43 lines
1.1 KiB
JavaScript
43 lines
1.1 KiB
JavaScript
/**
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* Implement `var_int` encoding/decoding.
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* @module bitmessage/varint
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*/
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"use strict";
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var assert = require("assert");
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// TODO(Kagami): Since `node-int64` and `int64-native` APIs are slightly
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// differ, there might be need in platform-dependent wrapper. Also think
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// that to do with 64bit arithmetic since `node-int64` doesn't implement
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// it.
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var Int64 = require("int64-native");
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exports.decode = function(buf) {
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assert(buf.length > 0, "Empty buffer");
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var value, length;
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switch (buf[0]) {
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case 253:
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value = buf.readUInt16BE(1);
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assert(value >= 253, "Impractical var_int");
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length = 3;
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break;
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case 254:
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value = buf.readUInt32BE(1);
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assert(value >= 65536, "Impractical var_int");
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length = 5;
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break;
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case 255:
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var hi = buf.readUInt32BE(1);
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var lo = buf.readUInt32BE(5);
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value = new Int64(hi, lo);
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assert(value >= 4294967296, "Impractical var_int");
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length = 9;
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break;
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default:
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value = buf[0];
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length = 1;
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}
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var rest = buf.slice(length);
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return {value: value, length: length, rest: rest};
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};
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