/*
* Copyright 2011 sunli [sunli1223@gmail.com][weibo.com@sunli1223]
*
* 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.
*/
package com.google.code.fqueue;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.google.code.fqueue.exception.FileEOFException;
import com.google.code.fqueue.exception.FileFormatException;
import com.google.code.fqueue.log.FileRunner;
import com.google.code.fqueue.log.LogEntity;
import com.google.code.fqueue.log.LogIndex;
/**
* 完成基于文件的先进先出的读写功能
*
* @author sunli
* @date 2010-8-13
* @version $Id: FSQueue.java 2 2011-07-31 12:25:36Z sunli1223@gmail.com $
*/
public class FSQueue {
private static final Log log = LogFactory.getLog(FSQueue.class);
public static final String filePrefix = "fqueue";
private int fileLimitLength = 1024 * 1024 * 100;
private static final String dbName = "icqueue.db";
private static final String fileSeparator = System.getProperty("file.separator");
private String path = null;
private final Executor executor = Executors.newSingleThreadExecutor();
/**
* 文件操作实例
*/
private LogIndex db = null;
private LogEntity writerHandle = null;
private LogEntity readerHandle = null;
/**
* 文件操作位置信息
*/
private int readerIndex = -1;
private int writerIndex = -1;
public FSQueue(String path) throws Exception {
this(path, 1024 * 1024 * 150);
}
/**
* 在指定的目录中，以fileLimitLength为单个数据文件的最大大小限制初始化队列存储
*
* @param dir
* 队列数据存储的路径
* @param fileLimitLength
* 单个数据文件的大小，不能超过2G
* @throws Exception
*/
public FSQueue(String dir, int fileLimitLength) throws Exception {
this.fileLimitLength = fileLimitLength;
File fileDir = new File(dir);
if (fileDir.exists() == false && fileDir.isDirectory() == false) {
if (fileDir.mkdirs() == false) {
throw new IOException("create dir error");
}
}
path = fileDir.getAbsolutePath();
// 打开db
db = new LogIndex(path + fileSeparator + dbName);
writerIndex = db.getWriterIndex();
readerIndex = db.getReaderIndex();
writerHandle = createLogEntity(path + fileSeparator + filePrefix + "data_" + writerIndex + ".idb", db,
writerIndex);
if (readerIndex == writerIndex) {
readerHandle = writerHandle;
} else {
readerHandle = createLogEntity(path + fileSeparator + filePrefix + "data_" + readerIndex + ".idb", db,
readerIndex);
}
FileRunner deleteFileRunner = new FileRunner(path + fileSeparator + filePrefix + "data_", fileLimitLength);
executor.execute(deleteFileRunner);
}
/**
* 创建或者获取一个数据读写实例
*
* @param dbpath
* @param db
* @param fileNumber
* @return
* @throws IOException
* @throws FileFormatException
*/
private LogEntity createLogEntity(String dbpath, LogIndex db, int fileNumber) throws IOException,
FileFormatException {
return new LogEntity(dbpath, db, fileNumber, this.fileLimitLength);
}
/**
* 一个文件的数据写入达到fileLimitLength的时候，滚动到下一个文件实例
*
* @throws IOException
* @throws FileFormatException
*/
private void rotateNextLogWriter() throws IOException, FileFormatException {
writerIndex = writerIndex + 1;
writerHandle.putNextFile(writerIndex);
if (readerHandle != writerHandle) {
writerHandle.close();
}
db.putWriterIndex(writerIndex);
writerHandle = createLogEntity(path + fileSeparator + filePrefix + "data_" + writerIndex + ".idb", db,
writerIndex);
}
/**
* 向队列存储添加一个字符串
*
* @param message
* message
* @throws IOException
* @throws FileFormatException
*/
public void add(String message) throws IOException, FileFormatException {
add(message.getBytes());
}
/**
* 向队列存储添加一个byte数组
*
* @param message
* @throws IOException
* @throws FileFormatException
*/
public void add(byte[] message) throws IOException, FileFormatException {
short status = writerHandle.write(message);
if (status == LogEntity.WRITEFULL) {
rotateNextLogWriter();
status = writerHandle.write(message);
}
if (status == LogEntity.WRITESUCCESS) {
db.incrementSize();
}
}
/**
* 从队列存储中取出最先入队的数据，并移除它
* @return
* @throws IOException
* @throws FileFormatException
*/
public byte[] readNextAndRemove() throws IOException, FileFormatException {
byte[] b = null;
try {
b = readerHandle.readNextAndRemove();
} catch (FileEOFException e) {
int deleteNum = readerHandle.getCurrentFileNumber();
int nextfile = readerHandle.getNextFile();
readerHandle.close();
FileRunner.addDeleteFile(path + fileSeparator + filePrefix + "data_" + deleteNum + ".idb");
// 更新下一次读取的位置和索引
db.putReaderPosition(LogEntity.messageStartPosition);
db.putReaderIndex(nextfile);
if (writerHandle.getCurrentFileNumber() == nextfile) {
readerHandle = writerHandle;
} else {
readerHandle = createLogEntity(path + fileSeparator + filePrefix + "data_" + nextfile + ".idb", db,
nextfile);
}
try {
b = readerHandle.readNextAndRemove();
} catch (FileEOFException e1) {
log.error("read new log file FileEOFException error occurred",e1);
}
}
if (b != null) {
db.decrementSize();
}
return b;
}
public void close() {
readerHandle.close();
writerHandle.close();
}
public int getQueuSize() {
return db.getSize();
}
}