de.intarsys.tools.randomaccess.BufferedRandomAccess Maven / Gradle / Ivy
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/*
* Copyright (c) 2007, intarsys consulting GmbH
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* - Neither the name of intarsys nor the names of its contributors may be used
* to endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package de.intarsys.tools.randomaccess;
import java.io.IOException;
/**
* todo 1 length reply may be invalid
*/
public class BufferedRandomAccess extends AbstractRandomAccess {
private static int DEFAULT_BUFFER_SIZE = 4096;
/**
* The buffer for the delegates data
*/
private byte[] bytes;
/**
* The relative index of the buffer's first byte in the delegates data
*/
private long bytesOffset = 0;
/**
* The number of valid bytes in the buffer
*/
private int count = 0;
/**
* The index into the buffer indicating the current byte
*/
private int localOffset = 0;
/**
* The buffered random access delegate
*/
private IRandomAccess randomAccess;
/**
* The total offset in the delegates data.
*
* totalOffset = bufferOffset + localOffset; or count == 0 (invalid/empty
* buffer);
*
*/
private long totalOffset = 0;
private boolean closed = false;
/**
* The length of the random access data
*/
private long length;
/**
* Flag if data in the buffer is currently changed.
*/
private boolean bufferChanged = false;
public BufferedRandomAccess(IRandomAccess randomAccess) throws IOException {
this(randomAccess, DEFAULT_BUFFER_SIZE);
}
public BufferedRandomAccess(IRandomAccess randomAccess, int bufferSize)
throws IOException {
this.randomAccess = randomAccess;
this.bytes = new byte[bufferSize];
this.length = randomAccess.getLength();
}
protected int basicRead(byte[] buffer, int start, int numBytes)
throws IOException {
if (localOffset >= count) {
if (numBytes >= bytes.length) {
flushBuffer();
randomAccess.seek(totalOffset);
int readBytes = randomAccess.read(buffer, start, numBytes);
if (readBytes > 0) {
totalOffset += readBytes;
localOffset = count;
}
return readBytes;
} else {
fillBuffer();
if (localOffset >= count) {
return -1;
}
}
}
int avail = count - localOffset;
int cnt = (avail < numBytes) ? avail : numBytes;
System.arraycopy(bytes, localOffset, buffer, start, cnt);
localOffset += cnt;
totalOffset += cnt;
return cnt;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#close()
*/
public void close() throws IOException {
if (isClosed()) {
return;
}
flushBuffer();
randomAccess.close();
setClosed(true);
}
protected void fillBuffer() throws IOException {
flushBuffer();
randomAccess.seek(totalOffset);
count = randomAccess.read(bytes, 0, bytes.length);
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccess#flush()
*/
public void flush() throws IOException {
if (isClosed()) {
throw new IOException("random access closed");
}
flushBuffer();
randomAccess.flush();
}
protected void flushBuffer() throws IOException {
if (bufferChanged && (count > 0)) {
randomAccess.seek(bytesOffset);
randomAccess.write(bytes, 0, count);
}
bytesOffset = totalOffset;
localOffset = 0;
count = 0;
bufferChanged = false;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#getLength()
*/
public long getLength() throws IOException {
if (isClosed()) {
throw new IOException("random access closed");
}
return length;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#getOffset()
*/
public long getOffset() throws IOException {
if (isClosed()) {
throw new IOException("random access closed");
}
return totalOffset;
}
protected boolean isClosed() {
return closed;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#isReadOnly()
*/
public boolean isReadOnly() {
return randomAccess.isReadOnly();
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#read()
*/
public int read() throws IOException {
if (closed) {
throw new IOException("random access closed");
}
if (localOffset >= count) {
fillBuffer();
if (localOffset >= count) {
return -1;
}
}
totalOffset++;
return bytes[localOffset++] & 0xff;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#read(byte[])
*/
public int read(byte[] buffer) throws IOException {
return read(buffer, 0, buffer.length);
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#read(byte[], int,
* int)
*/
public int read(byte[] buffer, int start, int numBytes) throws IOException {
if (closed) {
throw new IOException("random access closed");
}
if (numBytes == 0) {
return 0;
}
int totalByteCount = 0;
while (totalByteCount < numBytes) {
int byteCount = basicRead(buffer, start + totalByteCount, numBytes
- totalByteCount);
if (byteCount <= 0) {
break;
}
totalByteCount += byteCount;
}
if (totalByteCount == 0) {
return -1;
}
return totalByteCount;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#seek(long)
*/
public void seek(long offset) throws IOException {
if (closed) {
throw new IOException("random access closed");
}
totalOffset = offset;
long newLocalOffset = totalOffset - bytesOffset;
if ((newLocalOffset < 0) || (newLocalOffset >= count)) {
flushBuffer();
} else {
localOffset = (int) newLocalOffset;
}
}
public void seekBy(long delta) throws IOException {
if (closed) {
throw new IOException("random access closed");
}
totalOffset += delta;
long newLocalOffset = localOffset + delta;
if ((newLocalOffset < 0) || (newLocalOffset >= count)) {
flushBuffer();
} else {
localOffset = (int) newLocalOffset;
}
}
protected void setClosed(boolean closed) {
this.closed = closed;
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#setLength(int)
*/
public void setLength(long newLength) throws IOException {
if (closed) {
throw new IOException("random access closed");
}
if (newLength < (bytesOffset + bytes.length)) {
flushBuffer();
}
if (newLength < totalOffset) {
totalOffset = newLength;
bytesOffset = newLength;
}
length = newLength;
randomAccess.setLength(newLength);
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#write(byte[])
*/
public void write(byte[] buffer) throws IOException {
write(buffer, 0, buffer.length);
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#write(byte[], int,
* int)
*/
public void write(byte[] buffer, int start, int numBytes)
throws IOException {
if (closed) {
throw new IOException("random access closed");
}
if (numBytes >= bytes.length) {
// greater than local buffer size -> write directly
flushBuffer();
randomAccess.seek(totalOffset);
randomAccess.write(buffer, start, numBytes);
totalOffset += numBytes;
bytesOffset = totalOffset;
if (totalOffset > length) {
length = totalOffset;
}
return;
}
if (numBytes > (bytes.length - localOffset)) {
// greater than rest of buffer -> flush and fill new one
flushBuffer();
}
System.arraycopy(buffer, start, bytes, localOffset, numBytes);
bufferChanged = true;
totalOffset += numBytes;
localOffset += numBytes;
if (totalOffset > length) {
length = totalOffset;
}
if (localOffset >= count) {
count = localOffset;
}
}
/*
* (non-Javadoc)
*
* @see de.intarsys.tools.randomaccess.IRandomAccessData#write(int)
*/
public void write(int b) throws IOException {
if (closed) {
throw new IOException("random access closed");
}
if (localOffset >= bytes.length) {
flushBuffer();
}
bufferChanged = true;
if (localOffset == count) {
count++;
}
totalOffset++;
if (totalOffset > length) {
length = totalOffset;
}
bytes[localOffset++] = (byte) b;
}
}