Merge pull request #1135 from cosmos/decimal-ceil

Let calculateFee handle fee amounts that exceed the safe integer range

CHANGELOG.md

@@ -6,6 +6,15 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Added
+
+- @cosmjs/math: Add `Decimal.floor` and `Decimal.ceil`.
+
+### Changed
+
+- @cosmjs/stargate: Let `calculateFee` handle fee amounts that exceed the safe
+  integer range.
+
 ## [0.28.4] - 2022-04-15
 
 ### Added

packages/math/src/decimal.spec.ts

@@ -177,6 +177,42 @@ describe("Decimal", () => {
     });
   });
 
+  describe("floor", () => {
+    it("works", () => {
+      // whole numbers
+      expect(Decimal.fromUserInput("0", 0).floor().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1", 0).floor().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("44", 0).floor().toString()).toEqual("44");
+      expect(Decimal.fromUserInput("0", 3).floor().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1", 3).floor().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("44", 3).floor().toString()).toEqual("44");
+
+      // with fractional part
+      expect(Decimal.fromUserInput("0.001", 3).floor().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1.999", 3).floor().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("0.000000000000000001", 18).floor().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1.999999999999999999", 18).floor().toString()).toEqual("1");
+    });
+  });
+
+  describe("ceil", () => {
+    it("works", () => {
+      // whole numbers
+      expect(Decimal.fromUserInput("0", 0).ceil().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1", 0).ceil().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("44", 0).ceil().toString()).toEqual("44");
+      expect(Decimal.fromUserInput("0", 3).ceil().toString()).toEqual("0");
+      expect(Decimal.fromUserInput("1", 3).ceil().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("44", 3).ceil().toString()).toEqual("44");
+
+      // with fractional part
+      expect(Decimal.fromUserInput("0.001", 3).ceil().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("1.999", 3).ceil().toString()).toEqual("2");
+      expect(Decimal.fromUserInput("0.000000000000000001", 18).ceil().toString()).toEqual("1");
+      expect(Decimal.fromUserInput("1.999999999999999999", 18).ceil().toString()).toEqual("2");
+    });
+  });
+
   describe("toString", () => {
     it("displays no decimal point for full numbers", () => {
       expect(Decimal.fromUserInput("44", 0).toString()).toEqual("44");

packages/math/src/decimal.ts

@@ -113,6 +113,37 @@ export class Decimal {
     };
   }
 
+  /** Creates a new instance with the same value */
+  private clone(): Decimal {
+    return new Decimal(this.atomics, this.fractionalDigits);
+  }
+
+  /** Returns the greatest decimal <= this which has no fractional part (rounding down) */
+  public floor(): Decimal {
+    const factor = new BN(10).pow(new BN(this.data.fractionalDigits));
+    const whole = this.data.atomics.div(factor);
+    const fractional = this.data.atomics.mod(factor);
+
+    if (fractional.isZero()) {
+      return this.clone();
+    } else {
+      return Decimal.fromAtomics(whole.mul(factor).toString(), this.fractionalDigits);
+    }
+  }
+
+  /** Returns the smallest decimal >= this which has no fractional part (rounding up) */
+  public ceil(): Decimal {
+    const factor = new BN(10).pow(new BN(this.data.fractionalDigits));
+    const whole = this.data.atomics.div(factor);
+    const fractional = this.data.atomics.mod(factor);
+
+    if (fractional.isZero()) {
+      return this.clone();
+    } else {
+      return Decimal.fromAtomics(whole.addn(1).mul(factor).toString(), this.fractionalDigits);
+    }
+  }
+
   public toString(): string {
     const factor = new BN(10).pow(new BN(this.data.fractionalDigits));
     const whole = this.data.atomics.div(factor);

packages/stargate/src/fee.spec.ts

@@ -93,4 +93,15 @@ describe("calculateFee", () => {
       gas: "80000",
     });
   });
+
+  it("works with large gas price", () => {
+    // "The default gas price is 5000000000000 (5e^12), as the native coin has 18 decimals it is exceeding the max safe integer"
+    // https://github.com/cosmos/cosmjs/issues/1134
+    const gasPrice = GasPrice.fromString("5000000000000tiny");
+    const fee = calculateFee(500_000, gasPrice);
+    expect(fee).toEqual({
+      amount: [{ amount: "2500000000000000000", denom: "tiny" }],
+      gas: "500000",
+    });
+  });
 });

packages/stargate/src/fee.ts

@@ -60,7 +60,9 @@ export class GasPrice {
 export function calculateFee(gasLimit: number, gasPrice: GasPrice | string): StdFee {
   const processedGasPrice = typeof gasPrice === "string" ? GasPrice.fromString(gasPrice) : gasPrice;
   const { denom, amount: gasPriceAmount } = processedGasPrice;
-  const amount = Math.ceil(gasPriceAmount.multiply(new Uint53(gasLimit)).toFloatApproximation());
+  // Note: Amount can exceed the safe integer range (https://github.com/cosmos/cosmjs/issues/1134),
+  // which we handle by converting from Decimal to string without going through number.
+  const amount = gasPriceAmount.multiply(new Uint53(gasLimit)).ceil().toString();
   return {
     amount: coins(amount, denom),
     gas: gasLimit.toString(),