Merge pull request #1347 from CosmWasm/1186-decimals-rounding

`Decimal`/`Decimal256` - implement rounding `ceil` and `floor`
CosmWasm · Jul 11, 2022 · 0f90b99 · 0f90b99
2 parents 3b561e5 + 4f4bc2a
commit 0f90b99
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Showing 5 changed files with 121 additions and 3 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to
 - cosmwasm-std: Implement `checked_add`/`_sub`/`_div`/`_rem` for
   `Decimal`/`Decimal256`.
 - cosmwasm-std: Implement `pow`/`saturating_pow` for `Decimal`/`Decimal256`.
+- cosmwasm-std: Implement `ceil`/`floor` for `Decimal`/`Decimal256`.
 
 [#1334]: https://github.com/CosmWasm/cosmwasm/pull/1334
 

diff --git a/packages/std/src/errors/mod.rs b/packages/std/src/errors/mod.rs
@@ -6,7 +6,7 @@ mod verification_error;
 pub use recover_pubkey_error::RecoverPubkeyError;
 pub use std_error::{
     CheckedFromRatioError, CheckedMultiplyRatioError, ConversionOverflowError, DivideByZeroError,
-    OverflowError, OverflowOperation, StdError, StdResult,
+    OverflowError, OverflowOperation, RoundUpOverflowError, StdError, StdResult,
 };
 pub use system_error::SystemError;
 pub use verification_error::VerificationError;
diff --git a/packages/std/src/errors/std_error.rs b/packages/std/src/errors/std_error.rs
@@ -544,6 +544,10 @@ pub enum CheckedFromRatioError {
     Overflow,
 }
 
+#[derive(Error, Debug, PartialEq, Eq)]
+#[error("Round up operation failed because of overflow")]
+pub struct RoundUpOverflowError;
+
 #[cfg(test)]
 mod tests {
     use super::*;

diff --git a/packages/std/src/math/decimal.rs b/packages/std/src/math/decimal.rs
@@ -9,7 +9,7 @@ use thiserror::Error;
 
 use crate::errors::{
     CheckedFromRatioError, CheckedMultiplyRatioError, DivideByZeroError, OverflowError,
-    OverflowOperation, StdError,
+    OverflowOperation, RoundUpOverflowError, StdError,
 };
 
 use super::Fraction;
@@ -184,6 +184,31 @@ impl Decimal {
         Self::DECIMAL_PLACES as u32
     }
 
+    /// Rounds value down after decimal places.
+    pub fn floor(&self) -> Self {
+        Self((self.0 / Self::DECIMAL_FRACTIONAL) * Self::DECIMAL_FRACTIONAL)
+    }
+
+    /// Rounds value up after decimal places. Panics on overflow.
+    pub fn ceil(&self) -> Self {
+        match self.checked_ceil() {
+            Ok(value) => value,
+            Err(_) => panic!("attempt to ceil with overflow"),
+        }
+    }
+
+    /// Rounds value up after decimal places. Returns OverflowError on overflow.
+    pub fn checked_ceil(&self) -> Result<Self, RoundUpOverflowError> {
+        let floor = self.floor();
+        if &floor == self {
+            Ok(floor)
+        } else {
+            floor
+                .checked_add(Decimal::one())
+                .map_err(|_| RoundUpOverflowError)
+        }
+    }
+
     pub fn checked_add(self, other: Self) -> Result<Self, OverflowError> {
         self.0
             .checked_add(other.0)
@@ -1872,4 +1897,37 @@ mod tests {
         );
         assert_eq!(Decimal::MAX.saturating_pow(2u32), Decimal::MAX);
     }
+
+    #[test]
+    fn decimal_rounding() {
+        assert_eq!(Decimal::one().floor(), Decimal::one());
+        assert_eq!(Decimal::percent(150).floor(), Decimal::one());
+        assert_eq!(Decimal::percent(199).floor(), Decimal::one());
+        assert_eq!(Decimal::percent(200).floor(), Decimal::percent(200));
+        assert_eq!(Decimal::percent(99).floor(), Decimal::zero());
+
+        assert_eq!(Decimal::one().ceil(), Decimal::one());
+        assert_eq!(Decimal::percent(150).ceil(), Decimal::percent(200));
+        assert_eq!(Decimal::percent(199).ceil(), Decimal::percent(200));
+        assert_eq!(Decimal::percent(99).ceil(), Decimal::one());
+        assert_eq!(Decimal(Uint128::from(1u128)).ceil(), Decimal::one());
+    }
+
+    #[test]
+    #[should_panic(expected = "attempt to ceil with overflow")]
+    fn decimal_ceil_panics() {
+        let _ = Decimal::MAX.ceil();
+    }
+
+    #[test]
+    fn decimal_checked_ceil() {
+        assert_eq!(
+            Decimal::percent(199).checked_ceil(),
+            Ok(Decimal::percent(200))
+        );
+        assert!(matches!(
+            Decimal::MAX.checked_ceil(),
+            Err(RoundUpOverflowError { .. })
+        ));
+    }
 }
diff --git a/packages/std/src/math/decimal256.rs b/packages/std/src/math/decimal256.rs
@@ -9,7 +9,7 @@ use thiserror::Error;
 
