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package it.unimi.dsi.io;
/*
* DSI utilities
*
* Copyright (C) 2013-2019 Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your option)
* any later version.
*
* This library 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see Instances of this class keep track of a queue of bytes using a circular
* (and possibly {@linkplain ByteBuffer#allocateDirect(int) direct})
* {@link ByteBuffer} that contains the head and the tail of the queue.
* The central part of the queue, if necessary, is dumped on disk. Note that {@link #clear()}
* does empty the queue, but it does not remove the dump file on disk: use {@link #trim()} to trim
* the file at the smallest possible length. The dump file can be removed only with a call to
* {@link #close()}, or when the instance is finalised.
*
*
Since file handles are a precious resource, this class provides a {@link #suspend()} method
* that releases the file handle without deleting the dump file. All calls to methods accessing the
* file handle will reinitialise it lazily (which implies that a certain number of
* enqueues/dequeues can be performed on a suspended class without actually reopening
* the dump file).
*
*
You can create a queue {@linkplain #createNew(File, int, boolean) using a new or empty file}, or
* {@linkplain #createFromFile(File, int, boolean) using an existing file}, in which case the
* content of the file will become the content of the queue. A {@link #freeze()} method closes
* a queue but leaves behind a dump file containing the current content of the queue, so that it
* can be {@linkplain #createFromFile(File, int, boolean) reopened} later.
*
*
Warning: the {@link #close()} method will delete the queue file from
* disk. This implies that if a file with the same name has been created in the meanwhile, it will
* be deleted.
*/
public class ByteDiskQueue implements Closeable, Size64 {
private static final boolean DEBUG = false;
/** The file containing the disk-based part of the queue. */
private final File file;
/** Whether {@link #buffer} should be allocated using {@link ByteBuffer#allocateDirect(int)}. */
private final boolean direct;
/** The start of the {@linkplain #buffer circular buffer}. */
private int start;
/** The end of the {@linkplain #buffer circular buffer}. Might be equal
* to {@link #start} even if the queue is not empty, but in that case {@link #used} is not zero (actually, it will be
* equal to the {@linkplain ByteBuffer#capacity() capacity} of {@link #buffer}). */
private int end;
/** The number of bytes currently in the {@linkplain #buffer circular buffer}.
* Note that this number might be the {@linkplain ByteBuffer#capacity() capacity} of {@link #buffer} when {@link #start} is
* equal to {@link #end}. */
private int used;
/** The hole in the queue. If it is not -1, there are elements on
* disk that should be inserted at this position in the {@linkplain #buffer circular buffer}. */
private int hole;
/** The {@linkplain ByteBuffer#capacity() capacity} of the {@linkplain #buffer circular buffer} minus 1. */
private int mask;
/** The current read/write {@link FileChannel} open on {@link #file}; it is {@code null} while the queue is
* {@linkplain #suspend() suspended} or {@linkplain #close() closed}, but in the first case
* {@link #readPosition} and {@link #writePosition} will be nonnegative. */
private FileChannel channel;
/** The write position of {@link #channel}, or -1 if this queue has been {@linkplain #close() closed}.
* If it is equal to {@link #readPosition}, then {@link #buffer} contain all bytes in this queue. */
private long writePosition;
/** The current read position, or -1 if this queue has been closed.
* @see #writePosition */
private long readPosition;
/** The circular buffer. */
private ByteBuffer buffer;
/** Creates a new disk-based byte queue.
*
* @param file the file that will be used to dump the central part of the queue on disk.
* @param bufferSize the {@linkplain ByteBuffer#capacity() capacity} of the circular buffer (will be possibly decreased so to be a power of two).
* @param direct whether the circular {@link ByteBuffer} used by this queue should be {@linkplain ByteBuffer#allocateDirect(int) allocated directly}.
* @param useFileContent whether the queue is new or should use the content of an existing file; in the first case,
* we check that the file does not exists or has length zero.
*/
@SuppressWarnings("resource")
protected ByteDiskQueue(final File file, final int bufferSize, final boolean direct, final boolean useFileContent) throws IOException {
this.file = file;
this.direct = direct;
channel = new RandomAccessFile(file, "rw").getChannel();
if (useFileContent) writePosition = channel.size();
else channel.truncate(0);
hole = readPosition == writePosition ? -1 : 0;
buffer = direct ? ByteBuffer.allocateDirect(Integer.highestOneBit(bufferSize)) : ByteBuffer.allocate(Integer.highestOneBit(bufferSize));
mask = buffer.capacity() - 1;
}
/** Creates a new empty disk-based byte queue.
