Module: FFI::Library

Defined in:
lib/ffi/library.rb

Overview

This module is the base to use native functions.

A basic usage may be:

require 'ffi'

module Hello
  extend FFI::Library
  ffi_lib FFI::Library::LIBC
  attach_function 'puts', [ :string ], :int
end

Hello.puts("Hello, World")

Constant Summary collapse

CURRENT_PROCESS = 
FFI::CURRENT_PROCESS
LIBC = 
FFI::Platform::LIBC
FlagsMap =

Flags used in #ffi_lib.

This map allows you to supply symbols to #ffi_lib_flags instead of the actual constants.

{
  :global => DynamicLibrary::RTLD_GLOBAL,
  :local => DynamicLibrary::RTLD_LOCAL,
  :lazy => DynamicLibrary::RTLD_LAZY,
  :now => DynamicLibrary::RTLD_NOW
}

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.extended(mod) ⇒ nil

Test if extended object is a Module. If not, raise RuntimeError.

Parameters:

  • mod —

    extended object

Returns:

  • (nil)

Raises:

  • (RuntimeError) —

    if mod is not a Module



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# File 'lib/ffi/library.rb', line 80

def self.extended(mod)
  raise RuntimeError.new("must only be extended by module") unless mod.kind_of?(::Module)
end

Instance Method Details

#attach_function(func, args, returns, options = {}) ⇒ FFI::VariadicInvoker #attach_function(name, func, args, returns, options = {}) ⇒ FFI::VariadicInvoker

Attach C function func to this module.

Overloads:

  • #attach_function(func, args, returns, options = {}) ⇒ FFI::VariadicInvoker

    Examples:

    attach function without an explicit name

    module Foo
  extend FFI::Library
  ffi_lib FFI::Library::LIBC
  attach_function :malloc, [:size_t], :pointer
end
# now callable via Foo.malloc
  • #attach_function(name, func, args, returns, options = {}) ⇒ FFI::VariadicInvoker

    Examples:

    attach function with an explicit name

    module Bar
  extend FFI::Library
  ffi_lib FFI::Library::LIBC
  attach_function :c_malloc, :malloc, [:size_t], :pointer
end
# now callable via Bar.c_malloc

Parameters:

  • name (#to_s) —

    name of ruby method to attach as

  • func (#to_s) —

    name of C function to attach

  • args (Array<Symbol>) —

    an array of types

  • returns (Symbol) (defaults to: nil) —

    type of return value

  • options (Hash) (defaults to: nil) —

    a customizable set of options

Options Hash (options):

  • :blocking (Boolean) — default: @blocking —

    set to true if the C function is a blocking call

  • :convention (Symbol) — default: :default —

    calling convention (see #ffi_convention)

  • :enums (FFI::Enums)
  • :type_map (Hash)

Returns:

Raises:



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# File 'lib/ffi/library.rb', line 177

def attach_function(name, func, args, returns = nil, options = nil)
  mname, a2, a3, a4, a5 = name, func, args, returns, options
  cname, arg_types, ret_type, opts = (a4 && (a2.is_a?(String) || a2.is_a?(Symbol))) ? [ a2, a3, a4, a5 ] : [ mname.to_s, a2, a3, a4 ]

  # Convert :foo to the native type
  arg_types = arg_types.map { |e| find_type(e) }
  options = {
    :convention => ffi_convention,
    :type_map => defined?(@ffi_typedefs) ? @ffi_typedefs : nil,
    :blocking => defined?(@blocking) && @blocking,
    :enums => defined?(@ffi_enums) ? @ffi_enums : nil,
  }

  @blocking = false
  options.merge!(opts) if opts && opts.is_a?(Hash)

  # Try to locate the function in any of the libraries
  invokers = []
  ffi_libraries.each do |lib|
    if invokers.empty?
      begin
        function = nil
        function_names(cname, arg_types).find do |fname|
          function = lib.find_function(fname)
        end
        raise LoadError unless function

        invokers << if arg_types[-1] == FFI::NativeType::VARARGS
          VariadicInvoker.new(function, arg_types, find_type(ret_type), options)

        else
          Function.new(find_type(ret_type), arg_types, function, options)
        end

      rescue LoadError
      end
    end
  end
  invoker = invokers.compact.shift
  raise FFI::NotFoundError.new(cname.to_s, ffi_libraries.map { |lib| lib.name }) unless invoker

  invoker.attach(self, mname.to_s)
  invoker
end

#attach_variable(mname, cname, type) ⇒ DynamicLibrary::Symbol #attach_variable(cname, type) ⇒ DynamicLibrary::Symbol

Attach C variable cname to this module.

