483 lines
18 KiB
Java
483 lines
18 KiB
Java
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/*
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* Copyright (c) 1994, 2020, 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.concurrent.atomic.AtomicReferenceFieldUpdater;
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import jdk.internal.util.ArraysSupport;
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/**
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* A {@code BufferedInputStream} adds
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* functionality to another input stream-namely,
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* the ability to buffer the input and to
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* support the {@code mark} and {@code reset}
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* methods. When the {@code BufferedInputStream}
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* is created, an internal buffer array is
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* created. As bytes from the stream are read
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* or skipped, the internal buffer is refilled
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* as necessary from the contained input stream,
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* many bytes at a time. The {@code mark}
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* operation remembers a point in the input
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* stream and the {@code reset} operation
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* causes all the bytes read since the most
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* recent {@code mark} operation to be
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* reread before new bytes are taken from
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* the contained input stream.
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*
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* @author Arthur van Hoff
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* @since 1.0
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*/
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public class BufferedInputStream extends FilterInputStream {
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// Android-changed: made final
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private static final int DEFAULT_BUFFER_SIZE = 8192;
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/**
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* The internal buffer array where the data is stored. When necessary,
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* it may be replaced by another array of
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* a different size.
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*/
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protected volatile byte buf[];
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/**
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* Atomic updater to provide compareAndSet for buf. This is
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* necessary because closes can be asynchronous. We use nullness
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* of buf[] as primary indicator that this stream is closed. (The
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* "in" field is also nulled out on close.)
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*/
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private static final
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AtomicReferenceFieldUpdater<BufferedInputStream, byte[]> bufUpdater =
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AtomicReferenceFieldUpdater.newUpdater
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(BufferedInputStream.class, byte[].class, "buf");
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/**
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* The index one greater than the index of the last valid byte in
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* the buffer.
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* This value is always
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* in the range {@code 0} through {@code buf.length};
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* elements {@code buf[0]} through {@code buf[count-1]}
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* contain buffered input data obtained
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* from the underlying input stream.
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*/
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protected int count;
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/**
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* The current position in the buffer. This is the index of the next
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* character to be read from the {@code buf} array.
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* <p>
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* This value is always in the range {@code 0}
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* through {@code count}. If it is less
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* than {@code count}, then {@code buf[pos]}
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* is the next byte to be supplied as input;
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* if it is equal to {@code count}, then
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* the next {@code read} or {@code skip}
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* operation will require more bytes to be
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* read from the contained input stream.
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*
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* @see java.io.BufferedInputStream#buf
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*/
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protected int pos;
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/**
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* The value of the {@code pos} field at the time the last
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* {@code mark} method was called.
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* <p>
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* This value is always
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* in the range {@code -1} through {@code pos}.
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* If there is no marked position in the input
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* stream, this field is {@code -1}. If
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* there is a marked position in the input
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* stream, then {@code buf[markpos]}
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* is the first byte to be supplied as input
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* after a {@code reset} operation. If
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* {@code markpos} is not {@code -1},
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* then all bytes from positions {@code buf[markpos]}
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* through {@code buf[pos-1]} must remain
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* in the buffer array (though they may be
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* moved to another place in the buffer array,
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* with suitable adjustments to the values
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* of {@code count}, {@code pos},
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* and {@code markpos}); they may not
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* be discarded unless and until the difference
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* between {@code pos} and {@code markpos}
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* exceeds {@code marklimit}.
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*
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* @see java.io.BufferedInputStream#mark(int)
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* @see java.io.BufferedInputStream#pos
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*/
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protected int markpos = -1;
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/**
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* The maximum read ahead allowed after a call to the
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* {@code mark} method before subsequent calls to the
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* {@code reset} method fail.
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* Whenever the difference between {@code pos}
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* and {@code markpos} exceeds {@code marklimit},
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* then the mark may be dropped by setting
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* {@code markpos} to {@code -1}.
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*
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* @see java.io.BufferedInputStream#mark(int)
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* @see java.io.BufferedInputStream#reset()
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*/
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protected int marklimit;
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/**
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* Check to make sure that underlying input stream has not been
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* nulled out due to close; if not return it;
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*/
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private InputStream getInIfOpen() throws IOException {
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InputStream input = in;
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if (input == null)
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throw new IOException("Stream closed");
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return input;
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}
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/**
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* Check to make sure that buffer has not been nulled out due to
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* close; if not return it;
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*/
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private byte[] getBufIfOpen() throws IOException {
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byte[] buffer = buf;
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if (buffer == null)
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throw new IOException("Stream closed");
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return buffer;
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}
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/**
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* Creates a {@code BufferedInputStream}
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* and saves its argument, the input stream
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* {@code in}, for later use. An internal
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* buffer array is created and stored in {@code buf}.
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*
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* @param in the underlying input stream.
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*/
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public BufferedInputStream(InputStream in) {
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this(in, DEFAULT_BUFFER_SIZE);
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}
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/**
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* Creates a {@code BufferedInputStream}
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* with the specified buffer size,
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* and saves its argument, the input stream
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* {@code in}, for later use. An internal
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* buffer array of length {@code size}
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* is created and stored in {@code buf}.
