adds alternative implementation for rotate_left on u256

keep-starknet-strange · Nov 9, 2023 · 74be1ac · 74be1ac
1 parent 469c5af
commit 74be1ac
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Showing 2 changed files with 6 additions and 12 deletions.
diff --git a/src/math/src/lib.cairo b/src/math/src/lib.cairo
@@ -221,12 +221,8 @@ impl U128BitRotate of BitRotate<u128> {
 
 impl U256BitRotate of BitRotate<u256> {
     fn rotate_left(x: u256, n: u256) -> u256 {
-        // TODO(sveamarcus): missing non-zero implementation for u512
-        // let word = u256_wide_mul(x, pow(2, n));
-        // let (quotient, remainder) = DivRem::div_rem(word,
-        //     u512_as_non_zero(u512{limb0: 0, limb1: 0, limb2: 1, limb3: 0 }));
-        // (quotient + remainder).try_into().unwrap()
-        panic_with_felt252('missing impl')
+        // Alternative solution since we cannot divide u512 yet
+        BitShift::shl(x, n) + BitShift::shr(x, 256 - n)
     }
 
     fn rotate_right(x: u256, n: u256) -> u256 {

diff --git a/src/math/src/tests/math_test.cairo b/src/math/src/tests/math_test.cairo
@@ -170,27 +170,25 @@ fn shl_should_not_overflow() {
 }
 
 #[test]
-#[available_gas(2000000)]
+#[available_gas(3000000)]
 fn test_rotl_min() {
     assert(BitRotate::rotate_left(pow::<u8>(2, 7) + 1, 1) == 3, 'invalid result');
     assert(BitRotate::rotate_left(pow::<u16>(2, 15) + 1, 1) == 3, 'invalid result');
     assert(BitRotate::rotate_left(pow::<u32>(2, 31) + 1, 1) == 3, 'invalid result');
     assert(BitRotate::rotate_left(pow::<u64>(2, 63) + 1, 1) == 3, 'invalid result');
     assert(BitRotate::rotate_left(pow::<u128>(2, 127) + 1, 1) == 3, 'invalid result');
-//  TODO(sveamarcus): missing implementation
-//  assert(BitRotate::rotate_left(pow::<u256>(2, 255) + 1, 1) == 3, 'invalid result');
+    assert(BitRotate::rotate_left(pow::<u256>(2, 255) + 1, 1) == 3, 'invalid result');
 }
 
 #[test]
-#[available_gas(2000000)]
+#[available_gas(3000000)]
 fn test_rotl_max() {
     assert(BitRotate::rotate_left(0b101, 7) == pow::<u8>(2, 7) + 0b10, 'invalid result');
     assert(BitRotate::rotate_left(0b101, 15) == pow::<u16>(2, 15) + 0b10, 'invalid result');
     assert(BitRotate::rotate_left(0b101, 31) == pow::<u32>(2, 31) + 0b10, 'invalid result');
     assert(BitRotate::rotate_left(0b101, 63) == pow::<u64>(2, 63) + 0b10, 'invalid result');
     assert(BitRotate::rotate_left(0b101, 127) == pow::<u128>(2, 127) + 0b10, 'invalid result');
-//  TODO(sveamarcus): missing implementation
-//  assert(BitRotate::rotate_left(0b101, 255) == pow::<u256>(2, 255) + 0b10, 'invalid result');
+    assert(BitRotate::rotate_left(0b101, 255) == pow::<u256>(2, 255) + 0b10, 'invalid result');
 }
 
 #[test]