jtulach@118: /*
jtulach@118:  * Copyright (c) 1994, 2006, Oracle and/or its affiliates. All rights reserved.
jtulach@118:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jtulach@118:  *
jtulach@118:  * This code is free software; you can redistribute it and/or modify it
jtulach@118:  * under the terms of the GNU General Public License version 2 only, as
jtulach@118:  * published by the Free Software Foundation.  Oracle designates this
jtulach@118:  * particular file as subject to the "Classpath" exception as provided
jtulach@118:  * by Oracle in the LICENSE file that accompanied this code.
jtulach@118:  *
jtulach@118:  * This code is distributed in the hope that it will be useful, but WITHOUT
jtulach@118:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jtulach@118:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jtulach@118:  * version 2 for more details (a copy is included in the LICENSE file that
jtulach@118:  * accompanied this code).
jtulach@118:  *
jtulach@118:  * You should have received a copy of the GNU General Public License version
jtulach@118:  * 2 along with this work; if not, write to the Free Software Foundation,
jtulach@118:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jtulach@118:  *
jtulach@118:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jtulach@118:  * or visit www.oracle.com if you need additional information or have any
jtulach@118:  * questions.
jtulach@118:  */
jtulach@118: 
jtulach@118: package java.io;
jtulach@118: 
jtulach@118: /**
jtulach@118:  * This abstract class is the superclass of all classes representing
jtulach@118:  * an input stream of bytes.
jtulach@118:  *
jtulach@118:  * <p> Applications that need to define a subclass of <code>InputStream</code>
jtulach@118:  * must always provide a method that returns the next byte of input.
jtulach@118:  *
jtulach@118:  * @author  Arthur van Hoff
jtulach@118:  * @see     java.io.BufferedInputStream
jtulach@118:  * @see     java.io.ByteArrayInputStream
jtulach@118:  * @see     java.io.DataInputStream
jtulach@118:  * @see     java.io.FilterInputStream
jtulach@118:  * @see     java.io.InputStream#read()
jtulach@118:  * @see     java.io.OutputStream
jtulach@118:  * @see     java.io.PushbackInputStream
jtulach@118:  * @since   JDK1.0
jtulach@118:  */
jtulach@118: public abstract class InputStream implements Closeable {
jtulach@118: 
jtulach@118:     // SKIP_BUFFER_SIZE is used to determine the size of skipBuffer
jtulach@118:     private static final int SKIP_BUFFER_SIZE = 2048;
jtulach@118:     // skipBuffer is initialized in skip(long), if needed.
jtulach@118:     private static byte[] skipBuffer;
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Reads the next byte of data from the input stream. The value byte is
jtulach@118:      * returned as an <code>int</code> in the range <code>0</code> to
jtulach@118:      * <code>255</code>. If no byte is available because the end of the stream
jtulach@118:      * has been reached, the value <code>-1</code> is returned. This method
jtulach@118:      * blocks until input data is available, the end of the stream is detected,
jtulach@118:      * or an exception is thrown.
jtulach@118:      *
jtulach@118:      * <p> A subclass must provide an implementation of this method.
jtulach@118:      *
jtulach@118:      * @return     the next byte of data, or <code>-1</code> if the end of the
jtulach@118:      *             stream is reached.
jtulach@118:      * @exception  IOException  if an I/O error occurs.
jtulach@118:      */
jtulach@118:     public abstract int read() throws IOException;
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Reads some number of bytes from the input stream and stores them into
jtulach@118:      * the buffer array <code>b</code>. The number of bytes actually read is
jtulach@118:      * returned as an integer.  This method blocks until input data is
jtulach@118:      * available, end of file is detected, or an exception is thrown.
jtulach@118:      *
jtulach@118:      * <p> If the length of <code>b</code> is zero, then no bytes are read and
jtulach@118:      * <code>0</code> is returned; otherwise, there is an attempt to read at
jtulach@118:      * least one byte. If no byte is available because the stream is at the
jtulach@118:      * end of the file, the value <code>-1</code> is returned; otherwise, at
jtulach@118:      * least one byte is read and stored into <code>b</code>.
