FileDocCategorySizeDatePackage
ChunkFactory.javaAPI DocApache Poi 3.0.16328Wed Jun 27 19:51:54 BST 2007org.apache.poi.hdgf.chunks

ChunkFactory

public class ChunkFactory extends Object
Factor class to create the appropriate chunks, which needs the version of the file to process the chunk header and trailer areas. Makes use of chunks_parse_cmds.tbl from vsdump to be able to process the chunk value area

Fields Summary
private int
version
The version of the currently open document
private Hashtable
chunkCommandDefinitions
Key is a Chunk's type, value is an array of its CommandDefinitions
private static String
chunkTableName
What the name is of the chunk table
private POILogger
logger
For logging problems we spot with the file
Constructors Summary
public ChunkFactory(int version)

	
	     
		this.version = version;
		
		processChunkParseCommands();
Methods Summary
public org.apache.poi.hdgf.chunks.ChunkcreateChunk(byte[] data, int offset)
Creates the appropriate chunk at the given location.

param
data
param
offset
return

		// Create the header
		ChunkHeader header = 
			ChunkHeader.createChunkHeader(version, data, offset);
		int endOfDataPos = offset + header.getLength() + header.getSizeInBytes();
		
		// Check we have enough data, and tweak the header size
		//  as required
		if(endOfDataPos > data.length) {
			logger.log(POILogger.WARN,
				"Header called for " + header.getLength() +" bytes, but that would take us passed the end of the data!");
			
			endOfDataPos = data.length;
			header.length = data.length - offset - header.getSizeInBytes();
			
			if(header.hasTrailer()) {
				header.length -= 8;
				endOfDataPos  -= 8;
			}
			if(header.hasSeparator()) {
				header.length -= 4;
				endOfDataPos  -= 4;
			}
		}
		

		// Create the trailer and separator, if required
		ChunkTrailer trailer = null;
		ChunkSeparator separator = null;
		if(header.hasTrailer()) {
			if(endOfDataPos <= data.length-8) {
				trailer = new ChunkTrailer(
					data, endOfDataPos);
				endOfDataPos += 8;
			} else {
				System.err.println("Header claims a length to " + endOfDataPos + " there's then no space for the trailer in the data (" + data.length + ")");
			}
		}
		if(header.hasSeparator()) {
			if(endOfDataPos <= data.length-4) {
				separator = new ChunkSeparator(
						data, endOfDataPos);
			} else {
				System.err.println("Header claims a length to " + endOfDataPos + " there's then no space for the separator in the data (" + data.length + ")");
			}
		}

		// Now, create the chunk
		byte[] contents = new byte[header.getLength()];
		System.arraycopy(data, offset+header.getSizeInBytes(), contents, 0, contents.length);
		Chunk chunk = new Chunk(header, trailer, separator, contents);
		
		// Feed in the stuff from  chunks_parse_cmds.tbl
		CommandDefinition[] defs = (CommandDefinition[])
			chunkCommandDefinitions.get(new Integer(header.getType()));
		if(defs == null) defs = new CommandDefinition[0];
		chunk.commandDefinitions = defs;
		
		// Now get the chunk to process its commands
		chunk.processCommands();
		
		// All done
		return chunk;
public intgetVersion()

 return version;
private voidprocessChunkParseCommands()
Open chunks_parse_cmds.tbl and process it, to get the definitions of all the different possible chunk commands.

		String line;
		InputStream cpd = ChunkFactory.class.getResourceAsStream(chunkTableName);
		BufferedReader inp = new BufferedReader(new InputStreamReader(cpd));
		while( (line = inp.readLine()) != null ) {
			if(line.startsWith("#")) continue;
			if(line.startsWith(" ")) continue;
			if(line.startsWith("\t")) continue;
			if(line.length() == 0) continue;

			// Start xxx
			if(!line.startsWith("start")) {
				throw new IllegalStateException("Expecting start xxx, found " + line);
			}
			int chunkType = Integer.parseInt(line.substring(6));
			ArrayList defsL = new ArrayList();
			
			// Data entries
			while( ! (line = inp.readLine()).startsWith("end") ) {
				StringTokenizer st = new StringTokenizer(line, " ");
				int defType = Integer.parseInt(st.nextToken());
				int offset = Integer.parseInt(st.nextToken());
				String name = st.nextToken("\uffff").substring(1);
				
				CommandDefinition def = new CommandDefinition(defType,offset,name);
				defsL.add(def);
			}
			
			CommandDefinition[] defs = (CommandDefinition[])
				defsL.toArray(new CommandDefinition[defsL.size()]);
			
			// Add to the hashtable
			chunkCommandDefinitions.put(new Integer(chunkType), defs);
		}
		inp.close();
		cpd.close();