jaroslav@557: /*
jaroslav@557:  * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
jaroslav@557:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jaroslav@557:  *
jaroslav@557:  * This code is free software; you can redistribute it and/or modify it
jaroslav@557:  * under the terms of the GNU General Public License version 2 only, as
jaroslav@557:  * published by the Free Software Foundation.  Oracle designates this
jaroslav@557:  * particular file as subject to the "Classpath" exception as provided
jaroslav@557:  * by Oracle in the LICENSE file that accompanied this code.
jaroslav@557:  *
jaroslav@557:  * This code is distributed in the hope that it will be useful, but WITHOUT
jaroslav@557:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jaroslav@557:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jaroslav@557:  * version 2 for more details (a copy is included in the LICENSE file that
jaroslav@557:  * accompanied this code).
jaroslav@557:  *
jaroslav@557:  * You should have received a copy of the GNU General Public License version
jaroslav@557:  * 2 along with this work; if not, write to the Free Software Foundation,
jaroslav@557:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jaroslav@557:  *
jaroslav@557:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jaroslav@557:  * or visit www.oracle.com if you need additional information or have any
jaroslav@557:  * questions.
jaroslav@557:  */
jaroslav@557: 
jaroslav@557: package java.io;
jaroslav@557: 
jaroslav@557: 
jaroslav@557: /**
jaroslav@557:  * Abstract class for reading character streams.  The only methods that a
jaroslav@557:  * subclass must implement are read(char[], int, int) and close().  Most
jaroslav@557:  * subclasses, however, will override some of the methods defined here in order
jaroslav@557:  * to provide higher efficiency, additional functionality, or both.
jaroslav@557:  *
jaroslav@557:  *
jaroslav@557:  * @see BufferedReader
jaroslav@557:  * @see   LineNumberReader
jaroslav@557:  * @see CharArrayReader
jaroslav@557:  * @see InputStreamReader
jaroslav@557:  * @see   FileReader
jaroslav@557:  * @see FilterReader
jaroslav@557:  * @see   PushbackReader
jaroslav@557:  * @see PipedReader
jaroslav@557:  * @see StringReader
jaroslav@557:  * @see Writer
jaroslav@557:  *
jaroslav@557:  * @author      Mark Reinhold
jaroslav@557:  * @since       JDK1.1
jaroslav@557:  */
jaroslav@557: 
jaroslav@557: public abstract class Reader implements Readable, Closeable {
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * The object used to synchronize operations on this stream.  For
jaroslav@557:      * efficiency, a character-stream object may use an object other than
jaroslav@557:      * itself to protect critical sections.  A subclass should therefore use
jaroslav@557:      * the object in this field rather than <tt>this</tt> or a synchronized
jaroslav@557:      * method.
jaroslav@557:      */
jaroslav@557:     protected Object lock;
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Creates a new character-stream reader whose critical sections will
jaroslav@557:      * synchronize on the reader itself.
jaroslav@557:      */
jaroslav@557:     protected Reader() {
jaroslav@557:         this.lock = this;
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Creates a new character-stream reader whose critical sections will
jaroslav@557:      * synchronize on the given object.
jaroslav@557:      *
jaroslav@557:      * @param lock  The Object to synchronize on.
jaroslav@557:      */
jaroslav@557:     protected Reader(Object lock) {
jaroslav@557:         if (lock == null) {
jaroslav@557:             throw new NullPointerException();
jaroslav@557:         }
jaroslav@557:         this.lock = lock;
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Attempts to read characters into the specified character buffer.
jaroslav@557:      * The buffer is used as a repository of characters as-is: the only
jaroslav@557:      * changes made are the results of a put operation. No flipping or
jaroslav@557:      * rewinding of the buffer is performed.
jaroslav@557:      *
jaroslav@557:      * @param target the buffer to read characters into
jaroslav@557:      * @return The number of characters added to the buffer, or
jaroslav@557:      *         -1 if this source of characters is at its end
jaroslav@557:      * @throws IOException if an I/O error occurs
jaroslav@557:      * @throws NullPointerException if target is null
jaroslav@557:      * @throws ReadOnlyBufferException if target is a read only buffer
jaroslav@557:      * @since 1.5
jaroslav@557:      */
jaroslav@560: //    public int read(java.nio.CharBuffer target) throws IOException {
jaroslav@560: //        int len = target.remaining();
jaroslav@560: //        char[] cbuf = new char[len];
jaroslav@560: //        int n = read(cbuf, 0, len);
jaroslav@560: //        if (n > 0)
jaroslav@560: //            target.put(cbuf, 0, n);
jaroslav@560: //        return n;
jaroslav@560: //    }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Reads a single character.  This method will block until a character is
jaroslav@557:      * available, an I/O error occurs, or the end of the stream is reached.
jaroslav@557:      *
jaroslav@557:      * <p> Subclasses that intend to support efficient single-character input
jaroslav@557:      * should override this method.
jaroslav@557:      *
jaroslav@557:      * @return     The character read, as an integer in the range 0 to 65535
jaroslav@557:      *             (<tt>0x00-0xffff</tt>), or -1 if the end of the stream has
jaroslav@557:      *             been reached
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:     public int read() throws IOException {
jaroslav@557:         char cb[] = new char[1];
jaroslav@557:         if (read(cb, 0, 1) == -1)
jaroslav@557:             return -1;
jaroslav@557:         else
jaroslav@557:             return cb[0];
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Reads characters into an array.  This method will block until some input
jaroslav@557:      * is available, an I/O error occurs, or the end of the stream is reached.
