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35 lines
917 B
35 lines
917 B
import {toUint8, bytesMatch} from './byte-helpers.js';
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const ID3 = toUint8([0x49, 0x44, 0x33]);
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export const getId3Size = function(bytes, offset = 0) {
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bytes = toUint8(bytes);
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const flags = bytes[offset + 5];
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const returnSize = (bytes[offset + 6] << 21) |
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(bytes[offset + 7] << 14) |
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(bytes[offset + 8] << 7) |
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(bytes[offset + 9]);
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const footerPresent = (flags & 16) >> 4;
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if (footerPresent) {
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return returnSize + 20;
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}
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return returnSize + 10;
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};
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export const getId3Offset = function(bytes, offset = 0) {
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bytes = toUint8(bytes);
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if ((bytes.length - offset) < 10 || !bytesMatch(bytes, ID3, {offset})) {
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return offset;
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}
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offset += getId3Size(bytes, offset);
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// recursive check for id3 tags as some files
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// have multiple ID3 tag sections even though
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// they should not.
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return getId3Offset(bytes, offset);
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};
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