/*
* Copyright 2010 Cloud.com, Inc.
*
* 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.cloud.bridge.util;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
/**
* @author Kelven Yang
*/
public class FileRangeInputStream extends InputStream {
private RandomAccessFile randomAccessFile;
private long curPos;
private long endPos;
private long fileLength;
public FileRangeInputStream(File file, long startPos, long endPos) throws IOException {
fileLength = file.length();
if(startPos > fileLength)
startPos = fileLength;
if(endPos > fileLength)
endPos = fileLength;
if(startPos > endPos)
throw new IllegalArgumentException("Invalid file range " + startPos + "-" + endPos);
this.curPos = startPos;
this.endPos = endPos;
randomAccessFile = new RandomAccessFile(file, "r");
randomAccessFile.seek(startPos);
}
@Override
public int available() throws IOException {
return (int)(endPos - curPos);
}
@Override
public int read() throws IOException {
if(available() > 0) {
int value = randomAccessFile.read();
curPos++;
return value;
}
return -1;
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
int bytesToRead = Math.min(len, available());
if(bytesToRead == 0)
return -1;
int bytesRead = randomAccessFile.read(b, off, bytesToRead);
if(bytesRead < 0)
return -1;
curPos += bytesRead;
return bytesRead;
}
@Override
public long skip(long n) throws IOException {
long skipped = Math.min(n, available());
randomAccessFile.skipBytes((int)skipped);
curPos += skipped;
return skipped;
}
@Override
public void close() throws IOException {
randomAccessFile.close();
}
}