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import zlib = require('zlib') |
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import { |
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Flags, |
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getHeaderSize, |
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FrameHeader |
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} from './FrameHeader' |
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import * as Frames from './Frames' |
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import * as ID3Util from './ID3Util' |
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import { isKeyOf } from "./util" |
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type HeaderInfo = { |
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identifier: string |
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headerSize: number |
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bodySize: number |
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flags: Flags |
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} |
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export class Frame { |
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identifier: string |
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private value: unknown |
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flags: Flags |
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constructor(identifier: string, value: unknown, flags: Flags = {}) { |
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this.identifier = identifier |
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this.value = value |
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this.flags = flags |
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} |
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static createFromBuffer = createFromBuffer |
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makeBuffer() { |
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return makeFrameBuffer(this.identifier, this.value) |
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} |
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getValue() { |
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return this.value |
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} |
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} |
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function makeFrameBuffer(identifier: string, value: unknown) { |
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if (isKeyOf(identifier, Frames.Frames)) { |
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return Frames.Frames[identifier].create(value) |
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} |
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if (identifier.startsWith('T')) { |
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return Frames.GENERIC_TEXT.create(identifier, value) |
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} |
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if (identifier.startsWith('W')) { |
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return Frames.GENERIC_URL.create(identifier, value) |
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} |
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return null |
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} |
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function createFromBuffer( |
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frameBuffer: Buffer, |
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version: number |
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): Frame | null { |
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const headerSize = getHeaderSize(version) |
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// Specification requirement |
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if (frameBuffer.length < headerSize + 1) { |
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return null |
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} |
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const headerBuffer = frameBuffer.subarray(0, headerSize) |
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const header: HeaderInfo = { |
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headerSize, |
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...FrameHeader.createFromBuffer(headerBuffer, version) |
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} |
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if (header.flags.encryption) { |
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return null |
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} |
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const body = decompressBody( |
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header.flags, |
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getDataLength(header, frameBuffer), |
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getBody(header, frameBuffer) |
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) |
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if (!body) { |
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return null |
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} |
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const identifier = header.identifier |
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let value = null |
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if (isKeyOf(identifier, Frames.Frames)) { |
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value = Frames.Frames[identifier].read(body, version) |
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} else if (identifier.startsWith('T')) { |
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value = Frames.GENERIC_TEXT.read(body) |
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} else if (identifier.startsWith('W')) { |
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value = Frames.GENERIC_URL.read(body) |
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} else { |
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return null |
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} |
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return new Frame(identifier, value, header.flags) |
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} |
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function getBody({flags, headerSize, bodySize}: HeaderInfo, buffer: Buffer) { |
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const bodyOffset = flags.dataLengthIndicator ? 4 : 0 |
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const bodyStart = headerSize + bodyOffset |
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const bodyEnd = bodyStart + bodySize - bodyOffset |
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const body = buffer.subarray(bodyStart, bodyEnd) |
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if (flags.unsynchronisation) { |
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// This method should stay in ID3Util for now because it's also used in the Tag's header which we don't have a class for. |
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return ID3Util.processUnsynchronisedBuffer(body) |
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} |
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return body |
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} |
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function getDataLength({flags, headerSize}: HeaderInfo, buffer: Buffer) { |
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return flags.dataLengthIndicator ? buffer.readInt32BE(headerSize) : 0 |
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} |
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function decompressBody( |
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{compression}: Flags, |
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dataLength: number, |
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body: Buffer |
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) { |
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return compression ? decompressBuffer(body, dataLength) : body |
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} |
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function decompressBuffer(buffer: Buffer, expectedDecompressedLength: number) { |
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if (buffer.length < 5) { |
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return null |
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} |
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// ID3 spec defines that compression is stored in ZLIB format, |
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// but doesn't specify if header is present or not. |
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// ZLIB has a 2-byte header. |
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// 1. try if header + body decompression |
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// 2. else try if header is not stored (assume that all content is deflated "body") |
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// 3. else try if inflation works if the header is omitted (implementation dependent) |
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const tryDecompress = () => { |
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try { |
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return zlib.inflateSync(buffer) |
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} catch (error) { |
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try { |
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return zlib.inflateRawSync(buffer) |
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} catch (error) { |
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try { |
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return zlib.inflateRawSync(buffer.subarray(2)) |
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} catch (error) { |
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return null |
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} |
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} |
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} |
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} |
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const decompressed = tryDecompress() |
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if (decompressed && decompressed.length === expectedDecompressedLength) { |
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return decompressed |
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} |
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return null |
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} |
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Zazama /
node-id3
