java.lang.Object
- it.unimi.dsi.io.ByteDiskQueue

All Implemented Interfaces:

Size64, Closeable, AutoCloseable
```
public class ByteDiskQueue
extends Object
implements Closeable, Size64
```
A queue of bytes partially stored on disk.
Instances of this class keep track of a queue of bytes using a circular (and possibly direct) 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 clear() does empty the queue, but it does not remove the dump file on disk: use trim() to trim the file at the smallest possible length. The dump file can be removed only with a call to close(), or when the instance is finalised.
Since file handles are a precious resource, this class provides a 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 using a new or empty file, or using an existing file, in which case the content of the file will become the content of the queue. A freeze() method closes a queue but leaves behind a dump file containing the current content of the queue, so that it can be reopened later.
Warning: the 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.

Constructor Summary

Constructors
Modifier	Constructor	Description
`protected`	`ByteDiskQueue(File file, int bufferSize, boolean direct, boolean useFileContent)`	Creates a new disk-based byte queue.

Method Summary

Modifier and Type	Method	Description
`void`	`clear()`	Clears the queue.
`void`	`close()`	Deallocates all disk resources associated with this queue.
`static ByteDiskQueue`	`createFromFile(File file, int bufferSize, boolean direct)`	Creates a new disk-based byte queue using the content of an existing file.
`static ByteDiskQueue`	`createNew(File file, int bufferSize, boolean direct)`	Creates a new empty disk-based byte queue.
`byte`	`dequeue()`	Dequeues a byte from the queue.
`void`	`dequeue(byte[] a)`	Dequeues a sequence of bytes from this queue into an array.
`void`	`dequeue(byte[] a, int offset, int length)`	Dequeues a sequence of bytes from this queue into an array.
`int`	`dequeueInt()`	Dequeues from this queue a vByte-coded natural number.
`void`	`enlargeBuffer(int newBufferSize)`	Enlarge the size of the buffer of this queue to a given size.
`void`	`enqueue(byte b)`	Enqueues a byte to this queue.
`void`	`enqueue(byte[] a)`	Enqueues a byte array to this queue.
`void`	`enqueue(byte[] a, int offset, int length)`	Enqueues a fragment of byte array to this queue.
`void`	`enqueueInt(int x)`	Adds a vByte-coded natural number to this queue.
`protected void`	`finalize()`
`void`	`freeze()`
`boolean`	`isEmpty()`
`int`	`size()`	Deprecated.
`long`	`size64()`
`void`	`suspend()`	Suspends this queue, releasing the associated file handles.
`void`	`trim()`	Trims the queue dump file at the current write position.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ByteDiskQueue
```
protected ByteDiskQueue(File file,
                        int bufferSize,
                        boolean direct,
                        boolean useFileContent)
                 throws IOException
```
    Creates a new disk-based byte queue.
    
    Parameters:
    
    file - the file that will be used to dump the central part of the queue on disk.
    
    bufferSize - the capacity of the circular buffer (will be possibly decreased so to be a power of two).
    
    direct - whether the circular ByteBuffer used by this queue should be allocated directly.
    
    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.
    
    Throws:
    
    IOException
- Method Detail
  - createNew
```
public static ByteDiskQueue createNew(File file,
                                      int bufferSize,
                                      boolean direct)
                               throws IOException
```
    Creates a new empty disk-based byte queue.
    
    Parameters:
    
    file - the file that will be used to dump the central part of the queue on disk (must not exist or have length zero).
    
    bufferSize - the capacity of the circular buffer (will be possibly decreased so to be a power of two).
    
    direct - whether the circular ByteBuffer used by this queue should be allocated directly.
    
    Throws:
    
    IOException
  - createFromFile
```
public static ByteDiskQueue createFromFile(File file,
                                           int bufferSize,
                                           boolean direct)
                                    throws IOException
```
    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.
    
    Parameters:
    
    file - the file that will be used to dump the central part of the queue on disk (must exist).
    
    bufferSize - the capacity of the circular buffer (will be possibly decreased so to be a power of two).
    
    direct - whether the circular ByteBuffer used by this queue should be allocated directly.
    
