path: root/libgfortran/intrinsics/iso_c_binding.c

/* Implementation of the ISO_C_BINDING library helper functions.
   Copyright (C) 2007 Free Software Foundation, Inc.
   Contributed by Christopher Rickett.

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file.  (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)

Libgfortran 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 General Public License for more details.

You should have received a copy of the GNU General Public
License along with libgfortran; see the file COPYING.  If not,
write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */


/**
 * Implement the functions and subroutines provided by the intrinsic
 * iso_c_binding module.
 * --Rickett, 12.13.05
 */

#include <stdlib.h>

#include "libgfortran.h"
#include "iso_c_binding.h"


/* Set the fields of a Fortran pointer descriptor to point to the
   given C address.  It uses c_f_pointer_u0 for the common
   fields, and will set up the information necessary if this C address
   is to an array (i.e., offset, type, element size).  The parameter
   c_ptr_in represents the C address to have Fortran point to.  The
   parameter f_ptr_out is the Fortran pointer to associate with the C
   address.  The parameter shape is a one-dimensional array of integers
   specifying the upper bound(s) of the array pointed to by the given C
   address, if applicable.  The shape parameter is optional in Fortran,
   which will cause it to come in here as NULL.  The parameter type is
   the type of the data being pointed to (i.e.,libgfortran.h). The
   elem_size parameter is the size, in bytes, of the data element being
   pointed to.  If the address is for an array, then the size needs to
   be the size of a single element (i.e., for an array of doubles, it
   needs to be the number of bytes for the size of one double).  */

void
ISO_C_BINDING_PREFIX (c_f_pointer) (void * c_ptr_in,
                                    gfc_array_void *f_ptr_out,
                                    const array_t *shape,
                                    int type, int elemSize)
{
  if (shape != NULL)
    {
      f_ptr_out->offset = 0;
      /* Set the necessary dtype field for all pointers.  */
      f_ptr_out->dtype = 0;
      /* Put in the element size.  */
      f_ptr_out->dtype = f_ptr_out->dtype |
        (elemSize << GFC_DTYPE_SIZE_SHIFT);
      /* Set the data type (e.g., GFC_DTYPE_INTEGER).  */
      f_ptr_out->dtype = f_ptr_out->dtype | (type << GFC_DTYPE_TYPE_SHIFT);
    }
  
  /* Use the generic version of c_f_pointer to set common fields.  */
  ISO_C_BINDING_PREFIX (c_f_pointer_u0) (c_ptr_in, f_ptr_out, shape);
  
  return;
}


/* A generic function to set the common fields of all descriptors, no
   matter whether it's to a scalar or an array.  Fields set are: data,
   and if appropriate, rank, offset, dim[*].lbound, dim[*].ubound, and
   dim[*].stride.  Parameter shape is a rank 1 array of integers
   containing the upper bound of each dimension of what f_ptr_out
   points to.  The length of this array must be EXACTLY the rank of
   what f_ptr_out points to, as required by the draft (J3/04-007).  If
   f_ptr_out points to a scalar, then this parameter will be NULL.  */

void
ISO_C_BINDING_PREFIX (c_f_pointer_u0) (void * c_ptr_in,
                                       gfc_array_void *f_ptr_out,
                                       const array_t *shape)
{
  int i = 0;
  int shapeSize = 0;

  GFC_DESCRIPTOR_DATA (f_ptr_out) = c_ptr_in;

  if (shape != NULL)
    {
      f_ptr_out->offset = 0;
      shapeSize = 0;
      
      /* shape's length (rank of the output array) */
      shapeSize = shape->dim[0].ubound + 1 - shape->dim[0].lbound;
      for (i = 0; i < shapeSize; i++)
        {
          /* Lower bound is 1, as specified by the draft.  */
          f_ptr_out->dim[i].lbound = 1;
          f_ptr_out->dim[i].ubound = ((int *)(shape->data))[i];
        }

      /* Set the offset and strides.  */
      /* offset is (sum of (dim[i].lbound * dim[i].stride) for all
         dims) the -1 means we'll back the data pointer up that much
         perhaps we could just realign the data pointer and not change
         the offset?  */
      f_ptr_out->dim[0].stride = 1;
      f_ptr_out->offset = f_ptr_out->dim[0].lbound * f_ptr_out->dim[0].stride;
      for (i = 1; i < shapeSize; i++)
        {
          f_ptr_out->dim[i].stride = (f_ptr_out->dim[i-1].ubound+1)
            - f_ptr_out->dim[i-1].lbound;
          f_ptr_out->offset += f_ptr_out->dim[i].lbound
            * f_ptr_out->dim[i].stride;
        }

      f_ptr_out->offset *= -1;

