length_stream_protocol.rb in cosmos-3.5.2

- old
+ new
@@ -1,140 +1,140 @@
-# encoding: ascii-8bit
-
-# Copyright 2014 Ball Aerospace & Technologies Corp.
-# All Rights Reserved.
-#
-# This program is free software; you can modify and/or redistribute it
-# under the terms of the GNU General Public License
-# as published by the Free Software Foundation; version 3 with
-# attribution addendums as found in the LICENSE.txt
-
-require 'cosmos/packets/binary_accessor'
-require 'cosmos/streams/stream_protocol'
-require 'cosmos/config/config_parser'
-
-module Cosmos
-
-  # This StreamProtocol delineates packets using a length field at a fixed
-  # location in each packet.
-  class LengthStreamProtocol < StreamProtocol
-
-    # @param length_bit_offset [Integer] The bit offset of the length field
-    # @param length_bit_size [Integer] The size in bits of the length field
-    # @param length_value_offset [Integer] The offset to apply to the length
-    #   value once it has been read from the packet. The value in the length
-    #   field itself plus the length value offset MUST equal the total bytes in
-    #   the stream including any discarded bytes.
-    #   For example: if your length field really means "length - 1" this value should be 1.
-    # @param length_bytes_per_count [Integer] The number of bytes per each
-    #   length field 'count'. This is used if the units of the length field is
-    #   something other than bytes, for example words.
-    # @param length_endianness [String] The endianness of the length field.
-    #   Must be either BIG_ENDIAN or LITTLE_ENDIAN.
-    # @param discard_leading_bytes (see StreamProtocol#initialize)
-    # @param sync_pattern (see StreamProtocol#initialize)
-    # @param max_length [Integer] The maximum allowed value of the length field
-    # @param fill_length_and_sync_pattern [Boolean] Fill the length field and sync
-    #    pattern when writing packets
-    def initialize(
-      length_bit_offset = 0,
-      length_bit_size = 16,
-      length_value_offset = 0,
-      length_bytes_per_count = 1,
-      length_endianness = 'BIG_ENDIAN',
-      discard_leading_bytes = 0,
-      sync_pattern = nil,
-      max_length = nil,
-      fill_length_and_sync_pattern = false
-    )
-      super(discard_leading_bytes, sync_pattern, fill_length_and_sync_pattern)
-
-      # Save length field attributes
-      @length_bit_offset = Integer(length_bit_offset)
-      @length_bit_size = Integer(length_bit_size)
-      @length_value_offset = Integer(length_value_offset)
-      @length_bytes_per_count = Integer(length_bytes_per_count)
-
-      # Save endianness
-      if length_endianness.to_s.upcase == 'LITTLE_ENDIAN'
-        @length_endianness = :LITTLE_ENDIAN
-      else
-        @length_endianness = :BIG_ENDIAN
-      end
-
-      # Derive number of bytes required to contain entire length field
-      if @length_endianness == :BIG_ENDIAN or ((@length_bit_offset % 8) == 0)
-        length_bits_needed = @length_bit_offset + @length_bit_size
-        length_bits_needed += 8 if (length_bits_needed % 8) != 0
-        @length_bytes_needed = ((length_bits_needed - 1)/ 8) + 1
-      else
-        @length_bytes_needed = (length_bit_offset / 8) + 1
-      end
-
-      # Save max length setting
-      @max_length = ConfigParser.handle_nil(max_length)
-      @max_length = Integer(@max_length) if @max_length
-    end
-
-    # See StreamProtocol#pre_write_packet
-    def pre_write_packet(packet)
-      data = super(packet)
-      if @fill_sync_pattern # and length
-        # Fill the length field
-        length = (data.length - @length_value_offset) / @length_bytes_per_count
-        BinaryAccessor.write(length,
-          @length_bit_offset,
-          @length_bit_size,
-          :UINT,
-          data,
-          @length_endianness,
-          :ERROR)
-
-        # Also write the new length field into the packet that will be logged if it exists in the packet
-        if @discard_leading_bytes > 0
-          # The write above did not write into the original packet
-          original_length_bit_offset = @length_bit_offset - (@discard_leading_bytes * 8)
-          if original_length_bit_offset >= 0
-            original_data = packet.buffer(false)
-            BinaryAccessor.write(length,
-              original_length_bit_offset,
-              @length_bit_size,
-              :UINT,
-              original_data,
-              @length_endianness,
-              :ERROR)
-          end
-        end
-      end
-      data
-    end
-
-    protected
-
-    def reduce_to_single_packet
-      # Make sure we have at least enough data to reach the length field
-      read_minimum_size(@length_bytes_needed)
-      return nil if @data.length <= 0
-
-      # Determine the packet's length
-      length = BinaryAccessor.read(@length_bit_offset,
-                                   @length_bit_size,
-                                   :UINT,
-                                   @data,
-                                   @length_endianness)
-      raise "Length value received larger than max_length: #{length} > #{@max_length}" if @max_length and length > @max_length
-      packet_length = (length * @length_bytes_per_count) + @length_value_offset
-
-      # Make sure we have enough data for the packet
-      read_minimum_size(packet_length)
-      return nil if @data.length <= 0
-
-      # Reduce to packet data and setup current_data for next packet
-      packet_data = @data[0..(packet_length - 1)]
-      @data.replace(@data[packet_length..-1])
-
-      packet_data
-    end
-
-  end # class LengthStreamProtocol
-
-end # module Cosmos
+# encoding: ascii-8bit
+
+# Copyright 2014 Ball Aerospace & Technologies Corp.
