[bpt/guile.git] / libguile / foreign.c

/* Copyright (C) 2010  Free Software Foundation, Inc.
 * 
 * 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 3 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#if HAVE_CONFIG_H
#  include <config.h>
#endif

#include <ffi.h>

#include <alignof.h>
#include <string.h>
#include "libguile/_scm.h"
#include "libguile/bytevectors.h"
#include "libguile/instructions.h"
#include "libguile/foreign.h"

\f

SCM_SYMBOL (sym_void, "void");
SCM_SYMBOL (sym_float, "float");
SCM_SYMBOL (sym_double, "double");
SCM_SYMBOL (sym_uint8, "uint8");
SCM_SYMBOL (sym_int8, "int8");
SCM_SYMBOL (sym_uint16, "uint16");
SCM_SYMBOL (sym_int16, "int16");
SCM_SYMBOL (sym_uint32, "uint32");
SCM_SYMBOL (sym_int32, "int32");
SCM_SYMBOL (sym_uint64, "uint64");
SCM_SYMBOL (sym_int64, "int64");

/* that's for pointers, you know. */
SCM_SYMBOL (sym_asterisk, "*");


static SCM cif_to_procedure (SCM cif, SCM func_ptr);


static SCM foreign_weak_refs = SCM_BOOL_F;

static void
register_weak_reference (SCM from, SCM to)
{
  scm_hashq_set_x (foreign_weak_refs, from, to);
}
    
static void
foreign_finalizer_trampoline (GC_PTR ptr, GC_PTR data)
{
  scm_t_foreign_finalizer finalizer = data;
  finalizer (SCM_FOREIGN_POINTER (PTR2SCM (ptr), void));
}

SCM
scm_take_foreign_pointer (scm_t_foreign_type type, void *ptr, size_t len,
                          scm_t_foreign_finalizer finalizer)
{
  SCM ret;
  scm_t_bits word0;
    
  word0 = (scm_t_bits)(scm_tc7_foreign | (type<<8)
                       | (finalizer ? (1<<16) : 0) | (len<<17));
  if (SCM_UNLIKELY ((word0 >> 17) != len))
    scm_out_of_range ("scm_take_foreign_pointer", scm_from_size_t (len));
    
  ret = PTR2SCM (scm_gc_malloc_pointerless (sizeof (scm_t_bits) * 2,
                                            "foreign"));
  SCM_SET_CELL_WORD_0 (ret, word0);
  SCM_SET_CELL_WORD_1 (ret, (scm_t_bits)ptr);

  if (finalizer)
    {
      /* Register a finalizer for the newly created instance.  */
      GC_finalization_proc prev_finalizer;
      GC_PTR prev_finalizer_data;
      GC_REGISTER_FINALIZER_NO_ORDER (SCM2PTR (ret),
                                      foreign_finalizer_trampoline,
                                      finalizer,
                                      &prev_finalizer,
                                      &prev_finalizer_data);
    }

  return ret;
}

SCM_DEFINE (scm_foreign_ref, "foreign-ref", 1, 0, 0,
	    (SCM foreign),
	    "Reference the foreign value wrapped by @var{foreign}.\n\n"
            "The value will be referenced according to its type.")
#define FUNC_NAME s_scm_foreign_ref
{
  scm_t_foreign_type ftype;
  scm_t_uint8 *ptr;

  SCM_VALIDATE_FOREIGN (1, foreign);
  ptr = SCM_FOREIGN_POINTER (foreign, scm_t_uint8);
  ftype = SCM_FOREIGN_TYPE (foreign);
  
  /* FIXME: is there a window in which we can see ptr but not foreign? */
  /* FIXME: accessing unaligned pointers */
  switch (ftype)
    {
    case SCM_FOREIGN_TYPE_VOID:
      return scm_from_ulong ((unsigned long)ptr);
    case SCM_FOREIGN_TYPE_FLOAT:
      return scm_from_double (*(float*)ptr);
    case SCM_FOREIGN_TYPE_DOUBLE:
      return scm_from_double (*(double*)ptr);
    case SCM_FOREIGN_TYPE_UINT8:
      return scm_from_uint8 (*(scm_t_uint8*)ptr);
    case SCM_FOREIGN_TYPE_INT8:
      return scm_from_int8 (*(scm_t_int8*)ptr);
    case SCM_FOREIGN_TYPE_UINT16:
      return scm_from_uint16 (*(scm_t_uint16*)ptr);
    case SCM_FOREIGN_TYPE_INT16:
      return scm_from_int16 (*(scm_t_int16*)ptr);
    case SCM_FOREIGN_TYPE_UINT32:
      return scm_from_uint32 (*(scm_t_uint32*)ptr);
    case SCM_FOREIGN_TYPE_INT32:
      return scm_from_int32 (*(scm_t_int32*)ptr);
    case SCM_FOREIGN_TYPE_UINT64:
      return scm_from_uint64 (*(scm_t_uint64*)ptr);
    case SCM_FOREIGN_TYPE_INT64:
      return scm_from_int64 (*(scm_t_int64*)ptr);
    default:
      scm_wrong_type_arg_msg (FUNC_NAME, 1, foreign, "foreign");
    }
}
#undef FUNC_NAME

