| |
| /* ==================================================================== |
| 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.poi.poifs.filesystem; |
| |
| import java.io.IOException; |
| 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<ByteBuffer> |
| { |
| private BlockStore blockStore; |
| private int startBlock; |
| |
| /** |
| * 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<ByteBuffer> iterator() { |
| return getBlockIterator(); |
| } |
| |
| public Iterator<ByteBuffer> 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 { |
| // How many blocks are we going to need? |
| int blockSize = blockStore.getBlockStoreBlockSize(); |
| int blocks = (int)Math.ceil(contents.length / blockSize); |
| |
| // Make sure we don't encounter a loop whilst overwriting |
| // the existing blocks |
| ChainLoopDetector loopDetector = blockStore.getChainLoopDetector(); |
| |
| // Start writing |
| int prevBlock = POIFSConstants.END_OF_CHAIN; |
| int nextBlock = startBlock; |
| for(int i=0; i<blocks; i++) { |
| 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(this.startBlock == POIFSConstants.END_OF_CHAIN) { |
| this.startBlock = thisBlock; |
| } |
| } else { |
| loopDetector.claim(thisBlock); |
| nextBlock = blockStore.getNextBlock(thisBlock); |
| } |
| |
| // Write it |
| ByteBuffer buffer = blockStore.createBlockIfNeeded(thisBlock); |
| buffer.put(contents, i*blockSize, blockSize); |
| |
| // Update pointers |
| prevBlock = thisBlock; |
| } |
| int lastBlock = prevBlock; |
| |
| // 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(lastBlock, POIFSConstants.END_OF_CHAIN); |
| } |
| |
| // 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<ByteBuffer> { |
| 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(); |
| } |
| } |
| } |
| |