path: root/libgo/runtime/go-ffi.c

/* go-ffi.c -- convert Go type description to libffi.

   Copyright 2009 The Go Authors. All rights reserved.
   Use of this source code is governed by a BSD-style
   license that can be found in the LICENSE file.  */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

#include "runtime.h"
#include "go-alloc.h"
#include "go-assert.h"
#include "go-type.h"

#ifdef USE_LIBFFI

#include "ffi.h"

/* The functions in this file are only called from reflect_call and
   reflect.ffi.  As these functions call libffi functions, which will
   be compiled without -fsplit-stack, they will always run with a
   large stack.  */

static ffi_type *go_array_to_ffi (const struct __go_array_type *)
  __attribute__ ((no_split_stack));
static ffi_type *go_slice_to_ffi (const struct __go_slice_type *)
  __attribute__ ((no_split_stack));
static ffi_type *go_struct_to_ffi (const struct __go_struct_type *)
  __attribute__ ((no_split_stack));
static ffi_type *go_string_to_ffi (void) __attribute__ ((no_split_stack));
static ffi_type *go_interface_to_ffi (void) __attribute__ ((no_split_stack));
static ffi_type *go_type_to_ffi (const struct __go_type_descriptor *)
  __attribute__ ((no_split_stack));
static ffi_type *go_func_return_ffi (const struct __go_func_type *)
  __attribute__ ((no_split_stack));

/* Return an ffi_type for a Go array type.  The libffi library does
   not have any builtin support for passing arrays as values.  We work
   around this by pretending that the array is a struct.  */

static ffi_type *
go_array_to_ffi (const struct __go_array_type *descriptor)
{
  ffi_type *ret;
  uintptr_t len;
  ffi_type *element;
  uintptr_t i;

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  len = descriptor->__len;
  if (len == 0)
    {
      /* The libffi library won't accept an empty struct.  */
      ret->elements = (ffi_type **) __go_alloc (2 * sizeof (ffi_type *));
      ret->elements[0] = &ffi_type_void;
      ret->elements[1] = NULL;
      return ret;
    }
  ret->elements = (ffi_type **) __go_alloc ((len + 1) * sizeof (ffi_type *));
  element = go_type_to_ffi (descriptor->__element_type);
  for (i = 0; i < len; ++i)
    ret->elements[i] = element;
  ret->elements[len] = NULL;
  return ret;
}

/* Return an ffi_type for a Go slice type.  This describes the
   __go_open_array type defines in array.h.  */

static ffi_type *
go_slice_to_ffi (
    const struct __go_slice_type *descriptor __attribute__ ((unused)))
{
  ffi_type *ret;
  ffi_type *ffi_intgo;

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  ret->elements = (ffi_type **) __go_alloc (4 * sizeof (ffi_type *));
  ret->elements[0] = &ffi_type_pointer;
  ffi_intgo = sizeof (intgo) == 4 ? &ffi_type_sint32 : &ffi_type_sint64;
  ret->elements[1] = ffi_intgo;
  ret->elements[2] = ffi_intgo;
  ret->elements[3] = NULL;
  return ret;
}

/* Return an ffi_type for a Go struct type.  */

static ffi_type *
go_struct_to_ffi (const struct __go_struct_type *descriptor)
{
  ffi_type *ret;
  int field_count;
  const struct __go_struct_field *fields;
  int i;

  field_count = descriptor->__fields.__count;
  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  if (field_count == 0)
    {
      /* The libffi library won't accept an empty struct.  */
      ret->elements = (ffi_type **) __go_alloc (2 * sizeof (ffi_type *));
      ret->elements[0] = &ffi_type_void;
      ret->elements[1] = NULL;
      return ret;
    }
  fields = (const struct __go_struct_field *) descriptor->__fields.__values;
  ret->elements = (ffi_type **) __go_alloc ((field_count + 1)
					    * sizeof (ffi_type *));
  for (i = 0; i < field_count; ++i)
    ret->elements[i] = go_type_to_ffi (fields[i].__type);
  ret->elements[field_count] = NULL;
  return ret;
}

