Subversion Repositories mkgmap

/*
 * Copyright (C) 2007 Steve Ratcliffe
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License 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.
 *
 *
 * Author: Steve Ratcliffe
 * Create date: 25-Oct-2007
 */
package uk.me.parabola.imgfmt.sys;

import uk.me.parabola.imgfmt.MapFailedException;
import uk.me.parabola.log.Logger;

/**
 * This is used to allocate blocks for files in the filesystem/archive.
 *
 * @author Steve Ratcliffe
 */
class BlockManager {
        private static final Logger log = Logger.getLogger(BlockManager.class);

        private final int blockSize;
       
        private int currentBlock;
        private int maxBlock = 0xfffe;
        private int maxBlockAllocated;
        private final int initialBlock;

        BlockManager(int blockSize, int initialBlock) {
                this.blockSize = blockSize;
                this.currentBlock = initialBlock;
                this.initialBlock = initialBlock;
                this.maxBlockAllocated = initialBlock;
        }

        /**
         * Well the algorithm is pretty simple - you just get the next unused block
         * number.
         *
         * @return A block number that is free to be used.
         */
        public int allocate() {
                int n = currentBlock++;
                if (maxBlock > 0 && n > maxBlock) {
                        log.error("overflowed directory with max block " + maxBlock + ", current=" + n);

                        // This problem is fixable so give some useful advice on what
                        // to do about it
                        String message = String.format("Too many blocks." +
                                        " Use a larger block size with an option such as" +
                                        " --block-size=%d or --block-size=%d",
                                        blockSize * 2, blockSize * 4);
                        throw new MapFailedException(message);
                }
                maxBlockAllocated++;
                return n;
        }

        public int getBlockSize() {
                return blockSize;
        }

        public int getMaxBlock() {
                return maxBlock;
        }

        public void setMaxBlock(int maxBlock) {
                this.maxBlock = maxBlock;
        }

        public void setCurrentBlock(int n) {
                if (maxBlockAllocated != initialBlock)
                        throw new IllegalStateException("Blocks already allocated");
                currentBlock = n;
                maxBlockAllocated = n;
        }

        public int getMaxBlockAllocated() {
                return maxBlockAllocated;
        }
}