file-type/util.js

Detect the file type of a file, stream, or data

import {StringType} from 'token-types';

export function stringToBytes(string) {
	return [...string].map(character => character.charCodeAt(0)); // eslint-disable-line unicorn/prefer-code-point
}

/**
Checks whether the TAR checksum is valid.

@param {Uint8Array} arrayBuffer - The TAR header `[offset ... offset + 512]`.
@param {number} offset - TAR header offset.
@returns {boolean} `true` if the TAR checksum is valid, otherwise `false`.
*/
export function tarHeaderChecksumMatches(arrayBuffer, offset = 0) {
	const readSum = Number.parseInt(new StringType(6).get(arrayBuffer, 148).replace(/\0.*$/, '').trim(), 8); // Read sum in header
	if (Number.isNaN(readSum)) {
		return false;
	}

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

	for (let index = offset; index < offset + 148; index++) {
		sum += arrayBuffer[index];
	}

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

	return readSum === sum;
}

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