util.js

'use strict';

exports.stringToBytes = string => [...string].map(character => character.charCodeAt(0));

/**
Checks whether the TAR checksum is valid.

@param {Buffer} buffer - The TAR header `[offset ... offset + 512]`.
@param {number} offset - TAR header offset.
@returns {boolean} `true` if the TAR checksum is valid, otherwise `false`.
*/
exports.tarHeaderChecksumMatches = (buffer, offset = 0) => {
	const readSum = parseInt(buffer.toString('utf8', 148, 154).replace(/\0.*$/, '').trim(), 8); // Read sum in header
	if (isNaN(readSum)) {
		return false;
	}

	let sum = 8 * 0x20; // Initialize signed bit sum

	for (let i = offset; i < offset + 148; i++) {
		sum += buffer[i];
	}

	for (let i = offset + 156; i < offset + 512; i++) {
		sum += buffer[i];
	}

	return readSum === sum;
};

/**
ID3 UINT32 sync-safe tokenizer token.
28 bits (representing up to 256MB) integer, the msb is 0 to avoid "false syncsignals".
*/
exports.uint32SyncSafeToken = {
	get: (buffer, offset) => {
		return (buffer[offset + 3] & 0x7F) | ((buffer[offset + 2]) << 7) | ((buffer[offset + 1]) << 14) | ((buffer[offset]) << 21);
	},
	len: 4
};