diff options
Diffstat (limited to 'libjava/java/io/InputStream.java')
-rw-r--r-- | libjava/java/io/InputStream.java | 207 |
1 files changed, 182 insertions, 25 deletions
diff --git a/libjava/java/io/InputStream.java b/libjava/java/io/InputStream.java index 2da52b1..0cf1f43 100644 --- a/libjava/java/io/InputStream.java +++ b/libjava/java/io/InputStream.java @@ -1,56 +1,185 @@ -/* Copyright (C) 1998, 1999 Free Software Foundation +/* InputStream.java -- Base class for input + Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc. - This file is part of libgcj. +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., 59 Temple Place, Suite 330, Boston, MA +02111-1307 USA. + +As a special exception, if you link this library with other files to +produce an executable, this library does not by itself cause the +resulting executable to be covered by the GNU General Public License. +This exception does not however invalidate any other reasons why the +executable file might be covered by the GNU General Public License. */ -This software is copyrighted work licensed under the terms of the -Libgcj License. Please consult the file "LIBGCJ_LICENSE" for -details. */ package java.io; /** - * @author Warren Levy <warrenl@cygnus.com> - * @date October 2, 1998. - */ -/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 - * "The Java Language Specification", ISBN 0-201-63451-1 - * plus online API docs for JDK 1.2 beta from http://www.javasoft.com. - * Status: Believed complete and correct. - */ - + * 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) @@ -62,27 +191,55 @@ public abstract class InputStream for (i = 0; i < len; ++i) try - { - if ((ch = read()) < 0) - return i == 0 ? -1 : i; // EOF - b[off + i] = (byte) ch; - } + { + 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; - } + { + // 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[]. |