*
* @param file the file that will be used to dump the central part of the queue on disk (must not exist
* or have length zero).
* @param bufferSize the {@linkplain ByteBuffer#capacity() capacity} of the circular buffer (will be possibly decreased so to be a power of two).
* @param direct whether the circular {@link ByteBuffer} used by this queue should be {@linkplain ByteBuffer#allocateDirect(int) allocated directly}.
*/
public static ByteDiskQueue createNew(final File file, final int bufferSize, final boolean direct) throws IOException {
if (file.length() != 0) throw new IOException("File " + file + " is nonempty");
return new ByteDiskQueue(file, bufferSize, direct, false);
}
/** Creates a new disk-based byte queue using the content of an existing file.
* The stream of bytes contained in the provided file will form the initial content of the queue.
*
* @param file the file that will be used to dump the central part of the queue on disk (must exist).
* @param bufferSize the {@linkplain ByteBuffer#capacity() capacity} of the circular buffer (will be possibly decreased so to be a power of two).
* @param direct whether the circular {@link ByteBuffer} used by this queue should be {@linkplain ByteBuffer#allocateDirect(int) allocated directly}.
*/
public static ByteDiskQueue createFromFile(final File file, final int bufferSize, final boolean direct) throws IOException {
if (! file.exists()) throw new IOException("File " + file + " does not exist");
return new ByteDiskQueue(file, bufferSize, direct, true);
}
/** Throws an {@link IllegalStateException} if the queue has been {@linkplain #close() closed}. */
private void ensureNotClosed() {
if (readPosition == -1) throw new IllegalStateException();
}
/** Enqueues a byte to this queue.
*
* @param b the byte to be enqueued.
*/
public void enqueue(final byte b) throws IOException {
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + "] enqueue(" + b + ")");
ensureNotClosed();
if (used == buffer.capacity()) dumpTail();
buffer.put(end++, b);
end &= mask;
used++;
}
/** Adds a vByte-coded natural number to this queue.
*
* @param x the natural number to be added to the queue.
*/
public void enqueueInt(final int x) throws IOException {
assert x >= 0 : x;
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + "] enqueueInt(" + x + ")");
switch(Fast.mostSignificantBit(x) / 7 + 1) {
case 1:
enqueue((byte)x);
break;
case 2:
enqueue((byte)(x >>> 7 | 0x80));
enqueue((byte)(x & 0x7F));
break;
case 3:
enqueue((byte)(x >>> 14 | 0x80));
enqueue((byte)(x >>> 7 | 0x80));
enqueue((byte)(x & 0x7F));
break;
case 4:
enqueue((byte)(x >>> 21 | 0x80));
enqueue((byte)(x >>> 14 | 0x80));
enqueue((byte)(x >>> 7 | 0x80));
enqueue((byte)(x & 0x7F));
break;
case 5:
enqueue((byte)(x >>> 28 | 0x80));
enqueue((byte)(x >>> 21 | 0x80));
enqueue((byte)(x >>> 14 | 0x80));
enqueue((byte)(x >>> 7 | 0x80));
enqueue((byte)(x & 0x7F));
}
}
/** Enqueues a fragment of byte array to this queue.
*
* @param a a byte array.
* @param offset the first byte in {@code a} to be enqueued.
* @param length the number of bytes to enqueue.
*/
public void enqueue(final byte[] a, int offset, int length) throws IOException {
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + "] enqueue(" + offset + ", " + length + ")");
ensureNotClosed();
do {
if (used == buffer.capacity()) dumpTail();
assert used != buffer.capacity() : used + " == " + buffer.capacity();
final int toBePut = Math.min(length, buffer.capacity() - used);
buffer.clear();
buffer.position(end);
if (end < start) buffer.put(a, offset, toBePut);
else {
final int firstTransfer = Math.min(toBePut, buffer.capacity() - end);
buffer.put(a, offset, firstTransfer);
if (firstTransfer < toBePut) {
buffer.clear();
buffer.put(a, offset + firstTransfer, toBePut - firstTransfer);
}
}
offset += toBePut;
length -= toBePut;
used += toBePut;
end = end + toBePut & mask;
} while(length != 0);
buffer.clear();
}
/** Enqueues a byte array to this queue.
*
* @param a the array whose bytes have to be enqueued.
