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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.pdfbox.io;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
/**
* An implementation of the RandomAccess interface to store data in memory.
* The data will be stored in chunks organized in an ArrayList.
*/
public class RandomAccessBuffer implements RandomAccess, Cloneable
{
// default chunk size is 1kb
private static final int DEFAULT_CHUNK_SIZE = 1024;
// use the default chunk size
private int chunkSize = DEFAULT_CHUNK_SIZE;
// list containing all chunks
private List bufferList = null;
// current chunk
private byte[] currentBuffer;
// current pointer to the whole buffer
private long pointer;
// current pointer for the current chunk
private int currentBufferPointer;
// size of the whole buffer
private long size;
// current chunk list index
private int bufferListIndex;
// maximum chunk list index
private int bufferListMaxIndex;
/**
* Default constructor.
*/
public RandomAccessBuffer()
{
this(DEFAULT_CHUNK_SIZE);
}
/**
* Default constructor.
*/
private RandomAccessBuffer(int definedChunkSize)
{
// starting with one chunk
bufferList = new ArrayList();
chunkSize = definedChunkSize;
currentBuffer = new byte[chunkSize];
bufferList.add(currentBuffer);
pointer = 0;
currentBufferPointer = 0;
size = 0;
bufferListIndex = 0;
bufferListMaxIndex = 0;
}
/**
* Create a random access buffer using the given byte array.
*
* @param input the byte array to be read
*/
public RandomAccessBuffer(byte[] input)
{
// this is a special case. The given byte array is used as the one
// and only chunk.
bufferList = new ArrayList(1);
chunkSize = input.length;
currentBuffer = input;
bufferList.add(currentBuffer);
pointer = 0;
currentBufferPointer = 0;
size = chunkSize;
bufferListIndex = 0;
bufferListMaxIndex = 0;
}
/**
* Create a random access buffer of the given input stream by copying the data.
*
* @param input the input stream to be read
* @throws IOException if something went wrong while copying the data
*/
public RandomAccessBuffer(InputStream input) throws IOException
{
this();
byte[] byteBuffer = new byte[8192];
int bytesRead = 0;
while ((bytesRead = input.read(byteBuffer)) > -1)
{
write(byteBuffer, 0, bytesRead);
}
seek(0);
}
@Override
public RandomAccessBuffer clone()
{
RandomAccessBuffer copy = new RandomAccessBuffer(chunkSize);
copy.bufferList = new ArrayList(bufferList.size());
for (byte [] buffer : bufferList)
{
byte [] newBuffer = new byte [buffer.length];
System.arraycopy(buffer,0,newBuffer,0,buffer.length);
copy.bufferList.add(newBuffer);
}
if (currentBuffer!=null)
{
copy.currentBuffer = copy.bufferList.get(copy.bufferList.size()-1);
}
else
{
copy.currentBuffer = null;
}
copy.pointer = pointer;
copy.currentBufferPointer = currentBufferPointer;
copy.size = size;
copy.bufferListIndex = bufferListIndex;
copy.bufferListMaxIndex = bufferListMaxIndex;
return copy;
}
/**
* {@inheritDoc}
*/
@Override
public void close() throws IOException
{
currentBuffer = null;
bufferList.clear();
pointer = 0;
currentBufferPointer = 0;
size = 0;
bufferListIndex = 0;
}
/**
* {@inheritDoc}
*/
@Override
public void clear()
{
bufferList.clear();
currentBuffer = new byte[chunkSize];
bufferList.add(currentBuffer);
pointer = 0;
currentBufferPointer = 0;
size = 0;
bufferListIndex = 0;
bufferListMaxIndex = 0;
}
/**
* {@inheritDoc}
*/
@Override
public void seek(long position) throws IOException
{
checkClosed();
if (position < 0)
{
throw new IOException("Invalid position "+position);
}
pointer = position;
if (pointer < size)
{
// calculate the chunk list index
bufferListIndex = (int)(pointer / chunkSize);
currentBufferPointer = (int)(pointer % chunkSize);
currentBuffer = bufferList.get(bufferListIndex);
}
else
{
// it is allowed to jump beyond the end of the file
// jump to the end of the buffer
bufferListIndex = bufferListMaxIndex;
currentBuffer = bufferList.get(bufferListIndex);
currentBufferPointer = (int)(size % chunkSize);
}
}
/**
* {@inheritDoc}
*/
@Override
public long getPosition() throws IOException
{
checkClosed();
return pointer;
}
/**
* {@inheritDoc}
*/
@Override
public int read() throws IOException
{
checkClosed();
if (pointer >= this.size)
{
return -1;
}
if (currentBufferPointer >= chunkSize)
{
if (bufferListIndex >= bufferListMaxIndex)
{
return -1;
}
else
{
currentBuffer = bufferList.get(++bufferListIndex);
currentBufferPointer = 0;
}
}
pointer++;
return currentBuffer[currentBufferPointer++] & 0xff;
}
/**
* {@inheritDoc}
*/
@Override
public int read(byte[] b, int offset, int length) throws IOException
{
checkClosed();
if (pointer >= size)
{
return 0;
}
int bytesRead = readRemainingBytes(b, offset, length);
while (bytesRead < length && available() > 0)
{
bytesRead += readRemainingBytes(b, offset + bytesRead, length - bytesRead);
if (currentBufferPointer == chunkSize)
{
nextBuffer();
}
}
return bytesRead;
}
private int readRemainingBytes(byte[] b, int offset, int length) throws IOException
{
if (pointer >= size)
{
return 0;
}
int maxLength = (int) Math.min(length, size-pointer);
int remainingBytes = chunkSize - currentBufferPointer;
// no more bytes left
if (remainingBytes == 0)
{
return 0;
}
if (maxLength >= remainingBytes)
{
// copy the remaining bytes from the current buffer
System.arraycopy(currentBuffer, currentBufferPointer, b, offset, remainingBytes);
// end of file reached
currentBufferPointer += remainingBytes;
pointer += remainingBytes;
return remainingBytes;
}
else
{
// copy the remaining bytes from the whole buffer
System.arraycopy(currentBuffer, currentBufferPointer, b, offset, maxLength);
// end of file reached
currentBufferPointer += maxLength;
pointer += maxLength;
return maxLength;
}
}
/**
* {@inheritDoc}
*/
@Override
public long length() throws IOException
{
checkClosed();
return size;
}
/**
* {@inheritDoc}
*/
@Override
public void write(int b) throws IOException
{
checkClosed();
// end of buffer reached?
