Class: Cosmos::StructureItem

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

Overview

Maintains knowledge of an item in a Structure. Multiple StructureItems compose a Structure.

Constant Summary collapse

DATA_TYPES =

Valid data types adds :DERIVED to those defined by BinaryAccessor

BinaryAccessor::DATA_TYPES << :DERIVED
LARGE_BUFFER_SIZE_BITS =

A large buffer size in bits (1 Megabyte)

1024 * 1024 * 8

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, bit_offset, bit_size, data_type, endianness, array_size = nil, overflow = :ERROR) ⇒ StructureItem

Create a StructureItem by setting all the attributes. It calls all the setter routines to do the attribute verification and then verifies the overall integrity.

Parameters:

  • name (String) —

    The item name

  • bit_offset (Integer) —

    Offset to the item starting at 0

  • bit_size (Integer) —

    Size of the items in bits

  • data_type (Symbol) —

    DATA_TYPES

  • endianness (Symbol) —

    BinaryAccessor::ENDIANNESS

  • array_size (Integer, nil) (defaults to: nil) —

    Size of the array item in bits. For example, if the bit_size is 8, an array_size of 16 holds two values.



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# File 'lib/cosmos/packets/structure_item.rb', line 74

def initialize(name, bit_offset, bit_size, data_type, endianness, array_size = nil, overflow = :ERROR)
  @structure_item_constructed = false
  # Assignment order matters due to verifications!
  self.name = name
  self.endianness = endianness
  self.data_type = data_type
  self.bit_offset = bit_offset
  self.bit_size = bit_size
  self.array_size = array_size
  self.overflow = overflow
  @structure_item_constructed = true
  verify_overall()
end

Instance Attribute Details

#array_size ⇒ Integer?

The total number of bits in the binary buffer that create the array. The array size can be set to nil to indicate the StructureItem is not represented as an array. For example, if the bit_size is 8 bits, an array_size of 16 would result in two 8 bit items.

Returns:

  • (Integer, nil) —

    Array size of the item in bits



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# File 'lib/cosmos/packets/structure_item.rb', line 53

def array_size
  @array_size
end

#bit_offset ⇒ Integer

Indicates where in the binary buffer the StructureItem exists.

Returns:

  • (Integer) —

    0 based bit offset



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# File 'lib/cosmos/packets/structure_item.rb', line 29

def bit_offset
  @bit_offset
end

#bit_size ⇒ Integer

The number of bits which represent this StructureItem in the binary buffer.

Returns:

  • (Integer) —

    Size in bits



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# File 'lib/cosmos/packets/structure_item.rb', line 33

def bit_size
  @bit_size
end

#data_type ⇒ Symbol

The data type is what kind of data this StructureItem represents when extracted from the binary buffer. :INT and :UINT are turned into Integers (Ruby Fixnum). :FLOAT are turned into floating point numbers (Ruby Float). :STRING is turned into an ASCII string (Ruby String). :BLOCK is turned into a binary buffer (Ruby String). :DERIVED is interpreted by the subclass and can result in any type.

Returns:



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# File 'lib/cosmos/packets/structure_item.rb', line 42

def data_type
  @data_type
end

#endianness ⇒ Symbol

Used to interpret how to read the item from the binary data buffer.

Returns:



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# File 'lib/cosmos/packets/structure_item.rb', line 46

def endianness
  @endianness
end

#name ⇒ String

Name is used by higher level classes to access the StructureItem.

Returns:

  • (String) —

    Name of the item



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# File 'lib/cosmos/packets/structure_item.rb', line 25

def name
  @name
end

#overflow ⇒ Symbol

How to handle overflow for :INT, :UINT, :STRING, and :BLOCK data types Note: Has no meaning for :FLOAT data types

Returns:



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# File 'lib/cosmos/packets/structure_item.rb', line 58

def overflow
  @overflow
end

Instance Method Details

#<=>(other_item) ⇒ Object

Comparison Operator based on bit_offset. This means that StructureItems with different names or bit sizes are equal if they have the same bit offset.



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# File 'ext/cosmos/ext/structure/structure.c', line 1187

static VALUE structure_item_spaceship(VALUE self, VALUE other_item) {
  int bit_offset = FIX2INT(rb_ivar_get(self, id_ivar_bit_offset));
  int other_bit_offset = FIX2INT(rb_ivar_get(other_item, id_ivar_bit_offset));
  int bit_size = 0;
  int other_bit_size = 0;

  /* Handle same bit offset case */
  if ((bit_offset == 0) && (other_bit_offset == 0)) {
    /* Both bit_offsets are 0 so sort by bit_size
      * This allows derived items with bit_size of 0 to be listed first
      * Compare based on bit size */
    bit_size = FIX2INT(rb_ivar_get(self, id_ivar_bit_size));
    other_bit_size = FIX2INT(rb_ivar_get(other_item, id_ivar_bit_size));
    if (bit_size == other_bit_size) {
      return INT2FIX(0);
    } if (bit_size < other_bit_size) {
      return INT2FIX(-1);
    } else {
      return INT2FIX(1);
    }
  }

  /* Handle different bit offsets */
  if (((bit_offset >= 0) && (other_bit_offset >= 0)) || ((bit_offset < 0) && (other_bit_offset < 0))) {
    /* Both Have Same Sign */
    if (bit_offset == other_bit_offset) {
      return INT2FIX(0);
    } else if (bit_offset < other_bit_offset) {
      return INT2FIX(-1);
    } else {
      return INT2FIX(1);
    }
  } else {
    /* Different Signs */
    if (bit_offset == other_bit_offset) {
      return INT2FIX(0);
    } else if (bit_offset < other_bit_offset) {
      return INT2FIX(1);
    } else {
      return INT2FIX(-1);
    }
  }
}

#clone ⇒ Object Also known as: dup

Make a light weight clone of this item



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# File 'lib/cosmos/packets/structure_item.rb', line 180

def clone
  item = super()
  item.name = self.name.clone if self.name
  item
end

#to_hash ⇒ Object 



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# File 'lib/cosmos/packets/structure_item.rb', line 187

def to_hash
  hash = {}
  hash['name'] = self.name
  hash['bit_offset'] = self.bit_offset
  hash['bit_size'] = self.bit_size
  hash['data_type'] = self.data_type
  hash['endianness'] = self.endianness
  hash['array_size'] = self.array_size
  hash['overflow'] = self.overflow
  hash
end