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*
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* @param in the underlying input stream.
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* @param size the buffer size.
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* @throws IllegalArgumentException if {@code size <= 0}.
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*/
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public BufferedInputStream(InputStream in, int size) {
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super(in);
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if (size <= 0) {
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throw new IllegalArgumentException("Buffer size <= 0");
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}
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buf = new byte[size];
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}
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/**
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* Fills the buffer with more data, taking into account
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* shuffling and other tricks for dealing with marks.
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* Assumes that it is being called by a synchronized method.
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* This method also assumes that all data has already been read in,
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* hence pos > count.
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*/
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private void fill() throws IOException {
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byte[] buffer = getBufIfOpen();
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if (markpos < 0)
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pos = 0; /* no mark: throw away the buffer */
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else if (pos >= buffer.length) { /* no room left in buffer */
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if (markpos > 0) { /* can throw away early part of the buffer */
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int sz = pos - markpos;
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System.arraycopy(buffer, markpos, buffer, 0, sz);
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pos = sz;
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markpos = 0;
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} else if (buffer.length >= marklimit) {
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markpos = -1; /* buffer got too big, invalidate mark */
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pos = 0; /* drop buffer contents */
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} else { /* grow buffer */
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int nsz = ArraysSupport.newLength(pos,
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1, /* minimum growth */
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pos /* preferred growth */);
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if (nsz > marklimit)
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nsz = marklimit;
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byte[] nbuf = new byte[nsz];
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System.arraycopy(buffer, 0, nbuf, 0, pos);
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if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {
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// Can't replace buf if there was an async close.
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// Note: This would need to be changed if fill()
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// is ever made accessible to multiple threads.
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// But for now, the only way CAS can fail is via close.
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// assert buf == null;
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throw new IOException("Stream closed");
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}
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buffer = nbuf;
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}
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}
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count = pos;
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int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
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if (n > 0)
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count = n + pos;
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}
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/**
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* See
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* the general contract of the {@code read}
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* method of {@code InputStream}.
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*
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* @return the next byte of data, or {@code -1} if the end of the
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* stream is reached.
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* @throws IOException if this input stream has been closed by
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* invoking its {@link #close()} method,
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* or an I/O error occurs.
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* @see java.io.FilterInputStream#in
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*/
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public synchronized int read() throws IOException {
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if (pos >= count) {
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fill();
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if (pos >= count)
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return -1;
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}
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return getBufIfOpen()[pos++] & 0xff;
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}
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/**
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* Read characters into a portion of an array, reading from the underlying
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* stream at most once if necessary.
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*/
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private int read1(byte[] b, int off, int len) throws IOException {
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int avail = count - pos;
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if (avail <= 0) {
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/* If the requested length is at least as large as the buffer, and
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if there is no mark/reset activity, do not bother to copy the
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bytes into the local buffer. In this way buffered streams will
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cascade harmlessly. */
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if (len >= getBufIfOpen().length && markpos < 0) {
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return getInIfOpen().read(b, off, len);
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}
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fill();
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avail = count - pos;
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if (avail <= 0) return -1;
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}
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int cnt = (avail < len) ? avail : len;
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System.arraycopy(getBufIfOpen(), pos, b, off, cnt);
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pos += cnt;
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return cnt;
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}
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/**
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* Reads bytes from this byte-input stream into the specified byte array,
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* starting at the given offset.
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*
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* <p> This method implements the general contract of the corresponding
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* {@link InputStream#read(byte[], int, int) read} method of
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* the {@link InputStream} class. As an additional
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* convenience, it attempts to read as many bytes as possible by repeatedly
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* invoking the {@code read} method of the underlying stream. This
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* iterated {@code read} continues until one of the following
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* conditions becomes true: <ul>
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*
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* <li> The specified number of bytes have been read,
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*
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* <li> The {@code read} method of the underlying stream returns
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* {@code -1}, indicating end-of-file, or
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*
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* <li> The {@code available} method of the underlying stream
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* returns zero, indicating that further input requests would block.
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*
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* </ul> If the first {@code read} on the underlying stream returns
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* {@code -1} to indicate end-of-file then this method returns
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* {@code -1}. Otherwise this method returns the number of bytes
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* actually read.
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*
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* <p> Subclasses of this class are encouraged, but not required, to
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* attempt to read as many bytes as possible in the same fashion.
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*
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* @param b destination buffer.
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* @param off offset at which to start storing bytes.
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* @param len maximum number of bytes to read.
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* @return the number of bytes read, or {@code -1} if the end of
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* the stream has been reached.
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* @throws IOException if this input stream has been closed by
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* invoking its {@link #close()} method,
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* or an I/O error occurs.
