530 lines
24 KiB
Java
530 lines
24 KiB
Java
/*
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* Copyright (c) 1994, 2016, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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import java.util.Arrays;
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import java.util.Objects;
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/**
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* This abstract class is the superclass of all classes representing
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* an input stream of bytes.
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*
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* <p> Applications that need to define a subclass of <code>InputStream</code>
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* must always provide a method that returns the next byte of input.
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*
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* @author Arthur van Hoff
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* @see java.io.BufferedInputStream
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* @see java.io.ByteArrayInputStream
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* @see java.io.DataInputStream
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* @see java.io.FilterInputStream
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* @see java.io.InputStream#read()
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* @see java.io.OutputStream
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* @see java.io.PushbackInputStream
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* @since 1.0
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*/
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public abstract class InputStream implements Closeable {
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// MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
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// use when skipping.
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private static final int MAX_SKIP_BUFFER_SIZE = 2048;
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private static final int DEFAULT_BUFFER_SIZE = 8192;
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/**
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* Reads the next byte of data from the input stream. The value byte is
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* returned as an <code>int</code> in the range <code>0</code> to
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* <code>255</code>. If no byte is available because the end of the stream
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* has been reached, the value <code>-1</code> is returned. This method
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* blocks until input data is available, the end of the stream is detected,
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* or an exception is thrown.
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*
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* <p> A subclass must provide an implementation of this method.
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*
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* @return the next byte of data, or <code>-1</code> if the end of the
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* stream is reached.
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* @exception IOException if an I/O error occurs.
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*/
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public abstract int read() throws IOException;
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/**
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* Reads some number of bytes from the input stream and stores them into
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* the buffer array <code>b</code>. The number of bytes actually read is
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* returned as an integer. This method blocks until input data is
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* available, end of file is detected, or an exception is thrown.
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*
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* <p> If the length of <code>b</code> is zero, then no bytes are read and
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* <code>0</code> is returned; otherwise, there is an attempt to read at
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* least one byte. If no byte is available because the stream is at the
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* end of the file, the value <code>-1</code> is returned; otherwise, at
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* least one byte is read and stored into <code>b</code>.
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*
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* <p> The first byte read is stored into element <code>b[0]</code>, the
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* next one into <code>b[1]</code>, and so on. The number of bytes read is,
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* at most, equal to the length of <code>b</code>. Let <i>k</i> be the
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* number of bytes actually read; these bytes will be stored in elements
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* <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
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* leaving elements <code>b[</code><i>k</i><code>]</code> through
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* <code>b[b.length-1]</code> unaffected.
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*
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* <p> The <code>read(b)</code> method for class <code>InputStream</code>
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* has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
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*
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* @param b the buffer into which the data is read.
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* @return the total number of bytes read into the buffer, or
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* <code>-1</code> if there is no more data because the end of
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* the stream has been reached.
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* @exception IOException If the first byte cannot be read for any reason
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* other than the end of the file, if the input stream has been closed, or
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* if some other I/O error occurs.
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* @exception NullPointerException if <code>b</code> is <code>null</code>.
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* @see java.io.InputStream#read(byte[], int, int)
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*/
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public int read(byte b[]) throws IOException {
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return read(b, 0, b.length);
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}
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/**
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* Reads up to <code>len</code> bytes of data from the input stream into
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* an array of bytes. An attempt is made to read as many as
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* <code>len</code> bytes, but a smaller number may be read.
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* The number of bytes actually read is returned as an integer.
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*
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* <p> This method blocks until input data is available, end of file is
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* detected, or an exception is thrown.
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*
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* <p> If <code>len</code> is zero, then no bytes are read and
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* <code>0</code> is returned; otherwise, there is an attempt to read at
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* least one byte. If no byte is available because the stream is at end of
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* file, the value <code>-1</code> is returned; otherwise, at least one
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* byte is read and stored into <code>b</code>.
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*
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* <p> The first byte read is stored into element <code>b[off]</code>, the
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* next one into <code>b[off+1]</code>, and so on. The number of bytes read
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* is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
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* bytes actually read; these bytes will be stored in elements
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* <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
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* leaving elements <code>b[off+</code><i>k</i><code>]</code> through
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* <code>b[off+len-1]</code> unaffected.