Overloads:

  • #attach_variable(mname, cname, type) ⇒ DynamicLibrary::Symbol

    Examples:

    module Bar
  extend FFI::Library
  ffi_lib 'my_lib'
  attach_variable :c_myvar, :myvar, :long
end
# now callable via Bar.c_myvar

    Parameters:

    • mname (#to_s) —

      name of ruby method to attach as

    • cname (#to_s) —

      name of C variable to attach

    • type (DataConverter, Struct, Symbol, Type) —

      C variable’s type

  • #attach_variable(cname, type) ⇒ DynamicLibrary::Symbol

    Examples:

    module Bar
  extend FFI::Library
  ffi_lib 'my_lib'
  attach_variable :myvar, :long
end
# now callable via Bar.myvar

    Parameters:

    • mname (#to_s) —

      name of ruby method to attach as

    • type (DataConverter, Struct, Symbol, Type) —

      C variable’s type

Returns:

Raises:



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# File 'lib/ffi/library.rb', line 274

def attach_variable(mname, a1, a2 = nil)
  cname, type = a2 ? [ a1, a2 ] : [ mname.to_s, a1 ]
  mname = mname.to_sym
  address = nil
  ffi_libraries.each do |lib|
    begin
      address = lib.find_variable(cname.to_s)
      break unless address.nil?
    rescue LoadError
    end
  end

  raise FFI::NotFoundError.new(cname, ffi_libraries) if address.nil? || address.null?
  if type.is_a?(Class) && type < FFI::Struct
    # If it is a global struct, just attach directly to the pointer
    s = s = type.new(address) # Assigning twice to suppress unused variable warning
    self.module_eval <<-code, __FILE__, __LINE__
      @ffi_gsvars = {} unless defined?(@ffi_gsvars)
      @ffi_gsvars[#{mname.inspect}] = s
      def self.#{mname}
        @ffi_gsvars[#{mname.inspect}]
      end
    code

  else
    sc = Class.new(FFI::Struct)
    sc.layout :gvar, find_type(type)
    s = sc.new(address)
    #
    # Attach to this module as mname/mname=
    #
    self.module_eval <<-code, __FILE__, __LINE__
      @ffi_gvars = {} unless defined?(@ffi_gvars)
      @ffi_gvars[#{mname.inspect}] = s
      def self.#{mname}
        @ffi_gvars[#{mname.inspect}][:gvar]
      end
      def self.#{mname}=(value)
        @ffi_gvars[#{mname.inspect}][:gvar] = value
      end
    code

  end

  address
end

#attached_functions ⇒ Hash< Symbol => [FFI::Function, FFI::VariadicInvoker] >

Retrieve all attached functions and their function signature

This method returns a Hash of method names of attached functions connected by #attach_function and the corresponding function type. The function type responds to #return_type and #param_types which return the FFI types of the function signature.

Returns:



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# File 'lib/ffi/library.rb', line 544

def attached_functions
  @ffi_functions || {}
end

#attached_variables ⇒ Hash< Symbol => ffi_type >

Retrieve all attached variables and their type

This method returns a Hash of variable names and the corresponding type or variables connected by #attach_variable .

