Subversion Repositories mkgmap

/*
 * Copyright (C) 2016.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 or
 * version 2 as published by the Free Software Foundation.
 *
 * This program 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.
 */
package uk.me.parabola.io;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import uk.me.parabola.imgfmt.app.labelenc.CharacterEncoder;
import uk.me.parabola.imgfmt.app.labelenc.CodeFunctions;

/**
 * A block forming part of a file.
 *
 * Used for TDB and MPS files.  It will be read and written using the structured reader and
 * writer defined in this package.
 */
public abstract class FileBlock {
        private final byte blockId;

        private final ByteArrayOutputStream output = new ByteArrayOutputStream();

        public FileBlock(int blockId) {
                this.blockId = (byte) blockId;

                fillHeader();
        }

        /**
         * Write the body of the block.
         */
        protected abstract void writeBody(StructuredOutputStream output) throws IOException;

        private StructuredOutputStream getStructuredOutput(int codePage) {
                CharacterEncoder enc = CodeFunctions.createEncoderForLBL(0, codePage).getEncoder();
                return new StructuredOutputStream(output, enc);
        }

        /**
         * Write to an output stream.
         *
         * This will be to the actual TDB file.
         */
        public void writeTo(OutputStream os, int codePage) throws IOException {
                StructuredOutputStream output = getStructuredOutput(codePage);
                writeBody(output);

                byte[] b = this.output.toByteArray();

                // Fill in the actual full block length
                int blockLength = b.length - 3;
                b[1] = (byte) (blockLength & 0xff);
                b[2] = (byte) ((blockLength >> 8) & 0xff);
                os.write(b);
        }

        /**
         * Write the header to the internal buffer.  The length may not be known yet and so is re-written later.
         */
        private void fillHeader() {
                try {
                        byte[] b = new byte[3];
                        b[0] = this.blockId;

                        output.write(b);
                } catch (IOException ignore) {
                        // does not throw
                }
        }
}