package org.apache.lucene.store.je;

/**
 * Copyright 2002-2006 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import org.apache.lucene.store.IndexInput;

/**
 * Port of Andi Vajda's DbDirectory to Java Edition of Berkeley Database
 * 
 * @author Aaron Donovan
 */

public class JEIndexInput extends IndexInput {

    protected long position = 0L, length = 0L;

    protected JEDirectory directory;

    protected Block block;

    protected File file;

    protected JEIndexInput(JEDirectory directory, String name)
            throws IOException {
        super();

        this.directory = directory;

        this.file = new File(name);
        if (!file.exists(directory))
            throw new IOException("File does not exist: " + name);

        length = file.getLength();

        block = new Block(file);
        block.get(directory);
    }

    public Object clone() {
        try {
            JEIndexInput clone = (JEIndexInput) super.clone();

            clone.block = new Block(file);
            clone.block.seek(position);
            clone.block.get(directory);

            return clone;
        } catch (IOException e) {
            throw new RuntimeException(e.getMessage());
        }
    }

    public void close() throws IOException {
    }

    public long length() {
        return length;
    }

    public byte readByte() throws IOException {
        if (position + 1 > length)
            throw new IOException(file.getName() + ": Reading past end of file");

        int blockPos = (int) (position++ & JEIndexOutput.BLOCK_MASK);
        byte b = block.getData()[blockPos];

        if (blockPos + 1 == JEIndexOutput.BLOCK_LEN) {
            block.seek(position);
            block.get(directory);
        }

        return b;
    }

    public void readBytes(byte[] b, int offset, int len) throws IOException {
        if (position + len > length)
            throw new IOException("Reading past end of file");
        else {
            int blockPos = (int) (position & JEIndexOutput.BLOCK_MASK);

            while (blockPos + len >= JEIndexOutput.BLOCK_LEN) {
                int blockLen = JEIndexOutput.BLOCK_LEN - blockPos;

                System
                        .arraycopy(block.getData(), blockPos, b, offset,
                                blockLen);

                len -= blockLen;
                offset += blockLen;
                position += blockLen;

                block.seek(position);
                block.get(directory);
                blockPos = 0;
            }

            if (len > 0) {
                System.arraycopy(block.getData(), blockPos, b, offset, len);
                position += len;
            }
        }
    }

    public void seek(long pos) throws IOException {
        if (pos > length)
            throw new IOException("seeking past end of file");

        if ((pos >>> JEIndexOutput.BLOCK_SHIFT) != (position >>> JEIndexOutput.BLOCK_SHIFT)) {
            block.seek(pos);
            block.get(directory);
        }

        position = pos;
    }

    public long getFilePointer() {
        return position;
    }
}