117 lines
4.3 KiB
JavaScript
117 lines
4.3 KiB
JavaScript
import * as Token from 'token-types';
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import { FourCcToken } from '../common/FourCC.js';
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export const DataType = {
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text_utf8: 0,
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binary: 1,
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external_info: 2,
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reserved: 3
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};
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/**
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* APE_DESCRIPTOR: defines the sizes (and offsets) of all the pieces, as well as the MD5 checksum
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*/
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export const DescriptorParser = {
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len: 52,
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get: (buf, off) => {
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return {
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// should equal 'MAC '
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ID: FourCcToken.get(buf, off),
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// versionIndex number * 1000 (3.81 = 3810) (remember that 4-byte alignment causes this to take 4-bytes)
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version: Token.UINT32_LE.get(buf, off + 4) / 1000,
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// the number of descriptor bytes (allows later expansion of this header)
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descriptorBytes: Token.UINT32_LE.get(buf, off + 8),
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// the number of header APE_HEADER bytes
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headerBytes: Token.UINT32_LE.get(buf, off + 12),
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// the number of header APE_HEADER bytes
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seekTableBytes: Token.UINT32_LE.get(buf, off + 16),
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// the number of header data bytes (from original file)
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headerDataBytes: Token.UINT32_LE.get(buf, off + 20),
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// the number of bytes of APE frame data
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apeFrameDataBytes: Token.UINT32_LE.get(buf, off + 24),
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// the high order number of APE frame data bytes
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apeFrameDataBytesHigh: Token.UINT32_LE.get(buf, off + 28),
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// the terminating data of the file (not including tag data)
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terminatingDataBytes: Token.UINT32_LE.get(buf, off + 32),
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// the MD5 hash of the file (see notes for usage... it's a little tricky)
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fileMD5: new Token.Uint8ArrayType(16).get(buf, off + 36)
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};
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}
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};
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/**
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* APE_HEADER: describes all of the necessary information about the APE file
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*/
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export const Header = {
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len: 24,
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get: (buf, off) => {
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return {
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// the compression level (see defines I.E. COMPRESSION_LEVEL_FAST)
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compressionLevel: Token.UINT16_LE.get(buf, off),
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// any format flags (for future use)
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formatFlags: Token.UINT16_LE.get(buf, off + 2),
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// the number of audio blocks in one frame
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blocksPerFrame: Token.UINT32_LE.get(buf, off + 4),
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// the number of audio blocks in the final frame
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finalFrameBlocks: Token.UINT32_LE.get(buf, off + 8),
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// the total number of frames
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totalFrames: Token.UINT32_LE.get(buf, off + 12),
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// the bits per sample (typically 16)
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bitsPerSample: Token.UINT16_LE.get(buf, off + 16),
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// the number of channels (1 or 2)
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channel: Token.UINT16_LE.get(buf, off + 18),
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// the sample rate (typically 44100)
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sampleRate: Token.UINT32_LE.get(buf, off + 20)
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};
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}
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};
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/**
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* APE Tag Header/Footer Version 2.0
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* TAG: describes all the properties of the file [optional]
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*/
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export const TagFooter = {
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len: 32,
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get: (buf, off) => {
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return {
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// should equal 'APETAGEX'
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ID: new Token.StringType(8, 'ascii').get(buf, off),
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// equals CURRENT_APE_TAG_VERSION
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version: Token.UINT32_LE.get(buf, off + 8),
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// the complete size of the tag, including this footer (excludes header)
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size: Token.UINT32_LE.get(buf, off + 12),
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// the number of fields in the tag
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fields: Token.UINT32_LE.get(buf, off + 16),
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// reserved for later use (must be zero),
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flags: parseTagFlags(Token.UINT32_LE.get(buf, off + 20))
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};
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}
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};
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/**
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* APE Tag v2.0 Item Header
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*/
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export const TagItemHeader = {
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len: 8,
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get: (buf, off) => {
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return {
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// Length of assigned value in bytes
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size: Token.UINT32_LE.get(buf, off),
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// reserved for later use (must be zero),
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flags: parseTagFlags(Token.UINT32_LE.get(buf, off + 4))
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};
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}
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};
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export function parseTagFlags(flags) {
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return {
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containsHeader: isBitSet(flags, 31),
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containsFooter: isBitSet(flags, 30),
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isHeader: isBitSet(flags, 29),
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readOnly: isBitSet(flags, 0),
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dataType: (flags & 6) >> 1
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};
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}
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/**
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* @param num {number}
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* @param bit 0 is least significant bit (LSB)
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* @return {boolean} true if bit is 1; otherwise false
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*/
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export function isBitSet(num, bit) {
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return (num & 1 << bit) !== 0;
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}
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