SCM_DEFINE (scm_foreign_set_x, "foreign-set!", 2, 0, 0,
	    (SCM foreign, SCM val),
	    "Set the foreign value wrapped by @var{foreign}.\n\n"
            "The value will be set according to its type.")
#define FUNC_NAME s_scm_foreign_set_x
{
  scm_t_foreign_type ftype;
  scm_t_uint8 *ptr;

  SCM_VALIDATE_FOREIGN (1, foreign);
  ptr = SCM_FOREIGN_POINTER (foreign, scm_t_uint8);
  ftype = SCM_FOREIGN_TYPE (foreign);

  /* FIXME: is there a window in which we can see ptr but not foreign? */
  /* FIXME: unaligned access */
  switch (ftype)
    {
    case SCM_FOREIGN_TYPE_VOID:
      SCM_SET_CELL_WORD_1 (foreign, scm_to_ulong (val));
      break;
    case SCM_FOREIGN_TYPE_FLOAT:
      *(float*)ptr = scm_to_double (val);
      break;
    case SCM_FOREIGN_TYPE_DOUBLE:
      *(double*)ptr = scm_to_double (val);
      break;
    case SCM_FOREIGN_TYPE_UINT8:
      *(scm_t_uint8*)ptr = scm_to_uint8 (val);
      break;
    case SCM_FOREIGN_TYPE_INT8:
      *(scm_t_int8*)ptr = scm_to_int8 (val);
      break;
    case SCM_FOREIGN_TYPE_UINT16:
      *(scm_t_uint16*)ptr = scm_to_uint16 (val);
      break;
    case SCM_FOREIGN_TYPE_INT16:
      *(scm_t_int16*)ptr = scm_to_int16 (val);
      break;
    case SCM_FOREIGN_TYPE_UINT32:
      *(scm_t_uint32*)ptr = scm_to_uint32 (val);
      break;
    case SCM_FOREIGN_TYPE_INT32:
      *(scm_t_int32*)ptr = scm_to_int32 (val);
      break;
    case SCM_FOREIGN_TYPE_UINT64:
      *(scm_t_uint64*)ptr = scm_to_uint64 (val);
      break;
    case SCM_FOREIGN_TYPE_INT64:
      *(scm_t_int64*)ptr = scm_to_int64 (val);
      break;
    default:
      scm_wrong_type_arg_msg (FUNC_NAME, 1, val, "foreign");
    }

  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_foreign_to_bytevector, "foreign->bytevector", 1, 3, 0,
	    (SCM foreign, SCM uvec_type, SCM offset, SCM len),
	    "Return a bytevector aliasing the memory pointed to by\n"
            "@var{foreign}.\n\n"
            "@var{foreign} must be a void pointer, a foreign whose type is\n"
            "@var{void}. By default, the resulting bytevector will alias\n"
            "all of the memory pointed to by @var{foreign}, from beginning\n"
            "to end, treated as a @code{vu8} array.\n\n"
            "The user may specify an alternate default interpretation for\n"
            "the memory by passing the @var{uvec_type} argument, to indicate\n"
            "that the memory is an array of elements of that type.\n"
            "@var{uvec_type} should be something that\n"
            "@code{uniform-vector-element-type} would return, like @code{f32}\n"
            "or @code{s16}.\n\n"
            "Users may also specify that the bytevector should only alias a\n"
            "subset of the memory, by specifying @var{offset} and @var{len}\n"
            "arguments.")
#define FUNC_NAME s_scm_foreign_to_bytevector
{
  SCM ret;
  scm_t_int8 *ptr;
  size_t boffset, blen;
  scm_t_array_element_type btype;

  SCM_VALIDATE_FOREIGN_TYPED (1, foreign, VOID);
  ptr = SCM_FOREIGN_POINTER (foreign, scm_t_int8);
  
  if (SCM_UNBNDP (uvec_type))
    btype = SCM_ARRAY_ELEMENT_TYPE_VU8;
  else
    {
      int i;
      for (i = 0; i <= SCM_ARRAY_ELEMENT_TYPE_LAST; i++)
        if (scm_is_eq (uvec_type, scm_i_array_element_types[i]))
          break;
      switch (i)
        {
        case SCM_ARRAY_ELEMENT_TYPE_VU8:
        case SCM_ARRAY_ELEMENT_TYPE_U8:
        case SCM_ARRAY_ELEMENT_TYPE_S8:
        case SCM_ARRAY_ELEMENT_TYPE_U16:
        case SCM_ARRAY_ELEMENT_TYPE_S16:
        case SCM_ARRAY_ELEMENT_TYPE_U32:
        case SCM_ARRAY_ELEMENT_TYPE_S32:
        case SCM_ARRAY_ELEMENT_TYPE_U64:
        case SCM_ARRAY_ELEMENT_TYPE_S64:
        case SCM_ARRAY_ELEMENT_TYPE_F32:
        case SCM_ARRAY_ELEMENT_TYPE_F64:
        case SCM_ARRAY_ELEMENT_TYPE_C32:
        case SCM_ARRAY_ELEMENT_TYPE_C64:
          btype = i;
          break;
        default:
          scm_wrong_type_arg_msg (FUNC_NAME, SCM_ARG1, uvec_type,
                                  "uniform vector type");
        }
    }
  
