Build Status


This library builds and parses messages in the Compact Message Format (CMF).

CMF is a binary format that has the speed and compact size of a binary format combined with the provably correct markup and type-safety of formats like XML and JSON.

A CMF message is a flat list of tokens. Each token is comprised of 3 elements: a tag name, a type, and a value. Tag names are written to the message as numbers, so an external schema dictionary is typically used to map the tag numbers to names.

Each CMF token is completely self-contained. Even a reader that doesn't know the schema of the message it is parsing can still extract all tokens from the message. This makes the format exceptionally useful for extensibility because a reader can just skip over unknown tokens.


This library is distributed as a gem named cmf at To install it, run:

gem install cmf


First, require the gem:

require 'cmf'

Next, we'll build and parse a simple message with two tokens. The message will contain the string "Proxima Centauri", associated with the tag 0, and the floating point number 4.2421 associated with the tag 1.

message ={0 => "Proxima Centauri", 1 => 4.2421})
# => "\x02\x10Proxima Centauri\x0EGr\xF9\x0F\xE9\xF7\x10@"

# => {0=>"Proxima Centauri", 1=>4.2421}

Rather than using the tags 0, and 1, we can define a schema dictionary which maps human-readable names to tag numbers.

dictionary = {star: 0, distance: 1}
message ={star: "Proxima Centauri", distance: 4.2421}, dictionary)
# => "\x02\x10Proxima Centauri\x0EGr\xF9\x0F\xE9\xF7\x10@"

CMF.parse(message, dictionary)
# => {:star=>"Proxima Centauri", :distance=>4.2421}

For more flexibility in parsing and building messages, you can use the CMF::Builder and CMF::Parser classes.

builder =
builder.add(:star, "Proxima Centauri")
builder.add(:distance, 4.2421)
message = builder.to_octet

parser =
parser.message = message
parser.next_pair # => [:star, "Proxima Centauri"]
parser.next_pair # => [:distance, 4.2421]
parser.next_pair # => nil

parser.message = message     ##
parser.each do |tag, value|  # star: Proxima Centauri
  puts "#{tag}: #{value}"    # distance: 4.2421
end                          ##

Supported platforms

Ruby 2.1 and above, including jruby.


For complete documentation, see the CMF page on