1 /* FileInputStream.java -- An input stream that reads from disk files.
2 Copyright (C) 1998, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4 This file is part of GNU Classpath.
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
41 import gnu
.java
.nio
.channels
.FileChannelImpl
;
43 import java
.nio
.channels
.FileChannel
;
45 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
46 * "The Java Language Specification", ISBN 0-201-63451-1
47 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
48 * Status: Believed complete and correct.
52 * This class is a stream that reads its bytes from a file.
54 * @author Aaron M. Renn (arenn@urbanophile.com)
55 * @author Warren Levy (warrenl@cygnus.com)
57 public class FileInputStream
extends InputStream
60 * This is the native file handle for the file this stream is reading from
62 private FileDescriptor fd
;
64 private FileChannelImpl ch
;
67 * This method initializes a <code>FileInputStream</code> to read from the
68 * specified named file. A security check is first made to determine
69 * whether or not access to this file is allowed. This is done by
70 * calling the <code>checkRead()</code> method of the
71 * <code>SecurityManager</code>
72 * (if one exists) with the name of this file. An exception is thrown
73 * if reading is not allowed. If the file does not exist, an exception
76 * @param name The name of the file this stream should read from
78 * @exception SecurityException If read access to the file is not allowed
79 * @exception FileNotFoundException If the file does not exist
80 * or if it is a directory
82 public FileInputStream(String name
) throws FileNotFoundException
88 * This method initializes a <code>FileInputStream</code> to read from the
89 * specified <code>File</code> object. A security check is first
91 * whether or not access to this file is allowed. This is done by
92 * calling the <code>checkRead()</code> method of the
93 * <code>SecurityManager</code>
94 * (if one exists) with the name of this file. An exception is thrown
95 * if reading is not allowed. If the file does not exist, an exception
98 * @param file The <code>File</code> object this stream should read from
100 * @exception SecurityException If read access to the file is not allowed
101 * @exception FileNotFoundException If the file does not exist
102 * or if it is a directory.
104 public FileInputStream(File file
) throws FileNotFoundException
106 SecurityManager s
= System
.getSecurityManager();
108 s
.checkRead(file
.getPath());
110 ch
= FileChannelImpl
.create(file
, FileChannelImpl
.READ
);
114 * This method initializes a <code>FileInputStream</code> to read from the
115 * specified <code>FileDescriptor</code> object. A security
116 * check is first made to
117 * determine whether or not access to this file is allowed. This is done by
118 * calling the <code>checkRead()</code> method of the
119 * <code>SecurityManager</code>
120 * (if one exists) with the specified <code>FileDescriptor</code>
122 * thrown if reading is not allowed.
124 * @param fdObj The <code>FileDescriptor</code> object this stream
127 * @exception SecurityException If read access to the file is not allowed
129 public FileInputStream(FileDescriptor fdObj
)
131 SecurityManager s
= System
.getSecurityManager();
136 ch
= (FileChannelImpl
) fdObj
.channel
;
139 FileInputStream(FileChannelImpl ch
)
145 * This method returns the number of bytes that can be read from this
146 * stream before a read can block. A return of 0 indicates that blocking
147 * might (or might not) occur on the very next read attempt.
149 * This method returns the number of unread bytes remaining in the file if
150 * the descriptor being read from is an actual file. If this method is
151 * reading from a ''special'' file such a the standard input, this method
152 * will return the appropriate value for the stream being read.
154 * Be aware that reads on plain files that do not reside locally might
155 * possibly block even if this method says they should not. For example,
156 * a remote server might crash, preventing an NFS mounted file from being
159 * @return The number of bytes that can be read before blocking could occur
161 * @exception IOException If an error occurs
163 public int available() throws IOException
165 return ch
.available();
169 * This method closes the stream. Any futher attempts to read from the
170 * stream will likely generate an IOException since the underlying file
173 * @exception IOException If an error occurs.
175 public void close() throws IOException
180 protected void finalize() throws IOException
182 // We don't actually need this, but we include it because it is
183 // mentioned in the JCL.
187 * This method returns a <code>FileDescriptor</code> object representing the
188 * underlying native file handle of the file this stream is reading
191 * @return A <code>FileDescriptor</code> for this stream
193 * @exception IOException If an error occurs
195 public final FileDescriptor
getFD() throws IOException
200 fd
= new FileDescriptor (ch
);
206 * This method reads an unsigned byte from the input stream and returns it
207 * as an int in the range of 0-255. This method also will return -1 if
208 * the end of the stream has been reached.
210 * This method will block until the byte can be read.
212 * @return The byte read or -1 if end of stream
214 * @exception IOException If an error occurs
216 public int read() throws IOException
222 * This method reads bytes from a stream and stores them into a caller
223 * supplied buffer. This method attempts to completely fill the buffer,
224 * but can return before doing so. The actual number of bytes read is
225 * returned as an int. A -1 is returned to indicate the end of the stream.
227 * This method will block until some data can be read.
229 * This method operates by calling an overloaded read method like so:
230 * <code>read(buf, 0, buf.length)</code>
232 * @param buf The buffer into which the bytes read will be stored.
234 * @return The number of bytes read or -1 if end of stream.
236 * @exception IOException If an error occurs.
238 public int read(byte[] buf
) throws IOException
240 return read(buf
, 0, buf
.length
);
244 * This method read bytes from a stream and stores them into a caller
245 * supplied buffer. It starts storing the data at index
246 * <code>offset</code> into
247 * the buffer and attempts to read <code>len</code> bytes. This method can
248 * return before reading the number of bytes requested. The actual number
249 * of bytes read is returned as an int. A -1 is returned to indicate the
252 * This method will block until some data can be read.
254 * @param buf The array into which the bytes read should be stored
255 * @param offset The offset into the array to start storing bytes
256 * @param len The requested number of bytes to read
258 * @return The actual number of bytes read, or -1 if end of stream.
260 * @exception IOException If an error occurs.
262 public int read(byte[] buf
, int offset
, int len
) throws IOException
266 || offset
+ len
> buf
.length
)
267 throw new ArrayIndexOutOfBoundsException();
269 return ch
.read(buf
, offset
, len
);
273 * This method skips the specified number of bytes in the stream. It
274 * returns the actual number of bytes skipped, which may be less than the
277 * @param numBytes The requested number of bytes to skip
279 * @return The actual number of bytes skipped.
281 * @exception IOException If an error occurs
283 public synchronized long skip (long numBytes
) throws IOException
286 throw new IllegalArgumentException ("Can't skip negative bytes: " +
292 long oldPos
= ch
.position ();
293 ch
.position(oldPos
+ numBytes
);
294 return ch
.position() - oldPos
;
298 * This method creates a java.nio.channels.FileChannel.
299 * Nio does not allow one to create a file channel directly.
300 * A file channel must be created by first creating an instance of
301 * Input/Output/RandomAccessFile and invoking the getChannel() method on it.
303 public synchronized FileChannel
getChannel ()
308 } // class FileInputStream