Decimal/Decimal256: Implement checked_from_ratio

Author: ueco-jb

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to
 
 - cosmwasm-std: Implement `checked_multiply_ratio` for
   `Uint64`/`Uint128`/`Uint256`
+- cosmwasm-std: Implement `checked_from_ratio` for `Decimal`/`Decimal256`
 
 ### Changed
 

packages/std/src/math/decimal.rs

@@ -7,7 +7,7 @@ use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 use std::str::FromStr;
 use thiserror::Error;
 
-use crate::errors::StdError;
+use crate::errors::{CheckedMultiplyRatioError, StdError};
 use crate::OverflowError;
 
 use super::Fraction;
@@ -118,16 +118,30 @@ impl Decimal {
 
     /// Returns the ratio (numerator / denominator) as a Decimal
     pub fn from_ratio(numerator: impl Into<Uint128>, denominator: impl Into<Uint128>) -> Self {
+        match Decimal::checked_from_ratio(numerator, denominator) {
+            Ok(value) => value,
+            Err(CheckedMultiplyRatioError::DivideByZero) => {
+                panic!("Denominator must not be zero")
+            }
+            Err(CheckedMultiplyRatioError::Overflow) => panic!("Multiplication overflow"),
+        }
+    }
+
+    /// Returns the ratio (numerator / denominator) as a Decimal
+    pub fn checked_from_ratio(
+        numerator: impl Into<Uint128>,
+        denominator: impl Into<Uint128>,
+    ) -> Result<Self, CheckedMultiplyRatioError> {
         let numerator: Uint128 = numerator.into();
         let denominator: Uint128 = denominator.into();
         if denominator.is_zero() {
-            panic!("Denominator must not be zero");
+            return Err(CheckedMultiplyRatioError::DivideByZero);
         }
 
-        Decimal(
+        Ok(Decimal(
             // numerator * DECIMAL_FRACTIONAL / denominator
-            numerator.multiply_ratio(Self::DECIMAL_FRACTIONAL, denominator),
-        )
+            numerator.checked_multiply_ratio(Self::DECIMAL_FRACTIONAL, denominator)?,
+        ))
     }
 
     pub const fn is_zero(&self) -> bool {
@@ -658,6 +672,19 @@ mod tests {
         Decimal::from_ratio(1u128, 0u128);
     }
 
+    #[test]
+    fn decimal_checked_from_ratio_does_not_panic() {
+        assert_eq!(
+            Decimal::checked_from_ratio(1u128, 0u128),
+            Err(CheckedMultiplyRatioError::DivideByZero)
+        );
+
+        assert_eq!(
+            Decimal::checked_from_ratio(u128::MAX, 1u128),
+            Err(CheckedMultiplyRatioError::Overflow)
+        );
+    }
+
     #[test]
     fn decimal_implements_fraction() {
         let fraction = Decimal::from_str("1234.567").unwrap();

packages/std/src/math/decimal256.rs

@@ -7,7 +7,7 @@ use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 use std::str::FromStr;
 use thiserror::Error;
 
-use crate::errors::StdError;
+use crate::errors::{CheckedMultiplyRatioError, StdError};
 use crate::{OverflowError, Uint512};
 
 use super::Fraction;
@@ -130,16 +130,30 @@ impl Decimal256 {
 
     /// Returns the ratio (numerator / denominator) as a Decimal256
     pub fn from_ratio(numerator: impl Into<Uint256>, denominator: impl Into<Uint256>) -> Self {
+        match Decimal256::checked_from_ratio(numerator, denominator) {
+            Ok(value) => value,
+            Err(CheckedMultiplyRatioError::DivideByZero) => {
+                panic!("Denominator must not be zero")
+            }
+            Err(CheckedMultiplyRatioError::Overflow) => panic!("Multiplication overflow"),
+        }
+    }
+
+    /// Returns the ratio (numerator / denominator) as a Decimal256
+    pub fn checked_from_ratio(
+        numerator: impl Into<Uint256>,
+        denominator: impl Into<Uint256>,
+    ) -> Result<Self, CheckedMultiplyRatioError> {
         let numerator: Uint256 = numerator.into();
         let denominator: Uint256 = denominator.into();
         if denominator.is_zero() {
-            panic!("Denominator must not be zero");
+            return Err(CheckedMultiplyRatioError::DivideByZero);
         }
 
-        Self(
+        Ok(Self(
             // numerator * DECIMAL_FRACTIONAL / denominator
-            numerator.multiply_ratio(Self::DECIMAL_FRACTIONAL, denominator),
-        )
+            numerator.checked_multiply_ratio(Self::DECIMAL_FRACTIONAL, denominator)?,
+        ))
     }
 
     pub const fn is_zero(&self) -> bool {
@@ -690,6 +704,19 @@ mod tests {
         Decimal256::from_ratio(1u128, 0u128);
     }
 
+    #[test]
+    fn decimal256_checked_from_ratio_does_not_panic() {
+        assert_eq!(
+            Decimal256::checked_from_ratio(1u128, 0u128),
+            Err(CheckedMultiplyRatioError::DivideByZero)
+        );
+
+        assert_eq!(
+            Decimal256::checked_from_ratio(Uint256::MAX, 1u128),
+            Err(CheckedMultiplyRatioError::Overflow)
+        );
+    }
+
     #[test]
     fn decimal256_implements_fraction() {
         let fraction = Decimal256::from_str("1234.567").unwrap();