123456789_123456789_123456789_123456789_123456789_

Class: FFI::StructLayoutBuilder

Relationships & Source Files
Inherits: Object
Defined in: lib/ffi/struct_layout_builder.rb

Overview

Build a struct layout.

Constant Summary

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new ⇒ StructLayoutBuilder

[ GitHub ] 

  


# File 'lib/ffi/struct_layout_builder.rb', line 39



def initialize
  @size = 0
  @alignment = 1
  @min_alignment = 1
  @packed = false
  @union = false
  @fields = Array.new
end


  







Instance Attribute Details



  

    #alignment   (rw)
  

  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 37



attr_reader :alignment


  








  

    #alignment=(align)   (rw)
  



  

    

Set alignment attribute with #align only if it is greater than attribute value.


  





  
Parameters:


    
  
  • 
    align
    (Integer)
  
    • 





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 56



def alignment=(align)
  @alignment = align if align > @alignment
  @min_alignment = align
end


  








  

    

      #packed=(packed) Set alignment and packed attributes to)  ⇒ packed  (writeonly)
      #packed=(packed) Set packed attribute.)  ⇒ 0, 1 
    

  



  

    

Set packed attribute


  





  


  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 89



def packed=(packed)
  if packed.is_a?(0.class)
    @alignment = packed
    @packed = packed
  else
    @packed = packed ? 1 : 0
  end
end


  








  

    #size   (rw)
  

  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 36



attr_reader :size


  








  

    #size=(size)   (rw)
  



  

    

Set size attribute with #size only if #size is greater than attribute value.


  





  
Parameters:


    
  
  • 
    size
    (Integer)
  
    • 





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 50



def size=(size)
  @size = size if size > @size
end


  








  

    #union=(is_union)  ⇒ is_union  (rw)
  



  

    

Set union attribute. Set to true to build a Union instead of a Struct.


  





  
Parameters:


    
  
  • 
    is_union
    (Boolean)
  
    • 





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 65



def union=(is_union)
  @union = is_union
end


  








  

    #union?  ⇒ Boolean  (rw)
  



  

    

Building a Union or a Struct ?


  





  


  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 73



def union?
  @union
end


  







Instance Method Details



  

    #add(name, type, offset = nil)  ⇒ self 
  



  

    
  

    Note:
    


Setting offset to nil or -1 is equivalent to 0.



  




Add a field to the builder.


  





  
Parameters:





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 123



def add(name, type, offset = nil)

  if offset.nil? || offset == -1
    offset = @union ? 0 : align(@size, @packed ? [ @packed, type.alignment ].min : [ @min_alignment, type.alignment ].max)
  end

  #
  # If a FFI::Type type was passed in as the field arg, try and convert to a StructLayout::Field instance
  #
  field = type.is_a?(StructLayout::Field) ? type : field_for_type(name, offset, type)
  @fields << field
  @alignment = [ @alignment, field.alignment ].max unless @packed
  @size = [ @size, field.size + (@union ? 0 : field.offset) ].max

  return self
end


  








  

    #add_array(name, type, count, offset = nil)  
  



  

    

Add an array as a field to the builder.


  





  
Parameters:


    
  
  • 
    count
    (Integer)
—    
    

    array length
    

    
  
    • 





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 161



def add_array(name, type, count, offset = nil)
  add(name, Type::Array.new(type, count), offset)
end


  








  

    #add_field(name, type, offset = nil)  
  



  

    

Same as #add.


  





    
See Also:

  



  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 144



def add_field(name, type, offset = nil)
  add(name, type, offset)
end


  








  

    #add_struct(name, type, offset = nil)  
  



  

    

Add a struct as a field to the builder.


  



  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 151



def add_struct(name, type, offset = nil)
  add(name, Type::Struct.new(type), offset)
end


  








  

    #align(offset, align)  ⇒ Integer  (private)
  



  

    
  





  
Parameters:


    
  
  • 
    offset
    (Integer)
  
    • 
  
  • 
    align
    (Integer)
  
    • 





  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 181



def align(offset, align)
  align + ((offset - 1) & ~(align - 1));
end


  








  

    #build  ⇒ StructLayout 
  



  

    

Build and return the struct layout.


  





  


  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 167



def build
  # Add tail padding if the struct is not packed
  size = @packed ? @size : align(@size, @alignment)

  layout = StructLayout.new(@fields, size, @alignment)
  layout.__union! if @union
  layout
end


  








  

    #field_for_type(name, offset, type)  ⇒ StructLayout::Field  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/ffi/struct_layout_builder.rb', line 187



def field_for_type(name, offset, type)
  field_class = case
  when type.is_a?(Type::Function)
    StructLayout::Function

  when type.is_a?(Type::Struct)
    StructLayout::InnerStruct

  when type.is_a?(Type::Array)
    StructLayout::Array

  when type.is_a?(FFI::Enum)
    StructLayout::Enum

  when NUMBER_TYPES.include?(type)
    StructLayout::Number

  when type == Type::POINTER
    StructLayout::Pointer

  when type == Type::STRING
    StructLayout::String

  when type.is_a?(Class) && type < StructLayout::Field
    type

  when type.is_a?(DataConverter)
    return StructLayout::Mapped.new(name, offset, Type::Mapped.new(type), field_for_type(name, offset, type.native_type))

  when type.is_a?(Type::Mapped)
    return StructLayout::Mapped.new(name, offset, type, field_for_type(name, offset, type.native_type))

  else
    raise TypeError, "invalid struct field type #{type.inspect}"
  end

  field_class.new(name, offset, type)
end