Quadcap Embeddable Database

com/quadcap/sql/file/LogBuffer.java

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package com.quadcap.sql.file;

/* Copyright 1997 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;

import java.util.Properties;

import com.quadcap.util.Debug;
import com.quadcap.util.Util;

/**
 * A bounded buffer based on an underlying RandomAccess
 *
 * @author Stan Bailes
 */
public class LogBuffer {
    RandomAccess                                ra;

    /**
     * "Begin" pointer.
     */
    int                                         bX;

    /**
     * "End" pointer
     */
    int                                         eX;

    /**
     * "Checkpoint" pointer
     */
    int                                         cX;

    /**
     * Size Limit, in octets.
     */
    int                                         maxSize = 128 * 1024 * 1024;

    /**
     * Total header bytes
     */
    static final int                            headerSize = 16;

    /**
     * Default constructor (for factory)
     */
    public LogBuffer() {}

    /**
     * Initialize from existing randomaccess
     */
    public void init(RandomAccess ra, Properties props) throws IOException {
        this.ra = ra;
        this.bX = ra.readInt(0);
        this.eX = ra.readInt(4);
        this.cX = ra.readInt(8);
        maxSize = Integer.parseInt(props.getProperty("maxLogSize", "" + maxSize));
    }

    /**
     * Create a new one
     *
     * @param ra the underlying random access interface to the store
     * @param m the maximum size of this buffer.
     */
    public void init(RandomAccess ra, int m) throws IOException {
        this.ra = ra;
        this.bX = 0;
        this.eX = 0;
        this.cX = 0;
        this.maxSize = m;
        sync();
    }

    /**
     * Return an InputStream which will supply a subset of the buffer starting
     * at 'pos' and ending at the current buffer end
     */
    public InputStream getInputStream(int pos) {
        return new LogInputStream(this, pos, this.eX);
    }

    /**
     * Return an OutputStream which can be used to write to the end of
     * the buffer
     */
    public OutputStream getOutputStream() {
        return new LogOutputStream(this);
    }

    /**
     * Return the current end position (the position of the next byte to
     * be written)
     */
    public int getEnd() { return eX; }

    /**
     * Return the current begin position (the position of the first byte
     * written
     */
    public int getBegin() { return bX; }

    /**
     * Return the value marking the end of the last checkpoint
     */
    public int getCheckpoint() { return cX; }

    /**
     * Set the checkpoint value
     */
    public void checkpoint() { this.cX = this.eX; }

    /**
     * Move the begin pointer past some bytes.
     */
    public void setBegin(int b) {
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".setBegin(" + b + ")");
        }
        //#endif
        bX = b;
    }

    /**
     * Reset the buffer to its empty state
     */
    public void reset() {
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".reset()   -----------------------");
        }
        //#endif
        bX = 0;
        eX = 0;
        cX = 0;
    }

    /**
     * Truncate the underlying region to the current actual size of the
     * buffer
     */
    public void truncate() throws IOException {
        ra.resize(size() + headerSize);
    }

    /**
     * Return the size of the active area
     */
    public int size() {
        return eX - bX;
    }
    
    /**
     * Read a range of bytes from the buffer
     */
    public int read(int pos, byte[] buf, int off, int cnt)
        throws IOException
    {
        int ret = 0;
        if (cnt > 0) {
            ra.read(pos + headerSize, buf, off, cnt);
            ret = cnt;
        }
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".read(" + pos + ", " + cnt + ") = " +
                          ret + ", " + 
                          Util.hexBytes(buf, off, ret));
        }
        //#endif
        return ret;
    }

    /**
     * Read a single byte
     */
    public int readByte(int pos) throws IOException {
        int ret = ra.readByte(pos + headerSize);
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".read(" + pos + ") = " + ret);
        }
        //#endif
        return ret;
    }

    /**
     * Write a range of bytes to the end of the buffer, updating 'eX' to
     * point to the new end of the buffer.
     */
    public void write(byte[] buf, int off, int cnt)
        throws IOException
    {
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".write(" +
                          Util.hexBytes(buf, off, cnt) + ")");
        }
        //#endif
        if (eX + cnt > maxSize) {
            //#ifdef DEBUG
            Debug.println("eX: " + eX + ", write(" + off + ": " +
                          Util.strBytes(buf, off, cnt));
            //#endif
            throw new IOException("LogBuffer full: " + eX + " + " + cnt + " bytes");
        }
        if (cnt > 0) {
            ra.write(eX + headerSize, buf, off, cnt);
            eX += cnt;
        }
    }

    /**
     * Write a single byte to the buffer.  Do not modify eX.
     */
    public void writeByte(int pos, int b) throws IOException {
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".writeByte(" +
                          pos + ", " + b + ")");
        }
        //#endif
        ra.writeByte(pos + headerSize, b);
    }

    /**
     * Flush any changes to disk.
     */
    public void sync() throws IOException {
        //#ifdef DEBUG
        if (Trace.bit(13) || Trace.bit(24)) {
            Debug.println(toString() + ".sync()");
        }
        //#endif
        ra.writeInt(0, bX);
        ra.writeInt(4, eX);
        ra.writeInt(8, cX);
        ra.writeInt(12, maxSize);
        ra.flush();
    }

