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.FileChannelImpl;
43 import java.nio.ByteBuffer;
44 import java.nio.channels.FileChannel;
46 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
47 * "The Java Language Specification", ISBN 0-201-63451-1
48 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
49 * Status: Believed complete and correct.
53 * This class is a stream that reads its bytes from a file.
55 * @author Aaron M. Renn (arenn@urbanophile.com)
56 * @author Warren Levy (warrenl@cygnus.com)
58 public class FileInputStream extends InputStream
61 * This is the native file handle for the file this stream is reading from
63 private FileDescriptor fd;
65 private FileChannelImpl ch;
68 * This method initializes a <code>FileInputStream</code> to read from the
69 * specified named file. A security check is first made to determine
70 * whether or not access to this file is allowed. This is done by
71 * calling the <code>checkRead()</code> method of the
72 * <code>SecurityManager</code>
73 * (if one exists) with the name of this file. An exception is thrown
74 * if reading is not allowed. If the file does not exist, an exception
77 * @param name The name of the file this stream should read from
79 * @exception SecurityException If read access to the file is not allowed
80 * @exception FileNotFoundException If the file does not exist
81 * or if it is a directory
83 public FileInputStream(String name) throws FileNotFoundException
89 * This method initializes a <code>FileInputStream</code> to read from the
90 * specified <code>File</code> object. A security check is first
92 * whether or not access to this file is allowed. This is done by
93 * calling the <code>checkRead()</code> method of the
94 * <code>SecurityManager</code>
95 * (if one exists) with the name of this file. An exception is thrown
96 * if reading is not allowed. If the file does not exist, an exception
99 * @param file The <code>File</code> object this stream should read from
101 * @exception SecurityException If read access to the file is not allowed
102 * @exception FileNotFoundException If the file does not exist
103 * or if it is a directory.
105 public FileInputStream(File file) throws FileNotFoundException
107 SecurityManager s = System.getSecurityManager();
109 s.checkRead(file.getPath());
113 ch = FileChannelImpl.create(file, FileChannelImpl.READ);
115 catch (FileNotFoundException fnfe)
119 catch (IOException ioe)
121 FileNotFoundException fnfe = new FileNotFoundException(file.getPath());
128 * This method initializes a <code>FileInputStream</code> to read from the
129 * specified <code>FileDescriptor</code> object. A security
130 * check is first made to
131 * determine whether or not access to this file is allowed. This is done by
132 * calling the <code>checkRead()</code> method of the
133 * <code>SecurityManager</code>
134 * (if one exists) with the specified <code>FileDescriptor</code>
136 * thrown if reading is not allowed.
138 * @param fdObj The <code>FileDescriptor</code> object this stream
141 * @exception SecurityException If read access to the file is not allowed
143 public FileInputStream(FileDescriptor fdObj)
145 SecurityManager s = System.getSecurityManager();
150 ch = (FileChannelImpl) fdObj.channel;
153 FileInputStream(FileChannelImpl ch)
159 * This method returns the number of bytes that can be read from this
160 * stream before a read can block. A return of 0 indicates that blocking
161 * might (or might not) occur on the very next read attempt.
163 * This method returns the number of unread bytes remaining in the file if
164 * the descriptor being read from is an actual file. If this method is
165 * reading from a ''special'' file such a the standard input, this method
166 * will return the appropriate value for the stream being read.
168 * Be aware that reads on plain files that do not reside locally might
169 * possibly block even if this method says they should not. For example,
170 * a remote server might crash, preventing an NFS mounted file from being
173 * @return The number of bytes that can be read before blocking could occur
175 * @exception IOException If an error occurs
177 public int available() throws IOException
179 return ch.available();
183 * This method closes the stream. Any futher attempts to read from the
184 * stream will likely generate an IOException since the underlying file
187 * @exception IOException If an error occurs.
189 public void close() throws IOException
194 protected void finalize() throws IOException
196 // We don't actually need this, but we include it because it is
197 // mentioned in the JCL.
201 * This method returns a <code>FileDescriptor</code> object representing the
202 * underlying native file handle of the file this stream is reading
205 * @return A <code>FileDescriptor</code> for this stream
207 * @exception IOException If an error occurs
209 public final FileDescriptor getFD() throws IOException
214 fd = new FileDescriptor (ch);
220 * This method reads an unsigned byte from the input stream and returns it
221 * as an int in the range of 0-255. This method also will return -1 if
222 * the end of the stream has been reached.
224 * This method will block until the byte can be read.
226 * @return The byte read or -1 if end of stream
228 * @exception IOException If an error occurs
230 public int read() throws IOException
236 * This method reads bytes from a stream and stores them into a caller
237 * supplied buffer. This method attempts to completely fill the buffer,
238 * but can return before doing so. The actual number of bytes read is
239 * returned as an int. A -1 is returned to indicate the end of the stream.
241 * This method will block until some data can be read.
243 * This method operates by calling an overloaded read method like so:
244 * <code>read(buf, 0, buf.length)</code>
246 * @param buf The buffer into which the bytes read will be stored.
248 * @return The number of bytes read or -1 if end of stream.
250 * @exception IOException If an error occurs.
252 public int read(byte[] buf) throws IOException
254 return read(buf, 0, buf.length);
258 * This method read bytes from a stream and stores them into a caller
259 * supplied buffer. It starts storing the data at index
260 * <code>offset</code> into
261 * the buffer and attempts to read <code>len</code> bytes. This method can
262 * return before reading the number of bytes requested. The actual number
263 * of bytes read is returned as an int. A -1 is returned to indicate the
266 * This method will block until some data can be read.
268 * @param buf The array into which the bytes read should be stored
269 * @param offset The offset into the array to start storing bytes
270 * @param len The requested number of bytes to read
272 * @return The actual number of bytes read, or -1 if end of stream.
274 * @exception IOException If an error occurs.
276 public int read(byte[] buf, int offset, int len) throws IOException
280 || offset + len > buf.length)
281 throw new ArrayIndexOutOfBoundsException();
283 return ch.read(ByteBuffer.wrap(buf, offset, len));
287 * This method skips the specified number of bytes in the stream. It
288 * returns the actual number of bytes skipped, which may be less than the
291 * @param numBytes The requested number of bytes to skip
293 * @return The actual number of bytes skipped.
295 * @exception IOException If an error occurs
297 public synchronized long skip (long numBytes) throws IOException
300 throw new IllegalArgumentException ("Can't skip negative bytes: " +
306 long oldPos = ch.position ();
307 ch.position(oldPos + numBytes);
308 return ch.position() - oldPos;
312 * This method creates a java.nio.channels.FileChannel.
313 * Nio does not allow one to create a file channel directly.
314 * A file channel must be created by first creating an instance of
315 * Input/Output/RandomAccessFile and invoking the getChannel() method on it.
317 public synchronized FileChannel getChannel ()
322 } // class FileInputStream