121 lines
3.3 KiB
Solidity
121 lines
3.3 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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contract Proofs {
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mapping(bytes32=>bool) private ids;
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mapping(bytes32=>uint) private periods;
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mapping(bytes32=>uint) private timeouts;
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mapping(bytes32=>uint) private starts;
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mapping(bytes32=>uint) private ends;
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mapping(bytes32=>uint) private markers;
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mapping(bytes32=>uint) private missed;
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mapping(bytes32=>mapping(uint=>bool)) private received;
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mapping(bytes32=>mapping(uint=>bool)) private missing;
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function _period(bytes32 id) internal view returns (uint) {
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return periods[id];
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}
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function _timeout(bytes32 id) internal view returns (uint) {
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return timeouts[id];
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}
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function _end(bytes32 id) internal view returns (uint) {
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return ends[id];
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}
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function _missed(bytes32 id) internal view returns (uint) {
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return missed[id];
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}
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// Checks that proof timeout is <= 128. Only the latest 256 blocks can be
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// checked in a smart contract, so that leaves a period of at least 128 blocks
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// after timeout for a validator to signal the absence of a proof.
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function _checkTimeout(uint timeout) private pure {
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require(timeout <= 128, "Invalid proof timeout, needs to be <= 128");
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}
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function _expectProofs(
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bytes32 id,
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uint period,
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uint timeout,
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uint duration
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) internal {
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require(!ids[id], "Proof id already in use");
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_checkTimeout(timeout);
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ids[id] = true;
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periods[id] = period;
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timeouts[id] = timeout;
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starts[id] = block.number;
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ends[id] = block.number + duration + 2 * timeout;
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markers[id] = uint(blockhash(block.number - 1)) % period;
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}
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// Check whether a proof is required at the time of the block with the
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// specified block number. A proof has to be submitted within the proof
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// timeout for it to be valid. Whether a proof is required is determined
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// randomly, but on average it is once every proof period.
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function _isProofRequired(
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bytes32 id,
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uint blocknumber
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)
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internal view
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returns (bool)
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{
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if (blocknumber < starts[id] || blocknumber >= ends[id]) {
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return false;
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}
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bytes32 hash = blockhash(blocknumber - 1);
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return hash != 0 && uint(hash) % periods[id] == markers[id];
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}
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function _isProofTimedOut(
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bytes32 id,
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uint blocknumber
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)
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internal view
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returns (bool)
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{
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return block.number >= blocknumber + timeouts[id];
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}
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function _submitProof(
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bytes32 id,
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uint blocknumber,
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bool proof
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)
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internal
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{
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require(proof, "Invalid proof"); // TODO: replace bool by actual proof
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require(
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_isProofRequired(id, blocknumber),
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"No proof required for this block"
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);
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require(
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!_isProofTimedOut(id, blocknumber),
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"Proof not allowed after timeout"
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);
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require(!received[id][blocknumber], "Proof already submitted");
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received[id][blocknumber] = true;
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}
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function _markProofAsMissing(bytes32 id, uint blocknumber) internal {
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require(
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_isProofTimedOut(id, blocknumber),
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"Proof has not timed out yet"
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);
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require(
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!received[id][blocknumber],
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"Proof was submitted, not missing"
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);
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require(
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_isProofRequired(id, blocknumber),
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"Proof was not required"
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);
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require(!missing[id][blocknumber], "Proof already marked as missing");
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missing[id][blocknumber] = true;
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missed[id] += 1;
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}
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}
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