cbor

cbor

Documentation

This package provides an encoding/decoding package for the Concise Binary Object Representation as documented in RFC8949.

CBOR is increasingly used as a line protocol in the IOT world where the overhead of transmitting JSON on constrained devices can be large in packet size and processing overheads.

Features

• Streamlined encoding and decoding of CBOR, including indefinite length and streamed decoding.
• Set of types that semantically handles types, nesting, and tags.
• Automatic conversion for the smallest size needed for integers.
• Automatic conversion for the smallest precision needed for floating point numbers.
• Any value can be the key for a map.
• Optional simple API for encoding and decoding directly to Dart objects.
• Pretty-printing and conversion to JSON.
• Rational numbering encoding is supported on tag 30.

Usage

Two APIs are provided, cbor.dart and simple.dart.

cbor.dart

Encodes from CborValue and decodes to CborValue.

The CborValue contains the tags for this item, and its subtypes are used to identify the type and tags for the item. This allows one to handle information encoded in a more lossless way.

Inheritance tree for CborValue looks something like this:

CborValue
├── CborInt
│   ├── CborSmallInt
│   └── CborDateTimeInt
├── CborBytes
│   └── CborBigInt
├── CborString
│   ├── CborDateTimeString
│   ├── CborBase64
│   ├── CborBase64Url
│   ├── CborMime
│   └── CborRegex
├── CborFloat
│   └── CborDateTimeFloat
├── CborSimpleValue
│   ├── CborNull
│   ├── CborBool
│   └── CborUndefined
├── CborMap
└── CborList
    ├── CborDecimalFraction
    ├── CborRationalNumber
    └── CborBigFloat

Example

import 'package:cbor/cbor.dart';

test('{1:2,3:4}', () {
   final encoded = cbor.encode(CborMap({
      CborSmallInt(1): CborSmallInt(2),
      CborSmallInt(3): CborSmallInt(4),
   }));
   expect(encoded, [0xa2, 0x01, 0x02, 0x03, 0x04]);
});

Check out the example folder for more examples.

simple.dart

Less powerful, but may be the best option for simple applications that do not need any of the fancy features of the cbor API above.

The encoder in simple API will operate similarly to constructing a CborValue from the input and the encoding it.

Decoder will translate the input to a common Dart object, ignoring any extra tags after the type is decided.

Example

import 'package:cbor/simple.dart';

test('{1:2,3:4}', () {
   final encoded = cbor.encode({
      1: 2,
      3: 4,
   });
   expect(encoded, [0xa2, 0x01, 0x02, 0x03, 0x04]);
});

Additional RFC's implemented

The following CBOR RFC's have also been implemented in the package :-

• RFC8746 - Concise Binary Object Representation (CBOR) Tags for Typed Arrays.