H, 2019H, 201CH, 201DH, 2022H, 2013H, 2014H);
	init8(cp, n,   20H, 2122H, 0459H, 203AH, 045AH, 045CH, 045BH, 045FH);
	init8(cp, n, 00A0H, 040EH, 045EH, 0408H, 00A4H, 0490H, 00A6H, 00A7H);
	init8(cp, n, 0401H, 00A9H, 0404H, 00ABH, 00ACH, 00ADH, 00AEH, 0407H);
	init8(cp, n, 00B0H, 00B1H, 0406H, 0456H, 0491H, 00B5H, 00B6H, 00B7H);
	init8(cp, n, 0451H, 2116H, 0454H, 00BBH, 0458H, 0405H, 0455H, 0457H);
	FOR i := 0410H TO 044FH DO
		cp[i - 350H].code := i
	END;
	initCP(cp)
END init1251;


PROCEDURE init1252 (VAR cp: tCodePage);
VAR
	n, i: INTEGER;
BEGIN
	n := 80H;
	init8(cp, n, 20ACH,   20H, 201AH, 0192H, 201EH, 2026H, 2020H, 2021H);
	init8(cp, n, 02C6H, 2030H, 0160H, 2039H, 0152H,   20H, 017DH,   20H);
	init8(cp, n,   20H, 2018H, 2019H, 201CH, 201DH, 2022H, 2013H, 2014H);
	init8(cp, n, 02DCH, 2122H, 0161H, 203AH, 0153H,   20H, 017EH, 0178H);
	FOR i := 0A0H TO 0FFH DO
		cp[i].code := i
	END;
	initCP(cp)
END init1252;


PROCEDURE init866 (VAR cp: tCodePage);
VAR
	n, i: INTEGER;
BEGIN
	FOR i := 0410H TO 043FH DO
		cp[i - 0410H + 80H].code := i
	END;
	FOR i := 0440H TO 044FH DO
		cp[i - 0440H + 0E0H].code := i
	END;

	n := 0B0H;
	init8(cp, n, 2591H, 2592H, 2593H, 2502H, 2524H, 2561H, 2562H, 2556H);
	init8(cp, n, 2555H, 2563H, 2551H, 2557H, 255DH, 255CH, 255BH, 2510H);
	init8(cp, n, 2514H, 2534H, 252CH, 251CH, 2500H, 253CH, 255EH, 255FH);
	init8(cp, n, 255AH, 2554H, 2569H, 2566H, 2560H, 2550H, 256CH, 2567H);
	init8(cp, n, 2568H, 2564H, 2565H, 2559H, 2558H, 2552H, 2553H, 256BH);
	init8(cp, n, 256AH, 2518H, 250CH, 2588H, 2584H, 258CH, 2590H, 2580H);

	n := 0F0H;
	init8(cp, n, 0401H, 0451H, 0404H, 0454H, 0407H, 0457H, 040EH, 045EH);
	init8(cp, n, 00B0H, 2219H, 00B7H, 221AH, 2116H, 00A4H, 25A0H, 00A0H);

	initCP(cp)
END init866;


PROCEDURE init;
VAR
	i: INTEGER;
BEGIN
	init1250(cp1250);
	init1251(cp1251);
	init1252(cp1252);
	init866(cp866);
	FOR i := 0 TO TABLE_SIZE - 1 DO
		table1251[i] := ucs2to1251(i)
	END
END init;


BEGIN
	init
END Encoding.