Grid Application Toolkit A simple API for Grid Applications

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FileInputStream.java Go to the documentation of this file. package org.gridlab.gat.io; import java.io.IOException; import java.io.InputStream; import org.gridlab.gat.GATContext; import org.gridlab.gat.Preferences; import org.gridlab.gat.engine.GATEngine; import org.gridlab.gat.io.cpi.FileInputStreamCpi; import org.gridlab.gat.monitoring.Monitorable; /** * A FileStream represents a connection to open file, the file may be either * remote or local. * <p> * A FileStream represents a seekable connection to a file and has semantics * similar to a standard Unix filedescriptor. It provides methods to query the * current position in the file and to seek to new positions. * <p> * To Write data to a FileStream it is necessary to construct a Buffer and pack * it with data. Similarly, to read data a buffer must be created to store the * read data. Writes and reads may either be blocking, or asynchronous. * Asynchronous writes or reads must be completed by appropriate call. */ public abstract class FileInputStream extends InputStream implements Monitorable { protected GATContext gatContext; protected Preferences preferences; protected File file; /** * This creates a FileStream attached to the physical file at the specified * Location. The file may be opened in several modes: * <ul> * <li>FileStream.READ --- Open file for reading. The stream is positioned * at the beginning of the file.</li> * <li>FileStream.WRITE --- Truncate file to zero length or create file for * writing. The stream is positioned at the beginning of the file.</li> * <li>FileStream.READWRITE --- Open for reading and writing. The stream is * positioned at the beginning of the file.</li> * <li>FileStream.APPEND --- Open for appending (writing at end of file). * The file is created if it does not exist. The stream is positioned at the * end of the file.</li> * </ul> * * @param gatContext * The GATContext used to broker resources * @param preferences * The Preferences for this instance * @param location * The Location of the file to open. * @param mode * The mode to open it --- READ, WRITE, READWRITE, or APPEND, * member variables of this class * @throws java.lang.Exception * Thrown upon creation error of some sort */ protected FileInputStream(GATContext gatContext, Preferences preferences, File file) throws IOException { this.gatContext = gatContext; this.preferences = preferences; this.file = file; } /** * This creates a FileStream attached to the physical file at the specified * Location. The file may be opened in several modes: * <ul> * <li>FileStream.READ --- Open file for reading. The stream is positioned * at the beginning of the file.</li> * <li>FileStream.WRITE --- Truncate file to zero length or create file for * writing. The stream is positioned at the beginning of the file.</li> * <li>FileStream.READWRITE --- Open for reading and writing. The stream is * positioned at the beginning of the file.</li> * <li>FileStream.APPEND --- Open for appending (writing at end of file). * The file is created if it does not exist. The stream is positioned at the * end of the file.</li> * </ul> * * @param gatContext * The GATContext used to broker resources * @param location * The Location of the file to open. * @param mode * The mode to open it --- READ, WRITE, READWRITE, or APPEND, * member variables of this class * @throws java.lang.Exception * Thrown upon creation error of some sort */ public FileInputStream create(GATContext gatContext, File file) throws IOException { return create(gatContext, null, file); } /** * This creates a FileStream attached to the physical file at the specified * Location. The file may be opened in several modes: * <ul> * <li>FileStream.READ --- Open file for reading. The stream is positioned * at the beginning of the file.</li> * <li>FileStream.WRITE --- Truncate file to zero length or create file for * writing. The stream is positioned at the beginning of the file.</li> * <li>FileStream.READWRITE --- Open for reading and writing. The stream is * positioned at the beginning of the file.</li> * <li>FileStream.APPEND --- Open for appending (writing at end of file). * The file is created if it does not exist. The stream is positioned at the * end of the file.</li> * </ul> * * @param gatContext * The GATContext used to broker resources * @param preferences * The Preferences for this instance * @param location * The Location of the file to open. * @param mode * The mode to open it --- READ, WRITE, READWRITE, or APPEND, * member variables of this class * @throws java.lang.Exception * Thrown upon creation error of some sort */ public FileInputStream create(GATContext gatContext, Preferences preferences, File file) throws IOException { GATEngine gatEngine = GATEngine.getGATEngine(); Object[] array = new Object[1]; array[0] = file; FileInputStreamCpi f = (FileInputStreamCpi) gatEngine.getAdaptor( FileInputStreamCpi.class, gatContext, preferences, array); return f; } }