org.xerial.util.FastBufferedInputStream Maven / Gradle / Ivy
/*
* Copyright 1994-2006 Sun Microsystems, Inc. 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. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package org.xerial.util;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
/**
* A BufferedInputStream adds functionality to another input
* stream-namely, the ability to buffer the input and to support the
* mark and reset methods. When the
* BufferedInputStream is created, an internal buffer array is
* created. As bytes from the stream are read or skipped, the internal buffer is
* refilled as necessary from the contained input stream, many bytes at a time.
* The mark operation remembers a point in the input stream and the
* reset operation causes all the bytes read since the most recent
* mark operation to be reread before new bytes are taken from the
* contained input stream.
*
* @version 1.57, 06/07/06
*/
public final class FastBufferedInputStream extends FilterInputStream {
private static int defaultBufferSize = 8192;
/**
* The internal buffer array where the data is stored. When necessary, it
* may be replaced by another array of a different size.
*/
protected volatile byte buf[];
/**
* Atomic updater to provide compareAndSet for buf. This is necessary
* because closes can be asynchronous. We use nullness of buf[] as primary
* indicator that this stream is closed. (The "in" field is also nulled out
* on close.)
*/
private static final AtomicReferenceFieldUpdater bufUpdater = AtomicReferenceFieldUpdater
.newUpdater(FastBufferedInputStream.class, byte[].class, "buf");
/**
* The index one greater than the index of the last valid byte in the
* buffer. This value is always in the range 0 through
* buf.length; elements buf[0] through
* buf[count-1]
* contain buffered input data obtained from the underlying input
* stream.
*/
protected int count;
/**
* The current position in the buffer. This is the index of the next
* character to be read from the buf array.
*
* This value is always in the range 0 through
* count. If it is less than count, then
* buf[pos] is the next byte to be supplied as input; if it is
* equal to count, then the next read or
* skip operation will require more bytes to be read from the
* contained input stream.
*
* @see java.io.BufferedInputStream#buf
*/
protected int pos;
/**
* The value of the pos field at the time the last
* mark method was called.
*
* This value is always in the range -1 through
* pos. If there is no marked position in the input stream,
* this field is -1. If there is a marked position in the input
* stream, then buf[markpos] is the first byte to be supplied
* as input after a reset operation. If markpos is
* not -1, then all bytes from positions
* buf[markpos] through buf[pos-1] must remain in
* the buffer array (though they may be moved to another place in the buffer
* array, with suitable adjustments to the values of count,
* pos, and markpos); they may not be discarded
* unless and until the difference between pos and
* markpos exceeds marklimit.
*
* @see java.io.BufferedInputStream#mark(int)
* @see java.io.BufferedInputStream#pos
*/
protected int markpos = -1;
/**
* The maximum read ahead allowed after a call to the mark
* method before subsequent calls to the reset method fail.
* Whenever the difference between pos and markpos
* exceeds marklimit, then the mark may be dropped by setting
* markpos to -1.
*
* @see java.io.BufferedInputStream#mark(int)
* @see java.io.BufferedInputStream#reset()
*/
protected int marklimit;
/**
* Check to make sure that underlying input stream has not been nulled out
* due to close; if not return it;
*/
private InputStream getInIfOpen() throws IOException {
InputStream input = in;
if (input == null)
throw new IOException("Stream closed");
return input;
}
/**
* Check to make sure that buffer has not been nulled out due to close; if
* not return it;
*/
private byte[] getBufIfOpen() throws IOException {
byte[] buffer = buf;
if (buffer == null)
throw new IOException("Stream closed");
return buffer;
}
/**
* Creates a BufferedInputStream and saves its argument, the
* input stream in, for later use. An internal buffer array is
* created and stored in buf.
*
* @param in
* the underlying input stream.
*/
public FastBufferedInputStream(InputStream in) {
this(in, defaultBufferSize);
}
/**
* Creates a BufferedInputStream with the specified buffer
* size, and saves its argument, the input stream in, for later
* use. An internal buffer array of length size is created and
* stored in buf.
*
* @param in
* the underlying input stream.
* @param size
* the buffer size.
* @exception IllegalArgumentException
* if size <= 0.
*/
public FastBufferedInputStream(InputStream in, int size) {
super(in);
if (size <= 0) {
throw new IllegalArgumentException("Buffer size <= 0");
}
buf = new byte[size];
}
/**
* Fills the buffer with more data, taking into account shuffling and other
* tricks for dealing with marks. Assumes that it is being called by a
* synchronized method. This method also assumes that all data has already
* been read in, hence pos > count.
*/
private void fill() throws IOException {
byte[] buffer = getBufIfOpen();
if (markpos < 0)
pos = 0; /* no mark: throw away the buffer */
else if (pos >= buffer.length) /* no room left in buffer */
if (markpos > 0) { /* can throw away early part of the buffer */
int sz = pos - markpos;
System.arraycopy(buffer, markpos, buffer, 0, sz);
pos = sz;
markpos = 0;
}
else if (buffer.length >= marklimit) {
markpos = -1; /* buffer got too big, invalidate mark */
pos = 0; /* drop buffer contents */
}
else { /* grow buffer */
int nsz = pos * 2;
if (nsz > marklimit)
nsz = marklimit;
byte nbuf[] = new byte[nsz];
System.arraycopy(buffer, 0, nbuf, 0, pos);
if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {
// Can't replace buf if there was an async close.