if (currentBufferPointer >= chunkSize)
{
if (pointer + chunkSize >= Integer.MAX_VALUE)
{
throw new IOException("RandomAccessBuffer overflow");
}
expandBuffer();
}
currentBuffer[currentBufferPointer++] = (byte)b;
pointer++;
if (pointer > this.size)
{
this.size = pointer;
}
// end of buffer reached now?
if (currentBufferPointer >= chunkSize)
{
if (pointer + chunkSize >= Integer.MAX_VALUE)
{
throw new IOException("RandomAccessBuffer overflow");
}
expandBuffer();
}
}
/**
* {@inheritDoc}
*/
@Override
public void write(byte[] b) throws IOException
{
write(b, 0, b.length);
}
/**
* {@inheritDoc}
*/
@Override
public void write(byte[] b, int offset, int length) throws IOException
{
checkClosed();
long newSize = pointer + length;
int remainingBytes = chunkSize - currentBufferPointer;
if (length >= remainingBytes)
{
if (newSize > Integer.MAX_VALUE)
{
throw new IOException("RandomAccessBuffer overflow");
}
// copy the first bytes to the current buffer
System.arraycopy(b, offset, currentBuffer, currentBufferPointer, remainingBytes);
int newOffset = offset + remainingBytes;
long remainingBytes2Write = length - remainingBytes;
// determine how many buffers are needed for the remaining bytes
int numberOfNewArrays = (int)remainingBytes2Write / chunkSize;
for (int i=0;i= 0)
{
expandBuffer();
if (remainingBytes2Write > 0)
{
System.arraycopy(b, newOffset, currentBuffer, currentBufferPointer, (int)remainingBytes2Write);
}
currentBufferPointer = (int)remainingBytes2Write;
}
}
else
{
System.arraycopy(b, offset, currentBuffer, currentBufferPointer, length);
currentBufferPointer += length;
}
pointer += length;
if (pointer > this.size)
{
this.size = pointer;
}
}
/**
* create a new buffer chunk and adjust all pointers and indices.
*/
private void expandBuffer() throws IOException
{
if (bufferListMaxIndex > bufferListIndex)
{
// there is already an existing chunk
nextBuffer();
}
else
{
// create a new chunk and add it to the buffer
currentBuffer = new byte[chunkSize];
bufferList.add(currentBuffer);
currentBufferPointer = 0;
bufferListMaxIndex++;
bufferListIndex++;
}
}
/**
* switch to the next buffer chunk and reset the buffer pointer.
*/
private void nextBuffer() throws IOException
{
if (bufferListIndex == bufferListMaxIndex)
{
throw new IOException("No more chunks available, end of buffer reached");
}
currentBufferPointer = 0;
currentBuffer = bufferList.get(++bufferListIndex);
}
/**
* Ensure that the RandomAccessBuffer is not closed
* @throws IOException
*/
private void checkClosed() throws IOException
{
if (currentBuffer==null)
{
// consider that the rab is closed if there is no current buffer
throw new IOException("RandomAccessBuffer already closed");
}
}
/**
* {@inheritDoc}
*/
@Override
public boolean isClosed()
{
return currentBuffer == null;
}
/**
* {@inheritDoc}
*/
@Override
public boolean isEOF() throws IOException
{
checkClosed();
return pointer >= size;
}
/**
* {@inheritDoc}
*/
@Override
public int available() throws IOException
{
return (int) Math.min(length() - getPosition(), Integer.MAX_VALUE);
}
/**
* {@inheritDoc}
*/
@Override
public int peek() throws IOException
{
int result = read();
if (result != -1)
{
rewind(1);
}
return result;
}
/**
* {@inheritDoc}
*/
@Override
public void rewind(int bytes) throws IOException
{
checkClosed();
seek(getPosition() - bytes);
}
/**
* {@inheritDoc}
*/
@Override
public byte[] readFully(int length) throws IOException
{
byte[] b = new byte[length];
int bytesRead = read(b);
while (bytesRead < length)
{
bytesRead += read(b, bytesRead, length - bytesRead);
}
return b;
}
/**
* {@inheritDoc}
*/
@Override
public int read(byte[] b) throws IOException
{
return read(b, 0, b.length);
}
}