Implement to_uint_ceil without modulo operation

CosmWasm · Jan 30, 2023 · 3b7b3a4 · 3b7b3a4
1 parent 2bcc2d1
commit 3b7b3a4
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Showing 2 changed files with 14 additions and 6 deletions.
diff --git a/packages/std/src/math/decimal.rs b/packages/std/src/math/decimal.rs
@@ -399,10 +399,14 @@ impl Decimal {
     /// assert_eq!(d.to_uint_ceil(), Uint128::new(75));
     /// ```
     pub fn to_uint_ceil(self) -> Uint128 {
-        if (self.0 % Self::DECIMAL_FRACTIONAL).is_zero() {
-            self.0 / Self::DECIMAL_FRACTIONAL
+        // Using `q = 1 + ((x - 1) / y); // if x != 0` with unsigned integers x, y, q
+        // from https://stackoverflow.com/a/2745086/2013738. We know `x + y` CAN overflow.
+        let x = self.0;
+        let y = Self::DECIMAL_FRACTIONAL;
+        if x.is_zero() {
+            Uint128::zero()
         } else {
-            self.0 / Self::DECIMAL_FRACTIONAL + Uint128::one()
+            Uint128::one() + ((x - Uint128::one()) / y)
         }
     }
 }

diff --git a/packages/std/src/math/decimal256.rs b/packages/std/src/math/decimal256.rs
@@ -416,10 +416,14 @@ impl Decimal256 {
     /// assert_eq!(d.to_uint_ceil(), Uint256::from(75u64));
     /// ```
     pub fn to_uint_ceil(self) -> Uint256 {
-        if (self.0 % Self::DECIMAL_FRACTIONAL).is_zero() {
-            self.0 / Self::DECIMAL_FRACTIONAL
+        // Using `q = 1 + ((x - 1) / y); // if x != 0` with unsigned integers x, y, q
+        // from https://stackoverflow.com/a/2745086/2013738. We know `x + y` CAN overflow.
+        let x = self.0;
+        let y = Self::DECIMAL_FRACTIONAL;
+        if x.is_zero() {
+            Uint256::zero()
         } else {
-            self.0 / Self::DECIMAL_FRACTIONAL + Uint256::one()
+            Uint256::one() + ((x - Uint256::one()) / y)
         }
     }
 }