Consistent Overhead Byte Stuffing Library

This repository contains a fast C library of the COBS (Consistent Overhead Byte Stuffing) algorithm. It is designed for small embedded devices and the Internet of Things. When using any serial connection to transfer data, packet boundaries need to be unambiguous within the data stream.

The COBS encoder works by reencoding a dataframe to remove a a certain byte (typically 0x00), so that this byte can then be used as a special marker to denote the end of a frame. The encoding is especially efficient and requires little computational resources.

The implementation is both efficient and rquires little memory. It works in-place on the input data to save memory, but it is limited to a single COBS frame of 254 bytes, which is typically more than enough for small devices.

Usage

The example data is taken from the Wikipedia article on COBS. The code is written for the Arduino platform, but works on any platform.

#include "cobs.h"

void printBuffer(uint8_t* buffer, size_t size) {
  for (uint8_t i = 0; i < size; i++) {
    if (buffer[i] < 0x10) {
      Serial.print(0);
    }
    Serial.print(buffer[i], HEX);
    Serial.print(" ");
  }
}

void setup() {
  Serial.begin(115200);
  // This is example 3 from Wikipedia
  uint8_t buffer[] = {0xFF, 0x11, 0x22, 0x00, 0x33};  //Note, that there is an additional byte in front of the example data
  cobs::encode(buffer, sizeof(buffer));
  Serial.print("Encoded data: ");
  printBuffer(buffer, sizeof(buffer));
  Serial.println("00"); // Add the final delimiter to complete the message

  // Now decode the data again
  cobs::decode(buffer, sizeof(buffer));

  Serial.print("Decoded data: ");
  printBuffer(buffer+1, sizeof(buffer)-1);
}

void loop() {

}

Installation

Currently the library does not support the Arduino library manager, so it is highly recommended to copy the full library to a subfolder called

src/

within your Arduino project.