jtulach@118:      *
jtulach@118:      * <p> The first byte read is stored into element <code>b[0]</code>, the
jtulach@118:      * next one into <code>b[1]</code>, and so on. The number of bytes read is,
jtulach@118:      * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
jtulach@118:      * number of bytes actually read; these bytes will be stored in elements
jtulach@118:      * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
jtulach@118:      * leaving elements <code>b[</code><i>k</i><code>]</code> through
jtulach@118:      * <code>b[b.length-1]</code> unaffected.
jtulach@118:      *
jtulach@118:      * <p> The <code>read(b)</code> method for class <code>InputStream</code>
jtulach@118:      * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
jtulach@118:      *
jtulach@118:      * @param      b   the buffer into which the data is read.
jtulach@118:      * @return     the total number of bytes read into the buffer, or
jtulach@118:      *             <code>-1</code> if there is no more data because the end of
jtulach@118:      *             the stream has been reached.
jtulach@118:      * @exception  IOException  If the first byte cannot be read for any reason
jtulach@118:      * other than the end of the file, if the input stream has been closed, or
jtulach@118:      * if some other I/O error occurs.
jtulach@118:      * @exception  NullPointerException  if <code>b</code> is <code>null</code>.
jtulach@118:      * @see        java.io.InputStream#read(byte[], int, int)
jtulach@118:      */
jtulach@118:     public int read(byte b[]) throws IOException {
jtulach@118:         return read(b, 0, b.length);
jtulach@118:     }
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Reads up to <code>len</code> bytes of data from the input stream into
jtulach@118:      * an array of bytes.  An attempt is made to read as many as
jtulach@118:      * <code>len</code> bytes, but a smaller number may be read.
jtulach@118:      * The number of bytes actually read is returned as an integer.
jtulach@118:      *
jtulach@118:      * <p> This method blocks until input data is available, end of file is
jtulach@118:      * detected, or an exception is thrown.
jtulach@118:      *
jtulach@118:      * <p> If <code>len</code> is zero, then no bytes are read and
jtulach@118:      * <code>0</code> is returned; otherwise, there is an attempt to read at
jtulach@118:      * least one byte. If no byte is available because the stream is at end of
jtulach@118:      * file, the value <code>-1</code> is returned; otherwise, at least one
jtulach@118:      * byte is read and stored into <code>b</code>.
jtulach@118:      *
jtulach@118:      * <p> The first byte read is stored into element <code>b[off]</code>, the
jtulach@118:      * next one into <code>b[off+1]</code>, and so on. The number of bytes read
jtulach@118:      * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
jtulach@118:      * bytes actually read; these bytes will be stored in elements
jtulach@118:      * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
jtulach@118:      * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
jtulach@118:      * <code>b[off+len-1]</code> unaffected.
jtulach@118:      *
jtulach@118:      * <p> In every case, elements <code>b[0]</code> through
jtulach@118:      * <code>b[off]</code> and elements <code>b[off+len]</code> through
jtulach@118:      * <code>b[b.length-1]</code> are unaffected.
jtulach@118:      *
jtulach@118:      * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
jtulach@118:      * for class <code>InputStream</code> simply calls the method
jtulach@118:      * <code>read()</code> repeatedly. If the first such call results in an
jtulach@118:      * <code>IOException</code>, that exception is returned from the call to
jtulach@118:      * the <code>read(b,</code> <code>off,</code> <code>len)</code> method.  If
jtulach@118:      * any subsequent call to <code>read()</code> results in a
jtulach@118:      * <code>IOException</code>, the exception is caught and treated as if it
jtulach@118:      * were end of file; the bytes read up to that point are stored into
jtulach@118:      * <code>b</code> and the number of bytes read before the exception
jtulach@118:      * occurred is returned. The default implementation of this method blocks
jtulach@118:      * until the requested amount of input data <code>len</code> has been read,
jtulach@118:      * end of file is detected, or an exception is thrown. Subclasses are encouraged
jtulach@118:      * to provide a more efficient implementation of this method.
