org.eclipse.core.filebuffers/src/org/eclipse/core/internal/filebuffers/JavaFileBuffer.java

/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.filebuffers;

import java.io.File;

import org.eclipse.core.resources.IFile;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.ILog;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;

import org.eclipse.core.filebuffers.FileBuffers;

/**
 * @since 3.0
 */
public abstract class JavaFileBuffer extends AbstractFileBuffer  {
	
	/** The location */
	protected IPath fLocation;
	/** The element for which the info is stored */
	protected File fFile;
	/** How often the element has been connected */
	protected int fReferenceCount;
	/** Can the element be saved */
	protected boolean fCanBeSaved= false;
	/** The status of this element */
	protected IStatus fStatus;
	/** The time stamp at which this buffer synchronized with the underlying file. */
	protected long fSynchronizationStamp= IFile.NULL_STAMP;
	/** How often the synchronization context has been requested */
	protected int fSynchronizationContextCount;
	/** The text file buffer manager */
	protected TextFileBufferManager fManager;
	
	
	public JavaFileBuffer(TextFileBufferManager manager) {
		super();
		fManager= manager;
	}
	
	abstract protected void addFileBufferContentListeners();
	
	abstract protected void removeFileBufferContentListeners();
	
	abstract protected void initializeFileBufferContent(IProgressMonitor monitor) throws CoreException;
	
	abstract protected void commitFileBufferContent(IProgressMonitor monitor, boolean overwrite) throws CoreException;
	
	/**
	 * Returns the file at the given location or <code>null</code> if
	 * there is no such file.
	 * 
	 * @param location the location
	 * @return the file at the given location
	 */
	private File getFileAtLocation(IPath location) {
		File file=  FileBuffers.getSystemFileAtLocation(location);
		return file.exists() ? file : null;
	}
	
	public void create(IPath location, IProgressMonitor monitor) throws CoreException {
		File file= getFileAtLocation(location);
		if (file == null)
			throw new CoreException(new Status(IStatus.ERROR, FileBuffersPlugin.PLUGIN_ID, IStatus.OK, FileBuffersMessages.getString("FileBuffer.error.fileDoesNotExist"), null)); //$NON-NLS-1$
		
		fLocation= location;
		fFile= file;
		initializeFileBufferContent(monitor);
		fSynchronizationStamp= fFile.lastModified();
		
		addFileBufferContentListeners();
	}
	
	public void connect() {
		++ fReferenceCount;
	}
	
	public void disconnect() throws CoreException {
		-- fReferenceCount;
	}
	
	/**
	 * Returns whether this file buffer has already been disposed.
	 * 
	 * @return <code>true</code> if already disposed, <code>false</code> otherwise
	 */
	public boolean isDisposed() {
		return fReferenceCount <= 0;
	}
	
	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#getLocation()
	 */
	public IPath getLocation() {
		return fLocation;
	}

	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#commit(org.eclipse.core.runtime.IProgressMonitor, boolean)
	 */
	public void commit(IProgressMonitor monitor, boolean overwrite) throws CoreException {
		if (!isDisposed() && fCanBeSaved) {
			
			fManager.fireStateChanging(this);
			
			try {
				commitFileBufferContent(monitor, overwrite);
			} catch (CoreException x) {
				fManager.fireStateChangeFailed(this);
				throw x;
			} catch (RuntimeException x) {
				fManager.fireStateChangeFailed(this);
				throw x;				
			}
			
			fCanBeSaved= false;
			addFileBufferContentListeners();
			fManager.fireDirtyStateChanged(this, fCanBeSaved);
		}
	}

	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#isDirty()
	 */
	public boolean isDirty() {
		return fCanBeSaved;
	}
	
	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#isShared()
	 */
	public boolean isShared() {
		return fReferenceCount > 1;
	}

	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#validateState(org.eclipse.core.runtime.IProgressMonitor, java.lang.Object)
	 */
	public void validateState(IProgressMonitor monitor, Object computationContext) throws CoreException {
		// nop
	}

	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#isStateValidated()
	 */
	public boolean isStateValidated() {
		return true;
	}
	
	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#resetStateValidation()
	 */
	public void resetStateValidation() {
		// nop
	}

	/**
	 * Sends out the notification that the file serving as document input has been moved.
	 * 
	 * @param newLocation the path of the new location of the file
	 */
	protected void handleFileMoved(IPath newLocation) {
		fManager.fireUnderlyingFileMoved(this, newLocation);
	}

	/**
	 * Defines the standard procedure to handle <code>CoreExceptions</code>. Exceptions
	 * are written to the plug-in log.
	 *
	 * @param exception the exception to be logged
	 * @param message the message to be logged
	 */
	protected void handleCoreException(CoreException exception) {
		ILog log= FileBuffersPlugin.getDefault().getLog();
		log.log(exception.getStatus());
	}
	
	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#isSynchronized()
	 */
	public boolean isSynchronized() {
		return fSynchronizationStamp == fFile.lastModified();
	}
	
	/*
	 * @see org.eclipse.core.filebuffers.IFileBuffer#getModificationStamp()
	 */
	public long getModificationStamp() {
		return fFile.lastModified();
	}
	
	/**
	 * Requests the file buffer manager's synchronization context for this file buffer.
	 */
	public void requestSynchronizationContext() {
		++ fSynchronizationContextCount;
	}
	
	/**
	 * Releases the file buffer manager's synchronization context for this file buffer.
	 */
	public void releaseSynchronizationContext() {
		-- fSynchronizationContextCount;
	}
}