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*
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* <p> In every case, elements <code>b[0]</code> through
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* <code>b[off]</code> and elements <code>b[off+len]</code> through
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* <code>b[b.length-1]</code> are unaffected.
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*
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* <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
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* for class <code>InputStream</code> simply calls the method
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* <code>read()</code> repeatedly. If the first such call results in an
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* <code>IOException</code>, that exception is returned from the call to
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* the <code>read(b,</code> <code>off,</code> <code>len)</code> method. If
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* any subsequent call to <code>read()</code> results in a
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* <code>IOException</code>, the exception is caught and treated as if it
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* were end of file; the bytes read up to that point are stored into
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* <code>b</code> and the number of bytes read before the exception
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* occurred is returned. The default implementation of this method blocks
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* until the requested amount of input data <code>len</code> has been read,
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* end of file is detected, or an exception is thrown. Subclasses are encouraged
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* to provide a more efficient implementation of this method.
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*
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* @param b the buffer into which the data is read.
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* @param off the start offset in array <code>b</code>
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* at which the data is written.
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* @param len the maximum number of bytes to read.
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* @return the total number of bytes read into the buffer, or
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* <code>-1</code> if there is no more data because the end of
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* the stream has been reached.
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* @exception IOException If the first byte cannot be read for any reason
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* other than end of file, or if the input stream has been closed, or if
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* some other I/O error occurs.
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* @exception NullPointerException If <code>b</code> is <code>null</code>.
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* @exception IndexOutOfBoundsException If <code>off</code> is negative,
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* <code>len</code> is negative, or <code>len</code> is greater than
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* <code>b.length - off</code>
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* @see java.io.InputStream#read()
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*/
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public int read(byte b[], int off, int len) throws IOException {
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if (b == null) {
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throw new NullPointerException();
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} else if (off < 0 || len < 0 || len > b.length - off) {
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throw new IndexOutOfBoundsException();
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} else if (len == 0) {
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return 0;
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}
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int c = read();
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if (c == -1) {
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return -1;
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}
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b[off] = (byte)c;
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int i = 1;
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try {
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for (; i < len ; i++) {
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c = read();
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if (c == -1) {
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break;
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}
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b[off + i] = (byte)c;
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}
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} catch (IOException ee) {
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}
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return i;
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}
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/**
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* The maximum size of array to allocate.
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* Some VMs reserve some header words in an array.
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* Attempts to allocate larger arrays may result in
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* OutOfMemoryError: Requested array size exceeds VM limit
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*/
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private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
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/**
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* Reads all remaining bytes from the input stream. This method blocks until
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* all remaining bytes have been read and end of stream is detected, or an
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* exception is thrown. This method does not close the input stream.
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*
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* <p> When this stream reaches end of stream, further invocations of this
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* method will return an empty byte array.
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*
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* <p> Note that this method is intended for simple cases where it is
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* convenient to read all bytes into a byte array. It is not intended for
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* reading input streams with large amounts of data.
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*
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* <p> The behavior for the case where the input stream is <i>asynchronously
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* closed</i>, or the thread interrupted during the read, is highly input
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* stream specific, and therefore not specified.
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*
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* <p> If an I/O error occurs reading from the input stream, then it may do
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* so after some, but not all, bytes have been read. Consequently the input
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* stream may not be at end of stream and may be in an inconsistent state.
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* It is strongly recommended that the stream be promptly closed if an I/O
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* error occurs.
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*
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* @return a byte array containing the bytes read from this input stream
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* @throws IOException if an I/O error occurs
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* @throws OutOfMemoryError if an array of the required size cannot be
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* allocated. For example, if an array larger than {@code 2GB} would
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* be required to store the bytes.
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*
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* @since 9
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*/
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public byte[] readAllBytes() throws IOException {
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byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
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int capacity = buf.length;
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int nread = 0;
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int n;
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for (;;) {
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// read to EOF which may read more or less than initial buffer size
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while ((n = read(buf, nread, capacity - nread)) > 0)
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nread += n;
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// if the last call to read returned -1, then we're done
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if (n < 0)
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break;
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// need to allocate a larger buffer
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if (capacity <= MAX_BUFFER_SIZE - capacity) {
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capacity = capacity << 1;
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} else {
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if (capacity == MAX_BUFFER_SIZE)
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throw new OutOfMemoryError("Required array size too large");
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capacity = MAX_BUFFER_SIZE;
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}
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buf = Arrays.copyOf(buf, capacity);
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}
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return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
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}
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/**
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* Reads the requested number of bytes from the input stream into the given
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* byte array. This method blocks until {@code len} bytes of input data have
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* been read, end of stream is detected, or an exception is thrown. The
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* number of bytes actually read, possibly zero, is returned. This method
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* does not close the input stream.