/* Return an ffi_type for a Go string type.  This describes the String
   struct.  */

static ffi_type *
go_string_to_ffi (void)
{
  ffi_type *ret;
  ffi_type *ffi_intgo;

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  ret->elements = (ffi_type **) __go_alloc (3 * sizeof (ffi_type *));
  ret->elements[0] = &ffi_type_pointer;
  ffi_intgo = sizeof (intgo) == 4 ? &ffi_type_sint32 : &ffi_type_sint64;
  ret->elements[1] = ffi_intgo;
  ret->elements[2] = NULL;
  return ret;
}

/* Return an ffi_type for a Go interface type.  This describes the
   __go_interface and __go_empty_interface structs.  */

static ffi_type *
go_interface_to_ffi (void)
{
  ffi_type *ret;

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  ret->elements = (ffi_type **) __go_alloc (3 * sizeof (ffi_type *));
  ret->elements[0] = &ffi_type_pointer;
  ret->elements[1] = &ffi_type_pointer;
  ret->elements[2] = NULL;
  return ret;
}


#ifndef FFI_TARGET_HAS_COMPLEX_TYPE
/* If libffi hasn't been updated for this target to support complex,
   pretend complex is a structure.  Warning: This does not work for
   all ABIs.  Eventually libffi should be updated for all targets
   and this should go away.  */

static ffi_type *go_complex_to_ffi (ffi_type *)
  __attribute__ ((no_split_stack));

static ffi_type *
go_complex_to_ffi (ffi_type *float_type)
{
  ffi_type *ret;

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  ret->elements = (ffi_type **) __go_alloc (3 * sizeof (ffi_type *));
  ret->elements[0] = float_type;
  ret->elements[1] = float_type;
  ret->elements[2] = NULL;
  return ret;
}
#endif

/* Return an ffi_type for a type described by a
   __go_type_descriptor.  */

static ffi_type *
go_type_to_ffi (const struct __go_type_descriptor *descriptor)
{
  switch (descriptor->__code & GO_CODE_MASK)
    {
    case GO_BOOL:
      if (sizeof (_Bool) == 1)
	return &ffi_type_uint8;
      else if (sizeof (_Bool) == sizeof (int))
	return &ffi_type_uint;
      abort ();
    case GO_FLOAT32:
      if (sizeof (float) == 4)
	return &ffi_type_float;
      abort ();
    case GO_FLOAT64:
      if (sizeof (double) == 8)
	return &ffi_type_double;
      abort ();
    case GO_COMPLEX64:
      if (sizeof (float) == 4)
	{
#ifdef FFI_TARGET_HAS_COMPLEX_TYPE
	  return &ffi_type_complex_float;
#else
	  return go_complex_to_ffi (&ffi_type_float);
#endif
	}
      abort ();
    case GO_COMPLEX128:
      if (sizeof (double) == 8)
	{
#ifdef FFI_TARGET_HAS_COMPLEX_TYPE
	  return &ffi_type_complex_double;
#else
	  return go_complex_to_ffi (&ffi_type_double);
#endif
	}
      abort ();
    case GO_INT16:
      return &ffi_type_sint16;
    case GO_INT32:
      return &ffi_type_sint32;
    case GO_INT64:
      return &ffi_type_sint64;
    case GO_INT8:
      return &ffi_type_sint8;
    case GO_INT:
      return sizeof (intgo) == 4 ? &ffi_type_sint32 : &ffi_type_sint64;
    case GO_UINT16:
      return &ffi_type_uint16;
    case GO_UINT32:
      return &ffi_type_uint32;
    case GO_UINT64:
      return &ffi_type_uint64;
    case GO_UINT8:
      return &ffi_type_uint8;
    case GO_UINT:
      return sizeof (uintgo) == 4 ? &ffi_type_uint32 : &ffi_type_uint64;
    case GO_UINTPTR:
      if (sizeof (void *) == 2)
	return &ffi_type_uint16;
      else if (sizeof (void *) == 4)
	return &ffi_type_uint32;
      else if (sizeof (void *) == 8)
	return &ffi_type_uint64;
      abort ();
    case GO_ARRAY:
      return go_array_to_ffi ((const struct __go_array_type *) descriptor);
    case GO_SLICE:
      return go_slice_to_ffi ((const struct __go_slice_type *) descriptor);
    case GO_STRUCT:
      return go_struct_to_ffi ((const struct __go_struct_type *) descriptor);
    case GO_STRING:
      return go_string_to_ffi ();
    case GO_INTERFACE:
      return go_interface_to_ffi ();
    case GO_CHAN:
    case GO_FUNC:
    case GO_MAP:
    case GO_PTR:
    case GO_UNSAFE_POINTER:
      /* These types are always pointers, and for FFI purposes nothing
	 else matters.  */
      return &ffi_type_pointer;
    default:
      abort ();
    }
}

