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read_long.ts
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read_long.ts
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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
import { type BufReader } from "./buf_reader.ts";
import { readInt } from "./read_int.ts";
const MAX_SAFE_INTEGER = BigInt(Number.MAX_SAFE_INTEGER);
/**
* Read big endian 64bit long from BufReader
* @param buf
*/
export async function readLong(buf: BufReader): Promise<number | null> {
const high = await readInt(buf);
if (high === null) return null;
const low = await readInt(buf);
if (low === null) throw new Deno.errors.UnexpectedEof();
const big = (BigInt(high) << 32n) | BigInt(low);
// We probably should provide a similar API that returns BigInt values.
if (big > MAX_SAFE_INTEGER) {
throw new RangeError(
"Long value too big to be represented as a JavaScript number.",
);
}
return Number(big);
}