/*
* @(#)FileInputStream.java 1.28 95/11/15 Arthur van Hoff
*
* Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and without
* fee is hereby granted provided that this copyright notice
* appears in all copies. Please refer to the file "copyright.html"
* for further important copyright and licensing information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*/
package java.io;
/**
* File input stream, can be constructed from
* a file descriptor or a file name.
* @see FileOutputStream
* @see File
* @version 1.28, 15 Nov 1995
* @author Arthur van Hoff
*/
public
class FileInputStream extends InputStream
{
/* File Descriptor - handle to the open file */
private FileDescriptor fd;
/**
* Creates an input file with the specified system dependent file
* name.
* @param name the system dependent file name
* @exception IOException If the file is not found.
*/
public FileInputStream(String name) throws FileNotFoundException {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(name);
}
try {
fd = new FileDescriptor();
open(name);
} catch (IOException e) {
throw new FileNotFoundException(name);
}
}
/**
* Creates an input file from the specified File object.
* @param file the file to be opened for reading
* @exception IOException If the file is not found.
*/
public FileInputStream(File file) throws FileNotFoundException {
this(file.getPath());
}
/* This routine attaches a stream to existing FileDescriptor object.
* Subclass SocketInputStream uses this routine.
*/
public FileInputStream(FileDescriptor fdObj) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(fdObj);
}
fd = fdObj;
}
/**
* Opens the specified file for reading.
* @param name the name of the file
*/
private native void open(String name) throws IOException;
/**
* Reads a byte of data. This method will block if no input is
* available.
* @return the byte read, or -1 if the end of the
* stream is reached.
* @exception IOException If an I/O error has occurred.
*/
public native int read() throws IOException;
/**
* Reads a sub array as a sequence of bytes.
* @param b the data to be written
* @param off the start offset in the data
* @param len the number of bytes that are written
* @exception IOException If an I/O error has occurred.
*/
private native int readBytes(byte b[], int off, int len) throws IOException;
/**
* Reads data into an array of bytes.
* This method blocks until some input is available.
* @param b the buffer into which the data is read
* @return the actual number of bytes read, -1 is
* returned when the end of the stream is reached.
* @exception IOException If an I/O error has occurred.
*/
public int read(byte b[]) throws IOException {
return readBytes(b, 0, b.length);
}
/**
* Reads data into an array of bytes.
* This method blocks until some input is available.
* @param b the buffer into which the data is read
* @param off the start offset of the data
* @param len the maximum number of bytes read
* @return the actual number of bytes read, -1 is
* returned when the end of the stream is reached.
* @exception IOException If an I/O error has occurred.
*/
public int read(byte b[], int off, int len) throws IOException {
return readBytes(b, off, len);
}
/**
* Skips n bytes of input.
* @param n the number of bytes to be skipped
* @return the actual number of bytes skipped.
* @exception IOException If an I/O error has occurred.
*/
public native long skip(long n) throws IOException;
/**
* Returns the number of bytes that can be read
* without blocking.
* @return the number of available bytes, which is initially
* equal to the file size.
*/
public native int available() throws IOException;
/**
* Closes the input stream. This method must be called
* to release any resources associated with
* the stream.
* @exception IOException If an I/O error has occurred.
*/
public native void close() throws IOException;
/**
* Returns the opaque file descriptor object associated with this stream.
* @return the file descriptor.
*/
public final FileDescriptor getFD() throws IOException {
if (fd != null) return fd;
throw new IOException();
}
/**
* Closes the stream when garbage is collected.
*/
protected void finalize() throws IOException {
if (fd != null) close();
}
}