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import { buildFramesBuffer } from "./frames-builder" |
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import { getTags } from "./frames-reader" |
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import { Options } from "./types/Options" |
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import { WriteTags } from "./types/Tags" |
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import { decodeSize, encodeSize } from "./util-size" |
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const Header = { |
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identifier: "ID3", |
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size: 10, |
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offset: { |
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id: 0, |
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version: 3, |
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flags: 5, |
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size: 6 |
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} |
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} as const |
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const subarray = (buffer: Buffer, offset: number, size: number) => |
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buffer.subarray(offset, offset + size) |
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export function createId3Tag(tags: WriteTags) { |
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const frames = buildFramesBuffer(tags) |
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return embedFramesInId3Tag(frames) |
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} |
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export function embedFramesInId3Tag(frames: Buffer) { |
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const header = Buffer.alloc(Header.size) |
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header.fill(0) |
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header.write(Header.identifier, Header.offset.id) |
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header.writeUInt16BE(0x0300, Header.offset.version) |
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header.writeUInt16BE(0x0000, Header.offset.flags) |
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encodeSize(frames.length).copy(header, Header.offset.size) |
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return Buffer.concat([header, frames]) |
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} |
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/** |
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* Remove already written ID3-Frames from a buffer |
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*/ |
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export function removeId3Tag(data: Buffer) { |
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const tagPosition = findId3TagPosition(data) |
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if (tagPosition === -1) { |
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return data |
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} |
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const encodedSize = subarray(data, tagPosition + Header.offset.size, 4) |
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if (!isValidEncodedSize(encodedSize)) { |
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return false |
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} |
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if (data.length >= tagPosition + Header.size) { |
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const size = decodeSize(encodedSize) |
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return Buffer.concat([ |
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data.subarray(0, tagPosition), |
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data.subarray(tagPosition + size + Header.size) |
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]) |
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} |
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return data |
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} |
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export function getTagsFromId3Tag(buffer: Buffer, options: Options) { |
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const tagBody = getId3TagBody(buffer) |
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return getTags(tagBody, options) |
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} |
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function getId3TagBody(buffer: Buffer) { |
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const tagPosition = findId3TagPosition(buffer) |
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if (tagPosition === -1) { |
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return undefined |
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} |
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const encodedSize = subarray(buffer, tagPosition + Header.offset.size, 4) |
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const tagSize = Header.size + decodeSize(encodedSize) |
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const tagData = subarray(buffer, tagPosition, tagSize) |
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const tagHeader = tagData.subarray(0, Header.size) |
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// ID3 version e.g. 3 if ID3v2.3.0 |
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const version = tagHeader[Header.offset.version] |
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const tagFlags = parseTagHeaderFlags(tagHeader) |
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let extendedHeaderSize = 0 |
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if (tagFlags.extendedHeader) { |
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if (version === 3) { |
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extendedHeaderSize = 4 + tagData.readUInt32BE(Header.size) |
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} else if(version === 4) { |
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extendedHeaderSize = decodeSize(subarray(tagData, Header.size, 4)) |
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} |
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} |
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const totalHeaderSize = Header.size + extendedHeaderSize |
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const bodySize = tagSize - totalHeaderSize |
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// Copy for now, it might not be necessary, but we are not really sure for |
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// now, will be re-assessed if we can avoid the copy. |
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const body = Buffer.alloc(bodySize) |
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tagData.copy(body, 0, totalHeaderSize) |
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return { |
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version, buffer: body |
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} |
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} |
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function parseTagHeaderFlags(header: Buffer) { |
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if (header.length < Header.size) { |
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return {} |
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} |
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const version = header[3] |
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const flagsByte = header[5] |
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if (version === 3) { |
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return { |
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unsynchronisation: !!(flagsByte & 128), |
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extendedHeader: !!(flagsByte & 64), |
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experimentalIndicator: !!(flagsByte & 32) |
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} |
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} |
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if (version === 4) { |
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return { |
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unsynchronisation: !!(flagsByte & 128), |
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extendedHeader: !!(flagsByte & 64), |
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experimentalIndicator: !!(flagsByte & 32), |
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footerPresent: !!(flagsByte & 16) |
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} |
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} |
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return {} |
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} |
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126
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/** |
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127
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* Returns -1 if no tag was found. |
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128
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*/ |
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129
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function findId3TagPosition(buffer: Buffer) { |
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// Search Buffer for valid ID3 frame |
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let position = -1 |
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132
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let headerValid = false |
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do { |
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position = buffer.indexOf(Header.identifier, position + 1) |
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if (position !== -1) { |
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// It's possible that there is a "ID3" sequence without being an |
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// ID3 Frame, so we need to check for validity of the next 10 bytes. |
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headerValid = isValidId3Header( |
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buffer.subarray(position, position + Header.size) |
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) |
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} |
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} while (position !== -1 && !headerValid) |
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if (!headerValid) { |
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return -1 |
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146
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} |
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return position |
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} |
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149
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150
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function isValidId3Header(buffer: Buffer) { |
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151
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if (buffer.length < Header.size) { |
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152
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return false |
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153
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} |
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154
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if (buffer.readUIntBE(0, 3) !== 0x494433) { |
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return false |
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156
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} |
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157
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if ([0x02, 0x03, 0x04].indexOf(buffer[3]) === -1 || buffer[4] !== 0x00) { |
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158
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return false |
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159
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} |
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160
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return isValidEncodedSize(subarray(buffer, Header.offset.size, 4)) |
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161
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} |
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162
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163
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function isValidEncodedSize(encodedSize: Buffer) { |
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164
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// The size must not have the bit 7 set |
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165
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return (( |
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166
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encodedSize[0] | |
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167
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encodedSize[1] | |
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168
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encodedSize[2] | |
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169
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encodedSize[3] |
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170
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) & 128) === 0 |
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171
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} |
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Zazama /
node-id3
