ch.epfl.dedis.byzcoin.contracts

Class ValueInstance

java.lang.Object

ch.epfl.dedis.byzcoin.contracts.ValueInstance

public class ValueInstance
extends Object

ValueInstance represents a simple value store on byzcoin.

Field Summary

Fields

Modifier and Type	Field and Description
static String	ContractId

Constructor Summary

Constructors

Constructor and Description
ValueInstance(ByzCoinRPC bc, DarcId spawnerDarcId, Signer spawnerSigner, byte[] value) Instantiates a new value in ByzCoin by sending a spawn instruction to a darc that has a "spawn:value" rule in it.

Method Summary

Modifier and Type	Method and Description
void	evolveValue(byte[] newValue, Signer owner)
void	evolveValueAndWait(byte[] newValue, Signer owner, int wait) Asks byzcoin to update the value and waits until the new value has been stored in the global state.
Instruction	evolveValueInstruction(byte[] newValue, Signer owner, int pos, int len) Creates an instruction to evolve the value in byzcoin.
static ValueInstance	fromByzcoin(ByzCoinRPC bc, InstanceId id) Instantiates a new ValueInstance given a working byzcoin service and an instanceId.
static ValueInstance	fromByzcoin(ByzCoinRPC bc, Proof p) Convenience function to connect to an existing ValueInstance.
InstanceId	getId()
Instance	getInstance()
byte[]	getValue()
void	update() Updates the value by getting the latest instance and updating it.

Methods inherited from class java.lang.Object

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

Field Detail

ContractId

public static String ContractId

Constructor Detail

ValueInstance

public ValueInstance(ByzCoinRPC bc,
                     DarcId spawnerDarcId,
                     Signer spawnerSigner,
                     byte[] value)
              throws CothorityException

Instantiates a new value in ByzCoin by sending a spawn instruction to a darc that has a "spawn:value" rule in it.

Parameters:

bc - a running ByzCoin service

spawnerDarcId - a darc Id with a "spawn:value" rule in it

spawnerSigner - a signer having the right to sign for the "spawn:value" rule

value - the value to store in the instance

Throws:

CothorityException - if something goes wrong

Method Detail

update

public void update()
            throws CothorityException

Updates the value by getting the latest instance and updating it.

Throws:

CothorityException - if something goes wrong

evolveValueInstruction

public Instruction evolveValueInstruction(byte[] newValue,
                                          Signer owner,
                                          int pos,
                                          int len)
                                   throws CothorityCryptoException

Creates an instruction to evolve the value in byzcoin. The signer must have its identity in the current darc as "invoke:update" rule.

TODO: allow for evolution if the expression has more than one identity.

Parameters:

newValue - the value to replace the old value.

owner - must have its identity in the "invoke:update" rule

pos - position of the instruction in the ClientTransaction

len - total number of instructions in the ClientTransaction

Returns:

Instruction to be sent to byzcoin

Throws:

CothorityCryptoException - if there's a problem with the cryptography

evolveValue

public void evolveValue(byte[] newValue,
                        Signer owner)
                 throws CothorityException

Throws:

CothorityException

evolveValueAndWait

public void evolveValueAndWait(byte[] newValue,
                               Signer owner,
                               int wait)
                        throws CothorityException

Asks byzcoin to update the value and waits until the new value has been stored in the global state. TODO: check if there has been an error in the transaction!

Parameters:

newValue - the value to replace the old value.

owner - is the owner that can sign to evolve the darc

wait - how many blocks to wait for inclusion of the instruction

Throws:

CothorityException - if something goes wrong

getId

public InstanceId getId()

Returns:

the id of the instance

getValue

public byte[] getValue()

Returns:

a copy of the value stored in this instance.

getInstance

public Instance getInstance()

Returns:

the instance used.

fromByzcoin

public static ValueInstance fromByzcoin(ByzCoinRPC bc,
                                        InstanceId id)
                                 throws CothorityException

Instantiates a new ValueInstance given a working byzcoin service and an instanceId. This instantiator will contact byzcoin and try to get the current valueInstance. If the instance is not found, or is not of contractId "Value", an exception will be thrown.

Parameters:

bc - is a running ByzCoin service

id - of the value-instance to connect to

Returns:

the new ValueInstance

Throws:

CothorityException - if something goes wrong

fromByzcoin

public static ValueInstance fromByzcoin(ByzCoinRPC bc,
                                        Proof p)
                                 throws CothorityException

Convenience function to connect to an existing ValueInstance.

Parameters:

bc - a running ByzCoin service

p - the proof for the valueInstance

Returns:

the new ValueInstance

Throws:

CothorityException - if something goes wrong