node-SPOS

SPOS stands for Small Payload Object Serializer.

This is and implementation of the SPOS specification in Javascript. See HTTPS://github.com/luxedo/SPOS for details.

SPOS is a tool for serializing simple objects. This tool focuses in maintaining a consistent payload size while sacrificing precision. Applications with limited bandwidth like LoRa or Globalstar are ideal candidates for SPOS. SPOS has implementations for python3 (SPOS) and node.js (node-SPOS).

In this document we will be using JSON notation to describe payload specifications and payload data. For each programming language there's usually an analogous data type for each notation. Eg: object <=> dict, array <=> list, etc.

Quick Start

To encode data, SPOS needs two arguments to serialize the data: The payload_data to be serialized and the payload specification.

const spos = require("spos")
payload_spec = {
  name: "example payload",
  version: 1,
  body: [{
    type: "integer",
    key: "constant_data",
    value: 2,      // 10
    bits: 2
  }, {
    type: "integer",
    key: "int_data",
    bits: 6
  }, {
    type: "float",
    key: "float_data",
    bits: 6
}]
payload_data = {
  int_data: 13,    // 001101
  float_data: 0.6  // 010011 (19/32 or 0.59375)
                   // padding 000
}
message = spos.binEncode(payload_data, payload_spec, output="bin")
"1000110110011000"

Decoding data

const spos = require("spos")
const payload_spec = {
  name: "example payload",
  version: 1,
  body: [{
    type: "integer",
    key: "constant_data",
    value: 2,
    bits: 2
  }, {
    type: "integer",
    key: "int_data",
    bits: 6
  }, {
    type: "float",
    key: "float_data",
    bits: 6
}]
const message = "1000110110011000"
const decoded = spos.decode(message, payload_spec, input="bin")
decoded
{
  meta: {
    name: "example payload",
    version: 1,
  },
  body: {
    constant_data: 2,
    int_data: 13,
    float_data: 0.59375
  }
}

Installation

npm install spos

Functions

/*
 * Encodes the payloadData according to payloadSpec.
 * @param {array} payloadData The object containing the values to be encoded.
 * @param {object} payloadSpec Payload specifications.
 * @param {string} output the output message format (bytes|hex|bin)
 * @return {Uint8Array|hex string|bin string} message
 */
function encode(payloadData, payloadSpec, output = "bytes")

/*
 * Decodes message according to payloadSpec.
 * @param {Uint8Array|hex string|bin string} message
 * @param {object} payloadSpec Payload specifications.
 * @param {string} input the input message format (bytes|hex|bin)
 * @return {object} decoded The object containing the decoded values.
 */
function decode(message, payloadSpec, input = "bytes")

/*
 * Decodes message according to one payloadSpec in payloadSpecs.
 * @param {Uint8Array|hex string|bin string} message
 * @param {array} payloadSpecs Array of payload specifications.
 * @param {string} input the input message format (bytes|hex|bin)
 * @return {object} decoded The object containing the decoded values.
 */
function decodeFromSpecs(message, payloadSpecs, input = "bytes")

/*
 * Validates a payload specification, throwing errors if it is malformed.
 * @param {payloadSpec} block The block to be validated.
 * @throws ReferenceError, RangeError
 */
function validatePayloadSpec(payloadSpec)

License

MIT License

Copyright (c) 2020 Luiz Eduardo Amaral

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.