/*
* Syncany, www.syncany.org
* Copyright (C) 2011-2016 Philipp C. Heckel <philipp.heckel@gmail.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.syncany.chunk;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.syncany.database.MultiChunkEntry.MultiChunkId;
import org.syncany.util.StringUtil;
/**
* A multichunker combines a set of {@link Chunk}s into a single file. It can be implemented
* by a simple container or archive format. The multichunker is used by the {@link Deduper}
* to write multichunks, and by other parts of the application to read multichunks and
* re-assemble files.
*
* <p>The class supports two modes:
*
* <ul>
* <li>When writing a {@link MultiChunker}, the {@link #createMultiChunk(byte[], OutputStream)}
* must be used. The method emits a new implementation-specific {@link MultiChunk}
* to which new chunks can be added/written to.
*
* <li>When reading a multichunk from a file or input stream, the {@link #createMultiChunk(InputStream)}
* or {@link #createMultiChunk(File)} must be used. The emitted multichunk object can be read from.
* </ul>
*
* <p><b>Important:</b> Implementations must make sure that when providing a readable multichunk,
* the individual chunk objects must be randomly accessible. A sequential read (like with TAR, for
* instance), is not sufficient for the quick processing required in the application.
*
* @author Philipp C. Heckel <philipp.heckel@gmail.com>
*/
// TODO [low] The multichunk API is really odd; Think of something more sensible
public abstract class MultiChunker {
/**
* Minimal multi chunk size in KB.
*/
public static final String PROPERTY_SIZE = "size";
private static Logger logger = Logger.getLogger(MultiChunker.class.getSimpleName());
protected int minMultiChunkSize; // in KB
/**
* Creates new multichunker without setting the minimum size of a multichunk.
*/
public MultiChunker() {
// Nothing.
}
/**
* Initializes the multichunker using a settings map.
* <br>
* Required settings are:
* <ul>
* <li> key: {@link #PROPERTY_SIZE}, value: integer encoded as String
* </ul>
*/
public void init(Map<String, String> settings) {
String size = settings.get(PROPERTY_SIZE);
if (size == null) {
logger.log(Level.SEVERE, String.format("Property %s must not be null.", PROPERTY_SIZE));
throw new IllegalArgumentException(String.format("Property %s must not be null.", PROPERTY_SIZE));
}
try {
this.minMultiChunkSize = Integer.parseInt(size);
}
catch (NumberFormatException nfe) {
logger.log(Level.SEVERE, String.format("Property %s could not be parsed as Integer.", PROPERTY_SIZE));
throw new IllegalArgumentException(String.format("Property %s could not be parsed as Integer.", PROPERTY_SIZE));
}
}
/**
* Creates a new multichunker, and sets the minimum size of a multichunk.
*
* <p>Implementations should react on the minimum multichunk size by allowing
* at least the given amount of KBs to be written to a multichunk, and declaring
* a multichunk 'full' if this limit is reached.
*
* @param minMultiChunkSize Minimum multichunk file size in kilo-bytes
*/
public MultiChunker(int minMultiChunkSize) {
this.minMultiChunkSize = minMultiChunkSize;
}
/**
* Create a new multichunk in <b>write mode</b>.
*
* <p>Using this method only allows writing to the returned multichunk. The resulting
* data will be written to the underlying output stream given in the parameter.
*
* @param id Identifier of the newly created multichunk
* @param os Underlying output stream to write the new multichunk to
* @return Returns a new multichunk object which can only be used for writing
* @throws IOException
*/
public abstract MultiChunk createMultiChunk(MultiChunkId id, OutputStream os) throws IOException;
/**
* Open existing multichunk in <b>read mode</b> using an underlying input stream.
*
* <p>Using this method only allows reading from the returned multichunk. The underlying
* input stream is opened and can be used to retrieve chunk data.
*
* @param is InputStream to initialize an existing multichunk for read-operations only
* @return Returns an existing multichunk object that allows read operations only
*/
public abstract MultiChunk createMultiChunk(InputStream is);
/**
* Open existing multichunk in <b>read mode</b> using an underlying file.
*
* <p>Using this method only allows reading from the returned multichunk. The underlying
* input stream is opened and can be used to retrieve chunk data.
*
* @param is InputStream to initialize an existing multichunk for read-operations only
* @return Returns an existing multichunk object that allows read operations only
*/
public abstract MultiChunk createMultiChunk(File file) throws IOException;
/**
* Returns a comprehensive string representation of a multichunker
*/
public abstract String toString();
/**
* Instantiates a multichunker by its name using the default constructor.
* <br>
* After creating a new multichunker, it must be initialized using the
* {@link #init(Map) init()} method. The given type attribute is mapped to fully
* qualified class name (FQCN) of the form <tt>org.syncany.chunk.XMultiChunker</tt>,
* where <tt>X</tt> is the camel-cased type attribute.
*
* @param type Type/name of the multichunker (corresponds to its camel case class name)
* @return a new multichunker
* @throws Exception If the FQCN cannot be found or the class cannot be instantiated
*/
public static MultiChunker getInstance(String type) {
String thisPackage = MultiChunker.class.getPackage().getName();
String camelCaseName = StringUtil.toCamelCase(type);
String fqClassName = thisPackage + "." + camelCaseName + MultiChunker.class.getSimpleName();
// Try to load!
try {
Class<?> clazz = Class.forName(fqClassName);
return (MultiChunker) clazz.newInstance();
}
catch (Exception ex) {
logger.log(Level.INFO, "Could not find multichunker FQCN " + fqClassName, ex);
return null;
}
}
}