jaroslav@557:      *
jaroslav@557:      * @param       cbuf  Destination buffer
jaroslav@557:      *
jaroslav@557:      * @return      The number of characters read, or -1
jaroslav@557:      *              if the end of the stream
jaroslav@557:      *              has been reached
jaroslav@557:      *
jaroslav@557:      * @exception   IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:     public int read(char cbuf[]) throws IOException {
jaroslav@557:         return read(cbuf, 0, cbuf.length);
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Reads characters into a portion of an array.  This method will block
jaroslav@557:      * until some input is available, an I/O error occurs, or the end of the
jaroslav@557:      * stream is reached.
jaroslav@557:      *
jaroslav@557:      * @param      cbuf  Destination buffer
jaroslav@557:      * @param      off   Offset at which to start storing characters
jaroslav@557:      * @param      len   Maximum number of characters to read
jaroslav@557:      *
jaroslav@557:      * @return     The number of characters read, or -1 if the end of the
jaroslav@557:      *             stream has been reached
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:     abstract public int read(char cbuf[], int off, int len) throws IOException;
jaroslav@557: 
jaroslav@557:     /** Maximum skip-buffer size */
jaroslav@557:     private static final int maxSkipBufferSize = 8192;
jaroslav@557: 
jaroslav@557:     /** Skip buffer, null until allocated */
jaroslav@557:     private char skipBuffer[] = null;
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Skips characters.  This method will block until some characters are
jaroslav@557:      * available, an I/O error occurs, or the end of the stream is reached.
jaroslav@557:      *
jaroslav@557:      * @param  n  The number of characters to skip
jaroslav@557:      *
jaroslav@557:      * @return    The number of characters actually skipped
jaroslav@557:      *
jaroslav@557:      * @exception  IllegalArgumentException  If <code>n</code> is negative.
jaroslav@557:      * @exception  IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:     public long skip(long n) throws IOException {
jaroslav@557:         if (n < 0L)
jaroslav@557:             throw new IllegalArgumentException("skip value is negative");
jaroslav@557:         int nn = (int) Math.min(n, maxSkipBufferSize);
jaroslav@557:         synchronized (lock) {
jaroslav@557:             if ((skipBuffer == null) || (skipBuffer.length < nn))
jaroslav@557:                 skipBuffer = new char[nn];
jaroslav@557:             long r = n;
jaroslav@557:             while (r > 0) {
jaroslav@557:                 int nc = read(skipBuffer, 0, (int)Math.min(r, nn));
jaroslav@557:                 if (nc == -1)
jaroslav@557:                     break;
jaroslav@557:                 r -= nc;
jaroslav@557:             }
jaroslav@557:             return n - r;
jaroslav@557:         }
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Tells whether this stream is ready to be read.
jaroslav@557:      *
jaroslav@557:      * @return True if the next read() is guaranteed not to block for input,
jaroslav@557:      * false otherwise.  Note that returning false does not guarantee that the
jaroslav@557:      * next read will block.
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:     public boolean ready() throws IOException {
jaroslav@557:         return false;
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Tells whether this stream supports the mark() operation. The default
jaroslav@557:      * implementation always returns false. Subclasses should override this
jaroslav@557:      * method.
jaroslav@557:      *
jaroslav@557:      * @return true if and only if this stream supports the mark operation.
jaroslav@557:      */
jaroslav@557:     public boolean markSupported() {
jaroslav@557:         return false;
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Marks the present position in the stream.  Subsequent calls to reset()
jaroslav@557:      * will attempt to reposition the stream to this point.  Not all
jaroslav@557:      * character-input streams support the mark() operation.
jaroslav@557:      *
jaroslav@557:      * @param  readAheadLimit  Limit on the number of characters that may be
jaroslav@557:      *                         read while still preserving the mark.  After
jaroslav@557:      *                         reading this many characters, attempting to
jaroslav@557:      *                         reset the stream may fail.
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If the stream does not support mark(),
jaroslav@557:      *                          or if some other I/O error occurs
jaroslav@557:      */
jaroslav@557:     public void mark(int readAheadLimit) throws IOException {
jaroslav@557:         throw new IOException("mark() not supported");
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Resets the stream.  If the stream has been marked, then attempt to
jaroslav@557:      * reposition it at the mark.  If the stream has not been marked, then
jaroslav@557:      * attempt to reset it in some way appropriate to the particular stream,
jaroslav@557:      * for example by repositioning it to its starting point.  Not all
jaroslav@557:      * character-input streams support the reset() operation, and some support
jaroslav@557:      * reset() without supporting mark().
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If the stream has not been marked,
jaroslav@557:      *                          or if the mark has been invalidated,
jaroslav@557:      *                          or if the stream does not support reset(),
jaroslav@557:      *                          or if some other I/O error occurs
jaroslav@557:      */
jaroslav@557:     public void reset() throws IOException {
jaroslav@557:         throw new IOException("reset() not supported");
jaroslav@557:     }
jaroslav@557: 
jaroslav@557:     /**
jaroslav@557:      * Closes the stream and releases any system resources associated with
jaroslav@557:      * it.  Once the stream has been closed, further read(), ready(),
jaroslav@557:      * mark(), reset(), or skip() invocations will throw an IOException.
jaroslav@557:      * Closing a previously closed stream has no effect.
jaroslav@557:      *
jaroslav@557:      * @exception  IOException  If an I/O error occurs
jaroslav@557:      */
jaroslav@557:      abstract public void close() throws IOException;
jaroslav@557: 
jaroslav@557: }