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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.Closeable;
import java.io.IOException;
import java.util.ArrayList;
/**
* An implementation of the RandomAccess interface to store a pdf in memory.
* The data will be stored in 16kb chunks organized in an ArrayList.
*
*/
public class RandomAccessBuffer implements RandomAccess, Closeable
{
// chunk size is 16kb
private static final int BUFFER_SIZE = 16384;
// list containing all chunks
private ArrayList bufferList = null;
// current chunk
private byte[] currentBuffer;
// current pointer to the whole buffer
private long pointer;
// current pointer for the current chunk
private long 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()
{
// starting with one chunk
bufferList = new ArrayList();
currentBuffer = new byte[BUFFER_SIZE];
bufferList.add(currentBuffer);
pointer = 0;
currentBufferPointer = 0;
size = 0;
bufferListIndex = 0;
bufferListMaxIndex = 0;
}
@Override
public RandomAccessBuffer clone() {
RandomAccessBuffer copy = new RandomAccessBuffer();
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}
*/
public void close() throws IOException
{
currentBuffer = null;
bufferList.clear();
pointer = 0;
currentBufferPointer = 0;
size = 0;
bufferListIndex = 0;
}
/**
* {@inheritDoc}
*/
public void seek(long position) throws IOException
{
checkClosed();
pointer = position;
// calculate the chunk list index
bufferListIndex = (int)(position / BUFFER_SIZE);
currentBufferPointer = position % BUFFER_SIZE;
currentBuffer = bufferList.get(bufferListIndex);
}
/**
* {@inheritDoc}
*/
public long getPosition() throws IOException {
checkClosed();
return pointer;
}
/**
* {@inheritDoc}
*/
public int read() throws IOException
{
checkClosed();
if (pointer >= this.size)
{
return -1;
}
if (currentBufferPointer >= BUFFER_SIZE)
{
if (bufferListIndex >= bufferListMaxIndex)
{
return -1;
}
else
{
currentBuffer = bufferList.get(++bufferListIndex);
currentBufferPointer = 0;
}
}
pointer++;
return currentBuffer[(int)currentBufferPointer++] & 0xff;
}
/**
* {@inheritDoc}
*/
public int read(byte[] b, int offset, int length) throws IOException
{
checkClosed();
if (pointer >= this.size)
{
return 0;
}
int maxLength = (int) Math.min(length, this.size-pointer);
long remainingBytes = BUFFER_SIZE - currentBufferPointer;
if (remainingBytes == 0)
{
nextBuffer();
remainingBytes = BUFFER_SIZE;
}
if (maxLength >= remainingBytes)
{
// copy the first bytes from the current buffer
System.arraycopy(currentBuffer, (int)currentBufferPointer, b, offset, (int)remainingBytes);
currentBufferPointer += remainingBytes;
int newOffset = offset + (int)remainingBytes;
long remainingBytes2Read = length - remainingBytes;
// determine how many buffers are needed to get the remaining amount bytes
int numberOfArrays = (int)remainingBytes2Read / BUFFER_SIZE;
for (int i=0;i 0)
{
nextBuffer();
System.arraycopy(currentBuffer, 0, b, newOffset, (int)remainingBytes2Read);
currentBufferPointer += remainingBytes2Read;
}
}
else
{
System.arraycopy(currentBuffer, (int)currentBufferPointer, b, offset, maxLength);
currentBufferPointer += maxLength;
}
pointer += maxLength;
return maxLength;
}
/**
* {@inheritDoc}
*/
public long length() throws IOException
{
checkClosed();
return size;
}
/**
* {@inheritDoc}
*/
public void write(int b) throws IOException
{
checkClosed();
// end of buffer reached?
if (currentBufferPointer >= BUFFER_SIZE)
{
if (pointer + BUFFER_SIZE >= Integer.MAX_VALUE)
{
throw new IOException("RandomAccessBuffer overflow");
}
expandBuffer();
}
currentBuffer[(int)currentBufferPointer++] = (byte)b;
pointer++;
if (pointer > this.size)
{
this.size = pointer;
}
// end of buffer reached now?
if (currentBufferPointer >= BUFFER_SIZE)
{
if (pointer + BUFFER_SIZE >= Integer.MAX_VALUE)
{
throw new IOException("RandomAccessBuffer overflow");
}
expandBuffer();
}
}
/**
* {@inheritDoc}
*/
public void write(byte[] b, int offset, int length) throws IOException
{
checkClosed();
long newSize = pointer + length;
long remainingBytes = BUFFER_SIZE - 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, (int)currentBufferPointer, (int)remainingBytes);
int newOffset = offset + (int)remainingBytes;
long remainingBytes2Write = length - remainingBytes;
// determine how many buffers are needed for the remaining bytes
int numberOfNewArrays = (int)remainingBytes2Write / BUFFER_SIZE;
for (int i=0;i= 0)
{
expandBuffer();
if (remainingBytes2Write > 0)
{
System.arraycopy(b, newOffset, currentBuffer, (int)currentBufferPointer, (int)remainingBytes2Write);
}
currentBufferPointer = remainingBytes2Write;
}
}
else
{
System.arraycopy(b, offset, currentBuffer, (int)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()
{
if (bufferListMaxIndex > bufferListIndex)
{
// there is already an existing chunk
nextBuffer();
}
else
{
// create a new chunk and add it to the buffer
currentBuffer = new byte[BUFFER_SIZE];
bufferList.add(currentBuffer);
currentBufferPointer = 0;
bufferListMaxIndex++;
bufferListIndex++;
}
}
/**
* switch to the next buffer chunk and reset the buffer pointer.
*/
private void nextBuffer()
{
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");
}
}
}