@infinito/id3/src/valid.js

ID3 Tag Reader/Writer

import {constants} from './constants.js';

import getSyncSafe from './get.syncsafe.js';

export default function validID3(buf) {
	if(!(buf instanceof ArrayBuffer)) {
		throw new TypeError('parameter buf must be an instance of an ArrayBuffer');
	}
	if(buf.byteLength<constants.ID3_HEADER_LENGTH_BYTES) {
		throw new Error('buffer provided to validID3 must be at least as big as the ID3 header');
	}
	var res = {
		ver:0,
		subver:0,
		flags:0,
		size:0
	};
	const header = new Uint8Array(buf,0,constants.ID3_HEADER_LENGTH_BYTES-constants.ID3_HEADER_TAG_SIZE_LENGTH_BYTES);
	for(let i=0;i<constants.ID3_HEADER_IDENTIFIER_LENGTH_BYTES;i++) {
		if(header[i]!=constants.ID3_HEADER_IDENTIFIER[i]) {
			throw new Error("No valid id3 tags found");
			return false;
		}
	}
	res.ver = header[constants.ID3_HEADER_IDENTIFIER_LENGTH_BYTES];
	res.subver = header[constants.ID3_HEADER_IDENTIFIER_LENGTH_BYTES+1];
	res.flags = header[constants.ID3_HEADER_IDENTIFIER_LENGTH_BYTES+2];
	res.size = getSyncSafe(new Uint8Array(buf,constants.ID3_HEADER_IDENTIFIER_LENGTH_BYTES+3,constants.ID3_HEADER_TAG_SIZE_LENGTH_BYTES));
	return res;
};