Merge pull request #18 from dovgopoly/fix/add-bitlen

fixed bitlen calc
firoorg · Oct 9, 2024 · c77ffd7 · c77ffd7
2 parents f382bcf + a7d8d31
commit c77ffd7
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Showing 2 changed files with 31 additions and 2 deletions.
diff --git a/src/BigNumbers.sol b/src/BigNumbers.sol
@@ -997,8 +997,8 @@ library BigNumbers {
             // with addition, if we assume that some a is at least equal to some b, then the resulting bit length will
             // be a's bit length or (a's bit length)+1, depending on carry bit.this is cheaper than calling bitLength.
             let msword := mload(add(result,0x20))                             // get most significant word of result
-            // if(msword==1 || msword>>(max_bitlen % 256)==1):
-            if or( eq(msword, 1), eq(shr(mod(max_bitlen,256),msword),1) ) {
+            // if(carry==1 || msword>>(max_bitlen % 256)==1):
+            if or( eq(carry, 1), eq(shr(mod(max_bitlen,256),msword),1) ) {
                     max_bitlen := add(max_bitlen, 1)                          // if msword's bit length is 1 greater 
                                                                               // than max_bitlen, OR overflow occured,
                                                                               // new bitlen is max_bitlen+1.

diff --git a/test/BigNumbers.t.sol b/test/BigNumbers.t.sol
@@ -99,6 +99,35 @@ contract BigNumbersTest is Test {
         assertEq(BigNumbers.bitLength(1 << 255), 256);
     }
 
+    function testAdd() public {
+        BigNumber memory lhs = hex"010000000000000000000000000000000000000000000000000000000000000001".init(false);
+        BigNumber memory rhs = hex"01".init(false);
+
+        BigNumber memory r = lhs.add(rhs);
+
+        assertEq(r.val, hex"00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002");
+        assertEq(r.bitlen, 257);
+        assertEq(r.neg, false);
+
+        lhs = hex"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff".init(false);
+        rhs = hex"01".init(false);
+
+        r = lhs.add(rhs);
+
+        assertEq(r.val, hex"00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000");
+        assertEq(r.bitlen, 257);
+        assertEq(r.neg, false);
+
+        lhs = hex"0fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff".init(false);
+        rhs = hex"01".init(false);
+
+        r = lhs.add(rhs);
+
+        assertEq(r.val, hex"00000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000");
+        assertEq(r.bitlen, 261);
+        assertEq(r.neg, false);
+    }
+
     function testShiftRight() public {
         // shift by value greater than word length
         BigNumber memory r;