Class: PostgresPR::Message

Inherits:
Object
  • Object
show all
Defined in:
lib/postgres-pr/message.rb

Overview

Base class representing a PostgreSQL protocol message

Constant Summary collapse

MsgTypeMap =

One character message-typecode to class map

Hash.new { UnknownMessageType }

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.create(buffer) ⇒ Object


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# File 'lib/postgres-pr/message.rb', line 61

def self.create(buffer)
  obj = allocate
  obj.parse(buffer)
  obj
end

.dump(*args) ⇒ Object


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# File 'lib/postgres-pr/message.rb', line 67

def self.dump(*args)
  new(*args).dump
end

.fields(*attribs) ⇒ Object


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# File 'lib/postgres-pr/message.rb', line 86

def self.fields(*attribs)
  names = attribs.map {|name, type| name.to_s}
  arg_list = names.join(", ")
  ivar_list = names.map {|name| "@" + name }.join(", ")
  sym_list = names.map {|name| ":" + name }.join(", ")
  class_eval %[
    attr_accessor #{ sym_list } 
    def initialize(#{ arg_list })
      #{ ivar_list } = #{ arg_list }
    end
  ] 
end

.read(stream, startup = false) ⇒ Object

Raises:


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# File 'lib/postgres-pr/message.rb', line 46

def self.read(stream, startup=false)
  type = stream.read_exactly_n_bytes(1) unless startup
  length = stream.read_exactly_n_bytes(4).unpack('N').first  # FIXME: length should be signed, not unsigned

  raise ParseError unless length >= 4

  # initialize buffer
  buffer = Buffer.of_size(startup ? length : 1+length)
  buffer.write(type) unless startup
  buffer.write_int32_network(length)
  buffer.copy_from_stream(stream, length-4)
  
  (startup ? StartupMessage : MsgTypeMap[type]).create(buffer)
end

.register_message_type(type) ⇒ Object


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# File 'lib/postgres-pr/message.rb', line 37

def self.register_message_type(type)
  raise "duplicate message type registration" if MsgTypeMap.has_key?(type)

  MsgTypeMap[type] = self

  self.const_set(:MsgType, type) 
  class_eval "def message_type; MsgType end"
end

Instance Method Details

#dump(body_size = 0) {|buffer| ... } ⇒ Object

Yields:

  • (buffer)

Raises:


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# File 'lib/postgres-pr/message.rb', line 71

def dump(body_size=0)
  buffer = Buffer.of_size(5 +  body_size)
  buffer.write(self.message_type)
  buffer.write_int32_network(4 + body_size)
  yield buffer if block_given?
  raise DumpError  unless buffer.at_end?
  return buffer.content
end

#parse(buffer) {|buffer| ... } ⇒ Object

Yields:

  • (buffer)

Raises:


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# File 'lib/postgres-pr/message.rb', line 80

def parse(buffer)
  buffer.position = 5
  yield buffer if block_given?
  raise ParseError, buffer.inspect unless buffer.at_end?
end