 use crate::errors::{
     CheckedFromRatioError, CheckedMultiplyRatioError, DivideByZeroError, OverflowError,
-    OverflowOperation, StdError,
+    OverflowOperation, RoundUpOverflowError, StdError,
 };
 use crate::{Decimal, Uint512};
 
@@ -197,6 +197,31 @@ impl Decimal256 {
         Self::DECIMAL_PLACES as u32
     }
 
+    /// Rounds value down after decimal places.
+    pub fn floor(&self) -> Self {
+        Self((self.0 / Self::DECIMAL_FRACTIONAL) * Self::DECIMAL_FRACTIONAL)
+    }
+
+    /// Rounds value up after decimal places. Panics on overflow.
+    pub fn ceil(&self) -> Self {
+        match self.checked_ceil() {
+            Ok(value) => value,
+            Err(_) => panic!("attempt to ceil with overflow"),
+        }
+    }
+
+    /// Rounds value up after decimal places. Returns OverflowError on overflow.
+    pub fn checked_ceil(&self) -> Result<Self, RoundUpOverflowError> {
+        let floor = self.floor();
+        if &floor == self {
+            Ok(floor)
+        } else {
+            floor
+                .checked_add(Decimal256::one())
+                .map_err(|_| RoundUpOverflowError)
+        }
+    }
+
     pub fn checked_add(self, other: Self) -> Result<Self, OverflowError> {
         self.0
             .checked_add(other.0)
@@ -2022,4 +2047,34 @@ mod tests {
         );
         assert_eq!(Decimal256::MAX.saturating_pow(2u32), Decimal256::MAX);
     }
+
+    #[test]
+    fn decimal256_rounding() {
+        assert_eq!(Decimal256::one().floor(), Decimal256::one());
+        assert_eq!(Decimal256::percent(150).floor(), Decimal256::one());
+        assert_eq!(Decimal256::percent(199).floor(), Decimal256::one());
+        assert_eq!(Decimal256::percent(200).floor(), Decimal256::percent(200));
+        assert_eq!(Decimal256::percent(99).floor(), Decimal256::zero());
+
+        assert_eq!(Decimal256::one().ceil(), Decimal256::one());
+        assert_eq!(Decimal256::percent(150).ceil(), Decimal256::percent(200));
+        assert_eq!(Decimal256::percent(199).ceil(), Decimal256::percent(200));
+        assert_eq!(Decimal256::percent(99).ceil(), Decimal256::one());
+        assert_eq!(Decimal256(Uint256::from(1u128)).ceil(), Decimal256::one());
+    }
+
+    #[test]
+    #[should_panic(expected = "attempt to ceil with overflow")]
+    fn decimal256_ceil_panics() {
+        let _ = Decimal256::MAX.ceil();
+    }
+
+    #[test]
+    fn decimal256_checked_ceil() {
+        assert_eq!(
+            Decimal256::percent(199).checked_ceil(),
+            Ok(Decimal256::percent(200))
+        );
+        assert_eq!(Decimal256::MAX.checked_ceil(), Err(RoundUpOverflowError));
+    }
 }