  if (SCM_UNBNDP (offset))
    boffset = 0;
  else if (SCM_FOREIGN_LEN (foreign))
    boffset = scm_to_unsigned_integer (offset, 0,
                                       SCM_FOREIGN_LEN (foreign) - 1);
  else
    boffset = scm_to_size_t (offset);

  if (SCM_UNBNDP (len))
    {
      if (SCM_FOREIGN_LEN (foreign))
        blen = SCM_FOREIGN_LEN (foreign) - boffset;
      else
        scm_misc_error (FUNC_NAME,
                        "length needed to convert foreign pointer to bytevector",
                        SCM_EOL);
    }
  else
    {
      if (SCM_FOREIGN_LEN (foreign))
        blen = scm_to_unsigned_integer (len, 0,
                                        SCM_FOREIGN_LEN (foreign) - boffset);
      else
        blen = scm_to_size_t (len);
    }

  ret = scm_c_take_typed_bytevector (ptr + boffset, blen, btype);
  register_weak_reference (ret, foreign);
  return ret;
}
#undef FUNC_NAME

SCM_DEFINE (scm_bytevector_to_foreign, "bytevector->foreign", 1, 2, 0,
	    (SCM bv, SCM offset, SCM len),
	    "Return a foreign pointer aliasing the memory pointed to by\n"
            "@var{bv}.\n\n"
            "The resulting foreign will be a void pointer, a foreign whose\n"
            "type is @code{void}. By default it will alias all of the\n"
            "memory pointed to by @var{bv}, from beginning to end.\n\n"
            "Users may explicily specify that the foreign should only alias a\n"
            "subset of the memory, by specifying @var{offset} and @var{len}\n"
            "arguments.")
#define FUNC_NAME s_scm_bytevector_to_foreign
{
  SCM ret;
  scm_t_int8 *ptr;
  size_t boffset, blen;

  SCM_VALIDATE_BYTEVECTOR (1, bv);
  ptr = SCM_BYTEVECTOR_CONTENTS (bv);
  
  if (SCM_UNBNDP (offset))
    boffset = 0;
  else
    boffset = scm_to_unsigned_integer (offset, 0,
                                       SCM_BYTEVECTOR_LENGTH (bv) - 1);

  if (SCM_UNBNDP (len))
    blen = SCM_BYTEVECTOR_LENGTH (bv) - boffset;
  else
    blen = scm_to_unsigned_integer (len, 0,
                                    SCM_BYTEVECTOR_LENGTH (bv) - boffset);

  ret = scm_take_foreign_pointer (SCM_FOREIGN_TYPE_VOID, ptr + boffset, blen,
                                  NULL);
  register_weak_reference (ret, bv);
  return ret;
}
#undef FUNC_NAME

SCM_DEFINE (scm_foreign_set_finalizer_x, "foreign-set-finalizer!", 2, 0, 0,
            (SCM foreign, SCM finalizer),
            "Arrange for the C procedure wrapped by @var{finalizer} to be\n"
            "called on the pointer wrapped by @var{foreign} when @var{foreign}\n"
            "becomes unreachable. Note: the C procedure should not call into\n"
            "Scheme. If you need a Scheme finalizer, use guardians.")
#define FUNC_NAME s_scm_foreign_set_finalizer_x
{
  void *c_finalizer;
  GC_finalization_proc prev_finalizer;
  GC_PTR prev_finalizer_data;

  SCM_VALIDATE_FOREIGN_TYPED (1, foreign, VOID);
  SCM_VALIDATE_FOREIGN_TYPED (2, finalizer, VOID);
  
  c_finalizer = SCM_FOREIGN_POINTER (finalizer, void);

  SCM_SET_CELL_WORD_0 (foreign, SCM_CELL_WORD_0 (foreign) | (1<<16));

  GC_REGISTER_FINALIZER_NO_ORDER (SCM2PTR (foreign),
                                  foreign_finalizer_trampoline,
                                  c_finalizer,
                                  &prev_finalizer,
                                  &prev_finalizer_data);

