Merge pull request #4 from enriquefynn/geth-sharding

Validator manager contract in solidity

Former-commit-id: 41453f9a6262ca73e52ed93aa5e9539b7d6edc46 [formerly 5c8e92adeb56fc7b3de84cc5cf50125bf52e84db]
Former-commit-id: 75b3b72fd7bd5468a6d41a01474db3da90dc9061

sharding/contracts/validator_manager.sol

@@ -0,0 +1,249 @@
+pragma solidity ^0.4.19;
+
+contract VMC {
+  event TxToShard(address indexed to, int indexed shardId, int receiptId);
+  event CollationAdded(uint indexed shardId, bytes collationHeader, bool isNewHead, uint score);
+  event Deposit(address validator, int index);
+  event Withdraw(int validatorIndex);
+
+  struct Validator {
+    // Amount of wei the validator holds
+    uint deposit;
+    // The validator's address
+    address addr;
+  }
+
+  struct CollationHeader {
+    bytes32 parentHash;
+    int score;
+  }
+
+  struct Receipt {
+    int shardId;
+    uint txStartgas;
+    uint txGasprice;
+    uint value;
+    bytes32 data;
+    address sender;
+    address to;
+  }
+
+  // Packed variables to be used in addHeader
+  struct HeaderVars {
+    bytes32 entireHeaderHash;
+    int score;
+    address validatorAddr;
+    bool isNewHead;
+  }
+
+  // validatorId => Validators
+  mapping (int => Validator) validators;
+  // shardId => (headerHash => CollationHeader)
+  mapping (int => mapping (bytes32 => CollationHeader)) collationHeaders;
+  // receiptId => Receipt
+  mapping (int => Receipt) receipts;
+  // shardId => headerHash
+  mapping (int => bytes32) shardHead;
+  
+  // Number of validators
+  int numValidators;
+  // Number of receipts
+  int numReceipts;
+  // Indexs of empty slots caused by the function `withdraw`
+  mapping (int => int) emptySlotsStack;
+  // The top index of the stack in empty_slots_stack
+  int emptySlotsStackTop;
+  // Has the validator deposited before?
+  mapping (address => bool) isValidatorDeposited;
+
+  // Constant values
+  uint constant periodLength = 5;
+  int constant public shardCount = 100;
+  // The exact deposit size which you have to deposit to become a validator
+  uint constant depositSize = 100 ether;
+  // Number of periods ahead of current period, which the contract
+  // is able to return the collator of that period
+  uint constant lookAheadPeriods = 4;
+
+  // Log the latest period number of the shard
+  mapping (int => int) periodHead;
+
+  function VMC() public {
+  }
+
+  // Returns the gas limit that collations can currently have (by default make
+  // this function always answer 10 million).
+  function getCollationGasLimit() public pure returns(uint) {
+    return 10000000;
+  }
+
+  // Uses a block hash as a seed to pseudorandomly select a signer from the validator set.
+  // [TODO] Chance of being selected should be proportional to the validator's deposit.
+  // Should be able to return a value for the current period or any future period up to.
+  function getEligibleProposer(int _shardId, uint _period) public view returns(address) {
+    require(_period >= lookAheadPeriods);
+    require((_period - lookAheadPeriods) * periodLength < block.number);
+    require(numValidators > 0);
+    // [TODO] Should check further if this safe or not
+    return validators[
+      int(
+        uint(
+          keccak256(
+            uint(
+              block.blockhash(_period - lookAheadPeriods)
+            ) * periodLength,
+            _shardId
+          )
+        ) %
+        uint(getValidatorsMaxIndex())
+      )
+    ].addr;
+  }
+
+  function deposit() public payable returns(int) {
+    require(!isValidatorDeposited[msg.sender]);
+    require(msg.value == depositSize);
+    // Find the empty slot index in validators set
+    int index;
+    if (!isStackEmpty())
+      index = stackPop();
+    else
+      index = int(numValidators);
+      
+    validators[index] = Validator({
+      deposit: msg.value,
+      addr: msg.sender
+    });
+    ++numValidators;
+    isValidatorDeposited[msg.sender] = true;
+    
+    Deposit(msg.sender, index);
+    return index;
+  }
+
+  // Removes the validator from the validator set and refunds the deposited ether 
+  function withdraw(int _validatorIndex) public {
+    require(msg.sender == validators[_validatorIndex].addr);
+    // [FIXME] Should consider calling the validator's contract, might be useful
+    // when the validator is a contract.
+    validators[_validatorIndex].addr.transfer(validators[_validatorIndex].deposit);
+    isValidatorDeposited[validators[_validatorIndex].addr] = false;
