lib/mqtt/packet.rb in mqtt-0.0.1 vs lib/mqtt/packet.rb in mqtt-0.0.2

@@ -4,33 +4,42 @@
 
 module MQTT
 
   # Class representing a MQTT Packet
   # Performs binary encoding and decoding of headers
-  class Packet #:nodoc: all
+  class Packet
     attr_reader :type      # The packet type
     attr_reader :dup       # Duplicate delivery flag
     attr_reader :retain    # Retain flag
     attr_reader :qos       # Quality of Service level
     attr_reader :body      # Packet's body (everything after fixed header)
   
     # Read in a packet from a socket
-    def self.read(sock)
-      header = sock.read(2)
-      raise MQTT::ProtocolException if header.nil?
-      byte1,byte2 = header.unpack('C*')
+    def self.read(socket)
 
-      # FIXME: support decoding of multi-byte length header
-
+      # Create a packet object
+      header = read_byte(socket)
       packet = MQTT::Packet.new(
-        :type => ((byte1 & 0xF0) >> 4),
-        :dup => ((byte1 & 0x08) >> 3),
-        :qos => ((byte1 & 0x06) >> 1),
-        :retain => ((byte1 & 0x01) >> 0)
+        :type => ((header & 0xF0) >> 4),
+        :dup => ((header & 0x08) >> 3),
+        :qos => ((header & 0x06) >> 1),
+        :retain => ((header & 0x01) >> 0)
       )
-      packet.body = sock.read(byte2)
+      
+      # Read in the packet length
+      multiplier = 1 
+      body_len = 0 
+      begin
+        digit = read_byte(socket)
+        body_len += ((digit & 0x7F) * multiplier)
+        multiplier *= 0x80
+      end while ((digit & 0x80) != 0x00)
+      # FIXME: only allow 4 bytes?
 
+      # Read in the packet body
+      packet.body = socket.read(body_len)
+
       return packet
     end
 
     # Create a new empty packet
     def initialize(args={})
@@ -39,10 +48,14 @@
       self.qos = args[:qos] || 0
       self.retain = args[:retain] || false
       self.body = args[:body] || ''
     end
     
+    # Set the packet type
+    # Can either by the packet type id (integer)
+    # Or the packet type as a symbol/string
+    # See the MQTT module for an enumeration of packet types.
     def type=(arg)
       if arg.kind_of?(Integer)
         # Convert type identifier to symbol
         @type = MQTT::PACKET_TYPES[arg]
       else
@@ -57,31 +70,36 @@
       index = MQTT::PACKET_TYPES.index(@type)
       raise "Invalid packet type: #{@type}" if index.nil?
       return index
     end
     
+    # Set the dup flag (true/false)
     def dup=(arg)
       if arg.kind_of?(Integer)
         @dup = (arg != 0 ? true : false)
       else
         @dup = arg
       end
     end
     
+    # Set the retain flag (true/false)
     def retain=(arg)
       if arg.kind_of?(Integer)
         @retain = (arg != 0 ? true : false)
       else
         @retain = arg
       end
     end
     
+    # Set the Quality of Service level (0/1/2)
     def qos=(arg)
       @qos = arg.to_i
     end
     
+    # Set (replace) the packet body
     def body=(arg)
+      # FIXME: only allow 268435455 bytes?
       @body = arg.to_s
     end
 
 
 
@@ -135,25 +153,44 @@
     end
 
     
     # Serialise the packet
     def to_s
-      # Encode the 2-byte fixed header
+      # Encode the fixed header
       header = [
         ((type_id.to_i & 0x0F) << 4) |
         ((dup ? 0x1 : 0x0) << 3) |
         ((qos.to_i & 0x03) << 1) |
-        (retain ? 0x1 : 0x0),
-        (@body.length & 0x7F)
+        (retain ? 0x1 : 0x0)
       ]
-      # FIXME: support multi-byte length header
+      
+      # Build up the body length field bytes
+      body_size = @body.size
+      begin
+        digit = (body_size % 128)
+        body_size = (body_size / 128)
+        # if there are more digits to encode, set the top bit of this digit
+        digit |= 0x80 if (body_size > 0)
+        header.push(digit)
+      end while (body_size > 0)
+
+      # Convert header to binary and add on body
       header.pack('C*') + @body
     end
     
     def inspect
       format("#<MQTT::Packet:0x%01x ", object_id)+
       "type=#{@type}, dup=#{@dup}, retain=#{@retain}, "+
       "qos=#{@qos}, body.size=#{@body.size}>"
+    end
+    
+    private
+    
+    # Read and unpack a single byte from socket
+    def self.read_byte(socket)
+      byte = socket.read(1)
+      raise MQTT::ProtocolException if byte.nil?
+      byte.unpack('C').first
     end
     
   end
   
 end