      /* All we know is the rank, so set it, leaving the rest alone.
         Make NO assumptions about the state of dtype coming in!  If we
         shift right by TYPE_SHIFT bits we'll throw away the existing
         rank.  Then, shift left by the same number to shift in zeros
         and or with the new rank.  */
      f_ptr_out->dtype = ((f_ptr_out->dtype >> GFC_DTYPE_TYPE_SHIFT)
                          << GFC_DTYPE_TYPE_SHIFT) | shapeSize;
    }
  
  return;
}


/* Sets the descriptor fields for a Fortran pointer to a derived type,
   using c_f_pointer_u0 for the majority of the work.  */

void
ISO_C_BINDING_PREFIX (c_f_pointer_d0) (void * c_ptr_in,
                                       gfc_array_void *f_ptr_out,
                                       const array_t *shape)
{
  /* Set the common fields.  */
  ISO_C_BINDING_PREFIX (c_f_pointer_u0) (c_ptr_in, f_ptr_out, shape);

  /* Preserve the size and rank bits, but reset the type.  */
  if (shape != NULL)
    {
      f_ptr_out->dtype = f_ptr_out->dtype & (~GFC_DTYPE_TYPE_MASK);
      f_ptr_out->dtype = f_ptr_out->dtype |
        (GFC_DTYPE_DERIVED << GFC_DTYPE_TYPE_SHIFT);
    }

  return;
}


/* This function will change, once there is an actual f90 type for the
   procedure pointer.  */

void
ISO_C_BINDING_PREFIX (c_f_procpointer) (void * c_ptr_in,
                                        gfc_array_void *f_ptr_out)
{
  GFC_DESCRIPTOR_DATA(f_ptr_out) = c_ptr_in;
   
  return;
}


/* Test if the given c_ptr is associated or not.  This function is
   called if the user only supplied one c_ptr parameter to the
   c_associated function.  The second argument is optional, and the
   Fortran compiler will resolve the function to this version if only
   one arg was given.  Associated here simply means whether or not the
   c_ptr is NULL or not.  */

GFC_LOGICAL_4
ISO_C_BINDING_PREFIX (c_associated_1) (void * c_ptr_in_1)
{
  if (c_ptr_in_1 != NULL)
    return 1;
  else
    return 0;
}

/* Test if the two c_ptr arguments are associated with one another.
   This version of the c_associated function is called if the user
   supplied two c_ptr args in the Fortran source.  According to the
   draft standard (J3/04-007), if c_ptr_in_1 is NULL, the two pointers
   are NOT associated.  If c_ptr_in_1 is non-NULL and it is not equal
   to c_ptr_in_2, then either c_ptr_in_2 is NULL or is associated with
   another address; either way, the two pointers are not associated
   with each other then.  */

GFC_LOGICAL_4
ISO_C_BINDING_PREFIX (c_associated_2) (void * c_ptr_in_1, void * c_ptr_in_2)
{
  /* Since we have the second arg, if it doesn't equal the first,
     return false; true otherwise.  However, if the first one is null,
     then return false; otherwise compare the two ptrs for equality.  */
  if (c_ptr_in_1 == NULL)
    return 0;
  else if (c_ptr_in_1 != c_ptr_in_2)
    return 0;
  else
    return 1;
}


/* Return the C address of the given Fortran allocatable object.  */

void *
ISO_C_BINDING_PREFIX (c_loc) (void *f90_obj)
{
  if (f90_obj == NULL)
    {
      runtime_error ("C_LOC: Attempt to get C address for Fortran object"
                     " that has not been allocated or associated");
      abort ();
    }
   
  /* the "C" address should be the address of the object in Fortran */
  return f90_obj;
}


/*  Return the C address of the given Fortran procedure.  This
    routine is expected to return a derived type of type C_FUNPTR,
    which represents the C address of the given Fortran object.  */

void *
ISO_C_BINDING_PREFIX (c_funloc) (void *f90_obj)
{
  if (f90_obj == NULL)
    {
      runtime_error ("C_LOC: Attempt to get C address for Fortran object"
                     " that has not been allocated or associated");
      abort ();
    }

  /* the "C" address should be the address of the object in Fortran */
  return f90_obj;
}