    Throws:
    
    IOException
  - enqueue
```
public void enqueue(byte b)
             throws IOException
```
    Enqueues a byte to this queue.
    
    Parameters:
    
    b - the byte to be enqueued.
    
    Throws:
    
    IOException
  - enqueueInt
```
public void enqueueInt(int x)
                throws IOException
```
    Adds a vByte-coded natural number to this queue.
    
    Parameters:
    
    x - the natural number to be added to the queue.
    
    Throws:
    
    IOException
  - enqueue
```
public void enqueue(byte[] a,
                    int offset,
                    int length)
             throws IOException
```
    Enqueues a fragment of byte array to this queue.
    
    Parameters:
    
    a - a byte array.
    
    offset - the first byte in a to be enqueued.
    
    length - the number of bytes to enqueue.
    
    Throws:
    
    IOException
  - enqueue
```
public void enqueue(byte[] a)
             throws IOException
```
    Enqueues a byte array to this queue.
    
    Parameters:
    
    a - the array whose bytes have to be enqueued.
    
    Throws:
    
    IOException
  - dequeue
```
public byte dequeue()
             throws IOException
```
    Dequeues a byte from the queue.
    
    Returns:
    
    the first available byte in this queue.
    
    Throws:
    
    NoSuchElementException - if there are no bytes in this queue.
    
    IOException
  - dequeue
```
public void dequeue(byte[] a,
                    int offset,
                    int length)
             throws IOException
```
    Dequeues a sequence of bytes from this queue into an array.
    
    Parameters:
    
    a - a byte array.
    
    offset - the first position in a where dequeued bytes will be written.
    
    length - the number of bytes to dequeue.
    
    Throws:
    
    NoSuchElementException - if there are not enough bytes in this queue.
    
    IOException
  - dequeue
```
public void dequeue(byte[] a)
             throws IOException
```
    Dequeues a sequence of bytes from this queue into an array.
    
    Parameters:
    
    a - the array that will contain the dequeued bytes.
    
    Throws:
    
    NoSuchElementException - if there are not enough bytes in this queue.
    
    IOException
  - dequeueInt
```
public int dequeueInt()
               throws IOException
```
    Dequeues from this queue a vByte-coded natural number.
    
    Returns:
    
    the first available natural number in this queue.
    
    Throws:
    
    IOException
  - size
```
@Deprecated
public int size()
```
    Deprecated.
    
    Specified by:
    
    size in interface Size64
  - size64
```
public long size64()
```
    Specified by:
    
    size64 in interface Size64
  - isEmpty
```
public boolean isEmpty()
```
  - close
```
public void close()
           throws IOException
```
    Deallocates all disk resources associated with this queue. After calling this method, calls to any methods that would modify the queue will cause an IllegalStateException.
    
    Specified by:
    
    close in interface AutoCloseable
    
    Specified by:
    
    close in interface Closeable
    
    Throws:
    
    IOException
  - freeze
```
public void freeze()
            throws IOException
```
    Throws:
    
    IOException
  - clear
```
public void clear()
```
    Clears the queue. Note that we do not modify the dump file (use trim() to that purpose).
  - trim
```
public void trim()
          throws IOException
```
    Trims the queue dump file at the current write position.
    
    Throws:
    
    IOException
  - suspend
```
public void suspend()
             throws IOException
```
    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.
    
    Throws:
    
    IOException
  - finalize
```
protected void finalize()
                 throws Throwable
```
    Overrides:
    
    finalize in class Object
    
    Throws:
    
    Throwable
  - enlargeBuffer
```
public void enlargeBuffer(int newBufferSize)
```
    Enlarge the size of the buffer of this queue to a given size.
    
    Parameters:
    
    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.

Class ByteDiskQueue

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

ByteDiskQueue

Method Detail

createNew

createFromFile

enqueue

enqueueInt

enqueue

enqueue

dequeue

dequeue

dequeue

dequeueInt

size

size64

isEmpty

close

freeze

clear

trim

suspend

finalize

enlargeBuffer