// Note: This would need to be changed if fill()
// is ever made accessible to multiple threads.
// But for now, the only way CAS can fail is via close.
// assert buf == null;
throw new IOException("Stream closed");
}
buffer = nbuf;
}
count = pos;
int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
if (n > 0)
count = n + pos;
}
/**
* See the general contract of the read method of
* InputStream.
*
* @return the next byte of data, or -1 if the end of the
* stream is reached.
* @exception IOException
* if this input stream has been closed by invoking its
* {@link #close()} method, or an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
@Override
public int read() throws IOException {
if (pos >= count) {
fill();
if (pos >= count)
return -1;
}
return getBufIfOpen()[pos++] & 0xff;
}
/**
* Read characters into a portion of an array, reading from the underlying
* stream at most once if necessary.
*/
private int read1(byte[] b, int off, int len) throws IOException {
int avail = count - pos;
if (avail <= 0) {
/* If the requested length is at least as large as the buffer, and
if there is no mark/reset activity, do not bother to copy the
bytes into the local buffer. In this way buffered streams will
cascade harmlessly. */
if (len >= getBufIfOpen().length && markpos < 0) {
return getInIfOpen().read(b, off, len);
}
fill();
avail = count - pos;
if (avail <= 0)
return -1;
}
int cnt = (avail < len) ? avail : len;
System.arraycopy(getBufIfOpen(), pos, b, off, cnt);
pos += cnt;
return cnt;
}
/**
* Reads bytes from this byte-input stream into the specified byte array,
* starting at the given offset.
*
*
* This method implements the general contract of the corresponding
* {@link InputStream#read(byte[], int, int) read} method of
* the {@link InputStream} class. As an additional convenience,
* it attempts to read as many bytes as possible by repeatedly invoking the
* read method of the underlying stream. This iterated
* read continues until one of the following conditions becomes
* true:
*
*
* - The specified number of bytes have been read,
*
*
- The
read method of the underlying stream returns
* -1, indicating end-of-file, or
*
* - The
available method of the underlying stream returns
* zero, indicating that further input requests would block.
*
*
* If the first read on the underlying stream returns
* -1 to indicate end-of-file then this method returns
* -1. Otherwise this method returns the number of bytes
* actually read.
*
*
* Subclasses of this class are encouraged, but not required, to attempt to
* read as many bytes as possible in the same fashion.
*
* @param b
* destination buffer.
* @param off
* offset at which to start storing bytes.
* @param len
* maximum number of bytes to read.
* @return the number of bytes read, or -1 if the end of the
* stream has been reached.
* @exception IOException
* if this input stream has been closed by invoking its
* {@link #close()} method, or an I/O error occurs.
*/
@Override
public int read(byte b[], int off, int len) throws IOException {
getBufIfOpen(); // Check for closed stream
if ((off | len | (off + len) | (b.length - (off + len))) < 0) {
throw new IndexOutOfBoundsException();
}
else if (len == 0) {
return 0;
}
int n = 0;
for (;;) {
int nread = read1(b, off + n, len - n);
if (nread <= 0)
return (n == 0) ? nread : n;
n += nread;
if (n >= len)
return n;
// if not closed but no bytes available, return
InputStream input = in;
if (input != null && input.available() <= 0)
return n;
}
}
/**
* See the general contract of the skip method of
* InputStream.
*
* @exception IOException
* if the stream does not support seek, or if this input
* stream has been closed by invoking its {@link #close()}
* method, or an I/O error occurs.
*/
@Override
public long skip(long n) throws IOException {
getBufIfOpen(); // Check for closed stream
if (n <= 0) {
return 0;
}
long avail = count - pos;
if (avail <= 0) {
// If no mark position set then don't keep in buffer
if (markpos < 0)
return getInIfOpen().skip(n);
// Fill in buffer to save bytes for reset
fill();
avail = count - pos;
if (avail <= 0)
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.
*
* This method returns the sum of the number of bytes remaining to be read
* in the buffer (count - pos) and the result of calling
* the {@link java.io.FilterInputStream#in in}.available().
*
* @return an estimate of the number of bytes that can be read (or skipped
* over) from this input stream without blocking.
* @exception IOException
* if this input stream has been closed by invoking its
* {@link #close()} method, or an I/O error occurs.
*/
@Override
public int available() throws IOException {
return getInIfOpen().available() + (count - pos);
}
/**
* See the general contract of the mark method of
* InputStream.
*
* @param readlimit
* the maximum limit of bytes that can be read before the mark
* position becomes invalid.
* @see java.io.BufferedInputStream#reset()
*/
@Override
public void mark(int readlimit) {
marklimit = readlimit;
markpos = pos;
}
/**
* See the general contract of the reset method of
* InputStream.
*
* If markpos is -1 (no mark has been set or the
* mark has been invalidated), an IOException is thrown.
* Otherwise, pos is set equal to markpos.
*
* @exception 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)
*/
@Override
public 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 mark and
* reset methods. The markSupported method of
* BufferedInputStream returns true.
*
* @return a boolean indicating if this stream type supports
* the mark and reset methods.
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
@Override
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.
*
* @exception IOException
* if an I/O error occurs.
*/
@Override
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()
}
}
}