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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 ID3Frames from './ID3Frames' |
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import * as ID3Util from './ID3Util' |
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import { isKeyOf } from "./util" |
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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( |
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frameBuffer: Buffer, |
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version: number |
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): Frame | null { |
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const frameHeaderSize = getHeaderSize(version) |
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// Specification requirement |
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if (frameBuffer.length < frameHeaderSize + 1) { |
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return null |
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} |
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const frameHeaderBuffer = frameBuffer.subarray(0, frameHeaderSize) |
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const frameHeader = FrameHeader.createFromBuffer( |
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frameHeaderBuffer, version |
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) |
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if (frameHeader.flags.encryption) { |
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return null |
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} |
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const frameBodyOffset = frameHeader.flags.dataLengthIndicator ? 4 : 0 |
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const frameBodyStart = frameHeaderSize + frameBodyOffset |
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let frameBody = frameBuffer.subarray(frameBodyStart, frameBodyStart + frameHeader.bodySize - frameBodyOffset) |
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if (frameHeader.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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frameBody = ID3Util.processUnsynchronisedBuffer(frameBody) |
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} |
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const decompressedFrameBody = decompressBody( |
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frameHeader.flags, frameBuffer, frameHeaderSize, frameBody |
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) |
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if (!decompressedFrameBody) { |
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return null |
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} |
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frameBody = decompressedFrameBody |
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const identifier = frameHeader.identifier |
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let value = null |
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if (isKeyOf(identifier, ID3Frames.Frames)) { |
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value = ID3Frames.Frames[identifier].read(frameBody, version) |
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} else if (identifier.startsWith('T')) { |
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value = ID3Frames.GENERIC_TEXT.read(frameBody) |
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} else if (identifier.startsWith('W')) { |
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value = ID3Frames.GENERIC_URL.read(frameBody) |
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} else { |
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return null |
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} |
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return new Frame(identifier, value, frameHeader.flags) |
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} |
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getBuffer() { |
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if (isKeyOf(this.identifier, ID3Frames.Frames)) { |
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return ID3Frames.Frames[this.identifier].create(this.value) |
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} |
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if (this.identifier.startsWith('T')) { |
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return ID3Frames.GENERIC_TEXT.create(this.identifier, this.value) |
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} |
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if (this.identifier.startsWith('W')) { |
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return ID3Frames.GENERIC_URL.create(this.identifier, this.value) |
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} |
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return null |
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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 decompressBody( |
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flags: Flags, |
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frameBuffer: Buffer, |
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dataLengthOffset: number, |
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frameBody: Buffer |
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) { |
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let dataLength = 0 |
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if (flags.dataLengthIndicator) { |
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dataLength = frameBuffer.readInt32BE(dataLengthOffset) |
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} |
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if (flags.compression) { |
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return decompressBuffer(frameBody, dataLength) |
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} |
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return frameBody |
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} |
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function decompressBuffer(buffer: Buffer, expectedDecompressedLength: number) { |
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if (buffer.length < 5 || expectedDecompressedLength === undefined) { |
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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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127
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} |
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128
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} |
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129
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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 null |
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} |
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return decompressed |
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} |
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Zazama /
node-id3
