Purpose

The streaming unpacker allows incremental parsing of MessagePack data as it becomes available.

References

• IO streaming guide - Working with streams

• API reference - Unpacker class documentation

Concepts

Feeding data incrementally

unpacker = Messagepack::Unpacker.new
unpacker.feed("\x81")       # Feed partial data
unpacker.feed("\xA3")       # Feed more
unpacker.feed("foo")        # Feed final part
obj = unpacker.read         # => {"foo"=>nil}

Where,

• Unpacker.new creates a new unpacker instance

• feed(data) appends data to the buffer

• read returns one complete object or nil if more data is needed

Streaming from IO

unpacker = Messagepack::Unpacker.new(io)
obj = unpacker.read         # Reads from IO as needed

Where,

• Unpacker.new(io) creates an unpacker attached to an IO

• The unpacker automatically reads from the IO when needed

• Use full_unpack to read a single object and reset

Iterating over multiple objects

unpacker = Messagepack::Unpacker.new
unpacker.feed(data1)
unpacker.feed(data2)
unpacker.feed_each { |obj| process(obj) }

Where,

• feed_each yields each complete object as it’s parsed

• Useful for processing multiple objects from a stream

Examples

Example 1. Streaming unpacking from network

require 'socket'

# Simulate receiving data in chunks
unpacker = Messagepack::Unpacker.new

chunks = ["\x81\xA3", "foo", "\xA5", "world"]

chunks.each do |chunk|
  unpacker.feed(chunk)
  obj = unpacker.read
  if obj
    puts "Received: #{obj.inspect}"
  else
    puts "Waiting for more data..."
  end
end

# Output:
# Waiting for more data...
# Waiting for more data...
# Waiting for more data...
# Received: {"foo"=>"world"}