jtulach@118:      *
jtulach@118:      * @param      b     the buffer into which the data is read.
jtulach@118:      * @param      off   the start offset in array <code>b</code>
jtulach@118:      *                   at which the data is written.
jtulach@118:      * @param      len   the maximum number of bytes to read.
jtulach@118:      * @return     the total number of bytes read into the buffer, or
jtulach@118:      *             <code>-1</code> if there is no more data because the end of
jtulach@118:      *             the stream has been reached.
jtulach@118:      * @exception  IOException If the first byte cannot be read for any reason
jtulach@118:      * other than end of file, or if the input stream has been closed, or if
jtulach@118:      * some other I/O error occurs.
jtulach@118:      * @exception  NullPointerException If <code>b</code> is <code>null</code>.
jtulach@118:      * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
jtulach@118:      * <code>len</code> is negative, or <code>len</code> is greater than
jtulach@118:      * <code>b.length - off</code>
jtulach@118:      * @see        java.io.InputStream#read()
jtulach@118:      */
jtulach@118:     public int read(byte b[], int off, int len) throws IOException {
jtulach@118:         if (b == null) {
jtulach@118:             throw new NullPointerException();
jtulach@118:         } else if (off < 0 || len < 0 || len > b.length - off) {
jtulach@118:             throw new IndexOutOfBoundsException();
jtulach@118:         } else if (len == 0) {
jtulach@118:             return 0;
jtulach@118:         }
jtulach@118: 
jtulach@118:         int c = read();
jtulach@118:         if (c == -1) {
jtulach@118:             return -1;
jtulach@118:         }
jtulach@118:         b[off] = (byte)c;
jtulach@118: 
jtulach@118:         int i = 1;
jtulach@118:         try {
jtulach@118:             for (; i < len ; i++) {
jtulach@118:                 c = read();
jtulach@118:                 if (c == -1) {
jtulach@118:                     break;
jtulach@118:                 }
jtulach@118:                 b[off + i] = (byte)c;
jtulach@118:             }
jtulach@118:         } catch (IOException ee) {
jtulach@118:         }
jtulach@118:         return i;
jtulach@118:     }
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Skips over and discards <code>n</code> bytes of data from this input
jtulach@118:      * stream. The <code>skip</code> method may, for a variety of reasons, end
jtulach@118:      * up skipping over some smaller number of bytes, possibly <code>0</code>.
jtulach@118:      * This may result from any of a number of conditions; reaching end of file
jtulach@118:      * before <code>n</code> bytes have been skipped is only one possibility.
jtulach@118:      * The actual number of bytes skipped is returned.  If <code>n</code> is
jtulach@118:      * negative, no bytes are skipped.
jtulach@118:      *
jtulach@118:      * <p> The <code>skip</code> method of this class creates a
jtulach@118:      * byte array and then repeatedly reads into it until <code>n</code> bytes
jtulach@118:      * have been read or the end of the stream has been reached. Subclasses are
jtulach@118:      * encouraged to provide a more efficient implementation of this method.
jtulach@118:      * For instance, the implementation may depend on the ability to seek.
jtulach@118:      *
jtulach@118:      * @param      n   the number of bytes to be skipped.
jtulach@118:      * @return     the actual number of bytes skipped.
jtulach@118:      * @exception  IOException  if the stream does not support seek,
jtulach@118:      *                          or if some other I/O error occurs.