*/
public void enqueue(final byte[] a) throws IOException {
enqueue(a, 0, a.length);
}
private void dumpTail() throws IOException {
resume();
if (DEBUG) System.err.println("Dumping at " + writePosition + ", start = " + start+ ", end = " + end + ", hole = " + hole);
channel.position(writePosition);
if (hole == -1) hole = (start + buffer.capacity() / 2) & mask;
buffer.clear();
buffer.position(hole);
if (hole < end) {
buffer.limit(end);
channel.write(buffer);
used -= end - hole;
}
else {
channel.write(buffer);
used -= buffer.capacity() - hole;
buffer.position(0);
buffer.limit(end);
channel.write(buffer);
used -= end;
}
buffer.clear();
writePosition = channel.position();
end = hole;
if (DEBUG) System.err.println("start = " + start+ ", end = " + end + ", hole = " + hole + ", readPosition = " + readPosition + ", writePosition = " + writePosition);
}
private void loadHead() throws IOException {
assert readPosition != writePosition : readPosition + " == " + writePosition;
// There are items on disk. We must load them.
if (DEBUG) System.err.println("Reading at " + readPosition + "...");
// If there is not enough space, we dump the tail. It is large, anyway.
if (used > buffer.capacity() / 2) dumpTail();
resume();
assert size64() > used : size64() + " <= " + used;
final int toRead = (int)Math.min(writePosition - readPosition, buffer.capacity() / 2);
start = hole - toRead & mask;
channel.position(readPosition);
buffer.clear();
buffer.position(start);
if (start < hole) {
buffer.limit(hole);
channel.read(buffer);
}
else {
channel.read(buffer);
buffer.position(0);
buffer.limit(hole);
channel.read(buffer);
}
buffer.clear();
used += toRead;
readPosition = channel.position();
if (readPosition == writePosition) {
readPosition = writePosition = 0;
hole = -1;
}
assert start != hole : start + " == " + hole;
if (DEBUG) System.err.println("Now at " + readPosition);
}
/** Dequeues a byte from the queue.
*
* @return the first available byte in this queue.
* @throws NoSuchElementException if there are no bytes in this queue.
*/
public byte dequeue() throws IOException {
ensureNotClosed();
if (DEBUG) System.err.print("[start = " + start + ", end = " + end + ", hole = " + hole + "] dequeue() = ");
if (isEmpty()) throw new NoSuchElementException();
if (start == hole) loadHead();
final byte result = buffer.get(start++);
start &= mask;
used--;
if (DEBUG) System.err.println(result);
return result;
}
/** Dequeues a sequence of bytes from this queue into an array.
*
* @param a a byte array.
* @param offset the first position in {@code a} where dequeued bytes will be written.
* @param length the number of bytes to dequeue.
* @throws NoSuchElementException if there are not enough bytes in this queue.
*/
public void dequeue(final byte[] a, int offset, int length) throws IOException {
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + "] dequeue(" + offset + ", " + length + ")");
ensureNotClosed();
while(length != 0) {
if (isEmpty()) throw new NoSuchElementException();
else if (start == hole) loadHead();
assert start != hole : start + " == " + hole;
final int endOfTransfer = hole == -1 ? end : hole;
final int toTransfer = Math.min(length, endOfTransfer == start ? used : endOfTransfer - start & mask);
buffer.clear();
buffer.position(start);
if (start < endOfTransfer) buffer.get(a, offset, toTransfer);
else {
final int firstTransfer = Math.min(toTransfer, buffer.capacity() - start);
buffer.get(a, offset, firstTransfer);
if (firstTransfer < toTransfer) {
buffer.clear();
buffer.get(a, offset + firstTransfer, toTransfer - firstTransfer);
}
}
offset += toTransfer;
length -= toTransfer;
used -= toTransfer;
start = start + toTransfer & mask;
}
buffer.clear();
}
/** Dequeues a sequence of bytes from this queue into an array.
*
* @param a the array that will contain the dequeued bytes.
* @throws NoSuchElementException if there are not enough bytes in this queue.
*/
public void dequeue(final byte[] a) throws IOException {
dequeue(a, 0, a.length);
}
/** Dequeues from this queue a vByte-coded natural number.
*
* @return the first available natural number in this queue.
*/
public int dequeueInt() throws IOException {
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + "] dequeueInt()");
for(int x = 0; ;) {
final byte b = dequeue();
x |= b & 0x7F;
if (b >= 0) return x;
x <<= 7;
}
}
@Deprecated
@Override
public int size() {
throw new UnsupportedOperationException();
}
@Override
public long size64() {
return writePosition - readPosition + used;
}
public boolean isEmpty() {
return size64() == 0;
}
/** Deallocates all disk resources associated with this queue. After calling this method, calls
* to any methods that would modify the queue will cause an {@link IllegalStateException}. */
@Override
public void close() throws IOException {
// If the queue is not suspended, we close the file handles.
