Migrate code to BigInt where possible

Author: Shaptic

config/.eslintrc.js

@@ -1,6 +1,7 @@
 module.exports = {
   env: {
-    es6: true
+    es6: true,
+    es2020: true
   },
   extends: ['airbnb-base', 'prettier'],
   plugins: ['@babel', 'prettier', 'prefer-import'],

package.json

@@ -61,7 +61,7 @@
   "keywords": [
     "stellar"
   ],
-  "author": "George Kudrayvtsev <george@stellar.org>",
+  "author": "Stellar Development Foundation <hello@stellar.org>",
   "license": "Apache-2.0",
   "bugs": {
     "url": "https://github.com/stellar/js-stellar-base/issues"
@@ -83,6 +83,7 @@
     "buffer": "^6.0.3",
     "chai": "^4.3.7",
     "cross-env": "^7.0.3",
+    "crypto-browserify": "^3.12.0",
     "eslint": "^8.37.0",
     "eslint-config-airbnb-base": "^15.0.0",
     "eslint-config-prettier": "^8.8.0",
@@ -121,7 +122,6 @@
     "base32.js": "^0.1.0",
     "bignumber.js": "^9.1.1",
     "crc": "^4.3.2",
-    "crypto-browserify": "^3.12.0",
     "js-xdr": "^2.0.0",
     "lodash": "^4.17.21",
     "sha.js": "^2.3.6",

src/account.js

@@ -1,5 +1,4 @@
 import isString from 'lodash/isString';
-import BigNumber from 'bignumber.js';
 
 import { StrKey } from './strkey';
 
@@ -34,7 +33,11 @@ export class Account {
     }
 
     this._accountId = accountId;
-    this.sequence = new BigNumber(sequence);
+    try {
+      this.sequence = BigInt(sequence);
+    } catch (e) {
+      throw new Error(`sequence is not a number: ${sequence}`);
+    }
   }
 
   /**
@@ -58,6 +61,6 @@ export class Account {
    * @returns {void}
    */
   incrementSequenceNumber() {
-    this.sequence = this.sequence.plus(1);
+    this.sequence += 1n;
   }
 }

src/index.js

@@ -1,9 +1,6 @@
 /* eslint-disable import/no-import-module-exports */
-import BigNumber from 'bignumber.js';
 import xdr from './xdr';
 
-BigNumber.DEBUG = true; // gives us exceptions on bad constructor values
-
 export { xdr };
 export { hash } from './hashing';
 export { sign, verify, FastSigning } from './signing';

src/memo.js

@@ -2,7 +2,6 @@ import isUndefined from 'lodash/isUndefined';
 import isString from 'lodash/isString';
 import clone from 'lodash/clone';
 import { UnsignedHyper } from 'js-xdr';
-import BigNumber from 'bignumber.js';
 import xdr from './xdr';
 
 /**
@@ -105,22 +104,11 @@ export class Memo {
       throw error;
     }
 
-    let number;
     try {
-      number = new BigNumber(value);
+      BigInt(value); // throws on invalid, inf, or NaN
     } catch (e) {
       throw error;
     }
-
-    // Infinity
-    if (!number.isFinite()) {
-      throw error;
-    }
-
-    // NaN
-    if (number.isNaN()) {
-      throw error;
-    }
   }
 
   static _validateTextValue(value) {

src/operation.js

@@ -23,6 +23,8 @@ import {
 const ONE = 10000000;
 const MAX_INT64 = '9223372036854775807';
 