  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

\f

void
scm_i_foreign_print (SCM foreign, SCM port, scm_print_state *pstate)
{
  scm_puts ("#<foreign ", port);
  switch (SCM_FOREIGN_TYPE (foreign))
    {
    case SCM_FOREIGN_TYPE_FLOAT:
      scm_puts ("float ", port);
      break;
    case SCM_FOREIGN_TYPE_DOUBLE:
      scm_puts ("double ", port);
      break;
    case SCM_FOREIGN_TYPE_UINT8:
      scm_puts ("uint8 ", port);
      break;
    case SCM_FOREIGN_TYPE_INT8:
      scm_puts ("int8 ", port);
      break;
    case SCM_FOREIGN_TYPE_UINT16:
      scm_puts ("uint16 ", port);
      break;
    case SCM_FOREIGN_TYPE_INT16:
      scm_puts ("int16 ", port);
      break;
    case SCM_FOREIGN_TYPE_UINT32:
      scm_puts ("uint32 ", port);
      break;
    case SCM_FOREIGN_TYPE_INT32:
      scm_puts ("int32 ", port);
      break;
    case SCM_FOREIGN_TYPE_UINT64:
      scm_puts ("uint64 ", port);
      break;
    case SCM_FOREIGN_TYPE_INT64:
      scm_puts ("int64 ", port);
      break;
    case SCM_FOREIGN_TYPE_VOID:
      scm_puts ("pointer ", port);
      break;
    default:
      scm_wrong_type_arg_msg ("%print-foreign", 1, foreign, "foreign");
    }
  scm_display (scm_foreign_ref (foreign), port);
  scm_putc ('>', port);
}

\f


#define ROUND_UP(len,align) (align?(((len-1)|(align-1))+1):len)

SCM_DEFINE (scm_alignof, "alignof", 1, 0, 0, (SCM type), "")
#define FUNC_NAME s_scm_alignof
{
  if (SCM_I_INUMP (type))
    {
      switch (SCM_I_INUM (type))
        {
        case SCM_FOREIGN_TYPE_FLOAT:
          return scm_from_size_t (alignof (float));
        case SCM_FOREIGN_TYPE_DOUBLE:
          return scm_from_size_t (alignof (double));
        case SCM_FOREIGN_TYPE_UINT8:
          return scm_from_size_t (alignof (scm_t_uint8));
        case SCM_FOREIGN_TYPE_INT8:
          return scm_from_size_t (alignof (scm_t_int8));
        case SCM_FOREIGN_TYPE_UINT16:
          return scm_from_size_t (alignof (scm_t_uint16));
        case SCM_FOREIGN_TYPE_INT16:
          return scm_from_size_t (alignof (scm_t_int16));
        case SCM_FOREIGN_TYPE_UINT32:
          return scm_from_size_t (alignof (scm_t_uint32));
        case SCM_FOREIGN_TYPE_INT32:
          return scm_from_size_t (alignof (scm_t_int32));
        case SCM_FOREIGN_TYPE_UINT64:
          return scm_from_size_t (alignof (scm_t_uint64));
        case SCM_FOREIGN_TYPE_INT64:
          return scm_from_size_t (alignof (scm_t_int64));
        default:
          scm_wrong_type_arg (FUNC_NAME, 1, type);
        }
    }
  else if (scm_is_eq (type, sym_asterisk))
    /* a pointer */
    return scm_from_size_t (alignof (void*));
  else if (scm_is_pair (type))
    /* a struct, yo */
    return scm_alignof (scm_car (type));
  else
    scm_wrong_type_arg (FUNC_NAME, 1, type);
}
#undef FUNC_NAME

SCM_DEFINE (scm_sizeof, "sizeof", 1, 0, 0, (SCM type), "")
#define FUNC_NAME s_scm_sizeof
{
  if (SCM_I_INUMP (type))
    {
      switch (SCM_I_INUM (type))
        {
        case SCM_FOREIGN_TYPE_FLOAT:
          return scm_from_size_t (sizeof (float));
        case SCM_FOREIGN_TYPE_DOUBLE:
          return scm_from_size_t (sizeof (double));
        case SCM_FOREIGN_TYPE_UINT8:
          return scm_from_size_t (sizeof (scm_t_uint8));
        case SCM_FOREIGN_TYPE_INT8:
          return scm_from_size_t (sizeof (scm_t_int8));
        case SCM_FOREIGN_TYPE_UINT16:
          return scm_from_size_t (sizeof (scm_t_uint16));
        case SCM_FOREIGN_TYPE_INT16:
          return scm_from_size_t (sizeof (scm_t_int16));
        case SCM_FOREIGN_TYPE_UINT32:
          return scm_from_size_t (sizeof (scm_t_uint32));
        case SCM_FOREIGN_TYPE_INT32:
          return scm_from_size_t (sizeof (scm_t_int32));
        case SCM_FOREIGN_TYPE_UINT64:
          return scm_from_size_t (sizeof (scm_t_uint64));
        case SCM_FOREIGN_TYPE_INT64:
          return scm_from_size_t (sizeof (scm_t_int64));
        default:
          scm_wrong_type_arg (FUNC_NAME, 1, type);
        }
    }
  else if (scm_is_eq (type, sym_asterisk))
    /* a pointer */
    return scm_from_size_t (sizeof (void*));
  else if (scm_is_pair (type))
    {
      /* a struct */
      size_t off = 0;
      while (scm_is_pair (type))
        {
          off = ROUND_UP (off, scm_to_size_t (scm_alignof (scm_car (type))));
          off += scm_to_size_t (scm_sizeof (scm_car (type)));
          type = scm_cdr (type);
        }
      return scm_from_size_t (off);
    }
  else
    scm_wrong_type_arg (FUNC_NAME, 1, type);
}
#undef FUNC_NAME


