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fix: bound money conversion after cents scaling

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jb
2026-09-18 23:55:32 -04:00
parent aea41d8cea
commit 9ddd12fbc5
2 changed files with 15 additions and 9 deletions
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src/lib/domain/money.ts
+10 -7
View File
@@ -7,8 +7,9 @@
export type IskLike = string | bigint | number; export type IskLike = string | bigint | number;
const INTEGER_TEXT = /^-?\d+$/; const INTEGER_TEXT = /^-?\d+$/;
// The final lookahead makes the end assertion strict: JavaScript's `$` alone // The final lookahead makes the end assertion strict. This intentionally
// would also accept a match immediately before one trailing newline. // tightens the old ESI regex, because JavaScript's `$` alone also accepts a
// match immediately before one trailing newline.
const DECIMAL_TEXT = /^-?(?:0|[1-9][0-9]*)(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?$(?![\s\S])/; const DECIMAL_TEXT = /^-?(?:0|[1-9][0-9]*)(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?$(?![\s\S])/;
/** Resource bounds for signed decimal ingestion. These reject excess input; no truncation is performed. */ /** Resource bounds for signed decimal ingestion. These reject excess input; no truncation is performed. */
@@ -68,18 +69,20 @@ export function decimalIskToCents(value: string): string {
} }
const exponent = exponentText === undefined ? 0n : parseDecimalExponent(exponentText); const exponent = exponentText === undefined ? 0n : parseDecimalExponent(exponentText);
const decimalPlaces = BigInt(fraction.length) - exponent; // Convert the decimal coefficient to cents before applying the resource
if (decimalPlaces < -MAX_DECIMAL_SHIFT || decimalPlaces > MAX_DECIMAL_SHIFT) { // bound: value * 10^(exponent - fractionDigits) * 100.
const centsShift = exponent + 2n - BigInt(fraction.length);
if (centsShift < -MAX_DECIMAL_SHIFT || centsShift > MAX_DECIMAL_SHIFT) {
throw new RangeError('ISK decimal shift exceeds resource bounds'); throw new RangeError('ISK decimal shift exceeds resource bounds');
} }
const digits = `${whole}${fraction}`.replace(/^0+(?=\d)/, ''); const digits = `${whole}${fraction}`.replace(/^0+(?=\d)/, '');
const significand = BigInt(digits); const significand = BigInt(digits);
let magnitude: bigint; let magnitude: bigint;
if (decimalPlaces <= 2n) { if (centsShift >= 0n) {
magnitude = significand * 10n ** (2n - decimalPlaces); magnitude = significand * 10n ** centsShift;
} else { } else {
const divisor = 10n ** (decimalPlaces - 2n); const divisor = 10n ** -centsShift;
const quotient = significand / divisor; const quotient = significand / divisor;
const remainder = significand % divisor; const remainder = significand % divisor;
// Half-away-from-zero is half-up for this non-negative magnitude. // Half-away-from-zero is half-up for this non-negative magnitude.
tests/money-formatting.test.ts
+5 -2
View File
@@ -37,9 +37,12 @@ describe('exact decimal ISK conversion', () => {
expect(() => decimalIskToCents(`1e${'0'.repeat(8191)}`)).toThrow('input exceeds resource bounds'); expect(() => decimalIskToCents(`1e${'0'.repeat(8191)}`)).toThrow('input exceeds resource bounds');
expect(() => decimalIskToCents('1e1001')).toThrow('exponent is outside bounds'); expect(() => decimalIskToCents('1e1001')).toThrow('exponent is outside bounds');
expect(() => decimalIskToCents('1e-1001')).toThrow('exponent is outside bounds'); expect(() => decimalIskToCents('1e-1001')).toThrow('exponent is outside bounds');
expect(decimalIskToCents('1e1000')).toBe(`1${'0'.repeat(1002)}`); expect(decimalIskToCents('1e998')).toBe(`1${'0'.repeat(1000)}`);
expect(() => decimalIskToCents('1e999')).toThrow('shift exceeds resource bounds');
expect(() => decimalIskToCents('1e1000')).toThrow('shift exceeds resource bounds');
expect(decimalIskToCents(`1.${'0'.repeat(1002)}`)).toBe('100');
expect(() => decimalIskToCents(`1.${'0'.repeat(1003)}`)).toThrow('shift exceeds resource bounds');
expect(decimalIskToCents(`0.${'0'.repeat(999)}1`)).toBe('0'); expect(decimalIskToCents(`0.${'0'.repeat(999)}1`)).toBe('0');
expect(() => decimalIskToCents(`0.${'0'.repeat(1000)}1`)).toThrow('shift exceeds resource bounds');
expect(decimalIskToCents('1'.repeat(4096))).toBe(`${BigInt('1'.repeat(4096)) * 100n}`); expect(decimalIskToCents('1'.repeat(4096))).toBe(`${BigInt('1'.repeat(4096)) * 100n}`);
expect(() => decimalIskToCents('1'.repeat(4097))).toThrow('coefficient exceeds resource bounds'); expect(() => decimalIskToCents('1'.repeat(4097))).toThrow('coefficient exceeds resource bounds');
}); });