glib/girffi.c

/* GObject introspection: Helper functions for ffi integration
 *
 * Copyright (C) 2008 Red Hat, Inc
 * Copyright (C) 2005 Matthias Clasen
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <sys/types.h>
#include <sys/mman.h>

#include <config.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include "girffi.h"
#include "girepository.h"
#include "girepository-private.h"

/**
 * gi_type_tag_get_ffi_type:
 * @tag: A #GITypeTag
 * @is_pointer: Whether or not this is a pointer type
 *
 * Returns: A #ffi_type corresponding to the platform default C ABI for @tag and @is_pointer.
 */
ffi_type *
gi_type_tag_get_ffi_type (GITypeTag   tag,
			  gboolean    is_pointer)
{
  switch (tag)
    {
    case GI_TYPE_TAG_BOOLEAN:
      return &ffi_type_uint;
    case GI_TYPE_TAG_INT8:
      return &ffi_type_sint8;
    case GI_TYPE_TAG_UINT8:
      return &ffi_type_uint8;
    case GI_TYPE_TAG_INT16:
      return &ffi_type_sint16;
    case GI_TYPE_TAG_UINT16:
      return &ffi_type_uint16;
    case GI_TYPE_TAG_INT32:
      return &ffi_type_sint32;
    case GI_TYPE_TAG_UINT32:
    case GI_TYPE_TAG_UNICHAR:
      return &ffi_type_uint32;
    case GI_TYPE_TAG_INT64:
      return &ffi_type_sint64;
    case GI_TYPE_TAG_UINT64:
      return &ffi_type_uint64;
    case GI_TYPE_TAG_GTYPE:
#if GLIB_SIZEOF_SIZE_T == 4
      return &ffi_type_uint32;
#elif GLIB_SIZEOF_SIZE_T == 8
      return &ffi_type_uint64;
#else
#  error "Unexpected size for size_t: not 4 or 8"
#endif
    case GI_TYPE_TAG_FLOAT:
      return &ffi_type_float;
    case GI_TYPE_TAG_DOUBLE:
      return &ffi_type_double;
    case GI_TYPE_TAG_UTF8:
    case GI_TYPE_TAG_FILENAME:
    case GI_TYPE_TAG_ARRAY:
    case GI_TYPE_TAG_INTERFACE:
    case GI_TYPE_TAG_GLIST:
    case GI_TYPE_TAG_GSLIST:
    case GI_TYPE_TAG_GHASH:
    case GI_TYPE_TAG_ERROR:
      return &ffi_type_pointer;
    case GI_TYPE_TAG_VOID:
      if (is_pointer)
        return &ffi_type_pointer;
      else
        return &ffi_type_void;
    }

  g_assert_not_reached ();

  return NULL;
}

/**
 * g_type_info_get_ffi_type:
 * @info: A #GITypeInfo
 *
 * Returns: A #ffi_type corresponding to the platform default C ABI for @info.
 */
ffi_type *
g_type_info_get_ffi_type (GITypeInfo *info)
{
  return gi_type_tag_get_ffi_type (g_type_info_get_tag (info), g_type_info_is_pointer (info));
}

/**
 * g_callable_info_get_ffi_arg_types:
 * @callable_info: a callable info from a typelib
 *
 * Return value: an array of ffi_type*. The array itself
 * should be freed using g_free() after use.
 */
static ffi_type **
g_callable_info_get_ffi_arg_types (GICallableInfo *callable_info)
{
    ffi_type **arg_types;
    gint n_args, i;

    g_return_val_if_fail (callable_info != NULL, NULL);

    n_args = g_callable_info_get_n_args (callable_info);

    arg_types = (ffi_type **) g_new0 (ffi_type *, n_args + 1);

    for (i = 0; i < n_args; ++i)
      {
        GIArgInfo *arg_info = g_callable_info_get_arg (callable_info, i);
        GITypeInfo *arg_type = g_arg_info_get_type (arg_info);
        arg_types[i] = g_type_info_get_ffi_type (arg_type);
        g_base_info_unref ((GIBaseInfo *)arg_info);
        g_base_info_unref ((GIBaseInfo *)arg_type);
      }
    arg_types[n_args] = NULL;

    return arg_types;
}

/**
 * g_callable_info_get_ffi_return_type:
 * @callable_info: a callable info from a typelib
 *
 * Fetches the ffi_type for a corresponding return value of
 * a #GICallableInfo
 * Return value: the ffi_type for the return value
 */
static ffi_type *
g_callable_info_get_ffi_return_type (GICallableInfo *callable_info)
{
  GITypeInfo *return_type;
  GITypeTag type_tag;
  ffi_type *return_ffi_type;

  g_return_val_if_fail (callable_info != NULL, NULL);

  return_type = g_callable_info_get_return_type (callable_info);
  type_tag = g_type_info_get_tag (return_type);
  return_ffi_type = g_type_info_get_ffi_type (return_type);
  g_base_info_unref((GIBaseInfo*)return_type);

  return return_ffi_type;
}

/**
 * g_function_info_prep_invoker:
 * @info: A #GIFunctionInfo
 * @invoker: Output invoker structure
 * @error: A #GError
 *
 * Initialize the caller-allocated @invoker structure with a cache
 * of information needed to invoke the C function corresponding to
 * @info with the platform's default ABI.
 *
 * A primary intent of this function is that a dynamic structure allocated
 * by a language binding could contain a #GIFunctionInvoker structure
 * inside the binding's function mapping.
 *
 * Returns: %TRUE on success, %FALSE otherwise with @error set.
 */
gboolean
g_function_info_prep_invoker (GIFunctionInfo       *info,
                              GIFunctionInvoker    *invoker,
                              GError              **error)
{
  const char *symbol;
  ffi_type *rtype;
  ffi_type **atypes;
  GITypeInfo *tinfo;
  GIArgInfo *ainfo;
  gboolean is_method;
  gboolean throws;
  gint n_args, n_invoke_args, i;

