ffi_backend: convert numeric function args to pointers (#162)

This allows for passing integers as pointer arguments to functions when
using the FFI backend. This is a workaround until we can get JRuby's FFI
implementation to allow for it directly (see also
jruby/jruby#8423)
---------
Co-authored-by: Benoit Daloze <eregontp@gmail.com>

Author: danini-the-panini

lib/fiddle/ffi_backend.rb

@@ -159,15 +159,16 @@ def call(*args, &block)
 args[i]=Fiddle::FFIBackend.to_ffi_type(args[i])
 end
 else
-args.map!do |arg|
-ifarg.respond_to?(:to_ptr)
-begin
-arg=arg.to_ptr
-enduntilarg.is_a?(FFI::Pointer) || !arg.respond_to?(:to_ptr)
-arg
-else
-arg
-end
+@args.each_with_indexdo |arg_type,i|
+nextunlessarg_type == Types::VOIDP
+
+src=args[i]
+nextifsrc.nil?
+nextifsrc.is_a?(String)
+nextifsrc.is_a?(FFI::AbstractMemory)
+nextifsrc.is_a?(FFI::Struct)
+
+args[i]=Pointer[src]
 end
 end
 result=@function.call(*args, &block)
@@ -316,6 +317,8 @@ def initialize(addr, size = nil, free = nil)
 end
 elsifaddr.is_a?(IO)
 raiseNotImplementedError,"IO ptr isn't supported"
+else
+FFI::Pointer.new(Integer(addr))
 end
 
 @size=size ? size : ptr.size

test/fiddle/test_function.rb

@@ -98,6 +98,15 @@ def test_call
 assert_in_delta1.0,func.call(90 * Math::PI / 180),0.0001
 end
 
+deftest_integer_pointer_conversion
+func=Function.new(@libc['memcpy'],[TYPE_VOIDP,TYPE_VOIDP,TYPE_SIZE_T],TYPE_VOIDP)
+str='hello'
+Pointer.malloc(str.bytesize,Fiddle::RUBY_FREE)do |dst|
+func.call(dst.to_i,str,dst.size)
+assert_equal(str,dst.to_str)
+end
+end
+
 deftest_argument_count
 closure_class=Class.new(Closure)do
 defcallone

test/fiddle/test_pointer.rb

@@ -157,11 +157,17 @@ def test_to_ptr_with_ptr
 end
 end
 
-deftest_to_ptr_with_num
+deftest_to_ptr_with_int
 ptr=Pointer.new0
 assert_equalptr,Pointer[0]
 end
 
+MimicInteger=Struct.new(:to_int)
+deftest_to_ptr_with_to_int
+ptr=Pointer.new0
+assert_equalptr,Pointer[MimicInteger.new(0)]
+end
+
 deftest_equals
 ptr=Pointer.new0
 ptr2=Pointer.new0