org.apache.poi.poifs.filesystem.NPOIFSStream Maven / Gradle / Ivy
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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
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http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.poi.poifs.filesystem;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.Iterator;
import org.apache.poi.poifs.common.POIFSConstants;
import org.apache.poi.poifs.filesystem.BlockStore.ChainLoopDetector;
import org.apache.poi.poifs.property.Property;
import org.apache.poi.poifs.storage.HeaderBlock;
/**
* This handles reading and writing a stream within a
* {@link NPOIFSFileSystem}. It can supply an iterator
* to read blocks, and way to write out to existing and
* new blocks.
* Most users will want a higher level version of this,
* which deals with properties to track which stream
* this is.
* This only works on big block streams, it doesn't
* handle small block ones.
* This uses the new NIO code
*
* TODO Implement a streaming write method, and append
*/
public class NPOIFSStream implements Iterable
{
private BlockStore blockStore;
private int startBlock;
private OutputStream outStream;
/**
* Constructor for an existing stream. It's up to you
* to know how to get the start block (eg from a
* {@link HeaderBlock} or a {@link Property})
*/
public NPOIFSStream(BlockStore blockStore, int startBlock) {
this.blockStore = blockStore;
this.startBlock = startBlock;
}
/**
* Constructor for a new stream. A start block won't
* be allocated until you begin writing to it.
*/
public NPOIFSStream(BlockStore blockStore) {
this.blockStore = blockStore;
this.startBlock = POIFSConstants.END_OF_CHAIN;
}
/**
* What block does this stream start at?
* Will be {@link POIFSConstants#END_OF_CHAIN} for a
* new stream that hasn't been written to yet.
*/
public int getStartBlock() {
return startBlock;
}
/**
* Returns an iterator that'll supply one {@link ByteBuffer}
* per block in the stream.
*/
public Iterator iterator() {
return getBlockIterator();
}
public Iterator getBlockIterator() {
if(startBlock == POIFSConstants.END_OF_CHAIN) {
throw new IllegalStateException(
"Can't read from a new stream before it has been written to"
);
}
return new StreamBlockByteBufferIterator(startBlock);
}
/**
* Updates the contents of the stream to the new
* set of bytes.
* Note - if this is property based, you'll still
* need to update the size in the property yourself
*/
public void updateContents(byte[] contents) throws IOException {
OutputStream os = getOutputStream();
os.write(contents);
os.close();
}
public OutputStream getOutputStream() throws IOException {
if (outStream == null) {
outStream = new StreamBlockByteBuffer();
}
return outStream;
}
// TODO Streaming write support
// TODO then convert fixed sized write to use streaming internally
// TODO Append write support (probably streaming)
/**
* Frees all blocks in the stream
*/
public void free() throws IOException {
ChainLoopDetector loopDetector = blockStore.getChainLoopDetector();
free(loopDetector);
}
private void free(ChainLoopDetector loopDetector) {
int nextBlock = startBlock;
while(nextBlock != POIFSConstants.END_OF_CHAIN) {
int thisBlock = nextBlock;
loopDetector.claim(thisBlock);
nextBlock = blockStore.getNextBlock(thisBlock);
blockStore.setNextBlock(thisBlock, POIFSConstants.UNUSED_BLOCK);
}
this.startBlock = POIFSConstants.END_OF_CHAIN;
}
/**
* Class that handles a streaming read of one stream
*/
protected class StreamBlockByteBufferIterator implements Iterator {
private ChainLoopDetector loopDetector;
private int nextBlock;
protected StreamBlockByteBufferIterator(int firstBlock) {
this.nextBlock = firstBlock;
try {
this.loopDetector = blockStore.getChainLoopDetector();
} catch(IOException e) {
throw new RuntimeException(e);
}
}
public boolean hasNext() {
if(nextBlock == POIFSConstants.END_OF_CHAIN) {
return false;
}
return true;
}
public ByteBuffer next() {
if(nextBlock == POIFSConstants.END_OF_CHAIN) {
throw new IndexOutOfBoundsException("Can't read past the end of the stream");
}
try {
loopDetector.claim(nextBlock);
ByteBuffer data = blockStore.getBlockAt(nextBlock);
nextBlock = blockStore.getNextBlock(nextBlock);
return data;
} catch(IOException e) {
throw new RuntimeException(e);
}
}
public void remove() {
throw new UnsupportedOperationException();
}
}
protected class StreamBlockByteBuffer extends OutputStream {
byte oneByte[] = new byte[1];
ByteBuffer buffer;
// Make sure we don't encounter a loop whilst overwriting
// the existing blocks
ChainLoopDetector loopDetector;
int prevBlock, nextBlock;
protected StreamBlockByteBuffer() throws IOException {
loopDetector = blockStore.getChainLoopDetector();
prevBlock = POIFSConstants.END_OF_CHAIN;
nextBlock = startBlock;
}
protected void createBlockIfNeeded() throws IOException {
if (buffer != null && buffer.hasRemaining()) return;
int thisBlock = nextBlock;
// Allocate a block if needed, otherwise figure
// out what the next block will be
if(thisBlock == POIFSConstants.END_OF_CHAIN) {
thisBlock = blockStore.getFreeBlock();
loopDetector.claim(thisBlock);
// We're on the end of the chain
nextBlock = POIFSConstants.END_OF_CHAIN;
// Mark the previous block as carrying on to us if needed
if(prevBlock != POIFSConstants.END_OF_CHAIN) {
blockStore.setNextBlock(prevBlock, thisBlock);
}
blockStore.setNextBlock(thisBlock, POIFSConstants.END_OF_CHAIN);
// If we've just written the first block on a
// new stream, save the start block offset
if(startBlock == POIFSConstants.END_OF_CHAIN) {
startBlock = thisBlock;
}
} else {
loopDetector.claim(thisBlock);
nextBlock = blockStore.getNextBlock(thisBlock);
}
buffer = blockStore.createBlockIfNeeded(thisBlock);
// Update pointers
prevBlock = thisBlock;
}
public void write(int b) throws IOException {
oneByte[0] = (byte)(b & 0xFF);
write(oneByte);
}
public void write(byte[] b, int off, int len) throws IOException {
if ((off < 0) || (off > b.length) || (len < 0) ||
((off + len) > b.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
do {
createBlockIfNeeded();
int writeBytes = Math.min(buffer.remaining(), len);
buffer.put(b, off, writeBytes);
off += writeBytes;
len -= writeBytes;
} while (len > 0);
}
public void close() throws IOException {
// If we're overwriting, free any remaining blocks
NPOIFSStream toFree = new NPOIFSStream(blockStore, nextBlock);
toFree.free(loopDetector);
// Mark the end of the stream
blockStore.setNextBlock(prevBlock, POIFSConstants.END_OF_CHAIN);
}
}
}
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