+BigNumber.DEBUG = true; // gives us exceptions on bad constructor values
+
 /**
  * When set using `{@link Operation.setOptions}` option, requires the issuing
  * account to give other accounts permission before they can hold the issuing
@@ -489,10 +491,10 @@ export class Operation {
     if (price.n && price.d) {
       xdrObject = new xdr.Price(price);
     } else {
-      const approx = best_r(price);
+      const [n, d] = best_r(price);
       xdrObject = new xdr.Price({
-        n: parseInt(approx[0], 10),
-        d: parseInt(approx[1], 10)
+        n: parseInt(n, 10),
+        d: parseInt(d, 10)
       });
     }
 

src/operations/bump_sequence.js

@@ -1,5 +1,4 @@
 import { Hyper } from 'js-xdr';
-import BigNumber from 'bignumber.js';
 import isString from 'lodash/isString';
 import xdr from '../xdr';
 
@@ -20,8 +19,7 @@ export function bumpSequence(opts) {
   }
 
   try {
-    // eslint-disable-next-line no-new
-    new BigNumber(opts.bumpTo);
+    BigInt(opts.bumpTo);
   } catch (e) {
     throw new Error('bumpTo must be a stringified number');
   }

src/operations/change_trust.js

@@ -1,11 +1,10 @@
 import isUndefined from 'lodash/isUndefined';
 import { Hyper } from 'js-xdr';
-import BigNumber from 'bignumber.js';
 import xdr from '../xdr';
 import { Asset } from '../asset';
 import { LiquidityPoolAsset } from '../liquidity_pool_asset';
 
-const MAX_INT64 = '9223372036854775807';
+const MAX_INT64 = 9223372036854775807n;
 
 /**
  * Returns an XDR ChangeTrustOp. A "change trust" operation adds, removes, or updates a
@@ -37,7 +36,7 @@ export function changeTrust(opts) {
   if (opts.limit) {
     attributes.limit = this._toXDRAmount(opts.limit);
   } else {
-    attributes.limit = Hyper.fromString(new BigNumber(MAX_INT64).toString());
+    attributes.limit = Hyper.fromString(MAX_INT64.toString());
   }
 
   if (opts.source) {

src/transaction_builder.js

@@ -1,5 +1,4 @@
 import { UnsignedHyper } from 'js-xdr';
-import BigNumber from 'bignumber.js';
 import clone from 'lodash/clone';
 import isUndefined from 'lodash/isUndefined';
 import isString from 'lodash/isString';
@@ -444,10 +443,10 @@ export class TransactionBuilder {
    * @returns {Transaction} This method will return the built {@link Transaction}.
    */
   build() {
-    const sequenceNumber = new BigNumber(this.source.sequenceNumber()).plus(1);
-    const fee = new BigNumber(this.baseFee)
-      .times(this.operations.length)
-      .toNumber();
+    const sequenceNumber = BigInt(this.source.sequenceNumber()) + 1n;
+    const fee = Number(
+      BigInt.asIntN(32, BigInt(this.baseFee) * BigInt(this.operations.length))
+    ); // base tx is int32 in XDR, feebump is int64
     const attrs = {
       fee,
       seqNum: xdr.SequenceNumber.fromString(sequenceNumber.toString()),
@@ -572,23 +571,23 @@ export class TransactionBuilder {
     innerTx,
     networkPassphrase
   ) {
-    const innerOps = innerTx.operations.length;
-    const innerBaseFeeRate = new BigNumber(innerTx.fee).div(innerOps);
-    const base = new BigNumber(baseFee);
+    const innerOps = BigInt(innerTx.operations.length);
+    const innerBaseFeeRate = BigInt(innerTx.fee) / innerOps; // truncates
+    const base = BigInt(baseFee);
 
     // The fee rate for fee bump is at least the fee rate of the inner transaction
-    if (base.lt(innerBaseFeeRate)) {
+    if (base < innerBaseFeeRate) {
       throw new Error(
-        `Invalid baseFee, it should be at least ${innerBaseFeeRate} stroops.`
+        `Invalid baseFee (${baseFee}), it should be at least ${innerBaseFeeRate} stroops.`
       );
     }
 
-    const minBaseFee = new BigNumber(BASE_FEE);
+    const minBaseFee = BigInt(BASE_FEE);
 
