61 lines
2.1 KiB
Plaintext
61 lines
2.1 KiB
Plaintext
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const decoder = new TextDecoder();
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const toUTF8String = (input, start = 0, end = input.length) => decoder.decode(input.slice(start, end));
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const toHexString = (input, start = 0, end = input.length) => input.slice(start, end).reduce((memo, i) => memo + ("0" + i.toString(16)).slice(-2), "");
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const readInt16LE = (input, offset = 0) => {
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const val = input[offset] + input[offset + 1] * 2 ** 8;
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return val | (val & 2 ** 15) * 131070;
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};
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const readUInt16BE = (input, offset = 0) => input[offset] * 2 ** 8 + input[offset + 1];
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const readUInt16LE = (input, offset = 0) => input[offset] + input[offset + 1] * 2 ** 8;
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const readUInt24LE = (input, offset = 0) => input[offset] + input[offset + 1] * 2 ** 8 + input[offset + 2] * 2 ** 16;
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const readInt32LE = (input, offset = 0) => input[offset] + input[offset + 1] * 2 ** 8 + input[offset + 2] * 2 ** 16 + (input[offset + 3] << 24);
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const readUInt32BE = (input, offset = 0) => input[offset] * 2 ** 24 + input[offset + 1] * 2 ** 16 + input[offset + 2] * 2 ** 8 + input[offset + 3];
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const readUInt32LE = (input, offset = 0) => input[offset] + input[offset + 1] * 2 ** 8 + input[offset + 2] * 2 ** 16 + input[offset + 3] * 2 ** 24;
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const methods = {
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readUInt16BE,
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readUInt16LE,
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readUInt32BE,
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readUInt32LE
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};
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function readUInt(input, bits, offset, isBigEndian) {
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offset = offset || 0;
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const endian = isBigEndian ? "BE" : "LE";
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const methodName = "readUInt" + bits + endian;
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return methods[methodName](input, offset);
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}
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function readBox(buffer, offset) {
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if (buffer.length - offset < 4)
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return;
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const boxSize = readUInt32BE(buffer, offset);
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if (buffer.length - offset < boxSize)
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return;
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return {
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name: toUTF8String(buffer, 4 + offset, 8 + offset),
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offset,
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size: boxSize
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};
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}
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function findBox(buffer, boxName, offset) {
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while (offset < buffer.length) {
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const box = readBox(buffer, offset);
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if (!box)
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break;
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if (box.name === boxName)
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return box;
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offset += box.size;
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}
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}
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export {
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findBox,
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readInt16LE,
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readInt32LE,
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readUInt,
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readUInt16BE,
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readUInt16LE,
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readUInt24LE,
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readUInt32BE,
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readUInt32LE,
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toHexString,
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toUTF8String
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};
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