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