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Updated deposit contract for gas efficiency

This commit is contained in:
Vitalik Buterin 2019-01-23 00:05:50 -06:00
parent 93f2ee1d13
commit 722e201109
1 changed files with 41 additions and 24 deletions
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specs/core/0_beacon-chain.md
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@ -656,54 +656,71 @@ SECONDS_PER_DAY: constant(uint256) = 86400
Deposit: event({previous_deposit_root: bytes32, data: bytes[2064], merkle_tree_index: bytes[8]})
ChainStart: event({deposit_root: bytes32, time: bytes[8]})
deposit_tree: map(uint256, bytes32)
zerohashes: bytes32[32]
branch: bytes32[32]
deposit_count: uint256
full_deposit_count: uint256
@public
def __init__():
for i in range(31):
self.zerohashes[i+1] = sha3(concat(self.zerohashes[i], self.zerohashes[i]))
self.branch[i+1] = self.zerohashes[i+1]
@public
@constant
def get_deposit_root() -> bytes32:
root:bytes32 = 0x0000000000000000000000000000000000000000000000000000000000000000
size:uint256 = self.deposit_count
for h in range(32):
if size % 2 == 1:
root = sha3(concat(self.branch[h], root))
else:
root = sha3(concat(root, self.branch[h]))
size /= 2
return root
@payable
@public
def deposit(deposit_input: bytes[2048]):
assert msg.value >= as_wei_value(MIN_DEPOSIT_AMOUNT, "gwei")
assert msg.value <= as_wei_value(MAX_DEPOSIT_AMOUNT, "gwei")
index: uint256 = self.deposit_count + TWO_TO_POWER_OF_TREE_DEPTH
index: uint256 = self.deposit_count
deposit_amount: bytes[8] = slice(concat("", convert(msg.value / GWEI_PER_ETH, bytes32)), start=24, len=8)
deposit_timestamp: bytes[8] = slice(concat("", convert(block.timestamp, bytes32)), start=24, len=8)
deposit_data: bytes[2064] = concat(deposit_amount, deposit_timestamp, deposit_input)
merkle_tree_index: bytes[8] = slice(concat("", convert(index, bytes32)), start=24, len=8)
log.Deposit(self.deposit_tree[1], deposit_data, merkle_tree_index)
# add deposit to merkle tree
self.deposit_tree[index] = sha3(deposit_data)
for i in range(DEPOSIT_CONTRACT_TREE_DEPTH):
index /= 2
self.deposit_tree[index] = sha3(concat(self.deposit_tree[index * 2], self.deposit_tree[index * 2 + 1]))
i: int128 = 0
power_of_two: uint256 = 2
for _ in range(32):
if (index+1) % power_of_two != 0:
break
i += 1
power_of_two *= 2
value:bytes32 = sha3(deposit_data)
for j in range(32):
if j < i:
value = sha3(concat(self.branch[j], value))
self.branch[j] = self.zerohashes[j]
self.branch[i] = value
self.deposit_count += 1
log.Deposit(self.get_deposit_root(), deposit_data, merkle_tree_index)
if msg.value == as_wei_value(MAX_DEPOSIT_AMOUNT, "gwei"):
self.full_deposit_count += 1
if self.full_deposit_count == CHAIN_START_FULL_DEPOSIT_THRESHOLD:
timestamp_day_boundary: uint256 = as_unitless_number(block.timestamp) - as_unitless_number(block.timestamp) % SECONDS_PER_DAY + SECONDS_PER_DAY
chainstart_time: bytes[8] = slice(concat("", convert(timestamp_day_boundary, bytes32)), start=24, len=8)
log.ChainStart(self.deposit_tree[1], chainstart_time)
@public
@constant
def get_deposit_root() -> bytes32:
return self.deposit_tree[1]
@public
@constant
def get_branch(leaf: uint256) -> bytes32[32]: # size is DEPOSIT_CONTRACT_TREE_DEPTH (symbolic const not supported)
branch: bytes32[32] # size is DEPOSIT_CONTRACT_TREE_DEPTH
index: uint256 = leaf + TWO_TO_POWER_OF_TREE_DEPTH
for i in range(DEPOSIT_CONTRACT_TREE_DEPTH):
branch[i] = self.deposit_tree[bitwise_xor(index, 1)]
index /= 2
return branch
log.ChainStart(self.get_deposit_root(), chainstart_time)
```
Note: to save ~10x on gas this contract uses a somewhat unintuitive progressive Merkle root calculation algo that requires only O(log(n)) storage. See https://github.com/ethereum/research/blob/master/beacon_chain_impl/progressive_merkle_tree.py for an implementation of the same algo in python tested for correctness.
## Beacon chain processing
The beacon chain is the system chain for Ethereum 2.0. The main responsibilities of the beacon chain are: