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import { decodeSize, encodeSize } from "./util-size" |
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const headerSize = 10 |
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const sizeOffset = 6 |
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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(frames: Buffer) { |
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const header = Buffer.alloc(headerSize) |
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header.fill(0) |
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header.write("ID3", 0) // File identifier |
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header.writeUInt16BE(0x0300, 3) // Version 2.3.0 -- 03 00 |
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header.writeUInt16BE(0x0000, 5) // Flags 00 |
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encodeSize(frames.length).copy(header, sizeOffset) |
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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 = getId3TagPosition(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 + sizeOffset, 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 + headerSize) { |
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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 + headerSize) |
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]) |
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} |
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return data |
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} |
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export function getId3TagBody(buffer: Buffer) { |
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const tagPosition = getId3TagPosition(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 + sizeOffset, 4) |
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const tagSize = headerSize + decodeSize(encodedSize) |
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const tagData = subarray(buffer, tagPosition, tagSize) |
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const tagHeader = tagData.subarray(0, headerSize) |
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// ID3 version e.g. 3 if ID3v2.3.0 |
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const version = tagHeader[3] |
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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(headerSize) |
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} else if(version === 4) { |
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extendedHeaderSize = decodeSize(subarray(tagData, headerSize, 4)) |
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} |
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} |
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const totalHeaderSize = headerSize + 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, body |
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} |
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} |
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function parseTagHeaderFlags(header: Buffer) { |
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if (header.length < headerSize) { |
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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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104
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/** |
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105
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* Returns -1 if no tag was found. |
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106
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*/ |
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107
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function getId3TagPosition(buffer: Buffer) { |
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108
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// Search Buffer for valid ID3 frame |
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109
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let position = -1 |
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110
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let headerValid = false |
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111
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do { |
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112
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position = buffer.indexOf("ID3", position + 1) |
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113
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if (position !== -1) { |
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114
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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 + headerSize) |
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) |
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} |
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120
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} while (position !== -1 && !headerValid) |
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121
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122
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if (!headerValid) { |
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return -1 |
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124
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} |
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return position |
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126
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} |
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127
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128
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function isValidId3Header(buffer: Buffer) { |
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129
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if (buffer.length < headerSize) { |
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130
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return false |
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131
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} |
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132
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if (buffer.readUIntBE(0, 3) !== 0x494433) { |
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return false |
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134
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} |
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135
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if ([0x02, 0x03, 0x04].indexOf(buffer[3]) === -1 || buffer[4] !== 0x00) { |
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136
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return false |
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137
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} |
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138
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return isValidEncodedSize(subarray(buffer, sizeOffset, 4)) |
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139
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} |
|
140
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141
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function isValidEncodedSize(encodedSize: Buffer) { |
|
142
|
|
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// The size must not have the bit 7 set |
|
143
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return (( |
|
144
|
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encodedSize[0] | |
|
145
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encodedSize[1] | |
|
146
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encodedSize[2] | |
|
147
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encodedSize[3] |
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148
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) & 128) === 0 |
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149
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} |
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Zazama /
node-id3
