| /* InputStream.java -- Base class for input |
| Copyright (C) 1998, 1999, 2001, 2004, 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 implements Closeable |
| { |
| /** |
| * 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 || b.length - off < len) |
| throw new IndexOutOfBoundsException(); |
| |
| 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; |
| } |
| } |