Const conversions Uint128 -> Uint256 and Uint256 -> Uint512

CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to
   the contract call was executed in.
 - cosmwasm-std: Implement `ops::Mul` for `Decimal` and `Decimal256`.
 - cosmwasm-std: New const methods `Uint128::to_be_bytes`/`::to_le_bytes`.
+- cosmwasm-std: New const conversion methods `Uint256::from_uint128` and
+  `Uint512::from_uint256`.
 
 ### Changed
 
@@ -34,6 +36,7 @@ and this project adheres to
   such that `Decimal::numerator` and `::denominator` now return `Uint128`.
 - cosmwasm-std: Make methods `Uint256::to_be_bytes`/`::to_le_bytes` const.
 - cosmwasm-std: Make methods `Uint512::to_be_bytes`/`::to_le_bytes` const.
+- cosmwasm-std: Make method `Uint512::from_le_bytes` const.
 
 ### Removed
 

packages/std/src/math/decimal.rs

@@ -21,10 +21,6 @@ impl Decimal {
     const DECIMAL_FRACTIONAL: Uint128 = Uint128::new(1_000_000_000_000_000_000u128); // 1*10**18
     const DECIMAL_FRACTIONAL_SQUARED: Uint128 =
         Uint128::new(1_000_000_000_000_000_000_000_000_000_000_000_000u128); // (1*10**18)**2 = 1*10**36
-    const DECIMAL_FRACTIONAL_UINT256: Uint256 = Uint256::from_be_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, 13, 224, 182, 179,
-        167, 100, 0, 0,
-    ]); // Python: `[b for b in (1*10**18).to_bytes(32, "big")]`
     const DECIMAL_PLACES: usize = 18; // This needs to be an even number.
 
     pub const MAX: Self = Self(Uint128::MAX);
@@ -220,8 +216,8 @@ impl ops::Mul for Decimal {
         //       (a.numerator() * b.numerator()) / (a.denominator() * b.denominator())
         //     = (a.numerator() * b.numerator()) / a.denominator() / b.denominator()
 
-        let result_as_uint256 =
-            self.numerator().full_mul(other.numerator()) / Self::DECIMAL_FRACTIONAL_UINT256;
+        let result_as_uint256 = self.numerator().full_mul(other.numerator())
+            / Uint256::from_uint128(Self::DECIMAL_FRACTIONAL); // from_uint128 is a const method and should be "free"
         match result_as_uint256.try_into() {
             Ok(result) => Self(result),
             Err(_) => panic!("attempt to multiply with overflow"),

packages/std/src/math/decimal256.rs

@@ -32,11 +32,6 @@ impl Decimal256 {
             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 192, 151, 206, 123, 201, 7, 21, 179,
             75, 159, 16, 0, 0, 0, 0,
         ]);
-    const DECIMAL_FRACTIONAL_UINT512: Uint512 = Uint512::from_be_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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 13, 224, 182,
-        179, 167, 100, 0, 0,
-    ]); // Python: `[b for b in (1*10**18).to_bytes(32, "big")]`
 
     pub const MAX: Self = Self(Uint256::MAX);
 
@@ -231,8 +226,8 @@ impl ops::Mul for Decimal256 {
         //       (a.numerator() * b.numerator()) / (a.denominator() * b.denominator())
         //     = (a.numerator() * b.numerator()) / a.denominator() / b.denominator()
 
-        let result_as_uint512 =
-            self.numerator().full_mul(other.numerator()) / Self::DECIMAL_FRACTIONAL_UINT512;
+        let result_as_uint512 = self.numerator().full_mul(other.numerator())
+            / Uint512::from_uint256(Self::DECIMAL_FRACTIONAL); // from_uint256 is a const method and should be "free"
         match result_as_uint512.try_into() {
             Ok(result) => Self(result),
             Err(_) => panic!("attempt to multiply with overflow"),

packages/std/src/math/uint128.rs

@@ -47,7 +47,7 @@ impl Uint128 {
     }
 
     /// Returns a copy of the internal data
-    pub fn u128(&self) -> u128 {
+    pub const fn u128(&self) -> u128 {
         self.0
     }
 