if (channel != null) {
channel.close();
channel = null;
}
writePosition = readPosition = -1;
used = 0;
file.delete();
}
public void freeze() throws IOException {
if (DEBUG) System.err.println("[start = " + start + ", end = " + end + ", hole = " + hole + ", readPosition = " + readPosition + ", writePosition = " + writePosition + "] freeze()");
resume();
final File freezeFile = File.createTempFile(ByteDiskQueue.class.getSimpleName() + "-", ".freeze", file.getParentFile());
final FileOutputStream fos = new FileOutputStream(freezeFile);
final FileChannel freezeChannel = fos.getChannel();
// Dump head
buffer.clear();
buffer.position(start);
if (hole == -1) {
if (start < end) {
buffer.limit(end);
freezeChannel.write(buffer);
}
else if (used != 0) {
freezeChannel.write(buffer);
buffer.position(0);
buffer.limit(end);
freezeChannel.write(buffer);
}
}
else {
if (start < hole) {
buffer.limit(hole);
freezeChannel.write(buffer);
}
else if (start != hole){
freezeChannel.write(buffer);
buffer.position(0);
buffer.limit(hole);
freezeChannel.write(buffer);
}
for(long position = readPosition; position < writePosition;) position += channel.transferTo(position, writePosition - position, freezeChannel);
// Dump tail
buffer.clear();
buffer.position(hole);
if (hole < end) {
buffer.limit(end);
freezeChannel.write(buffer);
}
else if (hole != end) {
freezeChannel.write(buffer);
buffer.position(0);
buffer.limit(end);
freezeChannel.write(buffer);
}
}
assert size64() == freezeChannel.size() : size64() + " != " + freezeChannel.size();
fos.close();
channel.close();
file.delete();
if (! freezeFile.renameTo(file)) throw new IOException("Cannot rename freeze file " + freezeFile + " to " + file);
channel = null;
writePosition = readPosition = -1;
used = 0;
}
/** Clears the queue. Note that we do not modify the dump file (use {@link #trim()} to that purpose). */
public void clear() {
ensureNotClosed();
writePosition = readPosition = start = end = used = 0;
hole = -1;
}
/** Trims the queue dump file at the current write position. */
public void trim() throws IOException {
ensureNotClosed();
resume();
channel.truncate(writePosition);
}
/** Suspends this queue, releasing the associated file handles. If the deque is already
* suspended, does nothing. The queue will lazily resume its operations when necessary. */
public void suspend() throws IOException {
ensureNotClosed();
if (channel == null) return;
channel.close();
channel = null;
}
/** Resumes this queue, restoring the associated file handles. If the queue is already active, does nothing.
*
* @see #suspend()
*/
@SuppressWarnings("resource")
private void resume() throws IOException {
ensureNotClosed();
if (channel != null) return;
channel = new RandomAccessFile(file, "rw").getChannel();
}
@SuppressWarnings("deprecation")
@Override
protected void finalize() throws Throwable {
try {
if (channel != null || writePosition != -1) {
System.err.println("WARNING: This " + this.getClass().getName() + " [" + toString() + "] should have been closed.");
close();
}
}
finally {
super.finalize();
}
}
/** Enlarge the size of the buffer of this queue to a given size.
*
* @param newBufferSize the required buffer size (will be possibly decreased so to be a power of two).
* If the new buffer size is smaller than the current size, nothing happens.
*/
public void enlargeBuffer(int newBufferSize) {
if (DEBUG) System.err.print("Enlarging to size " + newBufferSize + " [start = " + start+ ", end = " + end + ", hole = " + hole + "]... ");
newBufferSize = Integer.highestOneBit(newBufferSize);
if (newBufferSize <= buffer.capacity()) return;
final ByteBuffer newByteBuffer = direct ? ByteBuffer.allocateDirect(newBufferSize) : ByteBuffer.allocate(newBufferSize);
buffer.clear();
if (start < end) {
buffer.position(start);
buffer.limit(end);
newByteBuffer.put(buffer);
end -= start;
if (hole >= 0) hole -= start;
}
else if (used != 0) {
buffer.position(start);
newByteBuffer.put(buffer);
buffer.position(0);
buffer.limit(end);
newByteBuffer.put(buffer);
end += buffer.capacity() - start;
if (hole >= 0)
if (hole >= start) hole -= start;
else hole += buffer.capacity() - start;
}
else { // This covers the case start == end, used == 0
end = 0;
if (hole > 0) hole = 0;
}
start = 0;
buffer = newByteBuffer;
mask = newBufferSize - 1;
if (DEBUG) System.err.println("[start = " + start+ ", end = " + end + ", hole = " + hole + "]");
}
}