Returns:

  • (Hash< Symbol => ffi_type >) 


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# File 'lib/ffi/library.rb', line 553

def attached_variables
  (
    (@ffi_gsvars || {}).map do |name, gvar|
      [name, gvar.class]
    end +
    (@ffi_gvars || {}).map do |name, gvar|
      [name, gvar.layout[:gvar].type]
    end
  ).to_h
end

#bitmask(name, values) ⇒ FFI::Bitmask #bitmask(*args) ⇒ FFI::Bitmask #bitmask(values) ⇒ FFI::Bitmask #bitmask(native_type, name, values) ⇒ FFI::Bitmask #bitmask(native_type, *args) ⇒ FFI::Bitmask #bitmask(native_type, values) ⇒ FFI::Bitmask

Create a new FFI::Bitmask

Overloads:

  • #bitmask(name, values) ⇒ FFI::Bitmask

    Create a named bitmask

    Examples:

    bitmask :foo, [:red, :green, :blue] # bits 0,1,2 are used
bitmask :foo, [:red, :green, 5, :blue] # bits 0,5,6 are used

    Parameters:

    • name (Symbol) —

      for new bitmask

    • values (Array<Symbol, Integer>) —

      for new bitmask

  • #bitmask(*args) ⇒ FFI::Bitmask

    Create an unamed bitmask

    Examples:

    bm = bitmask :red, :green, :blue # bits 0,1,2 are used
bm = bitmask :red, :green, 5, blue # bits 0,5,6 are used

    Parameters:

    • args (Symbol, Integer) —

      values for new bitmask

  • #bitmask(values) ⇒ FFI::Bitmask

    Create an unamed bitmask

    Examples:

    bm = bitmask [:red, :green, :blue] # bits 0,1,2 are used
bm = bitmask [:red, :green, 5, blue] # bits 0,5,6 are used

    Parameters:

    • values (Array<Symbol, Integer>) —

      for new bitmask

  • #bitmask(native_type, name, values) ⇒ FFI::Bitmask

    Create a named enum and specify the native type.

    Examples:

    bitmask FFI::Type::UINT64, :foo, [:red, :green, :blue]

    Parameters:

    • native_type (FFI::Type) —

      native type for new bitmask

    • name (Symbol) —

      for new bitmask

    • values (Array<Symbol, Integer>) —

      for new bitmask

  • #bitmask(native_type, *args) ⇒ FFI::Bitmask

    Examples:

    bitmask FFI::Type::UINT64, :red, :green, :blue

    Parameters:

    • native_type (FFI::Type) —

      native type for new bitmask

    • args (Symbol, Integer) —

      values for new bitmask

  • #bitmask(native_type, values) ⇒ FFI::Bitmask

    Create a named enum and specify the native type.

    Examples:

    bitmask FFI::Type::UINT64, [:red, :green, :blue]

    Parameters:

    • native_type (FFI::Type) —

      native type for new bitmask

    • values (Array<Symbol, Integer>) —

      for new bitmask

Returns:



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# File 'lib/ffi/library.rb', line 500

def bitmask(*args)
  generic_enum(FFI::Bitmask, *args)
end

#callback(name, params, ret) ⇒ FFI::CallbackInfo #callback(params, ret) ⇒ FFI::CallbackInfo

Overloads:

Returns:

Raises:

  • (ArgumentError) 


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# File 'lib/ffi/library.rb', line 330

def callback(*args)
  raise ArgumentError, "wrong number of arguments" if args.length < 2 || args.length > 3
  name, params, ret = if args.length == 3
    args
  else
    [ nil, args[0], args[1] ]
  end

  native_params = params.map { |e| find_type(e) }
  raise ArgumentError, "callbacks cannot have variadic parameters" if native_params.include?(FFI::Type::VARARGS)
  options = Hash.new
  options[:convention] = ffi_convention
  options[:enums] = @ffi_enums if defined?(@ffi_enums)
  ret_type = find_type(ret)
  if ret_type == Type::STRING
    raise TypeError, ":string is not allowed as return type of callbacks"
  end
  cb = FFI::CallbackInfo.new(ret_type, native_params, options)

  # Add to the symbol -> type map (unless there was no name)
  unless name.nil?
    typedef cb, name
  end

  cb
end

#enum(name, values) ⇒ FFI::Enum #enum(*args) ⇒ FFI::Enum #enum(values) ⇒ FFI::Enum #enum(native_type, name, values) ⇒ FFI::Enum #enum(native_type, *args) ⇒ FFI::Enum #enum(native_type, values) ⇒ FFI::Enum

Create a new Enum.