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*/
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public synchronized int read(byte b[], int off, int len)
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throws IOException
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{
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getBufIfOpen(); // Check for closed stream
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if ((off | len | (off + len) | (b.length - (off + len))) < 0) {
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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 n = 0;
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for (;;) {
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int nread = read1(b, off + n, len - n);
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if (nread <= 0)
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return (n == 0) ? nread : n;
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n += nread;
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if (n >= len)
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return n;
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// if not closed but no bytes available, return
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InputStream input = in;
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if (input != null && input.available() <= 0)
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return n;
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}
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}
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/**
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* See the general contract of the {@code skip}
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* method of {@code InputStream}.
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*
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* @throws IOException if this input stream has been closed by
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* invoking its {@link #close()} method,
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* {@code in.skip(n)} throws an IOException,
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* or an I/O error occurs.
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*/
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public synchronized long skip(long n) throws IOException {
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getBufIfOpen(); // Check for closed stream
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if (n <= 0) {
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return 0;
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}
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long avail = count - pos;
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if (avail <= 0) {
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// If no mark position set then don't keep in buffer
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if (markpos <0)
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return getInIfOpen().skip(n);
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// Fill in buffer to save bytes for reset
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fill();
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avail = count - pos;
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if (avail <= 0)
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||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
long skipped = (avail < n) ? avail : n;
|
||
|
|
pos += skipped;
|
||
|
|
return skipped;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* 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>
|
||
|
|
* This method returns the sum of the number of bytes remaining to be read in
|
||
|
|
* the buffer ({@code count - pos}) and the result of calling the
|
||
|
|
* {@link java.io.FilterInputStream#in in}{@code .available()}.
|
||
|
|
*
|
||
|
|
* @return an estimate of the number of bytes that can be read (or skipped
|
||
|
|
* over) from this input stream without blocking.
|
||
|
|
* @throws IOException if this input stream has been closed by
|
||
|
|
* invoking its {@link #close()} method,
|
||
|
|
* or an I/O error occurs.
|
||
|
|
*/
|
||
|
|
public synchronized int available() throws IOException {
|
||
|
|
int n = count - pos;
|
||
|
|
int avail = getInIfOpen().available();
|
||
|
|
return n > (Integer.MAX_VALUE - avail)
|
||
|
|
? Integer.MAX_VALUE
|
||
|
|
: n + avail;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* See the general contract of the {@code mark}
|
||
|
|
* method of {@code InputStream}.
|
||
|
|
*
|
||
|
|
* @param readlimit the maximum limit of bytes that can be read before
|
||
|
|
* the mark position becomes invalid.
|
||
|
|
* @see java.io.BufferedInputStream#reset()
|
||
|
|
*/
|
||
|
|
public synchronized void mark(int readlimit) {
|
||
|
|
marklimit = readlimit;
|
||
|
|
markpos = pos;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* See the general contract of the {@code reset}
|
||
|
|
* method of {@code InputStream}.
|
||
|
|
* <p>
|
||
|
|
* If {@code markpos} is {@code -1}
|
||
|
|
* (no mark has been set or the mark has been
|
||
|
|
* invalidated), an {@code IOException}
|
||
|
|
* is thrown. Otherwise, {@code pos} is
|
||
|
|
* set equal to {@code markpos}.
|
||
|
|
*
|
||
|
|
* @throws IOException if this stream has not been marked or,
|
||
|
|
* if the mark has been invalidated, or the stream
|
||
|
|
* has been closed by invoking its {@link #close()}
|
||
|
|
* method, or an I/O error occurs.
|
||
|
|
* @see java.io.BufferedInputStream#mark(int)
|
||
|
|
*/
|
||
|
|
public synchronized void reset() throws IOException {
|
||
|
|
getBufIfOpen(); // Cause exception if closed
|
||
|
|
if (markpos < 0)
|
||
|
|
throw new IOException("Resetting to invalid mark");
|
||
|
|
pos = markpos;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Tests if this input stream supports the {@code mark}
|
||
|
|
* and {@code reset} methods. The {@code markSupported}
|
||
|
|
* method of {@code BufferedInputStream} returns
|
||
|
|
* {@code true}.
|
||
|
|
*
|
||
|
|
* @return a {@code boolean} indicating if this stream type supports
|
||
|
|
* the {@code mark} and {@code reset} methods.
|
||
|
|
* @see java.io.InputStream#mark(int)
|
||
|
|
* @see java.io.InputStream#reset()
|
||
|
|
*/
|
||
|
|
public boolean markSupported() {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Closes this input stream and releases any system resources
|
||
|
|
* associated with the stream.
|
||
|
|
* Once the stream has been closed, further read(), available(), reset(),
|
||
|
|
* or skip() invocations will throw an IOException.
|
||
|
|
* Closing a previously closed stream has no effect.
|
||
|
|
*
|
||
|
|
* @throws IOException if an I/O error occurs.
|
||
|
|
*/
|
||
|
|
public void close() throws IOException {
|
||
|
|
byte[] buffer;
|
||
|
|
while ( (buffer = buf) != null) {
|
||
|
|
if (bufUpdater.compareAndSet(this, buffer, null)) {
|
||
|
|
InputStream input = in;
|
||
|
|
in = null;
|
||
|
|
if (input != null)
|
||
|
|
input.close();
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
// Else retry in case a new buf was CASed in fill()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|