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*
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* <p> In the case where end of stream is reached before {@code len} bytes
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* have been read, then the actual number of bytes read will be returned.
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* When this stream reaches end of stream, further invocations of this
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* method will return zero.
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*
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* <p> If {@code len} is zero, then no bytes are read and {@code 0} is
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* returned; otherwise, there is an attempt to read up to {@code len} bytes.
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*
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* <p> The first byte read is stored into element {@code b[off]}, the next
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* one in to {@code b[off+1]}, and so on. The number of bytes read is, at
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* most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
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* read; these bytes will be stored in elements {@code b[off]} through
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* {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
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* {@code ]} through {@code b[off+len-1]} unaffected.
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*
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* <p> The behavior for the case where the input stream is <i>asynchronously
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* closed</i>, or the thread interrupted during the read, is highly input
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* stream specific, and therefore not specified.
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*
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* <p> If an I/O error occurs reading from the input stream, then it may do
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* so after some, but not all, bytes of {@code b} have been updated with
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* data from the input stream. Consequently the input stream and {@code b}
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* may be in an inconsistent state. It is strongly recommended that the
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* stream be promptly closed if an I/O error occurs.
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*
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* @param b the byte array into which the data is read
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* @param off the start offset in {@code b} at which the data is written
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* @param len the maximum number of bytes to read
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* @return the actual number of bytes read into the buffer
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* @throws IOException if an I/O error occurs
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* @throws NullPointerException if {@code b} is {@code null}
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* @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
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* is negative, or {@code len} is greater than {@code b.length - off}
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*
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* @since 9
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*/
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public int readNBytes(byte[] b, int off, int len) throws IOException {
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Objects.requireNonNull(b);
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if (off < 0 || len < 0 || len > b.length - off)
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throw new IndexOutOfBoundsException();
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int n = 0;
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while (n < len) {
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int count = read(b, off + n, len - n);
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if (count < 0)
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break;
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n += count;
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}
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return n;
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}
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/**
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* Skips over and discards <code>n</code> bytes of data from this input
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* stream. The <code>skip</code> method may, for a variety of reasons, end
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* up skipping over some smaller number of bytes, possibly <code>0</code>.
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* This may result from any of a number of conditions; reaching end of file
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* before <code>n</code> bytes have been skipped is only one possibility.
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* The actual number of bytes skipped is returned. If {@code n} is
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* negative, the {@code skip} method for class {@code InputStream} always
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* returns 0, and no bytes are skipped. Subclasses may handle the negative
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* value differently.
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*
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* <p> The <code>skip</code> method implementation of this class creates a
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* byte array and then repeatedly reads into it until <code>n</code> bytes
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* have been read or the end of the stream has been reached. Subclasses are
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* encouraged to provide a more efficient implementation of this method.
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* For instance, the implementation may depend on the ability to seek.
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*
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* @param n the number of bytes to be skipped.
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* @return the actual number of bytes skipped.
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* @throws IOException if an I/O error occurs.
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*/
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public long skip(long n) throws IOException {
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long remaining = n;
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int nr;
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if (n <= 0) {
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return 0;
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}
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int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
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byte[] skipBuffer = new byte[size];
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while (remaining > 0) {
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nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
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if (nr < 0) {
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break;
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}
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remaining -= nr;
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}
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return n - remaining;
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}
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/**
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* Returns an estimate of the number of bytes that can be read (or
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* skipped over) from this input stream without blocking by the next
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* invocation of a method for this input stream. The next invocation
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* might be the same thread or another thread. A single read or skip of this
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* many bytes will not block, but may read or skip fewer bytes.
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*
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* <p> Note that while some implementations of {@code InputStream} will return
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* the total number of bytes in the stream, many will not. It is
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* never correct to use the return value of this method to allocate
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* a buffer intended to hold all data in this stream.
