Reverse endianness for Solana integer (#203)

* Reverse endianness for Solana

Author: alexkeating

evm/src/HubSolanaSpokeVoteDecoder.sol

@@ -156,7 +156,8 @@ contract HubSolanaSpokeVoteDecoder is ISpokeVoteDecoder, QueryResponse, ERC165 {
     // Verify the total length of the data (72 bytes)
     _data.checkLength(_offset);
 
-    return (_proposalIdBytes, _againstVotes, _forVotes, _abstainVotes, _voteStart);
+    return
+      (_proposalIdBytes, _reverse(_againstVotes), _reverse(_forVotes), _reverse(_abstainVotes), _reverse(_voteStart));
   }
 
   /// @notice Scales an amount from original decimals to target decimals
@@ -170,4 +171,20 @@ contract HubSolanaSpokeVoteDecoder is ISpokeVoteDecoder, QueryResponse, ERC165 {
     if (_fromDecimals > _toDecimals) return _amount / (10 ** (_fromDecimals - _toDecimals));
     else return _amount * (10 ** (_toDecimals - _fromDecimals));
   }
+
+  /// @notice Reverse the endianness of the passed in integer.
+  /// @param _input The integer for which to reverse the endianess.
+  /// @return An integer with the endianness reversed.
+  /// @dev This code was copied from
+  /// https://github.com/wormholelabs-xyz/example-queries-solana-pda/blob/4a01a0a6018b36a1d38d326362bfb672c5061c5f/src/OwnerVerifier.sol#L52.
+  function _reverse(uint64 _input) internal pure returns (uint64) {
+    uint64 v = _input;
+    // swap bytes
+    v = ((v & 0xFF00FF00FF00FF00) >> 8) | ((v & 0x00FF00FF00FF00FF) << 8);
+    // swap 2-byte long pairs
+    v = ((v & 0xFFFF0000FFFF0000) >> 16) | ((v & 0x0000FFFF0000FFFF) << 16);
+    // swap 4-byte long pairs
+    v = (v >> 32) | (v << 32);
+    return v;
+  }
 }

evm/test/HubSolanaSpokeVoteDecoder.t.sol

@@ -238,6 +238,16 @@ contract Decode is HubSolanaSpokeVoteDecoderTest, ProposalTest {
       * (10 ** (hubSolanaSpokeVoteDecoder.HUB_TOKEN_DECIMALS() - hubSolanaSpokeVoteDecoder.SOLANA_TOKEN_DECIMALS()));
   }
 
+  function _reverse(uint64 input) internal pure returns (uint64 v) {
+    v = input;
+    // swap bytes
+    v = ((v & 0xFF00FF00FF00FF00) >> 8) | ((v & 0x00FF00FF00FF00FF) << 8);
+    // swap 2-byte long pairs
+    v = ((v & 0xFFFF0000FFFF0000) >> 16) | ((v & 0x0000FFFF0000FFFF) << 16);
+    // swap 4-byte long pairs
+    v = (v >> 32) | (v << 32);
+  }
+
   function testFuzz_CorrectlyParseChainResponse(
     uint64 _againstVotes,
     uint64 _forVotes,
@@ -261,9 +271,9 @@ contract Decode is HubSolanaSpokeVoteDecoderTest, ProposalTest {
 
     assertEq(queryVote.proposalId, proposalId, "Proposal ID mismatch");
     assertEq(queryVote.spokeProposalId, keccak256(abi.encode(SPOKE_CHAIN_ID, proposalId)), "Spoke proposal ID mismatch");
-    assertEq(queryVote.proposalVote.abstainVotes, _scale(_abstainVotes), "Abstain votes mismatch");
-    assertEq(queryVote.proposalVote.againstVotes, _scale(_againstVotes), "Against votes mismatch");
-    assertEq(queryVote.proposalVote.forVotes, _scale(_forVotes), "For votes mismatch");
+    assertEq(queryVote.proposalVote.abstainVotes, _scale(_reverse(_abstainVotes)), "Abstain votes mismatch");
+    assertEq(queryVote.proposalVote.againstVotes, _scale(_reverse(_againstVotes)), "Against votes mismatch");
+    assertEq(queryVote.proposalVote.forVotes, _scale(_reverse(_forVotes)), "For votes mismatch");
     assertEq(queryVote.chainId, SPOKE_CHAIN_ID, "Chain ID mismatch");
   }