module Fiddle

A libffi wrapper for Ruby.

Description¶ ↑

Fiddle is an extension to translate a foreign function interface (FFI) with ruby.

It wraps libffi, a popular C library which provides a portable interface that allows code written in one language to call code written in another language.

Example¶ ↑

Here we will use Fiddle::Function to wrap floor(3) from libm

require 'fiddle'

libm = Fiddle.dlopen('/lib/libm.so.6')

floor = Fiddle::Function.new(
  libm['floor'],
  [Fiddle::TYPE_DOUBLE],
  Fiddle::TYPE_DOUBLE
)

puts floor.call(3.14159) #=> 3.0

Constants

ALIGN_BOOL

ALIGN_BOOL

The alignment size of a bool

ALIGN_CHAR

ALIGN_CHAR

The alignment size of a char

ALIGN_DOUBLE

ALIGN_DOUBLE

The alignment size of a double

ALIGN_FLOAT

ALIGN_FLOAT

The alignment size of a float

ALIGN_INT

ALIGN_INT

The alignment size of an int

ALIGN_INT16_T

ALIGN_INT16_T

The alignment size of a int16_t

ALIGN_INT32_T

ALIGN_INT32_T

The alignment size of a int32_t

ALIGN_INT64_T

ALIGN_INT64_T

The alignment size of a int64_t

ALIGN_INT8_T

ALIGN_INT8_T

The alignment size of a int8_t

ALIGN_INTPTR_T

ALIGN_INTPTR_T

The alignment size of a intptr_t

ALIGN_LONG

ALIGN_LONG

The alignment size of a long

ALIGN_LONG_LONG

ALIGN_LONG_LONG

The alignment size of a long long

ALIGN_PTRDIFF_T

ALIGN_PTRDIFF_T

The alignment size of a ptrdiff_t

ALIGN_SHORT

ALIGN_SHORT

The alignment size of a short

ALIGN_SIZE_T

ALIGN_SIZE_T

The alignment size of a size_t

ALIGN_SSIZE_T

ALIGN_SSIZE_T

The alignment size of a ssize_t

ALIGN_UINTPTR_T

ALIGN_UINTPTR_T

The alignment size of a uintptr_t

ALIGN_VOIDP

ALIGN_VOIDP

The alignment size of a void*

BUILD_RUBY_PLATFORM

BUILD_RUBY_PLATFORM

Platform built against (i.e. “x86_64-linux”, etc.)

Public Class Methods

dlopen(library) → Fiddle::Handle click to toggle source

Creates a new handler that opens library, and returns an instance of Fiddle::Handle.

If nil is given for the library, Fiddle::Handle::DEFAULT is used, which is the equivalent to RTLD_DEFAULT. See man 3 dlopen for more.

lib = Fiddle.dlopen(nil)

The default is dependent on OS, and provide a handle for all libraries already loaded. For example, in most cases you can use this to access libc functions, or ruby functions like rb_str_new.

See Fiddle::Handle.new for more.

# File lib/fiddle.rb, line 91
def dlopen library
  begin
    Fiddle::Handle.new(library)
  rescue DLError => error
    case RUBY_PLATFORM
    when /linux/
      case error.message
      when /\A(\/.+?): (?:invalid ELF header|file too short)/
        # This may be a linker script:
        # https://sourceware.org/binutils/docs/ld.html#Scripts
        path = $1
      else
        raise
      end
    else
      raise
    end

    File.open(path) do |input|
      input.each_line do |line|
        case line
        when /\A\s*(?:INPUT|GROUP)\s*\(\s*([^\s,\)]+)/
          # TODO: Should we support multiple files?
          first_input = $1
          if first_input.start_with?("-l")
            first_input = "lib#{first_input[2..-1]}.so"
          end
          return dlopen(first_input)
        end
      end
    end

    # Not found
    raise
  end
end

dlunwrap(addr) click to toggle source

Returns the Ruby object stored at the memory address addr

Example:

x = Object.new
# => #<Object:0x0000000107c7d870>
Fiddle.dlwrap(x)
# => 4425504880
Fiddle.dlunwrap(_)
# => #<Object:0x0000000107c7d870>

VALUE
rb_fiddle_ptr2value(VALUE self, VALUE addr)
{
    return (VALUE)NUM2PTR(addr);
}

dlwrap(val) click to toggle source

Returns the memory address of the Ruby object stored at val

Example:

x = Object.new
# => #<Object:0x0000000107c7d870>
Fiddle.dlwrap(x)
# => 4425504880

In the case val is not a heap allocated object, this method will return the tagged pointer value.