/* return 1 on success, 0 on failure */
static int
parse_ffi_type (SCM type, int return_p, long *n_structs, long *n_struct_elts)
{
  if (SCM_I_INUMP (type))
    {
      if ((SCM_I_INUM (type) < 0 )
          || (SCM_I_INUM (type) > SCM_FOREIGN_TYPE_LAST))
        return 0;
      else if (SCM_I_INUM (type) == SCM_FOREIGN_TYPE_VOID && !return_p)
        return 0;
      else
        return 1;
    }
  else if (scm_is_eq (type, sym_asterisk))
    /* a pointer */
    return 1;
  else
    {
      long len;
      
      len = scm_ilength (type);
      if (len < 1)
        return 0;
      while (len--)
        {
          if (!parse_ffi_type (scm_car (type), 0, n_structs, n_struct_elts))
            return 0;
          (*n_struct_elts)++;
          type = scm_cdr (type);
        }
      (*n_structs)++;
      return 1;
    }
}
    
static void
fill_ffi_type (SCM type, ffi_type *ftype, ffi_type ***type_ptrs,
               ffi_type **types)
{
  if (SCM_I_INUMP (type))
    {
      switch (SCM_I_INUM (type))
        {
        case SCM_FOREIGN_TYPE_FLOAT:
          *ftype = ffi_type_float;
          return;
        case SCM_FOREIGN_TYPE_DOUBLE:
          *ftype = ffi_type_double;
          return;
        case SCM_FOREIGN_TYPE_UINT8:
          *ftype = ffi_type_uint8;
          return;
        case SCM_FOREIGN_TYPE_INT8:
          *ftype = ffi_type_sint8;
          return;
        case SCM_FOREIGN_TYPE_UINT16:
          *ftype = ffi_type_uint16;
          return;
        case SCM_FOREIGN_TYPE_INT16:
          *ftype = ffi_type_sint16;
          return;
        case SCM_FOREIGN_TYPE_UINT32:
          *ftype = ffi_type_uint32;
          return;
        case SCM_FOREIGN_TYPE_INT32:
          *ftype = ffi_type_sint32;
          return;
        case SCM_FOREIGN_TYPE_UINT64:
          *ftype = ffi_type_uint64;
          return;
        case SCM_FOREIGN_TYPE_INT64:
          *ftype = ffi_type_sint64;
          return;
        case SCM_FOREIGN_TYPE_VOID:
          *ftype = ffi_type_void;
          return;
        default:
          scm_wrong_type_arg_msg ("make-foreign-function", 0, type,
                                  "foreign type");
        }
    }
  else if (scm_is_eq (type, sym_asterisk))
    /* a pointer */
    {
      *ftype = ffi_type_pointer;
      return;
    }
  else
    {
      long i, len;
      
      len = scm_ilength (type);

      ftype->size = 0;
      ftype->alignment = 0;
      ftype->type = FFI_TYPE_STRUCT;
      ftype->elements = *type_ptrs;
      *type_ptrs += len + 1;

      for (i = 0; i < len; i++)
        {
          ftype->elements[i] = *types;
          *types += 1;
          fill_ffi_type (scm_car (type), ftype->elements[i],
                         type_ptrs, types);
          type = scm_cdr (type);
        }
      ftype->elements[i] = NULL;
    }
}
    
SCM_DEFINE (scm_make_foreign_function, "make-foreign-function", 3, 0, 0,
            (SCM return_type, SCM func_ptr, SCM arg_types),
            "foo")
#define FUNC_NAME s_scm_make_foreign_function
{
  SCM walk, scm_cif;
  long i, nargs, n_structs, n_struct_elts;
  size_t cif_len;
  char *mem;
  ffi_cif *cif;
  ffi_type **type_ptrs;
  ffi_type *types;
  
  SCM_VALIDATE_FOREIGN_TYPED (2, func_ptr, VOID);
  nargs = scm_ilength (arg_types);
  SCM_ASSERT (nargs >= 0, arg_types, 3, FUNC_NAME);
  /* fixme: assert nargs < 1<<32 */
  n_structs = n_struct_elts = 0;

