tendermint/lib/varint.js

A light client which talks to your Tendermint node over RPC

'use strict';

var _require = require('./common.js'),
    safeParseInt = _require.safeParseInt;

function VarInt(signed) {
  function decode(buffer) {
    var start = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
    var end = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : buffer.length;

    throw Error('not implemented');
  }

  function encode(n) {
    var buffer = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : Buffer.alloc(encodingLength(n));
    var offset = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 0;

    n = safeParseInt(n);

    // amino signed varint is multiplied by 2 ¯\_(ツ)_/¯
    if (signed) n *= 2;

    var i = 0;
    while (n >= 0x80) {
      buffer[offset + i] = n & 0xff | 0x80;
      n >>= 7;
      i++;
    }
    buffer[offset + i] = n & 0xff;
    encode.bytes = i + 1;
    return buffer;
  }

  function encodingLength(n) {
    n = safeParseInt(n);

    if (signed) n *= 2;
    if (!signed && n < 0 || Math.abs(n) > Number.MAX_SAFE_INTEGER) {
      throw Error('varint value is out of bounds');
    }
    var bits = Math.log2(n + 1);
    return Math.ceil(bits / 7) || 1;
  }

  return { encode: encode, decode: decode, encodingLength: encodingLength };
}

module.exports = VarInt(true);
module.exports.UVarInt = VarInt(false);
module.exports.VarInt = module.exports;