Example:

Fiddle.dlwrap(123)
# => 247

static VALUE
rb_fiddle_value2ptr(VALUE self, VALUE val)
{
    return PTR2NUM((void*)val);
}

free(addr) click to toggle source

Free the memory at address addr

VALUE
rb_fiddle_free(VALUE self, VALUE addr)
{
    void *ptr = NUM2PTR(addr);

    ruby_xfree(ptr);
    return Qnil;
}

last_error() click to toggle source

Returns the last Error of the current executing Thread or nil if none

# File lib/fiddle.rb, line 57
def self.last_error
  if RUBY_ENGINE == 'jruby'
    errno = FFI.errno
    errno == 0 ? nil : errno
  else
    Thread.current[:__FIDDLE_LAST_ERROR__]
  end
end

last_error=(error) click to toggle source

Sets the last Error of the current executing Thread to error

# File lib/fiddle.rb, line 67
def self.last_error= error
  if RUBY_ENGINE == 'jruby'
    FFI.errno = error || 0
  else
    Thread.current[:__DL2_LAST_ERROR__] = error
    Thread.current[:__FIDDLE_LAST_ERROR__] = error
  end
end

malloc(size) click to toggle source

Allocate size bytes of memory and return the integer memory address for the allocated memory.

static VALUE
rb_fiddle_malloc(VALUE self, VALUE size)
{
    void *ptr;
    ptr = (void*)ruby_xcalloc(1, NUM2SIZET(size));
    return PTR2NUM(ptr);
}

realloc(addr, size) click to toggle source

Change the size of the memory allocated at the memory location addr to size bytes. Returns the memory address of the reallocated memory, which may be different than the address passed in.

static VALUE
rb_fiddle_realloc(VALUE self, VALUE addr, VALUE size)
{
    void *ptr = NUM2PTR(addr);

    ptr = (void*)ruby_xrealloc(ptr, NUM2SIZET(size));
    return PTR2NUM(ptr);
}

win32_last_error() click to toggle source

Returns the last win32 Error of the current executing Thread or nil if none

# File lib/fiddle.rb, line 16
def self.win32_last_error
  if RUBY_ENGINE == 'jruby'
    errno = FFI.errno
    errno == 0 ? nil : errno
  else
    Thread.current[:__FIDDLE_WIN32_LAST_ERROR__]
  end
end

win32_last_error=(error) click to toggle source

Sets the last win32 Error of the current executing Thread to error

# File lib/fiddle.rb, line 26
def self.win32_last_error= error
  if RUBY_ENGINE == 'jruby'
    FFI.errno = error || 0
  else
    Thread.current[:__FIDDLE_WIN32_LAST_ERROR__] = error
  end
end

win32_last_socket_error() click to toggle source

Returns the last win32 socket Error of the current executing Thread or nil if none

# File lib/fiddle.rb, line 36
def self.win32_last_socket_error
  if RUBY_ENGINE == 'jruby'
    errno = FFI.errno
    errno == 0 ? nil : errno
  else
    Thread.current[:__FIDDLE_WIN32_LAST_SOCKET_ERROR__]
  end
end

win32_last_socket_error=(error) click to toggle source

Sets the last win32 socket Error of the current executing Thread to error

# File lib/fiddle.rb, line 47
def self.win32_last_socket_error= error
  if RUBY_ENGINE == 'jruby'
    FFI.errno = error || 0
  else
    Thread.current[:__FIDDLE_WIN32_LAST_SOCKET_ERROR__] = error
  end
end

Private Instance Methods

dlopen(library) → Fiddle::Handle click to toggle source

Creates a new handler that opens library, and returns an instance of Fiddle::Handle.

If nil is given for the library, Fiddle::Handle::DEFAULT is used, which is the equivalent to RTLD_DEFAULT. See man 3 dlopen for more.

lib = Fiddle.dlopen(nil)

The default is dependent on OS, and provide a handle for all libraries already loaded. For example, in most cases you can use this to access libc functions, or ruby functions like rb_str_new.

See Fiddle::Handle.new for more.

# File lib/fiddle.rb, line 91
def dlopen library
  begin
    Fiddle::Handle.new(library)
  rescue DLError => error
    case RUBY_PLATFORM
    when /linux/
      case error.message
      when /\A(\/.+?): (?:invalid ELF header|file too short)/
        # This may be a linker script:
        # https://sourceware.org/binutils/docs/ld.html#Scripts
        path = $1
      else
        raise
      end
    else
      raise
    end

    File.open(path) do |input|
      input.each_line do |line|
        case line
        when /\A\s*(?:INPUT|GROUP)\s*\(\s*([^\s,\)]+)/
          # TODO: Should we support multiple files?
          first_input = $1
          if first_input.start_with?("-l")
            first_input = "lib#{first_input[2..-1]}.so"
          end
          return dlopen(first_input)
        end
      end
    end

    # Not found
    raise
  end
end