Class: Cosmos::Structure

Inherits:
Object show all
Defined in:
lib/cosmos/packets/structure.rb,
ext/cosmos/ext/structure/structure.c

Overview

Maintains knowledge of a raw binary structure. Uses structure_item to create individual structure items which are read and written by binary_accessor.

Defined Under Namespace

Modules: MethodMissing

Constant Summary collapse

ASCII_8BIT_STRING =

Used to force encoding

"ASCII-8BIT".freeze
ZERO_STRING =

String providing a single 0 byte

"\000".freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ Object

Structure constructor



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# File 'lib/cosmos/packets/structure.rb', line 69

def initialize(default_endianness = BinaryAccessor::HOST_ENDIANNESS, buffer = nil, item_class = StructureItem)
  if (default_endianness == :BIG_ENDIAN) || (default_endianness == :LITTLE_ENDIAN)
    @default_endianness = default_endianness
    if buffer
      raise TypeError, "wrong argument type #{buffer.class} (expected String)" unless String === buffer

      @buffer = buffer.force_encoding(ASCII_8BIT_STRING)
    else
      @buffer = nil
    end
    @item_class = item_class
    @items = {}
    @sorted_items = []
    @defined_length = 0
    @defined_length_bits = 0
    @pos_bit_size = 0
    @neg_bit_size = 0
    @fixed_size = true
    @short_buffer_allowed = false
    @mutex = nil
  else
    raise(ArgumentError, "Unknown endianness '#{default_endianness}', must be :BIG_ENDIAN or :LITTLE_ENDIAN")
  end
end

Instance Attribute Details

#default_endianness ⇒ Symbol (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 31

def default_endianness
  @default_endianness
end

#defined_length ⇒ Integer (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 41

def defined_length
  @defined_length
end

#defined_length_bits ⇒ Integer (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 44

def defined_length_bits
  @defined_length_bits
end

#fixed_size ⇒ Boolean (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 48

def fixed_size
  @fixed_size
end

#items ⇒ Hash (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 35

def items
  @items
end

#short_buffer_allowed ⇒ Boolean 



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# File 'lib/cosmos/packets/structure.rb', line 52

def short_buffer_allowed
  @short_buffer_allowed
end

#sorted_items ⇒ Array (readonly) 



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# File 'lib/cosmos/packets/structure.rb', line 38

def sorted_items
  @sorted_items
end

Instance Method Details

#allocate_buffer_if_needed ⇒ Object

Allocate a buffer if not available



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# File 'lib/cosmos/packets/structure.rb', line 137

def allocate_buffer_if_needed
  unless @buffer
    @buffer = ZERO_STRING * @defined_length
    @buffer.force_encoding(ASCII_8BIT_STRING)
  end
  return @buffer
end

#append(item) ⇒ StrutureItem

Adds an item at the end of the structure. It adds the item to the items hash and resizes the buffer to accomodate the new item.

Raises:

  • (ArgumentError) 


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# File 'lib/cosmos/packets/structure.rb', line 294

def append(item)
  raise ArgumentError, "Can't append an item after a variably sized item" if !@fixed_size

  if item.data_type == :DERIVED
    item.bit_offset = 0
  else
    item.bit_offset = @defined_length_bits
  end
  return define(item)
end

#append_item(name, bit_size, data_type, array_size = nil, endianness = @default_endianness, overflow = :ERROR) ⇒ StrutureItem

Define an item at the end of the structure. This creates a new instance of the item_class as given in the constructor and adds it to the items hash. It also resizes the buffer to accomodate the new item.

Raises:

  • (ArgumentError) 


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# File 'lib/cosmos/packets/structure.rb', line 280

def append_item(name, bit_size, data_type, array_size = nil, endianness = @default_endianness, overflow = :ERROR)
  raise ArgumentError, "Can't append an item after a variably sized item" if !@fixed_size
  if data_type == :DERIVED
    return define_item(name, 0, bit_size, data_type, array_size, endianness, overflow)
  else
    return define_item(name, @defined_length_bits, bit_size, data_type, array_size, endianness, overflow)
  end
end

#buffer(copy = true) ⇒ String

Get the buffer used by the structure. The current buffer is copied and thus modifications to the returned buffer will have no effect on the structure items.



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# File 'lib/cosmos/packets/structure.rb', line 438

def buffer(copy = true)
  local_buffer = allocate_buffer_if_needed()
  if copy
    return local_buffer.dup
  else
    return local_buffer
  end
end

#buffer=(buffer) ⇒ Object

Set the buffer to be used by the structure. The buffer is copied and thus further modifications to the buffer have no effect on the structure items.



