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// SPDX-License-Identifier: MIT
pragma solidity ^0.7.3;
contract MIPSMemory {
// This state is global
mapping(bytes32 => mapping (uint32 => uint64)) public state;
mapping(bytes32 => bytes) public preimage;
function AddPreimage(bytes calldata anything) public {
preimage[keccak256(anything)] = anything;
}
function AddMerkleState(bytes32 stateHash, uint32 addr, uint32 value, string calldata proof) public {
// TODO: check proof
state[stateHash][addr] = (1 << 32) | value;
}
function WriteMemory(bytes32 stateHash, uint32 addr, uint32 value) public pure returns (bytes32) {
require(addr & 3 == 0, "write memory must be 32-bit aligned");
// TODO: do the real stateHash mutation
bytes32 newstateHash = keccak256(abi.encodePacked(stateHash));
// note that zeros are never stored in the trie, so storing a 0 is a delete
// no proof required, this is obviously right
//state[newstateHash][addr] = (1 << 32) | value;
return newstateHash;
}
// needed for preimage oracle
function ReadBytes32(bytes32 stateHash, uint32 addr) public view returns (bytes32) {
uint256 ret = 0;
for (uint32 i = 0; i < 32; i += 4) {
ret <<= 32;
ret |= uint256(ReadMemory(stateHash, addr+i));
}
return bytes32(ret);
}
function ReadMemory(bytes32 stateHash, uint32 addr) public view returns (uint32) {
require(addr & 3 == 0, "read memory must be 32-bit aligned");
// zero register is always 0
if (addr == 0xc0000000) {
return 0;
}
// MMIO preimage oracle
if (addr >= 0x31000000 && addr < 0x32000000) {
bytes32 pihash = ReadBytes32(stateHash, 0x30001000);
if (addr == 0x31000000) {
return uint32(preimage[pihash].length);
}
uint offset = addr-0x31000004;
uint8 a0 = uint8(preimage[pihash][offset]);
uint8 a1 = uint8(preimage[pihash][offset+1]);
uint8 a2 = uint8(preimage[pihash][offset+2]);
uint8 a3 = uint8(preimage[pihash][offset+3]);
return (uint32(a0) << 24) |
(uint32(a1) << 16) |
(uint32(a2) << 8) |
(uint32(a3) << 0);
}
uint64 ret = state[stateHash][addr];
require((ret >> 32) == 1, "memory was not initialized");
return uint32(ret);
}
}