dioptre commented on code in PR #40729:
URL: https://github.com/apache/arrow/pull/40729#discussion_r1537957001
##########
js/src/util/bn.ts:
##########
@@ -68,24 +68,36 @@ Object.assign(SignedBigNum.prototype, BigNum.prototype, {
'constructor': SignedB
Object.assign(UnsignedBigNum.prototype, BigNum.prototype, { 'constructor':
UnsignedBigNum, 'signed': false, 'TypedArray': Uint32Array, 'BigIntArray':
BigUint64Array });
Object.assign(DecimalBigNum.prototype, BigNum.prototype, { 'constructor':
DecimalBigNum, 'signed': true, 'TypedArray': Uint32Array, 'BigIntArray':
BigUint64Array });
+//FOR ES2020 COMPATIBILITY
+const TWO_TO_THE_64 = BigInt(4294967296) * BigInt(4294967296); // 2^64 =
0x10000000000000000n
+const TWO_TO_THE_64_MINUS_1 = TWO_TO_THE_64 - BigInt(1); // (2^32 * 2^32) - 1
= 0xFFFFFFFFFFFFFFFFn
+
/** @ignore */
-function bigNumToNumber<T extends BN<BigNumArray>>(bn: T) {
- const { buffer, byteOffset, length, 'signed': signed } = bn;
- const words = new BigUint64Array(buffer, byteOffset, length);
+export function bigNumToNumber<T extends BN<BigNumArray>>(bn: T, scale?:
number) {
+ const { buffer, byteOffset, byteLength, 'signed': signed } = bn;
+ const words = new BigUint64Array(buffer, byteOffset, byteLength / 8);
const negative = signed && words.at(-1)! & (BigInt(1) << BigInt(63));
- let number = negative ? BigInt(1) : BigInt(0);
- let i = BigInt(0);
+ let number = BigInt(0);
+ let i = 0;
if (!negative) {
for (const word of words) {
- number += word * (BigInt(1) << (BigInt(32) * i++));
+ number |= word * (BigInt(1) << BigInt(64 * i++));
}
} else {
for (const word of words) {
- number += ~word * (BigInt(1) << (BigInt(32) * i++));
+ number |= (word ^ TWO_TO_THE_64_MINUS_1) * (BigInt(1) << BigInt(64
* i++));
}
number *= BigInt(-1);
+ number -= BigInt(1);
+ }
+ if (scale) {
Review Comment:
This is going to further slow down execution, also it won't account for NaN.
After all this I'd like to bring something back (maybe an additional method)
that is efficient after getting this change in. Think good enough it replaces
the broken method for now.
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