ArithmeticCoder (MG4J (big) 5.4.4)

java.lang.Object
- it.unimi.di.big.mg4j.io.ArithmeticCoder

```
public final class ArithmeticCoder
extends Object
```
An arithmetic coder.
This class provides an arithmetic coder. The output of the coder goes to an OutputBitStream. You must first create a coder specifying the number of input symbols, then call encode(int, OutputBitStream) for all symbols to be coded, and finally flush(OutputBitStream). This last operation will output some bits so that the last symbol is encoded nonambiguously.
The code is inspired by the arithmetic coder by John Carpinelli, Radford M. Neal, Wayne Salamonsen and Lang Stuiver, which is in turn based on Arithmetic Coding Revisited, by Alistair Moffat, Radford M. Neal and Ian H. Witten (Proc. IEEE Data Compression Conference, Snowbird, Utah, March 1995).

Since:

0.1

Author:

Sebastiano Vigna

See Also:

ArithmeticDecoder

- Field Summary
  
  Fields
  Modifier and Type Field Description
  
  static int BITS
  Number of bits used by the coder.
- Constructor Summary
  
  Constructors
  Constructor Description
  
  ArithmeticCoder(int n)
  Creates a new coder.
- Method Summary
  
  Modifier and Type Method Description
  
  int encode(int x, OutputBitStream obs)
  Encodes a symbol.
  
  int flush(OutputBitStream obs)
  Flushes the last bits.
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - BITS
```
public static final int BITS
```
    Number of bits used by the coder.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - ArithmeticCoder
```
public ArithmeticCoder(int n)
```
    Creates a new coder.
    
    Parameters:
    
    n - number of symbols used by the coder.
- Method Detail
  - encode
```
public int encode(int x,
                  OutputBitStream obs)
           throws IOException
```
    Encodes a symbol.
    
    Parameters:
    
    x - a bit.
    
    obs - the output stream.
    
    Returns:
    
    the number of bits written (note that it can be 0, as arithmetic compression can encode a symbol in a fraction of a bit).
    
    Throws:
    
    IOException - if obs does.
  - flush
```
public int flush(OutputBitStream obs)
          throws IOException
```
    Flushes the last bits.
    This method must be called when coding is over. It guarantees that enough bits are output to make the decoding of the last symbol nonambiguous, whichever bits follow in the stream.
    
    Parameters:
    
    obs - the output stream.
    
    Returns:
    
    the number of bits written.
    
    Throws:
    
    IOException - if obs does.