packages/std/src/math/uint256.rs

@@ -99,6 +99,18 @@ impl Uint256 {
         Uint256(U256(words))
     }
 
+    /// A conversion from `Uint128` that, unlike the one provided by the `From` trait,
+    /// can be used in a `const` context.
+    pub const fn from_uint128(num: Uint128) -> Self {
+        let bytes = num.to_le_bytes();
+
+        Self::from_le_bytes([
+            bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7],
+            bytes[8], bytes[9], bytes[10], bytes[11], bytes[12], bytes[13], bytes[14], bytes[15],
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        ])
+    }
+
     /// Returns a copy of the number as big endian bytes.
     pub const fn to_be_bytes(self) -> [u8; 32] {
         let words = [
@@ -1006,6 +1018,19 @@ mod tests {
         );
     }
 
+    #[test]
+    fn uint256_from_uint128() {
+        assert_eq!(
+            Uint256::from_uint128(Uint128::new(123)),
+            Uint256::from_str("123").unwrap()
+        );
+
+        assert_eq!(
+            Uint256::from_uint128(Uint128::new(9785746283745)),
+            Uint256::from_str("9785746283745").unwrap()
+        );
+    }
+
     #[test]
     fn uint256_implements_display() {
         let a = Uint256::from(12345u32);

packages/std/src/math/uint512.rs

@@ -95,8 +95,48 @@ impl Uint512 {
         Self(U512(words))
     }
 
-    pub fn from_le_bytes(value: [u8; 64]) -> Self {
-        Uint512(U512::from_little_endian(&value))
+    pub const fn from_le_bytes(data: [u8; 64]) -> Self {
+        let words: [u64; 8] = [
+            u64::from_le_bytes([
+                data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7],
+            ]),
+            u64::from_le_bytes([
+                data[8], data[9], data[10], data[11], data[12], data[13], data[14], data[15],
+            ]),
+            u64::from_le_bytes([
+                data[16], data[17], data[18], data[19], data[20], data[21], data[22], data[23],
+            ]),
+            u64::from_le_bytes([
+                data[24], data[25], data[26], data[27], data[28], data[29], data[30], data[31],
+            ]),
+            u64::from_le_bytes([
+                data[32], data[33], data[34], data[35], data[36], data[37], data[38], data[39],
+            ]),
+            u64::from_le_bytes([
+                data[40], data[41], data[42], data[43], data[44], data[45], data[46], data[47],
+            ]),
+            u64::from_le_bytes([
+                data[48], data[49], data[50], data[51], data[52], data[53], data[54], data[55],
+            ]),
+            u64::from_le_bytes([
+                data[56], data[57], data[58], data[59], data[60], data[61], data[62], data[63],
+            ]),
+        ];
+        Self(U512(words))
+    }
+
+    /// A conversion from `Uint256` that, unlike the one provided by the `From` trait,
+    /// can be used in a `const` context.
+    pub const fn from_uint256(num: Uint256) -> Self {
+        let bytes = num.to_le_bytes();
+        Self::from_le_bytes([
+            bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7],
+            bytes[8], bytes[9], bytes[10], bytes[11], bytes[12], bytes[13], bytes[14], bytes[15],
+            bytes[16], bytes[17], bytes[18], bytes[19], bytes[20], bytes[21], bytes[22], bytes[23],
+            bytes[24], bytes[25], bytes[26], bytes[27], bytes[28], bytes[29], bytes[30], bytes[31],
+            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,
+        ])
     }
 
     /// Returns a copy of the number as big endian bytes.
@@ -719,6 +759,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn uint512_from_uint256() {
+        assert_eq!(
+            Uint512::from_uint256(Uint256::from_str("123").unwrap()),
+            Uint512::from_str("123").unwrap()
+        );
+
+        assert_eq!(
+            Uint512::from_uint256(Uint256::from_str("9785746283745").unwrap()),
+            Uint512::from_str("9785746283745").unwrap()
+        );
+
+        assert_eq!(
+            Uint512::from_uint256(
+                Uint256::from_str(
+                    "97857462837575757832978493758398593853985452378423874623874628736482736487236"
+                )
+                .unwrap()
+            ),
+            Uint512::from_str(
+                "97857462837575757832978493758398593853985452378423874623874628736482736487236"
+            )
+            .unwrap()
+        );
+    }
+
     #[test]
     fn uint512_implements_display() {
         let a = Uint512::from(12345u32);