  g_return_val_if_fail (info != NULL, FALSE);
  g_return_val_if_fail (invoker != NULL, FALSE);

  symbol = g_function_info_get_symbol ((GIFunctionInfo*) info);

  if (!g_typelib_symbol (g_base_info_get_typelib((GIBaseInfo *) info),
                         symbol, &(invoker->native_address)))
    {
      g_set_error (error,
                   G_INVOKE_ERROR,
                   G_INVOKE_ERROR_SYMBOL_NOT_FOUND,
                   "Could not locate %s: %s", symbol, g_module_error ());

      return FALSE;
    }

  is_method = (g_function_info_get_flags (info) & GI_FUNCTION_IS_METHOD) != 0
    && (g_function_info_get_flags (info) & GI_FUNCTION_IS_CONSTRUCTOR) == 0;
  throws = g_function_info_get_flags (info) & GI_FUNCTION_THROWS;

  tinfo = g_callable_info_get_return_type ((GICallableInfo *)info);
  rtype = g_type_info_get_ffi_type (tinfo);
  g_base_info_unref ((GIBaseInfo *)tinfo);

  n_args = g_callable_info_get_n_args ((GICallableInfo *)info);
  if (is_method)
    n_invoke_args = n_args+1;
  else
    n_invoke_args = n_args;

  if (throws)
    /* Add an argument for the GError */
    n_invoke_args ++;

  /* TODO: avoid malloc here? */
  atypes = g_malloc0 (sizeof (ffi_type*) * n_invoke_args);

  if (is_method)
    {
      atypes[0] = &ffi_type_pointer;
    }
  for (i = 0; i < n_args; i++)
    {
      int offset = (is_method ? 1 : 0);
      ainfo = g_callable_info_get_arg ((GICallableInfo *)info, i);
      switch (g_arg_info_get_direction (ainfo))
        {
          case GI_DIRECTION_IN:
            tinfo = g_arg_info_get_type (ainfo);
            atypes[i+offset] = g_type_info_get_ffi_type (tinfo);
            g_base_info_unref ((GIBaseInfo *)tinfo);
            break;
          case GI_DIRECTION_OUT:
          case GI_DIRECTION_INOUT:
            atypes[i+offset] = &ffi_type_pointer;
    	    break;
          default:
            g_assert_not_reached ();
        }
      g_base_info_unref ((GIBaseInfo *)ainfo);
    }

  if (throws)
    {
      atypes[n_invoke_args - 1] = &ffi_type_pointer;
    }

  return ffi_prep_cif (&(invoker->cif), FFI_DEFAULT_ABI, n_invoke_args, rtype, atypes) == FFI_OK;
}

/**
 * g_function_info_invoker_destroy:
 * @invoker: A #GIFunctionInvoker
 *
 * Release all resources allocated for the internals of @invoker; callers
 * are responsible for freeing any resources allocated for the structure
 * itself however.
 */
void
g_function_invoker_destroy (GIFunctionInvoker    *invoker)
{
  g_free (invoker->cif.arg_types);
}

typedef struct {
  ffi_closure ffi_closure;
  gpointer writable_self;
} GIClosureWrapper;

/**
 * g_callable_info_prepare_closure:
 * @callable_info: a callable info from a typelib
 * @cif: a ffi_cif structure
 * @callback: the ffi callback
 * @user_data: data to be passed into the callback
 *
 * Prepares a callback for ffi invocation.
 *
 * Return value: the ffi_closure or NULL on error.
 * The return value should be freed by calling g_callable_info_free_closure().
 */
ffi_closure *
g_callable_info_prepare_closure (GICallableInfo       *callable_info,
                                 ffi_cif              *cif,
                                 GIFFIClosureCallback  callback,
                                 gpointer              user_data)
{
  gpointer exec_ptr;
  GIClosureWrapper *closure;
  ffi_status status;

  g_return_val_if_fail (callable_info != NULL, FALSE);
  g_return_val_if_fail (cif != NULL, FALSE);
  g_return_val_if_fail (callback != NULL, FALSE);

  closure = ffi_closure_alloc (sizeof (GIClosureWrapper), &exec_ptr);
  if (!closure)
    {
      g_warning ("could not allocate closure\n");
      return NULL;
    }
  closure->writable_self = closure;

  status = ffi_prep_cif (cif, FFI_DEFAULT_ABI,
                         g_callable_info_get_n_args (callable_info),
                         g_callable_info_get_ffi_return_type (callable_info),
                         g_callable_info_get_ffi_arg_types (callable_info));
  if (status != FFI_OK)
    {
      g_warning ("ffi_prep_cif failed: %d\n", status);
      ffi_closure_free (closure);
      return NULL;
    }

  status = ffi_prep_closure_loc (&closure->ffi_closure, cif, callback, user_data, exec_ptr);
  if (status != FFI_OK)
    {
      g_warning ("ffi_prep_closure failed: %d\n", status);
      ffi_closure_free (closure);
      return NULL;
    }

  /* Return exec_ptr, which points to the same underlying memory as
   * closure, but via an executable-non-writable mapping.
   */
  return exec_ptr;
}

/**
 * g_callable_info_free_closure:
 * @callable_info: a callable info from a typelib
 * @closure: ffi closure
 *
 * Frees a ffi_closure returned from g_callable_info_prepare_closure()
 */
void
g_callable_info_free_closure (GICallableInfo *callable_info,
                              ffi_closure    *closure)
{
  GIClosureWrapper *wrapper = (GIClosureWrapper *)closure;

  ffi_closure_free (wrapper->writable_self);
}