jtulach@118:      */
jtulach@118:     public long skip(long n) throws IOException {
jtulach@118: 
jtulach@118:         long remaining = n;
jtulach@118:         int nr;
jtulach@118:         if (skipBuffer == null)
jtulach@118:             skipBuffer = new byte[SKIP_BUFFER_SIZE];
jtulach@118: 
jtulach@118:         byte[] localSkipBuffer = skipBuffer;
jtulach@118: 
jtulach@118:         if (n <= 0) {
jtulach@118:             return 0;
jtulach@118:         }
jtulach@118: 
jtulach@118:         while (remaining > 0) {
jtulach@118:             nr = read(localSkipBuffer, 0,
jtulach@118:                       (int) Math.min(SKIP_BUFFER_SIZE, remaining));
jtulach@118:             if (nr < 0) {
jtulach@118:                 break;
jtulach@118:             }
jtulach@118:             remaining -= nr;
jtulach@118:         }
jtulach@118: 
jtulach@118:         return n - remaining;
jtulach@118:     }
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Returns an estimate of the number of bytes that can be read (or
jtulach@118:      * skipped over) from this input stream without blocking by the next
jtulach@118:      * invocation of a method for this input stream. The next invocation
jtulach@118:      * might be the same thread or another thread.  A single read or skip of this
jtulach@118:      * many bytes will not block, but may read or skip fewer bytes.
jtulach@118:      *
jtulach@118:      * <p> Note that while some implementations of {@code InputStream} will return
jtulach@118:      * the total number of bytes in the stream, many will not.  It is
jtulach@118:      * never correct to use the return value of this method to allocate
jtulach@118:      * a buffer intended to hold all data in this stream.
jtulach@118:      *
jtulach@118:      * <p> A subclass' implementation of this method may choose to throw an
jtulach@118:      * {@link IOException} if this input stream has been closed by
jtulach@118:      * invoking the {@link #close()} method.
jtulach@118:      *
jtulach@118:      * <p> The {@code available} method for class {@code InputStream} always
jtulach@118:      * returns {@code 0}.
jtulach@118:      *
jtulach@118:      * <p> This method should be overridden by subclasses.
jtulach@118:      *
jtulach@118:      * @return     an estimate of the number of bytes that can be read (or skipped
jtulach@118:      *             over) from this input stream without blocking or {@code 0} when
jtulach@118:      *             it reaches the end of the input stream.
jtulach@118:      * @exception  IOException if an I/O error occurs.
jtulach@118:      */
jtulach@118:     public int available() throws IOException {
jtulach@118:         return 0;
jtulach@118:     }
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Closes this input stream and releases any system resources associated
jtulach@118:      * with the stream.
jtulach@118:      *
jtulach@118:      * <p> The <code>close</code> method of <code>InputStream</code> does
jtulach@118:      * nothing.
jtulach@118:      *
jtulach@118:      * @exception  IOException  if an I/O error occurs.
jtulach@118:      */
jtulach@118:     public void close() throws IOException {}
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Marks the current position in this input stream. A subsequent call to
jtulach@118:      * the <code>reset</code> method repositions this stream at the last marked
jtulach@118:      * position so that subsequent reads re-read the same bytes.
jtulach@118:      *
jtulach@118:      * <p> The <code>readlimit</code> arguments tells this input stream to
jtulach@118:      * allow that many bytes to be read before the mark position gets
jtulach@118:      * invalidated.
jtulach@118:      *
jtulach@118:      * <p> The general contract of <code>mark</code> is that, if the method
jtulach@118:      * <code>markSupported</code> returns <code>true</code>, the stream somehow
jtulach@118:      * remembers all the bytes read after the call to <code>mark</code> and
jtulach@118:      * stands ready to supply those same bytes again if and whenever the method
jtulach@118:      * <code>reset</code> is called.  However, the stream is not required to
jtulach@118:      * remember any data at all if more than <code>readlimit</code> bytes are
jtulach@118:      * read from the stream before <code>reset</code> is called.
jtulach@118:      *
jtulach@118:      * <p> Marking a closed stream should not have any effect on the stream.
jtulach@118:      *
jtulach@118:      * <p> The <code>mark</code> method of <code>InputStream</code> does
jtulach@118:      * nothing.