  /* For want of talloc, we're going to have to do this in two passes: first we
     figure out how much memory is needed for all types, then we allocate the
     cif and the types all in one block. */
  if (!parse_ffi_type (return_type, 1, &n_structs, &n_struct_elts))
    scm_wrong_type_arg (FUNC_NAME, 1, return_type);
  for (walk = arg_types; scm_is_pair (walk); walk = scm_cdr (walk))
    if (!parse_ffi_type (scm_car (walk), 0, &n_structs, &n_struct_elts))
      scm_wrong_type_arg (FUNC_NAME, 3, scm_car (walk));
  
  /* the memory: with space for the cif itself */
  cif_len = sizeof (ffi_cif);

  /* then ffi_type pointers: one for each arg, one for each struct
     element, and one for each struct (for null-termination) */
  cif_len = (ROUND_UP (cif_len, alignof(void*))
             + (nargs + n_structs + n_struct_elts)*sizeof(void*));
  
  /* then the ffi_type structs themselves, one per arg and struct element, and
     one for the return val */
  cif_len = (ROUND_UP (cif_len, alignof(ffi_type))
             + (nargs + n_struct_elts + 1)*sizeof(ffi_type));
  
  mem = scm_malloc (cif_len);
  scm_cif = scm_take_foreign_pointer (SCM_FOREIGN_TYPE_VOID, mem, cif_len, free);
  cif = (ffi_cif*)mem;
  /* reuse cif_len to walk through the mem */
  cif_len = ROUND_UP (sizeof (ffi_cif), alignof(void*));
  type_ptrs = (ffi_type**)(mem + cif_len);
  cif_len = ROUND_UP (cif_len
                      + (nargs + n_structs + n_struct_elts)*sizeof(void*),
                      alignof(ffi_type));
  types = (ffi_type*)(mem + cif_len);
  
  /* whew. now knit the pointers together. */
  cif->rtype = types++;
  fill_ffi_type (return_type, cif->rtype, &type_ptrs, &types);
  cif->arg_types = type_ptrs;
  type_ptrs += nargs;
  for (walk = arg_types, i = 0; scm_is_pair (walk); walk = scm_cdr (walk), i++)
    {
      cif->arg_types[i] = types++;
      fill_ffi_type (scm_car (walk), cif->arg_types[i], &type_ptrs, &types);
    }

  /* round out the cif, and we're done. */
  cif->abi = FFI_DEFAULT_ABI;
  cif->nargs = nargs;
  cif->bytes = 0;
  cif->flags = 0;
  
  if (FFI_OK != ffi_prep_cif (cif, FFI_DEFAULT_ABI, cif->nargs, cif->rtype,
                              cif->arg_types))
    scm_misc_error (FUNC_NAME, "ffi_prep_cif failed", SCM_EOL);

  return cif_to_procedure (scm_cif, func_ptr);
}
#undef FUNC_NAME

\f

/* Pre-generate trampolines for less than 10 arguments. */

#ifdef WORDS_BIGENDIAN
#define OBJCODE_HEADER 0, 0, 0, 8, 0, 0, 0, 40
#define META_HEADER    0, 0, 0, 32, 0, 0, 0, 0
#else
#define OBJCODE_HEADER 8, 0, 0, 0, 40, 0, 0, 0
#define META_HEADER    32, 0, 0, 0, 0, 0, 0, 0
#endif

#define CODE(nreq)                                                      \
  OBJCODE_HEADER,                                                       \
  /* 0 */ scm_op_assert_nargs_ee, 0, nreq, /* assert number of args */  \
  /* 3 */ scm_op_object_ref, 0, /* push the pair with the cif and the function pointer */ \
  /* 5 */ scm_op_foreign_call, nreq, /* and call (will return value as well) */ \
  /* 7 */ scm_op_nop,                                                   \
  /* 8 */ META (3, 7, nreq)

#define META(start, end, nreq)                              		\
  META_HEADER,                                                          \
  /* 0 */ scm_op_make_eol, /* bindings */                               \
  /* 1 */ scm_op_make_eol, /* sources */                                \
  /* 2 */ scm_op_make_int8, start, scm_op_make_int8, end, /* arity: from ip N to ip N */ \
  /* 6 */ scm_op_make_int8, nreq, /* the arity is N required args */    \
  /* 8 */ scm_op_list, 0, 3, /* make a list of those 3 vals */         \
  /* 11 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */ \
  /* 14 */ scm_op_load_symbol, 0, 0, 4, 'n', 'a', 'm', 'e', /* `name' */ \
  /* 22 */ scm_op_object_ref, 1, /* the name from the object table */   \
  /* 24 */ scm_op_cons, /* make a pair for the properties */            \
  /* 25 */ scm_op_list, 0, 4, /* pack bindings, sources, and arities into list */ \
  /* 28 */ scm_op_return, /* and return */                              \
  /* 29 */ scm_op_nop, scm_op_nop, scm_op_nop                           \
  /* 32 */

static const struct
{
  scm_t_uint64 dummy; /* ensure 8-byte alignment; perhaps there's a better way */
  const scm_t_uint8 bytes[10 * (sizeof (struct scm_objcode) + 8
                                + sizeof (struct scm_objcode) + 32)];
} raw_bytecode = {
  0,
  {
    CODE (0), CODE (1), CODE (2), CODE (3), CODE (4),
    CODE (5), CODE (6), CODE (7), CODE (8), CODE (9)
  }
};