    /**
     * Close the file
     */
    public void close() throws IOException {
        //#ifdef DEBUG
        if (Trace.bit(13)) {
            Debug.println(toString() + ".close()");
        }
        //#endif
        sync();
        ra.close();
    }

    /**
     * Perform buffer-wrapping address incrementing math
     */
    public int addPos(int pos, int amt) {
        int ret = pos + amt;
        return ret;
    }

    /**
     * Inner input stream
     */
    class LogInputStream extends InputStream {
        LogBuffer b;
        int pos;
        int lim;

        LogInputStream(LogBuffer b, int pos, int lim) {
            //#ifdef DEBUG
            if (Trace.bit(13)) {
                Debug.println("CIS(" + pos + "-" + lim + ")");
            }
            //#endif
            this.b = b;
            this.pos = pos;
            this.lim = lim;
        }

        public int read(byte[] buf, int off, int cnt)
            throws IOException
        {
            //#ifdef DEBUG
            int xpos = pos;
            //#endif
            int xpos2 = pos + cnt;
            if (xpos2 > lim) {
                cnt -= (xpos2 - lim);
            }
            int ret = -1;
            if (cnt > 0) {
                ret = b.read(pos, buf, off, cnt);
                if (ret > 0) {
                    pos = b.addPos(pos, ret);
                } else {
                    ret = -1;
                }
            }
            //#ifdef DEBUG
            if (Trace.bit(14)) {
                Debug.println("CIS[" + xpos + "-" + lim +
                              "].read() = " + ret + ": " +
                              Util.hexBytes(buf, off, ret));
            }
            //#endif
            return ret;
        }
        
        public int read() throws IOException {
            //#ifdef DEBUG
            int xpos = pos;
            //#endif
            int ret = b.readByte(pos);
            if (ret >= 0) {
                pos = b.addPos(pos, 1);
            }
            //#ifdef DEBUG
            if (Trace.bit(14)) {
                Debug.println("CIS[" + xpos + "].read() = " + ret);
            }
            //#endif
            return ret;
        }
    }

    /**
     * Inner output stream
     */
    class LogOutputStream extends OutputStream {
        LogBuffer b;

        LogOutputStream(LogBuffer b) {
            this.b = b;
        }
        
        public void write(byte[] buf, int off, int cnt) throws IOException {
            //#ifdef DEBUG
            if (Trace.bit(14)) {
                Debug.println("COS[" + b.eX + "].write(" +
                              Util.hexBytes(buf, off, cnt) + ")");
            }
            //#endif
            b.write(buf, off, cnt);
        }

        public void write(int x) throws IOException {
            //#ifdef DEBUG
            if (Trace.bit(14)) {
                Debug.println("COS[" + b.eX + "].write(" + x + ")");
            }
            //#endif
            if (false) {
                b.writeByte(b.eX, x);
                b.eX = addPos(b.eX, 1);
            } else {
                byte[] fu = new byte[1];
                fu[0] = (byte)x;
                write(fu, 0, 1);
            }
        }
    }
    
    //#ifdef DEBUG

    public String toString() {
        return "LogBuffer(" + maxSize + "," + bX + "," + eX + "," + cX + ")";
    }

    public static void main(String[] args) {
        try {
            test1();
        } catch (Throwable t) {
            Debug.print(t);
        }
    }

    static void test1() throws Exception {
        int size = 100000;
        ByteArrayRandomAccess bra = new ByteArrayRandomAccess(size + 12);
        BufferedRandomAccess bbra = new BufferedRandomAccess(bra);
        LogBuffer cb = new LogBuffer();
        cb.init(bbra, size);
 
//          for (int i = 0; i < size; i++) {
//              cb.writeByte(i, (byte)(i & 0xff));
//          }
//          for (int i = 0; i < size; i++) {
//              int ret = cb.readByte(i);
//              if (ret  != (i & 0xff)) {
//                  throw new Exception("LogBuffer.test1 " + i +
//                                      " (" + (i&0xff) + ")" +
//                                      ", got " + ret);
//              }
//          }

        int xs = 12;
        int[] poss = new int[xs];
        int[] sizz = new int[xs];
        int beg = cb.getBegin();
        byte[] buf = new byte[4096];
        byte[] rbuf = new byte[4096];
        OutputStream os = cb.getOutputStream();
        int wsize = 1;
        for (int i = 0; i < xs; i++) {
            poss[i] = cb.getEnd();
            sizz[i] = wsize+1;
            wsize += wsize;
            makeBuf(buf, i, sizz[i]);
            os.write(buf, 0, sizz[i]);
            for (int j = 0; j < i; j++) {
                makeBuf(buf, j, sizz[j]);
                InputStream is = cb.getInputStream(poss[j]);
                is.read(rbuf, 0, sizz[i]);
                if (Util.compareBytes(buf, 0, sizz[j], rbuf, 0, sizz[j]) != 0){
                    throw new Exception("R " + i + ": " +
                                        Util.hexBytes(buf, 0, sizz[i]) +
                                        " vs " + j + ": " +
                                        Util.hexBytes(rbuf, 0, sizz[i]));
                }
            }
        }
        
    }

    static void makeBuf(byte[] buf, int x, int siz) {
        x *= 13;
        for (int i = 0; i < siz; i++) {
            buf[i] = (byte)(x++);
        }
    }

    //#endif

}