FFI::Library

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")

Constants

CURRENT_PROCESS
FlagsMap

Flags used in {ffi_lib}.

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

LIBC

Public Class Methods

extended(mod) click to toggle source

@param mod extended object @return [nil] @raise {RuntimeError} if mod is not a Module Test if extended object is a Module. If not, raise RuntimeError.

# File lib/ffi/library.rb, line 77
def self.extended(mod)
  raise RuntimeError.new("must only be extended by module") unless mod.kind_of?(Module)
end

Public Instance Methods

attach_function(name, func, args, returns = nil, options = nil) click to toggle source

@overload attach_function(func, args, returns, options = {})

@example 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

@overload attach_function(name, func, args, returns, options = {})

@example 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

Attach C function func to this module.

@param [to_s] name name of ruby method to attach as @param [to_s] func name of C function to attach @param [Array<Symbol>] args an array of types @param [Symbol] returns type of return value @option options [Boolean] :blocking (@blocking) set to true if the C function is a blocking call @option options [Symbol] :convention (:default) calling convention (see {ffi_convention}) @option options [FFI::Enums] :enums @option options [Hash] :type_map

@return [FFI::VariadicInvoker]

@raise [FFI::NotFoundError] if func cannot be found in the attached libraries (see {ffi_lib})

# File lib/ffi/library.rb, line 212
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, a1, a2 = nil) click to toggle source

@overload attach_variable(mname, cname, type)

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

@overload attach_variable(cname, type)

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

@param [to_s] mname name of ruby method to attach as @param [to_s] cname name of C variable to attach @param [DataConverter, Struct, Symbol, Type] type C varaible's type @return [DynamicLibrary::Symbol] @raise {FFI::NotFoundError} if cname cannot be found in libraries

Attach C variable cname to this module.

# File lib/ffi/library.rb, line 307
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           @@ffi_gvar_#{mname} = s          def self.#{mname}            @@ffi_gvar_#{mname}          end, __FILE__, __LINE__

  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           @@ffi_gvar_#{mname} = s          def self.#{mname}            @@ffi_gvar_#{mname}[:gvar]          end          def self.#{mname}=(value)            @@ffi_gvar_#{mname}[:gvar] = value          end, __FILE__, __LINE__

  end

  address
end
callback(*args) click to toggle source

@overload callback(name, params, ret) @overload callback(params, ret) @param name callback name to add to type map @param [Array] params array of parameters' types @param [DataConverter, Struct, Symbol, Type] ret callback return type @return [FFI::CallbackInfo]

# File lib/ffi/library.rb, line 358
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(*args) click to toggle source

@overload enum(name, values)

Create a named enum.
@example
 enum :foo, [:zero, :one, :two]  # named enum
@param [Symbol] name name for new enum
@param [Array] values values for enum

@overload enum(*args)

Create an unnamed enum.
@example
 enum :zero, :one, :two  # unnamed enum
@param args values for enum

@overload enum(values)

Create an unnamed enum.
@example
 enum [:zero, :one, :two]  # unnamed enum, equivalent to above example
@param [Array] values values for enum

@return [FFI::Enum] Create a new {FFI::Enum}.

# File lib/ffi/library.rb, line 439
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) click to toggle source

@param name @return [FFI::Enum] Find an enum by name.

# File lib/ffi/library.rb, line 458
def enum_type(name)
  @ffi_enums.find(name) if defined?(@ffi_enums)
end
enum_value(symbol) click to toggle source

@param symbol @return [FFI::Enum] Find an enum by a symbol it contains.

# File lib/ffi/library.rb, line 465
def enum_value(symbol)
  @ffi_enums.__map_symbol(symbol)
end
ffi_convention(convention = nil) click to toggle source

Set the calling convention for {attach_function} and {callback}

@see en.wikipedia.org/wiki/Stdcall#stdcall @note :stdcall is typically used for attaching Windows API functions

@param [Symbol] convention one of :default, :stdcall @return [Symbol] the new calling convention

# File lib/ffi/library.rb, line 141
def ffi_convention(convention = nil)
  @ffi_convention ||= :default
  @ffi_convention = convention if convention
  @ffi_convention
end
ffi_lib(*names) click to toggle source

@param [Array] names names of libraries to load @return [Array<DynamicLibrary>] @raise {LoadError} if a library cannot be opened Load native libraries.

# File lib/ffi/library.rb, line 86
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/
            if File.read($1) =~ /GROUP *\( *([^ \)]+) *\)/
              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) click to toggle source

Sets library flags for {ffi_lib}.

@example

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

@param [Symbol, …] flags (see {FlagsMap}) @return [Fixnum] the new value

# File lib/ffi/library.rb, line 174
def ffi_lib_flags(*flags)
  @ffi_lib_flags = flags.inject(0) { |result, f| result | FlagsMap[f] }
end
ffi_libraries() click to toggle source

@see ffi_lib @return [Array<FFI::DynamicLibrary>] array of currently loaded FFI libraries @raise [LoadError] if no libraries have been loaded (using {ffi_lib}) Get FFI libraries loaded using {ffi_lib}.

# File lib/ffi/library.rb, line 151
def ffi_libraries
  raise LoadError.new("no library specified") if !defined?(@ffi_libs) || @ffi_libs.empty?
  @ffi_libs
end
find_type(t) click to toggle source

@param [DataConverter, Type, Struct, Symbol] t type to find @return [Type] Find a type definition.

# File lib/ffi/library.rb, line 472
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) click to toggle source

@param [to_s] name function name @param [Array] arg_types function's argument types @return [Array<String>] This function returns a list of possible names to lookup. @note Function names on windows may be decorated if they are using stdcall. See

* http://en.wikipedia.org/wiki/Name_mangling#C_name_decoration_in_Microsoft_Windows
* http://msdn.microsoft.com/en-us/library/zxk0tw93%28v=VS.100%29.aspx
* http://en.wikibooks.org/wiki/X86_Disassembly/Calling_Conventions#STDCALL
Note that decorated names can be overridden via def files.  Also note that the
windows api, although using, doesn't have decorated names.
# File lib/ffi/library.rb, line 267
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) click to toggle source

@param [DataConverter, Symbol, Type] old @param add @param [] info @return [FFI::Enum, FFI::Type] Register or get an already registered type definition.

To register a new type definition, old should be a {FFI::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.

# File lib/ffi/library.rb, line 397
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

[Validate]

Generated with the Darkfish Rdoc Generator 2.