- /*
- * @(#)InputStream.java 1.45 04/02/19
- *
- * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- 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
- * @version 1.45, 02/19/04
- * @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 <code>b</code> is <code>null</code>, a
- * <code>NullPointerException</code> is thrown. 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 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[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> If the first byte cannot be read for any reason other than end of
- * file, then an <code>IOException</code> is thrown. In particular, an
- * <code>IOException</code> is thrown if the input stream has been closed.
- *
- * <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> is there is no more data because the end of
- * the stream has been reached.
- * @exception IOException if an 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>b</code> is <code>null</code>, a
- * <code>NullPointerException</code> is thrown.
- *
- * <p> If <code>off</code> is negative, or <code>len</code> is negative, or
- * <code>off+len</code> is greater than the length of the array
- * <code>b</code>, then an <code>IndexOutOfBoundsException</code> 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> If the first byte cannot be read for any reason other than end of
- * file, then an <code>IOException</code> is thrown. In particular, an
- * <code>IOException</code> is thrown if the input stream has been closed.
- *
- * <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. 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 an I/O error occurs.
- * @exception NullPointerException if <code>b</code> is <code>null</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) || (off > b.length) || (len < 0) ||
- ((off + len) > b.length) || ((off + len) < 0)) {
- 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;
- }
- if (b != null) {
- 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 <code>InputStream</code> 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.
- *
- * @param n the number of bytes to be skipped.
- * @return the actual number of bytes skipped.
- * @exception IOException if an 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 the number of bytes that can be read (or skipped over) from
- * this input stream without blocking by the next caller of a method for
- * this input stream. The next caller might be the same thread or
- * another thread.
- *
- * <p> The <code>available</code> method for class <code>InputStream</code>
- * always returns <code>0</code>.
- *
- * <p> This method should be overridden by subclasses.
- *
- * @return the number of bytes that can be read from this input stream
- * without blocking.
- * @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> 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;
- }
-
- }