+# All Rights Reserved.
+#
+# This program is free software; you can modify and/or redistribute it
+# under the terms of the GNU General Public License
+# as published by the Free Software Foundation; version 3 with
+# attribution addendums as found in the LICENSE.txt
+
+require 'cosmos/packets/binary_accessor'
+require 'cosmos/streams/stream_protocol'
+require 'cosmos/config/config_parser'
+
+module Cosmos
+
+  # This StreamProtocol delineates packets using a length field at a fixed
+  # location in each packet.
+  class LengthStreamProtocol < StreamProtocol
+
+    # @param length_bit_offset [Integer] The bit offset of the length field
+    # @param length_bit_size [Integer] The size in bits of the length field
+    # @param length_value_offset [Integer] The offset to apply to the length
+    #   value once it has been read from the packet. The value in the length
+    #   field itself plus the length value offset MUST equal the total bytes in
+    #   the stream including any discarded bytes.
+    #   For example: if your length field really means "length - 1" this value should be 1.
+    # @param length_bytes_per_count [Integer] The number of bytes per each
+    #   length field 'count'. This is used if the units of the length field is
+    #   something other than bytes, for example words.
+    # @param length_endianness [String] The endianness of the length field.
+    #   Must be either BIG_ENDIAN or LITTLE_ENDIAN.
+    # @param discard_leading_bytes (see StreamProtocol#initialize)
+    # @param sync_pattern (see StreamProtocol#initialize)
+    # @param max_length [Integer] The maximum allowed value of the length field
+    # @param fill_length_and_sync_pattern [Boolean] Fill the length field and sync
+    #    pattern when writing packets
+    def initialize(
+      length_bit_offset = 0,
+      length_bit_size = 16,
+      length_value_offset = 0,
+      length_bytes_per_count = 1,
+      length_endianness = 'BIG_ENDIAN',
+      discard_leading_bytes = 0,
+      sync_pattern = nil,
+      max_length = nil,
+      fill_length_and_sync_pattern = false
+    )
+      super(discard_leading_bytes, sync_pattern, fill_length_and_sync_pattern)
+
+      # Save length field attributes
+      @length_bit_offset = Integer(length_bit_offset)
+      @length_bit_size = Integer(length_bit_size)
+      @length_value_offset = Integer(length_value_offset)
+      @length_bytes_per_count = Integer(length_bytes_per_count)
+
+      # Save endianness
+      if length_endianness.to_s.upcase == 'LITTLE_ENDIAN'
+        @length_endianness = :LITTLE_ENDIAN
+      else
+        @length_endianness = :BIG_ENDIAN
+      end
+
+      # Derive number of bytes required to contain entire length field
+      if @length_endianness == :BIG_ENDIAN or ((@length_bit_offset % 8) == 0)
+        length_bits_needed = @length_bit_offset + @length_bit_size
+        length_bits_needed += 8 if (length_bits_needed % 8) != 0
+        @length_bytes_needed = ((length_bits_needed - 1)/ 8) + 1
+      else
+        @length_bytes_needed = (length_bit_offset / 8) + 1
+      end
+
+      # Save max length setting
+      @max_length = ConfigParser.handle_nil(max_length)
+      @max_length = Integer(@max_length) if @max_length
+    end
+
+    # See StreamProtocol#pre_write_packet
+    def pre_write_packet(packet)
+      data = super(packet)
+      if @fill_sync_pattern # and length
+        # Fill the length field
+        length = (data.length - @length_value_offset) / @length_bytes_per_count
+        BinaryAccessor.write(length,
+          @length_bit_offset,
+          @length_bit_size,
+          :UINT,
+          data,
+          @length_endianness,
+          :ERROR)
+
+        # Also write the new length field into the packet that will be logged if it exists in the packet
+        if @discard_leading_bytes > 0
+          # The write above did not write into the original packet
+          original_length_bit_offset = @length_bit_offset - (@discard_leading_bytes * 8)
+          if original_length_bit_offset >= 0
+            original_data = packet.buffer(false)
+            BinaryAccessor.write(length,
+              original_length_bit_offset,
+              @length_bit_size,
+              :UINT,
+              original_data,
+              @length_endianness,
+              :ERROR)
+          end
+        end
+      end
+      data
+    end
+
+    protected
+
+    def reduce_to_single_packet
+      # Make sure we have at least enough data to reach the length field
+      read_minimum_size(@length_bytes_needed)
+      return nil if @data.length <= 0
+
+      # Determine the packet's length
+      length = BinaryAccessor.read(@length_bit_offset,
+                                   @length_bit_size,
+                                   :UINT,
+                                   @data,
+                                   @length_endianness)
+      raise "Length value received larger than max_length: #{length} > #{@max_length}" if @max_length and length > @max_length
+      packet_length = (length * @length_bytes_per_count) + @length_value_offset
+
+      # Make sure we have enough data for the packet
+      read_minimum_size(packet_length)
+      return nil if @data.length <= 0
+
+      # Reduce to packet data and setup current_data for next packet
+      packet_data = @data[0..(packet_length - 1)]
+      @data.replace(@data[packet_length..-1])
+
+      packet_data
+    end
+
+  end # class LengthStreamProtocol
+
+end # module Cosmos