Class: Kafka::Protocol::Decoder

Inherits:
Object
  • Object
show all
Defined in:
lib/kafka/protocol/decoder.rb

Overview

A decoder wraps an IO object, making it easy to read specific data types from it. The Kafka protocol is not self-describing, so a client must call these methods in just the right order for things to work.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(io) ⇒ Decoder

Initializes a new decoder.

Parameters:

  • io (IO) —

    an object that acts as an IO.



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# File 'lib/kafka/protocol/decoder.rb', line 17

def initialize(io)
  @io = io
end

Class Method Details

.from_string(str) ⇒ Object 



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# File 'lib/kafka/protocol/decoder.rb', line 10

def self.from_string(str)
  new(StringIO.new(str))
end

Instance Method Details

#array(&block) ⇒ Array

Decodes an array from the IO object.

The provided block will be called once for each item in the array. It is the responsibility of the block to decode the proper type in the block, since there's no information that allows the type to be inferred automatically.

Returns:

  • (Array) 


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# File 'lib/kafka/protocol/decoder.rb', line 68

def array(&block)
  size = int32
  size.times.map(&block)
end

#boolean ⇒ Boolean

Decodes an 8-bit boolean from the IO object.

Returns:

  • (Boolean) 


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# File 'lib/kafka/protocol/decoder.rb', line 28

def boolean
  read(1) == 0x1
end

#bytes ⇒ String

Decodes a list of bytes from the IO object.

Returns:

  • (String) 


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# File 'lib/kafka/protocol/decoder.rb', line 89

def bytes
  size = int32

  if size == -1
    nil
  else
    read(size)
  end
end

#eof? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/kafka/protocol/decoder.rb', line 21

def eof?
  @io.eof?
end

#int16 ⇒ Integer

Decodes a 16-bit integer from the IO object.

Returns:

  • (Integer) 


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# File 'lib/kafka/protocol/decoder.rb', line 42

def int16
  read(2).unpack("s>").first
end

#int32 ⇒ Integer

Decodes a 32-bit integer from the IO object.

Returns:

  • (Integer) 


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# File 'lib/kafka/protocol/decoder.rb', line 49

def int32
  read(4).unpack("l>").first
end

#int64 ⇒ Integer

Decodes a 64-bit integer from the IO object.

Returns:

  • (Integer) 


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# File 'lib/kafka/protocol/decoder.rb', line 56

def int64
  read(8).unpack("q>").first
end

#int8 ⇒ Integer

Decodes an 8-bit integer from the IO object.

Returns:

  • (Integer) 


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# File 'lib/kafka/protocol/decoder.rb', line 35

def int8
  read(1).unpack("C").first
end

#read(number_of_bytes) ⇒ String

Reads the specified number of bytes from the IO object, returning them as a String.

Returns:

  • (String)

Raises:

  • (EOFError) 


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# File 'lib/kafka/protocol/decoder.rb', line 103

def read(number_of_bytes)
  return "" if number_of_bytes == 0

  data = @io.read(number_of_bytes) or raise EOFError

  # If the `read` call returned less data than expected we should not
  # proceed.
  raise EOFError if data.size != number_of_bytes

  data
end

#string ⇒ String

Decodes a string from the IO object.

Returns:

  • (String) 


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# File 'lib/kafka/protocol/decoder.rb', line 76

def string
  size = int16

  if size == -1
    nil
  else
    read(size)
  end
end