/*
 * @(#) $Id: ByteToCharUTF7.java,v 1.2 2001/03/04 07:42:28 shin Exp $
 * $Revision: 1.2 $
 * Copyright (c) 2000 Shin Kinoshita All Rights Reserved.
 */
package com.sk_jp.io;

import java.io.*;

/**
 * UTF-7のデコーダです。
 * <p>
 * </p>
 * @author Shin
 */
public class ByteToCharUTF7 extends sun.io.ByteToCharConverter {
    public String getCharacterEncoding() {
        return "UTF7";
    }

    public int flush(char[] chars, int off, int len) {
        byteOff = 0;
        charOff = 0;
        b64Context = false;
        currentB64Off = 0;
        currentChar = 0;
        return 0;
    }
    public void reset() {
        byteOff = 0;
        charOff = 0;
        b64Context = false;
        currentB64Off = 0;
        currentChar = 0;
    }

    private boolean b64Context = false;
    private int currentB64Off = 0;
    private char currentChar = 0;

    public int convert(byte[] bytes, int byteStart, int byteEnd,
                       char[] chars, int charStart, int charEnd)
                throws sun.io.ConversionBufferFullException,
                       sun.io.UnknownCharacterException {
        charOff = charStart;

        for (byteOff = byteStart; byteOff < byteEnd; byteOff++) {
            if (charOff >= charEnd) {
                throw new sun.io.ConversionBufferFullException();
            }
            if (b64Context) {
                if (bytes[byteOff] == '-') {
                    if (currentB64Off != 0 && currentChar > 0) {
                        chars[charOff] = currentChar;
                        charOff++;
                    }
                    b64Context = false;
                    continue;
                }
                int part = ("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                            "abcdefghijklmnopqrstuvwxyz0123456789+/").
                                indexOf(bytes[byteOff]);
                if (part == -1) {
                    throw new sun.io.UnknownCharacterException(
                            "Invalid UTF-7 code: " + (char)bytes[byteOff]);
                }

                switch (currentB64Off) {
                    case 0:
                        currentChar = (char)(part << 10);
                        break;
                    case 1:
                        currentChar |= (char)(part << 4);
                        break;
                    case 2:
                        currentChar |= (char)(part >> 2);
                        chars[charOff] = currentChar;
                        charOff++;
                        currentChar = (char)((part & 0x03) << 14);
                        break;
                    case 3:
                        currentChar |= (char)(part << 8);
                        break;
                    case 4:
                        currentChar |= (char)(part << 2);
                        break;
                    case 5:
                        currentChar |= (char)(part >> 4);
                        chars[charOff] = currentChar;
                        charOff++;
                        currentChar = (char)((part & 0x0f) << 12);
                        break;
                    case 6:
                        currentChar |= (char)(part << 6);
                        break;
                    case 7:
                        currentChar |= (char)part;
                        chars[charOff] = currentChar;
                        charOff++;
                        break;
                }
                currentB64Off = (currentB64Off + 1) % 8;
                continue;
            }

            if (bytes[byteOff] =='+') {
                // shift character
                // This is start of the Base64 sequence.
                b64Context = true;
                currentB64Off = 0;
                continue;
            }
            chars[charOff] = (char)bytes[byteOff];
            charOff++;
        }
        return charOff - charStart;
    }

/*
    public static void main(String[] args) throws Exception {
        System.setProperty("file.encoding.pkg", "com.sk_jp.io");
        ByteArrayOutputStream o = new ByteArrayOutputStream();
        byte[] b = new byte[2048];
        int len;
        while ((len = System.in.read(b)) != -1) {
            o.write(b, 0, len);
        }
        byte[] bytes = o.toByteArray();

        System.out.println(new String(bytes, "UTF7"));
    }
*/
}