fix lib_keccak256

contracts/MIPSMemory.sol

@@ -44,10 +44,7 @@ contract MIPSMemory {
     c.A = largePreimage[msg.sender];
     // TODO: do this properly and save the hash
     // when this is updated, it won't be "view"
-    return bytes32((uint256(c.A[0]) << 192) |
-                   (uint256(c.A[1]) << 128) |
-                   (uint256(c.A[2]) << 64) |
-                   (uint256(c.A[3]) << 0));
+    return Lib_Keccak256.get_hash(c);
   }
 
   function AddMerkleState(bytes32 stateHash, uint32 addr, uint32 value, string calldata proof) public {

contracts/lib/Lib_Keccak256.sol

@@ -101,4 +101,18 @@ library Lib_Keccak256 {
     }
   }
 
+  // https://stackoverflow.com/questions/2182002/convert-big-endian-to-little-endian-in-c-without-using-provided-func
+  function flip(uint64 val) internal pure returns (uint64) {
+    val = ((val << 8) & 0xFF00FF00FF00FF00 ) | ((val >> 8) & 0x00FF00FF00FF00FF );
+    val = ((val << 16) & 0xFFFF0000FFFF0000 ) | ((val >> 16) & 0x0000FFFF0000FFFF );
+    return (val << 32) | (val >> 32);
+  }
+
+  function get_hash(CTX memory c) internal pure returns (bytes32) {
+    return bytes32((uint256(flip(c.A[0])) << 192) |
+                   (uint256(flip(c.A[1])) << 128) |
+                   (uint256(flip(c.A[2])) << 64) |
+                   (uint256(flip(c.A[3])) << 0));
+  }
+
 }
\ No newline at end of file

test/libkeccak.js

@@ -13,7 +13,8 @@ describe("MIPSMemory contract", function () {
     console.log("preimage initted");
 
     // block size is 136
-    const a = ["0x0100000000000000",0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0x80];
+    //const a = ["0x0100000000000000",0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0x80];
+    const a = [0x1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,"0x8000000000000000"];
     await mm.AddLargePreimageUpdate(a);
     console.log("preimage updated");