Overloads:

  • #enum(name, values) ⇒ FFI::Enum

    Create a named enum.

    Examples:

    enum :foo, [:zero, :one, :two]  # named enum

    Parameters:

    • name (Symbol) —

      name for new enum

    • values (Array) —

      values for enum

  • #enum(*args) ⇒ FFI::Enum

    Create an unnamed enum.

    Examples:

    enum :zero, :one, :two  # unnamed enum

    Parameters:

    • args —

      values for enum

  • #enum(values) ⇒ FFI::Enum

    Create an unnamed enum.

    Examples:

    enum [:zero, :one, :two]  # unnamed enum, equivalent to above example

    Parameters:

    • values (Array) —

      values for enum

  • #enum(native_type, name, values) ⇒ FFI::Enum

    Create a named enum and specify the native type.

    Examples:

    enum FFI::Type::UINT64, :foo, [:zero, :one, :two]  # named enum

    Parameters:

    • native_type (FFI::Type) —

      native type for new enum

    • name (Symbol) —

      name for new enum

    • values (Array) —

      values for enum

  • #enum(native_type, *args) ⇒ FFI::Enum

    Create an unnamed enum and specify the native type.

    Examples:

    enum FFI::Type::UINT64, :zero, :one, :two  # unnamed enum

    Parameters:

    • native_type (FFI::Type) —

      native type for new enum

    • args —

      values for enum

  • #enum(native_type, values) ⇒ FFI::Enum

    Create an unnamed enum and specify the native type.

    Examples:

    enum Type::UINT64, [:zero, :one, :two]  # unnamed enum, equivalent to above example

    Parameters:

    • native_type (FFI::Type) —

      native type for new enum

    • values (Array) —

      values for enum

Returns:



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# File 'lib/ffi/library.rb', line 457

def enum(*args)
  generic_enum(FFI::Enum, *args)
end

#enum_type(name) ⇒ FFI::Enum

Find an enum by name.

Parameters:

  • name

Returns:



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# File 'lib/ffi/library.rb', line 507

def enum_type(name)
  @ffi_enums.find(name) if defined?(@ffi_enums)
end

#enum_value(symbol) ⇒ FFI::Enum

Find an enum by a symbol it contains.

Parameters:

  • symbol

Returns:



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# File 'lib/ffi/library.rb', line 514

def enum_value(symbol)
  @ffi_enums.__map_symbol(symbol)
end

#ffi_convention(convention = nil) ⇒ Symbol

Note:

:stdcall is typically used for attaching Windows API functions

Set the calling convention for #attach_function and #callback

Parameters:

  • convention (Symbol) (defaults to: nil) —

    one of :default, :stdcall

Returns:

  • (Symbol) —

    the new calling convention

See Also:



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# File 'lib/ffi/library.rb', line 106

def ffi_convention(convention = nil)
  @ffi_convention ||= :default
  @ffi_convention = convention if convention
  @ffi_convention
end

#ffi_lib(*names) ⇒ Array<DynamicLibrary>

Load native libraries.

Parameters:

  • names (Array) —

    names of libraries to load

Returns:

Raises:

  • (LoadError) —

    if a library cannot be opened



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

def ffi_lib(*names)
  raise LoadError.new("library names list must not be empty") if names.empty?

  lib_flags = defined?(@ffi_lib_flags) && @ffi_lib_flags

  @ffi_libs = names.map do |name|
    FFI::DynamicLibrary.send(:load_library, name, lib_flags)
  end
end

#ffi_lib_flags(*flags) ⇒ Fixnum

Sets library flags for #ffi_lib.

Examples:

ffi_lib_flags(:lazy, :local) # => 5

Parameters:

  • flags (Symbol, …) —

    (see FlagsMap)

Returns:

  • (Fixnum) —

    the new value



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# File 'lib/ffi/library.rb', line 139

def ffi_lib_flags(*flags)
  @ffi_lib_flags = flags.inject(0) { |result, f| result | FlagsMap[f] }
end

#ffi_libraries ⇒ Array<FFI::DynamicLibrary>

Get FFI libraries loaded using #ffi_lib.