jtulach@118:      *
jtulach@118:      * @param   readlimit   the maximum limit of bytes that can be read before
jtulach@118:      *                      the mark position becomes invalid.
jtulach@118:      * @see     java.io.InputStream#reset()
jtulach@118:      */
jtulach@118:     public synchronized void mark(int readlimit) {}
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Repositions this stream to the position at the time the
jtulach@118:      * <code>mark</code> method was last called on this input stream.
jtulach@118:      *
jtulach@118:      * <p> The general contract of <code>reset</code> is:
jtulach@118:      *
jtulach@118:      * <p><ul>
jtulach@118:      *
jtulach@118:      * <li> If the method <code>markSupported</code> returns
jtulach@118:      * <code>true</code>, then:
jtulach@118:      *
jtulach@118:      *     <ul><li> If the method <code>mark</code> has not been called since
jtulach@118:      *     the stream was created, or the number of bytes read from the stream
jtulach@118:      *     since <code>mark</code> was last called is larger than the argument
jtulach@118:      *     to <code>mark</code> at that last call, then an
jtulach@118:      *     <code>IOException</code> might be thrown.
jtulach@118:      *
jtulach@118:      *     <li> If such an <code>IOException</code> is not thrown, then the
jtulach@118:      *     stream is reset to a state such that all the bytes read since the
jtulach@118:      *     most recent call to <code>mark</code> (or since the start of the
jtulach@118:      *     file, if <code>mark</code> has not been called) will be resupplied
jtulach@118:      *     to subsequent callers of the <code>read</code> method, followed by
jtulach@118:      *     any bytes that otherwise would have been the next input data as of
jtulach@118:      *     the time of the call to <code>reset</code>. </ul>
jtulach@118:      *
jtulach@118:      * <li> If the method <code>markSupported</code> returns
jtulach@118:      * <code>false</code>, then:
jtulach@118:      *
jtulach@118:      *     <ul><li> The call to <code>reset</code> may throw an
jtulach@118:      *     <code>IOException</code>.
jtulach@118:      *
jtulach@118:      *     <li> If an <code>IOException</code> is not thrown, then the stream
jtulach@118:      *     is reset to a fixed state that depends on the particular type of the
jtulach@118:      *     input stream and how it was created. The bytes that will be supplied
jtulach@118:      *     to subsequent callers of the <code>read</code> method depend on the
jtulach@118:      *     particular type of the input stream. </ul></ul>
jtulach@118:      *
jtulach@118:      * <p>The method <code>reset</code> for class <code>InputStream</code>
jtulach@118:      * does nothing except throw an <code>IOException</code>.
jtulach@118:      *
jtulach@118:      * @exception  IOException  if this stream has not been marked or if the
jtulach@118:      *               mark has been invalidated.
jtulach@118:      * @see     java.io.InputStream#mark(int)
jtulach@118:      * @see     java.io.IOException
jtulach@118:      */
jtulach@118:     public synchronized void reset() throws IOException {
jtulach@118:         throw new IOException("mark/reset not supported");
jtulach@118:     }
jtulach@118: 
jtulach@118:     /**
jtulach@118:      * Tests if this input stream supports the <code>mark</code> and
jtulach@118:      * <code>reset</code> methods. Whether or not <code>mark</code> and
jtulach@118:      * <code>reset</code> are supported is an invariant property of a
jtulach@118:      * particular input stream instance. The <code>markSupported</code> method
jtulach@118:      * of <code>InputStream</code> returns <code>false</code>.
jtulach@118:      *
jtulach@118:      * @return  <code>true</code> if this stream instance supports the mark
jtulach@118:      *          and reset methods; <code>false</code> otherwise.
jtulach@118:      * @see     java.io.InputStream#mark(int)
jtulach@118:      * @see     java.io.InputStream#reset()
jtulach@118:      */
jtulach@118:     public boolean markSupported() {
jtulach@118:         return false;
jtulach@118:     }
jtulach@118: 
jtulach@118: }