misskey/packages/backend/src/misc/bigint.ts

41 lines
1.1 KiB
TypeScript

/*
* SPDX-FileCopyrightText: syuilo and misskey-project
* SPDX-License-Identifier: AGPL-3.0-only
*/
function parseBigIntChunked(str: string, base: number, chunkSize: number, powerOfChunkSize: bigint): bigint {
const chunks = [];
while (str.length > 0) {
chunks.unshift(str.slice(-chunkSize));
str = str.slice(0, -chunkSize);
}
let result = 0n;
for (const chunk of chunks) {
result *= powerOfChunkSize;
const int = parseInt(chunk, base);
if (Number.isNaN(int)) {
throw new Error('Invalid base36 string');
}
result += BigInt(int);
}
return result;
}
export function parseBigInt36(str: string): bigint {
// log_36(Number.MAX_SAFE_INTEGER) => 10.251599391715352
// so we process 10 chars at once
return parseBigIntChunked(str, 36, 10, 36n ** 10n);
}
export function parseBigInt16(str: string): bigint {
// log_16(Number.MAX_SAFE_INTEGER) => 13.25
// so we process 13 chars at once
return parseBigIntChunked(str, 16, 13, 16n ** 13n);
}
export function parseBigInt32(str: string): bigint {
// log_32(Number.MAX_SAFE_INTEGER) => 10.6
// so we process 10 chars at once
return parseBigIntChunked(str, 32, 10, 32n ** 10n);
}