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*
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* <p> A subclass' implementation of this method may choose to throw an
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* {@link IOException} if this input stream has been closed by
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* invoking the {@link #close()} method.
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*
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* <p> The {@code available} method for class {@code InputStream} always
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* returns {@code 0}.
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*
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* <p> This method should be overridden by subclasses.
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*
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* @return an estimate of the number of bytes that can be read (or skipped
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* over) from this input stream without blocking or {@code 0} when
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* it reaches the end of the input stream.
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* @exception IOException if an I/O error occurs.
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*/
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public int available() throws IOException {
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return 0;
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}
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/**
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* Closes this input stream and releases any system resources associated
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* with the stream.
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*
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* <p> The <code>close</code> method of <code>InputStream</code> does
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* nothing.
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*
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* @exception IOException if an I/O error occurs.
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*/
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public void close() throws IOException {}
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/**
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* Marks the current position in this input stream. A subsequent call to
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* the <code>reset</code> method repositions this stream at the last marked
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* position so that subsequent reads re-read the same bytes.
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*
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* <p> The <code>readlimit</code> arguments tells this input stream to
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* allow that many bytes to be read before the mark position gets
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* invalidated.
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*
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* <p> The general contract of <code>mark</code> is that, if the method
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* <code>markSupported</code> returns <code>true</code>, the stream somehow
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* remembers all the bytes read after the call to <code>mark</code> and
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* stands ready to supply those same bytes again if and whenever the method
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* <code>reset</code> is called. However, the stream is not required to
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* remember any data at all if more than <code>readlimit</code> bytes are
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* read from the stream before <code>reset</code> is called.
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*
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* <p> Marking a closed stream should not have any effect on the stream.
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*
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* <p> The <code>mark</code> method of <code>InputStream</code> does
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* nothing.
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*
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* @param readlimit the maximum limit of bytes that can be read before
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* the mark position becomes invalid.
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* @see java.io.InputStream#reset()
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*/
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public synchronized void mark(int readlimit) {}
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/**
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* Repositions this stream to the position at the time the
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* <code>mark</code> method was last called on this input stream.
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*
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* <p> The general contract of <code>reset</code> is:
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*
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* <ul>
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* <li> If the method <code>markSupported</code> returns
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* <code>true</code>, then:
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*
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* <ul><li> If the method <code>mark</code> has not been called since
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* the stream was created, or the number of bytes read from the stream
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* since <code>mark</code> was last called is larger than the argument
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* to <code>mark</code> at that last call, then an
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* <code>IOException</code> might be thrown.
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*
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* <li> If such an <code>IOException</code> is not thrown, then the
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* 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;
|
|
}
|
|
|
|
/**
|
|
* Reads all bytes from this input stream and writes the bytes to the
|
|
* given output stream in the order that they are read. On return, this
|
|
* input stream will be at end of stream. This method does not close either
|
|
* stream.
|
|
* <p>
|
|
* This method may block indefinitely reading from the input stream, or
|
|
* writing to the output stream. The behavior for the case where the input
|
|
* and/or output stream is <i>asynchronously closed</i>, or the thread
|
|
* interrupted during the transfer, is highly input and output stream
|
|
* specific, and therefore not specified.
|
|
* <p>
|
|
* If an I/O error occurs reading from the input stream or writing to the
|
|
* output stream, then it may do so after some bytes have been read or
|
|
* written. Consequently the input stream may not be at end of stream and
|
|
* one, or both, streams may be in an inconsistent state. It is strongly
|
|
* recommended that both streams be promptly closed if an I/O error occurs.
|
|
*
|
|
* @param out the output stream, non-null
|
|
* @return the number of bytes transferred
|
|
* @throws IOException if an I/O error occurs when reading or writing
|
|
* @throws NullPointerException if {@code out} is {@code null}
|
|
*
|
|
* @since 9
|
|
*/
|
|
public long transferTo(OutputStream out) throws IOException {
|
|
Objects.requireNonNull(out, "out");
|
|
long transferred = 0;
|
|
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
|
|
int read;
|
|
while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
|
|
out.write(buffer, 0, read);
|
|
transferred += read;
|
|
}
|
|
return transferred;
|
|
}
|
|
}
|