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

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 87

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 222

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.length > 0 && arg_types[arg_types.length - 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
  • #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

  • cname (#to_s)

    name of C variable to attach

  • type (DataConverter, Struct, Symbol, Type)

    C varaible's type

Returns:

Raises:



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# File 'lib/ffi/library.rb', line 317

def attach_variable(mname, a1, a2 = nil)
  cname, type = a2 ? [ a1, a2 ] : [ mname.to_s, a1 ]
  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 = type.new(address)
    self.module_eval <<-code, __FILE__, __LINE__
      @@ffi_gvar_#{mname} = s
      def self.#{mname}
        @@ffi_gvar_#{mname}
      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_gvar_#{mname} = s
      def self.#{mname}
        @@ffi_gvar_#{mname}[:gvar]
      end
      def self.#{mname}=(value)
        @@ffi_gvar_#{mname}[:gvar] = value
      end
    code

  end

  address
end

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

Parameters:

  • name

    callback name to add to type map

  • params (Array)

    array of parameters' types

  • ret (DataConverter, Struct, Symbol, Type)

    callback return type

Returns:

Raises:

  • (ArgumentError)


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# File 'lib/ffi/library.rb', line 368

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)
  cb = FFI::CallbackInfo.new(find_type(ret), 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

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

Returns:



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# File 'lib/ffi/library.rb', line 449

def enum(*args)
  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 = FFI::Enum.new(values, name))

  # If called as enum :foo, [ :zero, :one, :two ], add a typedef alias
  typedef(e, name) if name
  e
end

#enum_type(name) ⇒ FFI::Enum

Find an enum by name.

Parameters:

  • name

Returns:



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# File 'lib/ffi/library.rb', line 468

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 475

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 151

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 96

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::DynamicLibrary::RTLD_LAZY | FFI::DynamicLibrary::RTLD_LOCAL
  ffi_libs = names.map do |name|

    if name == FFI::CURRENT_PROCESS
      FFI::DynamicLibrary.open(nil, FFI::DynamicLibrary::RTLD_LAZY | FFI::DynamicLibrary::RTLD_LOCAL)

    else
      libnames = (name.is_a?(::Array) ? name : [ name ]).map { |n| [ n, FFI.map_library_name(n) ].uniq }.flatten.compact
      lib = nil
      errors = {}

      libnames.each do |libname|
        begin
          lib = FFI::DynamicLibrary.open(libname, lib_flags)
          break if lib

        rescue Exception => ex
          ldscript = false
          if ex.message =~ /(([^ \t()])+\.so([^ \t:()])*):([ \t])*(invalid ELF header|file too short)/
            if File.read($1) =~ /(?:GROUP|INPUT) *\( *([^ \)]+)/
              libname = $1
              ldscript = true
            end
          end

          if ldscript
            retry
          else
            errors[libname] = ex
          end
        end
      end

      if lib.nil?
        raise LoadError.new(errors.values.join(".\n"))
      end

      # return the found lib
      lib
    end
  end

  @ffi_libs = ffi_libs
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 184

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

#ffi_librariesArray<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 161

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 482

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

#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 277

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|
      mem + arg.size
    end

    # Next, the size must be a multiple of 4
    size += (4 - size) % 4

    result << "_#{name.to_s}@#{size}" # win32
    result << "#{name.to_s}@#{size}" # win64
  end
  result
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 407

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