org.eclipse.jgit.util.sha1

Class SHA1

java.lang.Object

org.eclipse.jgit.util.sha1.SHA1

public abstract class SHA1
extends Object

SHA-1 interface from FIPS 180-1 / RFC 3174 with optional collision detection. Some implementations may not support collision detection.

See RFC 3174.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SHA1.Sha1Implementation SHA1 implementations available in JGit

Constructor Summary

Constructors

Constructor and Description
SHA1()

Method Summary

Modifier and Type	Method and Description
abstract byte[]	digest() Finish the digest and return the resulting hash.
abstract void	digest(MutableObjectId id) Finish the digest and return the resulting hash.
abstract boolean	hasCollision() Check if a collision was detected.
static SHA1	newInstance() Create a new context to compute a SHA-1 hash of data.
abstract SHA1	reset() Reset this instance to compute another hash.
abstract SHA1	setDetectCollision(boolean detect) Enable likely collision detection.
abstract ObjectId	toObjectId() Finish the digest and return the resulting hash.
abstract void	update(byte b) Update the digest computation by adding a byte.
abstract void	update(byte[] in) Update the digest computation by adding bytes to the message.
abstract void	update(byte[] in, int p, int len) Update the digest computation by adding bytes to the message.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SHA1

public SHA1()

Method Detail

newInstance

public static SHA1 newInstance()

Create a new context to compute a SHA-1 hash of data.

If core.sha1Implementation = jdkNative in the user level global git configuration or the system property org.eclipse.jgit.util.sha1.implementation = jdkNative it will create an object using the implementation in the JDK. If both are set the system property takes precedence. Otherwise the pure Java implementation will be used which supports collision detection but is slower.

Returns:

a new context to compute a SHA-1 hash of data.

update

public abstract void update(byte b)

Update the digest computation by adding a byte.

Parameters:

b - a byte.

update

public abstract void update(byte[] in)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

update

public abstract void update(byte[] in,
                            int p,
                            int len)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

p - offset to start at from in.

len - number of bytes to hash.

digest

public abstract byte[] digest()
                       throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the bytes for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

toObjectId

public abstract ObjectId toObjectId()
                             throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the ObjectId for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

digest

public abstract void digest(MutableObjectId id)
                     throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Parameters:

id - destination to copy the digest to.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

reset

public abstract SHA1 reset()

Reset this instance to compute another hash.

Returns:

this.

setDetectCollision

public abstract SHA1 setDetectCollision(boolean detect)

Enable likely collision detection.

Default for implementations supporting collision detection is true.

Implementations not supporting collision detection ignore calls to this method.

Parameters:

detect - a boolean.

Returns:

this

hasCollision

public abstract boolean hasCollision()

Check if a collision was detected. This method only returns an accurate result after the digest was obtained through digest(), digest(MutableObjectId) or toObjectId(), as the hashing function must finish processing to know the final state.

Implementations not supporting collision detection always return false.

Returns:

true if a likely collision was detected.