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# File 'lib/cosmos/packets/structure.rb', line 452

def buffer=(buffer)
  synchronize() do
    internal_buffer_equals(buffer)
  end
end

#clone ⇒ Structure Also known as: dup

Make a light weight clone of this structure. This only creates a new buffer of data. The defined structure items are the same.



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# File 'lib/cosmos/packets/structure.rb', line 463

def clone
  structure = super()
  # Use instance_variable_set since we have overriden buffer= to do
  # additional work that isn't neccessary here
  structure.instance_variable_set("@buffer".freeze, @buffer.clone) if @buffer
  return structure
end

#define(item) ⇒ StrutureItem

Adds the given item to the items hash. It also resizes the buffer to accomodate the new item.



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# File 'lib/cosmos/packets/structure.rb', line 196

def define(item)
  # Handle Overwriting Existing Item
  if @items[item.name]
    item_index = nil
    @sorted_items.each_with_index do |sorted_item, index|
      if sorted_item.name == item.name
        item_index = index
        break
      end
    end
    @sorted_items.delete_at(item_index) if item_index < @sorted_items.length
  end

  # Add to Sorted Items
  unless @sorted_items.empty?
    last_item = @sorted_items[-1]
    @sorted_items << item
    # If the current item or last item have a negative offset then we have
    # to re-sort. We also re-sort if the current item is less than the last
    # item because we are inserting.
    if last_item.bit_offset <= 0 or item.bit_offset <= 0 or item.bit_offset < last_item.bit_offset
      @sorted_items = @sorted_items.sort
    end
  else
    @sorted_items << item
  end

  # Add to the overall hash of defined items
  @items[item.name] = item
  # Update fixed size knowledge
  @fixed_size = false if (item.data_type != :DERIVED and item.bit_size <= 0) or (item.array_size and item.array_size <= 0)

  # Recalculate the overall defined length of the structure
  update_needed = false
  if item.bit_offset >= 0
    if item.bit_size > 0
      if item.array_size
        if item.array_size >= 0
          item_defined_length_bits = item.bit_offset + item.array_size
        else
          item_defined_length_bits = item.bit_offset
        end
      else
        item_defined_length_bits = item.bit_offset + item.bit_size
      end
      if item_defined_length_bits > @pos_bit_size
        @pos_bit_size = item_defined_length_bits
        update_needed = true
      end
    else
      if item.bit_offset > @pos_bit_size
        @pos_bit_size = item.bit_offset
        update_needed = true
      end
    end
  else
    if item.bit_offset.abs > @neg_bit_size
      @neg_bit_size = item.bit_offset.abs
      update_needed = true
    end
  end
  if update_needed
    @defined_length_bits = @pos_bit_size + @neg_bit_size
    @defined_length = @defined_length_bits / 8
    @defined_length += 1 if @defined_length_bits % 8 != 0
  end

  # Resize the buffer if necessary
  resize_buffer() if @buffer

  return item
end

#define_item(name, bit_offset, bit_size, data_type, array_size = nil, endianness = @default_endianness, overflow = :ERROR) ⇒ StrutureItem

Define an item in the structure. This creates a new instance of the item_class as given in the constructor and adds it to the items hash. It also resizes the buffer to accomodate the new item.



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# File 'lib/cosmos/packets/structure.rb', line 182

def define_item(name, bit_offset, bit_size, data_type, array_size = nil, endianness = @default_endianness, overflow = :ERROR)
  # Handle case-insensitive naming
  name_upcase = name.upcase

  # Create the item
  item = @item_class.new(name_upcase, bit_offset, bit_size, data_type, endianness, array_size, overflow)
  define(item)
end

#defined? ⇒ TrueClass or FalseClass

Indicates if any items have been defined for this structure



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# File 'lib/cosmos/packets/structure.rb', line 147

def defined?
  @sorted_items.length > 0
end

#delete_item(name) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/cosmos/packets/structure.rb', line 325

def delete_item(name)
  item = @items[name.upcase]
  raise ArgumentError, "Unknown item: #{name}" unless item

  # Find the item to delete in the sorted_items array
  item_index = nil
  @sorted_items.each_with_index do |sorted_item, index|
    if sorted_item.name == item.name
      item_index = index
      break
    end
  end
  @sorted_items.delete_at(item_index)
  @items.delete(name.upcase)
end

#enable_method_missing ⇒ Object

Enable the ability to read and write item values as if they were methods to the class



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# File 'lib/cosmos/packets/structure.rb', line 474

def enable_method_missing
  extend(MethodMissing)
end

#formatted(value_type = :RAW, indent = 0, buffer = @buffer, ignored = nil) ⇒ String