/* Return the return type for a function, given the number of out
   parameters and their types.  */

static ffi_type *
go_func_return_ffi (const struct __go_func_type *func)
{
  int count;
  const struct __go_type_descriptor **types;
  ffi_type *ret;
  int i;

  count = func->__out.__count;
  if (count == 0)
    return &ffi_type_void;

  types = (const struct __go_type_descriptor **) func->__out.__values;

  if (count == 1)
    {

#if defined (__i386__) && !defined (__x86_64__)
      /* FFI does not support complex types.  On 32-bit x86, a
	 complex64 will be returned in %eax/%edx.  We normally tell
	 FFI that a complex64 is a struct of two floats.  On 32-bit
	 x86 a struct of two floats is returned via a hidden first
	 pointer parameter.  Fortunately we can make everything work
	 by pretending that complex64 is int64.  */
      if ((types[0]->__code & GO_CODE_MASK) == GO_COMPLEX64)
	return &ffi_type_sint64;
#endif

      return go_type_to_ffi (types[0]);
    }

  ret = (ffi_type *) __go_alloc (sizeof (ffi_type));
  ret->type = FFI_TYPE_STRUCT;
  ret->elements = (ffi_type **) __go_alloc ((count + 1) * sizeof (ffi_type *));
  for (i = 0; i < count; ++i)
    ret->elements[i] = go_type_to_ffi (types[i]);
  ret->elements[count] = NULL;
  return ret;
}

/* Build an ffi_cif structure for a function described by a
   __go_func_type structure.  */

void
__go_func_to_cif (const struct __go_func_type *func, _Bool is_interface,
		_Bool is_method, ffi_cif *cif)
{
  int num_params;
  const struct __go_type_descriptor **in_types;
  size_t num_args;
  ffi_type **args;
  int off;
  int i;
  ffi_type *rettype;
  ffi_status status;

  num_params = func->__in.__count;
  in_types = ((const struct __go_type_descriptor **)
	      func->__in.__values);

  num_args = num_params + (is_interface ? 1 : 0);
  args = (ffi_type **) __go_alloc (num_args * sizeof (ffi_type *));
  i = 0;
  off = 0;
  if (is_interface)
    {
      args[0] = &ffi_type_pointer;
      off = 1;
    }
  else if (is_method)
    {
      args[0] = &ffi_type_pointer;
      i = 1;
    }
  for (; i < num_params; ++i)
    args[i + off] = go_type_to_ffi (in_types[i]);

  rettype = go_func_return_ffi (func);

  status = ffi_prep_cif (cif, FFI_DEFAULT_ABI, num_args, rettype, args);
  __go_assert (status == FFI_OK);
}

#endif /* defined(USE_LIBFFI) */