     // The fee rate is at least the minimum fee
-    if (base.lt(minBaseFee)) {
+    if (base < minBaseFee) {
       throw new Error(
-        `Invalid baseFee, it should be at least ${minBaseFee} stroops.`
+        `Invalid baseFee (${baseFee}), it should be at least ${minBaseFee} stroops.`
       );
     }
 
@@ -623,7 +622,7 @@ export class TransactionBuilder {
 
     const tx = new xdr.FeeBumpTransaction({
       feeSource: feeSourceAccount,
-      fee: xdr.Int64.fromString(base.times(innerOps + 1).toString()),
+      fee: xdr.Int64.fromString(BigInt.asIntN(64, (base * (innerOps + 1n)).toString())),
       innerTx: xdr.FeeBumpTransactionInnerTx.envelopeTypeTx(
         innerTxEnvelope.v1()
       ),

src/util/continued_fraction.js

@@ -4,24 +4,62 @@ import BigNumber from 'bignumber.js';
 const MAX_INT = ((1 << 31) >>> 0) - 1;
 
 /**
- * Calculates and returns the best rational approximation of the given real number.
+ * Calculates and returns the best rational (fractional) approximation of the
+ * given real number.
+ *
  * @private
- * @param {string|number|BigNumber} rawNumber Real number
- * @throws Error Throws `Error` when the best rational approximation cannot be found.
- * @returns {array} first element is n (numerator), second element is d (denominator)
+ *
+ * This is used internally to convert real-number-like prices into fractions for
+ * XDR to use as part of DEX offer & LP management.
+ *
+ * @param {string|number|BigInt} rawNumber  the "real" number to approximate
+ *
+ * @returns {number[]} the numerator and denominator of the fractional
+ *  approximation, respectively, where neither value exceeds `MAX_INT32`
+ *
+ * @throws {Error} throws an `Error` when no good rational approximation can be
+ *  found.
  */
 export function best_r(rawNumber) {
-  let number = new BigNumber(rawNumber);
+  BigNumber.DEBUG = true; // gives us exceptions on bad constructor values
+
+  // NOTE: We can't convert this to use BigInt because the rational component is
+  // crucial to calculating the approximation.
+  let number = BigNumber(rawNumber);
   let a;
   let f;
+
+  // We start with 0/1 and 1/0 as our approximations (the latter is technically
+  // undefined but we need it as a starting point)
   const fractions = [
     [new BigNumber(0), new BigNumber(1)],
     [new BigNumber(1), new BigNumber(0)]
   ];
   let i = 2;
 
+  /*
+  The algorithm is a form of the continued fraction expansion (hinted at by the
+  filename):
+
+  > A continued fraction is an expression obtained through an iterative process
+  > of representing a number as the sum of its integer part and the reciprocal
+  > of another number, then writing this other number as the sum of its integer
+  > part and another reciprocal, and so on.
+
+  https://en.wikipedia.org/wiki/Continued_fraction
+
+  We run this loop until either:
+
+   - any part of the fraction exceeds MAX_INT (though JS can handle bigger
+     numbers just fine, the xdr.Price object uses int32 values), OR
+
+   - the "remainder" (`f` in the below loop) is zero (this means we've gotten a
+     perfect approximation)
+   */
   // eslint-disable-next-line no-constant-condition
   while (true) {
+    // Compare the delta between the rational `number` and its truncated integer
+    // equivalent: `f` is everything after the decimal point.
     if (number.gt(MAX_INT)) {
       break;
     }
@@ -39,8 +77,8 @@ export function best_r(rawNumber) {
     number = new BigNumber(1).div(f);
     i += 1;
   }
-  const [n, d] = fractions[fractions.length - 1];
 
+  const [n, d] = fractions[fractions.length - 1];
   if (n.isZero() || d.isZero()) {
     throw new Error("Couldn't find approximation");
   }