Fingerprinter (Syncany API Documentation)

java.lang.Object
- org.syncany.chunk.Fingerprinter

Direct Known Subclasses:

Adler32Fingerprinter
```
public abstract class Fingerprinter
extends java.lang.Object
```
A fingerprinter is used in content based Chunkers to determine at which byte to break a file into Chunks.
Implementations should make sure that the underlying algorithm is fast, because the roll()-method is called for each byte of a file. It should rely on a rolling checksum algorithm (also: rolling hash) to reach optimal performance.

See Also:

http://en.wikipedia.org/wiki/Rolling_hash

Constructor Summary

Constructors
Constructor Description

Fingerprinter()

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`abstract void`	`check(byte[] buf, int off, int len)`	Update the checksum with an entirely different block, and potentially a different block length.
`static Fingerprinter`	`getInstance(java.lang.String name)`
`abstract int`	`getValue()`	Return the value of the currently computed checksum.
`abstract void`	`reset()`	Reset the checksum.
`abstract void`	`roll(byte bt)`	"Roll" the checksum, i.e.
`abstract java.lang.String`	`toString()`	Returns a string representation of the fingerprinter implementation.

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

- Constructor Detail
  - Fingerprinter
```
public Fingerprinter()
```
- Method Detail
  - getInstance
```
public static Fingerprinter getInstance(java.lang.String name)
                                 throws java.security.NoSuchAlgorithmException
```
    Throws:
    
    java.security.NoSuchAlgorithmException
  - getValue
```
public abstract int getValue()
```
    Return the value of the currently computed checksum.
    
    Returns:
    
    The currently computed checksum.
  - reset
```
public abstract void reset()
```
    Reset the checksum.
  - roll
```
public abstract void roll(byte bt)
```
    "Roll" the checksum, i.e. update the underlying rolling checksum by the given content byte.
    
    Parameters:
    
    bt - The next byte.
  - check
```
public abstract void check(byte[] buf,
                           int off,
                           int len)
```
    Update the checksum with an entirely different block, and potentially a different block length.
    
    Parameters:
    
    buf - The byte array that holds the new block.
    
    off - From whence to begin reading.
    
    len - The length of the block to read.
  - toString
```
public abstract java.lang.String toString()
```
    Returns a string representation of the fingerprinter implementation.
    
    Overrides:
    
    toString in class java.lang.Object