Returns:

Raises:

  • (LoadError) —

    if no libraries have been loaded (using #ffi_lib)

See Also:



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# File 'lib/ffi/library.rb', line 116

def ffi_libraries
  raise LoadError.new("no library specified") if !defined?(@ffi_libs) || @ffi_libs.empty?
  @ffi_libs
end

#find_type(t) ⇒ Type

Find a type definition.

Parameters:

Returns:



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# File 'lib/ffi/library.rb', line 521

def find_type(t)
  if t.kind_of?(Type)
    t

  elsif defined?(@ffi_typedefs) && @ffi_typedefs.has_key?(t)
    @ffi_typedefs[t]

  elsif t.is_a?(Class) && t < Struct
    Type::POINTER

  elsif t.is_a?(DataConverter)
    # Add a typedef so next time the converter is used, it hits the cache
    typedef Type::Mapped.new(t), t

  end || FFI.find_type(t)
end

#freeze ⇒ Object

Freeze all definitions of the module

This freezes the module’s definitions, so that it can be used in a Ractor. No further methods or variables can be attached and no further enums or typedefs can be created in this module afterwards.



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# File 'lib/ffi/library.rb', line 568

def freeze
  instance_variables.each do |name|
    var = instance_variable_get(name)
    FFI.make_shareable(var)
  end
  nil
end

#function_names(name, arg_types) ⇒ Array<String>

Note:

Function names on windows may be decorated if they are using stdcall. See

Note that decorated names can be overridden via def files. Also note that the windows api, although using, doesn’t have decorated names.

This function returns a list of possible names to lookup.

Parameters:

  • name (#to_s) —

    function name

  • arg_types (Array) —

    function’s argument types

Returns:

  • (Array<String>) 


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# File 'lib/ffi/library.rb', line 232

def function_names(name, arg_types)
  result = [name.to_s]
  if ffi_convention == :stdcall
    # Get the size of each parameter
    size = arg_types.inject(0) do |mem, arg|
      size = arg.size
      # The size must be a multiple of 4
      size += (4 - size) % 4
      mem + size
    end

    result << "_#{name.to_s}@#{size}" # win32
    result << "#{name.to_s}@#{size}" # win64
  end
  result
end

#generic_enum(klass, *args) ⇒ Object (private)

Generic enum builder

@param [Class] klass can be one of FFI::Enum or FFI::Bitmask
@param args (see #enum or #bitmask)



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# File 'lib/ffi/library.rb', line 402

def generic_enum(klass, *args)
  native_type = args.first.kind_of?(FFI::Type) ? args.shift : nil
  name, values = if args[0].kind_of?(Symbol) && args[1].kind_of?(Array)
    [ args[0], args[1] ]
  elsif args[0].kind_of?(Array)
    [ nil, args[0] ]
  else
    [ nil, args ]
  end
  @ffi_enums = FFI::Enums.new unless defined?(@ffi_enums)
  @ffi_enums << (e = native_type ? klass.new(native_type, values, name) : klass.new(values, name))

  # If called with a name, add a typedef alias
  typedef(e, name) if name
  e
end

#typedef(old, add, info = nil) ⇒ FFI::Enum, FFI::Type

Register or get an already registered type definition.

To register a new type definition, old should be a Type. add is in this case the type definition.

If old is a DataConverter, a Type::Mapped is returned.

If old is :enum

  • and add is an Array, a call to #enum is made with add as single parameter;

  • in others cases, info is used to create a named enum.

If old is a key for type map, #typedef get old type definition.

Parameters:

Returns:



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# File 'lib/ffi/library.rb', line 374

def typedef(old, add, info=nil)
  @ffi_typedefs = Hash.new unless defined?(@ffi_typedefs)

  @ffi_typedefs[add] = if old.kind_of?(FFI::Type)
    old

  elsif @ffi_typedefs.has_key?(old)
    @ffi_typedefs[old]

  elsif old.is_a?(DataConverter)
    FFI::Type::Mapped.new(old)

  elsif old == :enum
    if add.kind_of?(Array)
      self.enum(add)
    else
      self.enum(info, add)
    end

  else
    FFI.find_type(old)
  end
end