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67 lines
1.4 KiB
67 lines
1.4 KiB
'use strict' |
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var Buffer = require('safe-buffer').Buffer |
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var max = 65536 |
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var cache = {} |
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function generateBuffer (i) { |
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var buffer = Buffer.allocUnsafe(2) |
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buffer.writeUInt8(i >> 8, 0) |
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buffer.writeUInt8(i & 0x00FF, 0 + 1) |
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return buffer |
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} |
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function generateCache () { |
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for (var i = 0; i < max; i++) { |
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cache[i] = generateBuffer(i) |
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} |
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} |
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/** |
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* calcVariableByteIntLength - calculate the variable byte integer |
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* length field |
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* |
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* @api private |
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*/ |
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function calcVariableByteIntLength (length) { |
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if (length >= 0 && length < 128) return 1 |
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else if (length >= 128 && length < 16384) return 2 |
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else if (length >= 16384 && length < 2097152) return 3 |
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else if (length >= 2097152 && length < 268435456) return 4 |
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else return 0 |
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} |
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function genBufVariableByteInt (num) { |
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var digit = 0 |
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var pos = 0 |
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var length = calcVariableByteIntLength(num) |
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var buffer = Buffer.allocUnsafe(length) |
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do { |
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digit = num % 128 | 0 |
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num = num / 128 | 0 |
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if (num > 0) digit = digit | 0x80 |
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buffer.writeUInt8(digit, pos++) |
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} while (num > 0) |
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return { |
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data: buffer, |
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length: length |
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} |
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} |
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function generate4ByteBuffer (num) { |
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var buffer = Buffer.allocUnsafe(4) |
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buffer.writeUInt32BE(num, 0) |
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return buffer |
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} |
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module.exports = { |
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cache: cache, |
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generateCache: generateCache, |
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generateNumber: generateBuffer, |
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genBufVariableByteInt: genBufVariableByteInt, |
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generate4ByteBuffer: generate4ByteBuffer |
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}
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