Create a string that shows the name and value of each item in the structure



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# File 'lib/cosmos/packets/structure.rb', line 407

def formatted(value_type = :RAW, indent = 0, buffer = @buffer, ignored = nil)
  indent_string = ' ' * indent
  string = ''
  synchronize_allow_reads(true) do
    @sorted_items.each do |item|
      next if ignored && ignored.include?(item.name)

      if (item.data_type != :BLOCK) ||
         (item.data_type == :BLOCK and value_type != :RAW and
          item.respond_to? :read_conversion and item.read_conversion)
        string << "#{indent_string}#{item.name}: #{read_item(item, value_type, buffer)}\n"
      else
        value = read_item(item, value_type, buffer)
        if String === value
          string << "#{indent_string}#{item.name}:\n"
          string << value.formatted(1, 16, ' ', indent + 2)
        else
          string << "#{indent_string}#{item.name}: #{value}\n"
        end
      end
    end
  end
  return string
end

#get_item(name) ⇒ StructureItem

Returns StructureItem or one of its subclasses.

Raises:

  • (ArgumentError) 


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# File 'lib/cosmos/packets/structure.rb', line 307

def get_item(name)
  item = @items[name.upcase]
  raise ArgumentError, "Unknown item: #{name}" unless item

  return item
end

#length ⇒ Object

Returns the actual structure length.

structure.length #=> 324



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# File 'lib/cosmos/packets/structure.rb', line 116

def length
  allocate_buffer_if_needed()
  return @buffer.length
end

#read(name, value_type = :RAW, buffer = @buffer) ⇒ Object

Read an item in the structure by name



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# File 'lib/cosmos/packets/structure.rb', line 366

def read(name, value_type = :RAW, buffer = @buffer)
  return read_item(get_item(name), value_type, buffer)
end

#read_all(value_type = :RAW, buffer = @buffer, top = true) ⇒ Array<Array>

Read all items in the structure into an array of arrays

[[item name, item value], ...]



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# File 'lib/cosmos/packets/structure.rb', line 391

def read_all(value_type = :RAW, buffer = @buffer, top = true)
  item_array = []
  synchronize_allow_reads(top) do
    @sorted_items.each { |item| item_array << [item.name, read_item(item, value_type, buffer)] }
  end
  return item_array
end

#read_item(*args) ⇒ Object

Read an item in the structure



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# File 'lib/cosmos/packets/structure.rb', line 102

def read_item(item, value_type = :RAW, buffer = @buffer)
  return nil if item.data_type == :DERIVED

  buffer = allocate_buffer_if_needed() unless buffer
  if item.array_size
    return BinaryAccessor.read_array(item.bit_offset, item.bit_size, item.data_type, item.array_size, buffer, item.endianness)
  else
    return BinaryAccessor.read(item.bit_offset, item.bit_size, item.data_type, buffer, item.endianness)
  end
end

#rename_item(item_name, new_item_name) ⇒ Object

Rename an existing item



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# File 'lib/cosmos/packets/structure.rb', line 155

def rename_item(item_name, new_item_name)
  item = get_item(item_name)
  item.name = new_item_name
  @items.delete(item_name)
  @items[new_item_name] = item
  # Since @sorted_items contains the actual item reference it is
  # updated when we set the item.name
  item
end

#resize_buffer ⇒ Object

Resize the buffer at least the defined length of the structure



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# File 'lib/cosmos/packets/structure.rb', line 122

def resize_buffer
  if @buffer
    # Extend data size
    if @buffer.length < @defined_length
      @buffer << (ZERO_STRING * (@defined_length - @buffer.length))
    end
  else
    allocate_buffer_if_needed()
  end

  return self
end

#set_item(item) ⇒ Object 



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# File 'lib/cosmos/packets/structure.rb', line 316

def set_item(item)
  if @items[item.name]
    @items[item.name] = item
  else
    raise ArgumentError, "Unknown item: #{item.name} - Ensure item name is uppercase"
  end
end

#write(name, value, value_type = :RAW, buffer = @buffer) ⇒ Object

Write an item in the structure by name



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# File 'lib/cosmos/packets/structure.rb', line 378

def write(name, value, value_type = :RAW, buffer = @buffer)
  write_item(get_item(name), value, value_type, buffer)
end

#write_item(item, value, value_type = :RAW, buffer = @buffer) ⇒ Object

Write a value to the buffer based on the item definition



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# File 'lib/cosmos/packets/structure.rb', line 349

def write_item(item, value, value_type = :RAW, buffer = @buffer)
  buffer = allocate_buffer_if_needed() unless buffer
  if item.array_size
    BinaryAccessor.write_array(value, item.bit_offset, item.bit_size, item.data_type, item.array_size, buffer, item.endianness, item.overflow)
  else
    BinaryAccessor.write(value, item.bit_offset, item.bit_size, item.data_type, buffer, item.endianness, item.overflow)
  end
end