pointercontainingstream.java

来自「EXCEL read and write」· Java 代码 · 共 104 行

/* ====================================================================
   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.hdgf.streams;

import org.apache.poi.hdgf.chunks.ChunkFactory;
import org.apache.poi.hdgf.pointers.Pointer;
import org.apache.poi.hdgf.pointers.PointerFactory;
import org.apache.poi.util.LittleEndian;

/**
 * A stream that holds pointers, possibly in addition to some
 *  other data too.
 */
public class PointerContainingStream extends Stream {
	private Pointer[] childPointers;
	private Stream[] childStreams;
	
	private ChunkFactory chunkFactory;
	private PointerFactory pointerFactory;
	private int numPointersLocalOffset;
	
	protected PointerContainingStream(Pointer pointer, StreamStore store, ChunkFactory chunkFactory, PointerFactory pointerFactory) {
		super(pointer, store);
		this.chunkFactory = chunkFactory;
		this.pointerFactory = pointerFactory;
		
		// Find the offset to the number of child pointers we have
		// This ought to be the first thing stored in us
		numPointersLocalOffset = (int)LittleEndian.getUInt(
				store.getContents(), 0
		);
		
		// Generate the objects for the pointers we contain
		int numPointers = (int)LittleEndian.getUInt(
				store.getContents(), numPointersLocalOffset
		);
		childPointers = new Pointer[numPointers];
		
		// After the number of pointers is another (unknown)
		//  4 byte value
		int pos = numPointersLocalOffset + 4 + 4;
		
		// Now create the pointer objects
		for(int i=0; i<numPointers; i++) {
			childPointers[i] = pointerFactory.createPointer(
					store.getContents(), pos
			);
			pos += childPointers[i].getSizeInBytes();
		}
	}
	
	/**
	 * Returns all the pointers that we contain
	 */
	protected Pointer[] getChildPointers() { return childPointers; }
	/**
	 * Returns all the "child" streams.
	 * These are all the streams pointed to by the pointers
	 *  that we contain.
	 */
	public Stream[] getPointedToStreams() { return childStreams; } 
	
	/**
	 * Performs a recursive search, identifying the pointers we contain,
	 *  creating the Streams for where they point to, then searching
	 *  those if appropriate.
	 */
	public void findChildren(byte[] documentData) {
		// For each pointer, generate the Stream it points to
		childStreams = new Stream[childPointers.length];
		for(int i=0; i<childPointers.length; i++) {
			Pointer ptr = childPointers[i];
			childStreams[i] = Stream.createStream(ptr, documentData, chunkFactory, pointerFactory);
			
			// Process chunk streams into their chunks
			if(childStreams[i] instanceof ChunkStream) {
				ChunkStream child = (ChunkStream)childStreams[i];
				child.findChunks();
			}
			
			// Recurse into pointer containing streams
			if(childStreams[i] instanceof PointerContainingStream) {
				PointerContainingStream child = 
					(PointerContainingStream)childStreams[i];
				child.findChildren(documentData);
			}
		}
	}
}