Make from_le_bytes const

CosmWasm · Sep 2, 2021 · f32b576 · f32b576
1 parent ff232e0
commit f32b576
Showing 1 changed file with 72 additions and 2 deletions.
diff --git a/packages/std/src/math/uint256.rs b/packages/std/src/math/uint256.rs
@@ -65,8 +65,22 @@ impl Uint256 {
         Uint256(U256::from_big_endian(&value))
     }
 
-    pub fn from_le_bytes(value: [u8; 32]) -> Self {
-        Uint256(U256::from_little_endian(&value))
+    pub const fn from_le_bytes(val: [u8; 32]) -> Self {
+        let words: [u64; 4] = [
+            u64::from_le_bytes([
+                val[0], val[1], val[2], val[3], val[4], val[5], val[6], val[7],
+            ]),
+            u64::from_le_bytes([
+                val[8], val[9], val[10], val[11], val[12], val[13], val[14], val[15],
+            ]),
+            u64::from_le_bytes([
+                val[16], val[17], val[18], val[19], val[20], val[21], val[22], val[23],
+            ]),
+            u64::from_le_bytes([
+                val[24], val[25], val[26], val[27], val[28], val[29], val[30], val[31],
+            ]),
+        ];
+        Uint256(U256(words))
     }
 
     /// Returns a copy of the number as big endian bytes.
@@ -483,6 +497,62 @@ mod tests {
         assert_eq!(be_bytes, resulting_bytes);
     }
 
+    #[test]
+    fn uint256_from_le_bytes() {
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(0u128));
+        let a = Uint256::from_le_bytes([
+            42, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(42u128));
+        let a = Uint256::from_le_bytes([
+            1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(1u128));
+        let a = Uint256::from_le_bytes([
+            0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(256u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(65536u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(16777216u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(4294967296u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(72057594037927936u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(18446744073709551616u128));
+        let a = Uint256::from_le_bytes([
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0,
+        ]);
+        assert_eq!(a, Uint256::from(1329227995784915872903807060280344576u128));
+
+        // TODO: test values that exceed the u128 range
+    }
+
     #[test]
     fn uint256_endianness() {
         let be_bytes = [