#undef CODE
#undef META
#undef OBJCODE_HEADER
#undef META_HEADER

/*
 (defun generate-objcode-cells (n)
   "Generate objcode cells for up to N arguments"
   (interactive "p")
   (let ((i 0))
     (while (< i n)
       (insert
        (format "    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + %d) },\n"
                (* (+ 4 4 8 4 4 32) i)))
       (insert "    { SCM_BOOL_F, SCM_PACK (0) },\n")
       (setq i (1+ i)))))
*/
#define STATIC_OBJCODE_TAG                                      \
  SCM_PACK (scm_tc7_objcode | (SCM_F_OBJCODE_IS_STATIC << 8))

static const struct
{
  scm_t_uint64 dummy; /* alignment */
  scm_t_cell cells[10 * 2]; /* 10 double cells */
} objcode_cells = {
  0,
  /* C-u 1 0 M-x generate-objcode-cells RET */
  {
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 0) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 56) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 112) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 168) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 224) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 280) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 336) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 392) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 448) },
    { SCM_BOOL_F, SCM_PACK (0) },
    { STATIC_OBJCODE_TAG, SCM_PACK (raw_bytecode.bytes + 504) },
    { SCM_BOOL_F, SCM_PACK (0) }
  }
};

static const SCM objcode_trampolines[10] = {
  SCM_PACK (objcode_cells.cells+0),
  SCM_PACK (objcode_cells.cells+2),
  SCM_PACK (objcode_cells.cells+4),
  SCM_PACK (objcode_cells.cells+6),
  SCM_PACK (objcode_cells.cells+8),
  SCM_PACK (objcode_cells.cells+10),
  SCM_PACK (objcode_cells.cells+12),
  SCM_PACK (objcode_cells.cells+14),
  SCM_PACK (objcode_cells.cells+16),
  SCM_PACK (objcode_cells.cells+18),
};

static SCM
cif_to_procedure (SCM cif, SCM func_ptr)
{
  unsigned nargs = SCM_FOREIGN_POINTER (cif, ffi_cif)->nargs;
  SCM objcode, table, ret;
  
  if (nargs < 10)
    objcode = objcode_trampolines[nargs];
  else
    scm_misc_error ("make-foreign-function", "args >= 10 currently unimplemented",
                    SCM_EOL);
  
  table = scm_c_make_vector (2, SCM_UNDEFINED);
  SCM_SIMPLE_VECTOR_SET (table, 0, scm_cons (cif, func_ptr));
  SCM_SIMPLE_VECTOR_SET (table, 1, SCM_BOOL_F); /* name */
  ret = scm_make_program (objcode, table, SCM_BOOL_F);
  
  return ret;
}

static void
unpack (ffi_type *type, void *loc, SCM x)
{
  switch (type->type)
    {
    case FFI_TYPE_FLOAT:
      *(float*)loc = scm_to_double (x);
      break;
    case FFI_TYPE_DOUBLE:
      *(double*)loc = scm_to_double (x);
      break;
    case FFI_TYPE_UINT8:
      *(scm_t_uint8*)loc = scm_to_uint8 (x);
      break;
    case FFI_TYPE_SINT8:
      *(scm_t_int8*)loc = scm_to_int8 (x);
      break;
    case FFI_TYPE_UINT16:
      *(scm_t_uint16*)loc = scm_to_uint16 (x);
      break;
    case FFI_TYPE_SINT16:
      *(scm_t_int16*)loc = scm_to_int16 (x);
      break;
    case FFI_TYPE_UINT32:
      *(scm_t_uint32*)loc = scm_to_uint32 (x);
      break;
    case FFI_TYPE_SINT32:
      *(scm_t_int32*)loc = scm_to_int32 (x);
      break;
    case FFI_TYPE_UINT64:
      *(scm_t_uint64*)loc = scm_to_uint64 (x);
      break;
    case FFI_TYPE_SINT64:
      *(scm_t_int64*)loc = scm_to_int64 (x);
      break;
    case FFI_TYPE_STRUCT:
      if (!SCM_FOREIGN_TYPED_P (x, VOID))
        scm_wrong_type_arg_msg ("foreign-call", 0, x,
                                "foreign void pointer");
      if (SCM_FOREIGN_LEN (x) && SCM_FOREIGN_LEN (x) != type->size)
        scm_wrong_type_arg_msg ("foreign-call", 0, x,
                                "foreign void pointer of correct length");
      memcpy (loc, SCM_FOREIGN_POINTER (x, void), type->size);
      break;
    case FFI_TYPE_POINTER:
      if (!SCM_FOREIGN_TYPED_P (x, VOID))
        scm_wrong_type_arg_msg ("foreign-call", 0, x,
                                "foreign void pointer");
      *(void**)loc = SCM_FOREIGN_POINTER (x, void);
      break;
    default:
      abort ();
    }
}