+    delete validators[_validatorIndex];
+    stackPush(_validatorIndex);
+    --numValidators;
+    Withdraw(_validatorIndex);
+  }
+
+  // Attempts to process a collation header, returns true on success, reverts on failure.
+  function addHeader(int _shardId, uint _expectedPeriodNumber, bytes32 _periodStartPrevHash,
+                     bytes32 _parentHash, bytes32 _transactionRoot,
+                     address _coinbase, bytes32 _stateRoot, bytes32 _receiptRoot,
+                     int _number) public returns(bool) {
+    HeaderVars memory headerVars;
+
+    // Check if the header is valid
+    require((_shardId >= 0) && (_shardId < shardCount));
+    require(block.number >= periodLength);
+    require(_expectedPeriodNumber == block.number / periodLength);
+    require(_periodStartPrevHash == block.blockhash(_expectedPeriodNumber * periodLength - 1));
+
+    // Check if this header already exists
+    headerVars.entireHeaderHash = keccak256(_shardId, _expectedPeriodNumber, _periodStartPrevHash,
+                                   _parentHash, _transactionRoot, bytes32(_coinbase),
+                                   _stateRoot, _receiptRoot, _number);
+    assert(collationHeaders[_shardId][headerVars.entireHeaderHash].score == 0);
+    // Check whether the parent exists.
+    // if (parent_collation_hash == 0), i.e., is the genesis,
+    // then there is no need to check.
+    if (_parentHash != 0x0)
+        assert(collationHeaders[_shardId][_parentHash].score > 0);
+    // Check if only one collation in one period
+    assert(periodHead[_shardId] < int(_expectedPeriodNumber));
+
+    // Check the signature with validation_code_addr
+    headerVars.validatorAddr = getEligibleProposer(_shardId, block.number/periodLength);
+    require(headerVars.validatorAddr != 0x0);
+    require(msg.sender == headerVars.validatorAddr);
+
+    // Check score == collationNumber
+    headerVars.score = collationHeaders[_shardId][_parentHash].score + 1;
+    require(_number == headerVars.score);
+
+    // Add the header
+    collationHeaders[_shardId][headerVars.entireHeaderHash] = CollationHeader({
+      parentHash: _parentHash,
+      score: headerVars.score
+    });
+
+    // Update the latest period number
+    periodHead[_shardId] = int(_expectedPeriodNumber);
+
+    // Determine the head
+    if (headerVars.score > collationHeaders[_shardId][shardHead[_shardId]].score) {
+      shardHead[_shardId] = headerVars.entireHeaderHash;
+      headerVars.isNewHead = true;
+    }
+    // [TODO] Log
+    //CollationAdded(headerBytes, isNewHead, _score);
+
+    return true;
+  }
+
+  // Records a request to deposit msg.value ETH to address to in shard shard_id
+  // during a future collation. Saves a `receipt ID` for this request,
+  // also saving `msg.sender`, `msg.value`, `to`, `shard_id`, `startgas`,
+  // `gasprice`, and `data`.
+  function txToShard(address _to, int _shardId, uint _txStartgas, uint _txGasprice, 
+                     bytes12 _data) public payable returns(int) {
+    receipts[numReceipts] = Receipt({
+      shardId: _shardId,
+      txStartgas: _txStartgas,
+      txGasprice: _txGasprice,
+      value: msg.value,
+      sender: msg.sender,
+      to: _to,
+      data: _data
+    });
+    var receiptId = numReceipts;
+    ++numReceipts;
+    
+    TxToShard(_to, _shardId, receiptId);
+    return receiptId;
+  }
+  
+  function updateGasPrice(int _receiptId, uint _txGasprice) public payable returns(bool) {
+    require(receipts[_receiptId].sender == msg.sender);
+    receipts[_receiptId].txGasprice = _txGasprice;
+    return true;
+  }
+
+  function isStackEmpty() internal view returns(bool) {
+    return emptySlotsStackTop == 0;
+  }
+
+  function stackPush(int index) internal {
+    emptySlotsStack[emptySlotsStackTop] = index;
+    ++emptySlotsStackTop;
+  }
+  
+  function stackPop() internal returns(int) {
+    if (isStackEmpty())
+      return -1;
+    --emptySlotsStackTop;
+    return emptySlotsStack[emptySlotsStackTop];
+  }
+
+  function getValidatorsMaxIndex() internal view returns(int) {
+    int activateValidatorNum = 0;
+    int allValidatorSlotsNum = numValidators + emptySlotsStackTop;
+
+    // TODO: any better way to iterate the mapping?
+    for (int i = 0; i < 1024; ++i) {
+        if (i >= allValidatorSlotsNum)
+            break;
+        if (validators[i].addr != 0x0)
+            activateValidatorNum += 1;
+    }
+    return activateValidatorNum + emptySlotsStackTop;
+  }
+}