@polkadot/util
Version:
A collection of useful utilities for @polkadot
71 lines (70 loc) • 2.57 kB
JavaScript
import { BigInt } from '@polkadot/x-bigint';
import { _1n } from '../bi/consts.js';
const U8_MAX = BigInt(256);
const U16_MAX = BigInt(256 * 256);
const U64_MAX = BigInt('0x10000000000000000');
/**
* @name u8aToBigInt
* @summary Creates a BigInt from a Uint8Array object.
*/
export function u8aToBigInt(value, { isLe = true, isNegative = false } = {}) {
// slice + reverse is expensive, however SCALE is LE by default so this is the path
// we are most interested in (the BE is added for the sake of being comprehensive)
if (!isLe) {
value = value.slice().reverse();
}
const count = value.length;
if (isNegative && count && (value[count - 1] & 0x80)) {
switch (count) {
case 0:
return BigInt(0);
case 1:
return BigInt(((value[0] ^ 0x0000_00ff) * -1) - 1);
case 2:
return BigInt((((value[0] + (value[1] << 8)) ^ 0x0000_ffff) * -1) - 1);
case 4:
return BigInt((((value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00)) ^ 0xffff_ffff) * -1) - 1);
}
const dvI = new DataView(value.buffer, value.byteOffset);
if (count === 8) {
return dvI.getBigInt64(0, true);
}
let result = BigInt(0);
const mod = count % 2;
for (let i = count - 2; i >= mod; i -= 2) {
result = (result * U16_MAX) + BigInt(dvI.getUint16(i, true) ^ 0xffff);
}
if (mod) {
result = (result * U8_MAX) + BigInt(value[0] ^ 0xff);
}
return (result * -_1n) - _1n;
}
switch (count) {
case 0:
return BigInt(0);
case 1:
return BigInt(value[0]);
case 2:
return BigInt(value[0] + (value[1] << 8));
case 4:
return BigInt(value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00));
}
const dvI = new DataView(value.buffer, value.byteOffset);
switch (count) {
case 8:
return dvI.getBigUint64(0, true);
case 16:
return (dvI.getBigUint64(8, true) * U64_MAX) + dvI.getBigUint64(0, true);
default: {
let result = BigInt(0);
const mod = count % 2;
for (let i = count - 2; i >= mod; i -= 2) {
result = (result * U16_MAX) + BigInt(dvI.getUint16(i, true));
}
if (mod) {
result = (result * U8_MAX) + BigInt(value[0]);
}
return result;
}
}
}