static SCM
pack (ffi_type *type, void *loc)
{
  switch (type->type)
    {
    case FFI_TYPE_VOID:
      return SCM_UNSPECIFIED;
    case FFI_TYPE_FLOAT:
      return scm_from_double (*(float*)loc);
    case FFI_TYPE_DOUBLE:
      return scm_from_double (*(double*)loc);
    case FFI_TYPE_UINT8:
      return scm_from_uint8 (*(scm_t_uint8*)loc);
    case FFI_TYPE_SINT8:
      return scm_from_int8 (*(scm_t_int8*)loc);
    case FFI_TYPE_UINT16:
      return scm_from_uint16 (*(scm_t_uint16*)loc);
    case FFI_TYPE_SINT16:
      return scm_from_int16 (*(scm_t_int16*)loc);
    case FFI_TYPE_UINT32:
      return scm_from_uint32 (*(scm_t_uint32*)loc);
    case FFI_TYPE_SINT32:
      return scm_from_int32 (*(scm_t_int32*)loc);
    case FFI_TYPE_UINT64:
      return scm_from_uint64 (*(scm_t_uint64*)loc);
    case FFI_TYPE_SINT64:
      return scm_from_int64 (*(scm_t_int64*)loc);
    case FFI_TYPE_STRUCT:
      {
        void *mem = scm_malloc (type->size);
        memcpy (mem, loc, type->size);
        return scm_take_foreign_pointer (SCM_FOREIGN_TYPE_VOID,
                                         mem, type->size, free);
      }
    case FFI_TYPE_POINTER:
      return scm_take_foreign_pointer (SCM_FOREIGN_TYPE_VOID,
                                       *(void**)loc, 0, NULL);
    default:
      abort ();
    }
}

SCM
scm_i_foreign_call (SCM foreign, SCM *argv)
{
  /* FOREIGN is the pair that cif_to_procedure set as the 0th element of the
     objtable. */
  ffi_cif *cif;
  void (*func)();
  scm_t_uint8 *data;
  void *rvalue;
  void **args;
  unsigned i;
  scm_t_ptrdiff off;

  cif = SCM_FOREIGN_POINTER (scm_car (foreign), ffi_cif);
  func = SCM_FOREIGN_POINTER (scm_cdr (foreign), void);
  
  /* arg pointers */
  args = alloca (sizeof(void*) * cif->nargs);
  /* arg values, then return type value */
  data = alloca (ROUND_UP (cif->bytes, cif->rtype->alignment)
                 + cif->rtype->size);
  /* unpack argv to native values, setting argv pointers */
  off = 0;
  for (i = 0; i < cif->nargs; i++)
    {
      off = ROUND_UP (off, cif->arg_types[i]->alignment);
      args[i] = data + off;
      unpack (cif->arg_types[i], args[i], argv[i]);
      off += cif->arg_types[i]->size;
    }
  /* prep space for the return value */
  off = ROUND_UP (off, cif->rtype->alignment);
  rvalue = data + off;

  /* off we go! */
  ffi_call (cif, func, rvalue, args);

  return pack (cif->rtype, rvalue);
}

\f

static void
scm_init_foreign (void)
{
#ifndef SCM_MAGIC_SNARFER
#include "libguile/foreign.x"
#endif
  scm_define (sym_void, scm_from_uint8 (SCM_FOREIGN_TYPE_VOID));
  scm_define (sym_float, scm_from_uint8 (SCM_FOREIGN_TYPE_FLOAT));
  scm_define (sym_double, scm_from_uint8 (SCM_FOREIGN_TYPE_DOUBLE));
  scm_define (sym_uint8, scm_from_uint8 (SCM_FOREIGN_TYPE_UINT8));
  scm_define (sym_int8, scm_from_uint8 (SCM_FOREIGN_TYPE_INT8));
  scm_define (sym_uint16, scm_from_uint8 (SCM_FOREIGN_TYPE_UINT16));
  scm_define (sym_int16, scm_from_uint8 (SCM_FOREIGN_TYPE_INT16));
  scm_define (sym_uint32, scm_from_uint8 (SCM_FOREIGN_TYPE_UINT32));
  scm_define (sym_int32, scm_from_uint8 (SCM_FOREIGN_TYPE_INT32));
  scm_define (sym_uint64, scm_from_uint8 (SCM_FOREIGN_TYPE_UINT64));
  scm_define (sym_int64, scm_from_uint8 (SCM_FOREIGN_TYPE_INT64));
}

void
scm_register_foreign (void)
{
  scm_c_register_extension ("libguile", "scm_init_foreign",
                            (scm_t_extension_init_func)scm_init_foreign,
                            NULL);
  foreign_weak_refs = scm_make_weak_key_hash_table (SCM_UNDEFINED);
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/