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Diffstat (limited to 'libjava/classpath/java/io/InputStream.java')
| -rw-r--r-- | libjava/classpath/java/io/InputStream.java | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/libjava/classpath/java/io/InputStream.java b/libjava/classpath/java/io/InputStream.java new file mode 100644 index 00000000000..86d1cd74914 --- /dev/null +++ b/libjava/classpath/java/io/InputStream.java @@ -0,0 +1,272 @@ +/* InputStream.java -- Base class for input + Copyright (C) 1998, 1999, 2001, 2005 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + + +package java.io; + +/** + * This abstract class forms the base of the hierarchy of classes that read + * input as a stream of bytes. It provides a common set of methods for + * reading bytes from streams. Subclasses implement and extend these + * methods to read bytes from a particular input source such as a file + * or network connection. + * + * @author Aaron M. Renn (arenn@urbanophile.com) + * @author Warren Levy (warrenl@cygnus.com) + */ +public abstract class InputStream +{ + /** + * Default, no-arg, public constructor + */ + public InputStream() + { + } + + /** + * This method returns the number of bytes that can be read from this + * stream before a read can block. A return of 0 indicates that blocking + * might (or might not) occur on the very next read attempt. + * <p> + * This method always returns 0 in this class + * + * @return The number of bytes that can be read before blocking could occur + * + * @exception IOException If an error occurs + */ + public int available() throws IOException + { + return 0; + } + + /** + * This method closes the stream. Any futher attempts to read from the + * stream may generate an <code>IOException</code> + * <p> + * This method does nothing in this class, but subclasses may override + * this method in order to provide additional functionality. + * + * @exception IOException If an error occurs, which can only happen + * in a subclass + */ + public void close() throws IOException + { + // Do nothing + } + + /** + * This method marks a position in the input to which the stream can + * be "reset" by calling the <code>reset()</code> method. The + * parameter @code{readlimit} is the number of bytes that can be read + * from the stream after setting the mark before the mark becomes + * invalid. For example, if <code>mark()</code> is called with a + * read limit of 10, then when 11 bytes of data are read from the + * stream before the <code>reset()</code> method is called, then the + * mark is invalid and the stream object instance is not required to + * remember the mark. + * <p> + * This method does nothing in this class, but subclasses may override it + * to provide mark/reset functionality. + * + * @param readLimit The number of bytes that can be read before the + * mark becomes invalid + */ + public void mark(int readLimit) + { + // Do nothing + } + + /** + * This method returns a boolean that indicates whether the mark/reset + * methods are supported in this class. Those methods can be used to + * remember a specific point in the stream and reset the stream to that + * point. + * <p> + * This method always returns <code>false</code> in this class, but + * subclasses can override this method to return <code>true</code> + * if they support mark/reset functionality. + * + * @return <code>true</code> if mark/reset functionality is + * supported, <code>false</code> otherwise + */ + public boolean markSupported() + { + return false; + } + + /** + * This method reads an unsigned byte from the input stream and returns it + * as an int in the range of 0-255. This method also will return -1 if + * the end of the stream has been reached. + * <p> + * This method will block until the byte can be read. + * + * @return The byte read or -1 if end of stream + * + * @exception IOException If an error occurs + */ + public abstract int read() throws IOException; + + /** + * This method reads bytes from a stream and stores them into a caller + * supplied buffer. This method attempts to completely fill the buffer, + * but can return before doing so. The actual number of bytes read is + * returned as an int. A -1 is returned to indicate the end of the stream. + * <p> + * This method will block until some data can be read. + * <p> + * This method operates by calling an overloaded read method like so: + * <code>read(b, 0, b.length)</code> + * + * @param b The buffer into which the bytes read will be stored. + * + * @return The number of bytes read or -1 if end of stream. + * + * @exception IOException If an error occurs. + */ + public int read(byte[] b) throws IOException + { + return read(b, 0, b.length); + } + + /** + * This method read bytes from a stream and stores them into a + * caller supplied buffer. It starts storing the data at index + * <code>off</code> into the buffer and attempts to read + * <code>len</code> bytes. This method can return before reading the + * number of bytes requested. The actual number of bytes read is + * returned as an int. A -1 is returned to indicate the end of the + * stream. + * <p> + * This method will block until some data can be read. + * <p> + * This method operates by calling the single byte <code>read()</code> method + * in a loop until the desired number of bytes are read. The read loop + * stops short if the end of the stream is encountered or if an IOException + * is encountered on any read operation except the first. If the first + * attempt to read a bytes fails, the IOException is allowed to propagate + * upward. And subsequent IOException is caught and treated identically + * to an end of stream condition. Subclasses can (and should if possible) + * override this method to provide a more efficient implementation. + * + * @param b The array into which the bytes read should be stored + * @param off The offset into the array to start storing bytes + * @param len The requested number of bytes to read + * + * @return The actual number of bytes read, or -1 if end of stream. + * + * @exception IOException If an error occurs. + */ + public int read(byte[] b, int off, int len) throws IOException + { + if (off < 0 || len < 0 || off + len > b.length) + throw new IndexOutOfBoundsException(); + if (b.length == 0) + return 0; + + int i, ch; + + for (i = 0; i < len; ++i) + try + { + if ((ch = read()) < 0) + return i == 0 ? -1 : i; // EOF + b[off + i] = (byte) ch; + } + catch (IOException ex) + { + // Only reading the first byte should cause an IOException. + if (i == 0) + throw ex; + return i; + } + + return i; + } + + /** + * This method resets a stream to the point where the + * <code>mark()</code> method was called. Any bytes that were read + * after the mark point was set will be re-read during subsequent + * reads. + * <p> + * This method always throws an IOException in this class, but subclasses + * can override this method if they provide mark/reset functionality. + * + * @exception IOException Always thrown for this class + */ + public void reset() throws IOException + { + throw new IOException("mark/reset not supported"); + } + + /** + * This method skips the specified number of bytes in the stream. It + * returns the actual number of bytes skipped, which may be less than the + * requested amount. + * <p> + * This method reads and discards bytes into a byte array until the + * specified number of bytes were skipped or until either the end of stream + * is reached or a read attempt returns a short count. Subclasses can + * override this metho to provide a more efficient implementation where + * one exists. + * + * @param n The requested number of bytes to skip + * + * @return The actual number of bytes skipped. + * + * @exception IOException If an error occurs + */ + public long skip(long n) throws IOException + { + // Throw away n bytes by reading them into a temp byte[]. + // Limit the temp array to 2Kb so we don't grab too much memory. + final int buflen = n > 2048 ? 2048 : (int) n; + byte[] tmpbuf = new byte[buflen]; + final long origN = n; + + while (n > 0L) + { + int numread = read(tmpbuf, 0, n > buflen ? buflen : (int) n); + if (numread <= 0) + break; + n -= numread; + } + + return origN - n; + } +} |