Class: FFI::DRY::DSLStructLayoutBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/ffi/dry.rb

Overview

This class provides the DSL for StructHelper.dsl_layout. You probably don’t want to use this directly but if you do, to use the DSL, you may either pass a structure definition into ‘instance_eval’ or call methods on the object. The methods __metadata and __layout_args return structure information back to the caller, which can use them to create a new structure.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pbind) {|_self| ... } ⇒ DSLStructLayoutBuilder

Initializes the a new builder class.

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/ffi/dry.rb', line 223

def initialize(pbind)
  @pbind = pbind
  @__layout_args = []
  @__metadata = []
  yield self if block_given?
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name, type, *extra) ⇒ Object

Experimental - Allows specifying structure fields by taking a missing method name as field name for the structure.



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# File 'lib/ffi/dry.rb', line 268

def method_missing(name, type, *extra)
  o={}
  if extra.size > 1
    raise(ArgumentError, 
      "Bad field definition. Use: name :type, {optional extra parameters}")
  elsif h=extra.first
    if h.kind_of? Hash
      o=h
    else
      raise(ArgumentError, "Options must be provided as a hash.")
    end
  end
  opts = o.merge(:name => name, :type => type)
  offset = opts[:offset]

  @__layout_args << name
  @__layout_args << type
  @__layout_args << offset if offset

  @__metadata << opts
  return opts
end

Instance Attribute Details

#__layout_args ⇒ Object (readonly)

Returns the value of attribute __layout_args.



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# File 'lib/ffi/dry.rb', line 220

def __layout_args
  @__layout_args
end

#__metadata ⇒ Object (readonly)

Returns the value of attribute __metadata.



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# File 'lib/ffi/dry.rb', line 220

def __metadata
  @__metadata
end

Instance Method Details

#field(name, type, o = {}) ⇒ Object Also known as: array, struct, union

Declaratively adds a field to the structure.

Syntax:

field field_name, ctype, { ... metadata ... }

:offset is a special key in metadata, specifies the offset of the field.



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# File 'lib/ffi/dry.rb', line 250

def field(name, type, o={})
  opts = o.merge(:name => name, :type => type)
  offset = opts[:offset]

  @__layout_args << name
  @__layout_args << type
  @__layout_args << offset if offset

  @__metadata << opts
  return opts
end

#p_struct(name, klass, o = {}) ⇒ Object

A pointer to a structure. The structure does not allocate the entire space for the structure pointed to, just a pointer. When calling the accessor for a p_struct field, a new instance of the FFI::Struct type for the pointer will be returned.



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# File 'lib/ffi/dry.rb', line 234

def p_struct(name, klass, o={})
  unless klass.kind_of?(Class)
    raise(::ArgumentError, "klass must be a Class")
  end
  opts = o.merge(:p_struct => klass)
  offset = opts[:offset]
  field(name, :pointer, opts)
end