/* Copyright (C) 1996-2001, 2003-2004, 2006-2013, 2015,
 *               2017 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
 */

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

#include <alloca.h>
#include <assert.h>

#define SCM_BUILDING_DEPRECATED_CODE

#include "libguile/_scm.h"
#include "libguile/async.h"
#include "libguile/chars.h"
#include "libguile/deprecation.h"
#include "libguile/eval.h"
#include "libguile/alist.h"
#include "libguile/hashtab.h"
#include "libguile/ports.h"
#include "libguile/strings.h"
#include "libguile/srfi-13.h"

#include "libguile/validate.h"
#include "libguile/struct.h"

#include "libguile/eq.h"

#ifdef HAVE_STRING_H
#include <string.h>
#endif

#include "libguile/bdw-gc.h"



/* A needlessly obscure test. */
#define SCM_LAYOUT_TAILP(X)		(((X) & 32) == 0) /* R, W or O */

static SCM required_vtable_fields = SCM_BOOL_F;
static SCM required_applicable_fields = SCM_BOOL_F;
static SCM required_applicable_with_setter_fields = SCM_BOOL_F;
SCM scm_applicable_struct_vtable_vtable;
SCM scm_applicable_struct_with_setter_vtable_vtable;
SCM scm_standard_vtable_vtable;



SCM_DEFINE (scm_make_struct_layout, "make-struct-layout", 1, 0, 0, 
            (SCM fields),
	    "Return a new structure layout object.\n\n"
	    "@var{fields} must be a string made up of pairs of characters\n"
	    "strung together.  The first character of each pair describes a field\n"
	    "type, the second a field protection.  Allowed types are 'p' for\n"
	    "GC-protected Scheme data, 'u' for unprotected binary data.  \n"
            "Allowed protections\n"
	    "are 'w' for mutable fields, 'h' for hidden fields, and\n"
            "'r' for read-only fields.\n\n"
            "Hidden fields are writable, but they will not consume an initializer arg\n"
            "passed to @code{make-struct}. They are useful to add slots to a struct\n"
            "in a way that preserves backward-compatibility with existing calls to\n"
            "@code{make-struct}, especially for derived vtables.")
#define FUNC_NAME s_scm_make_struct_layout
{
  SCM new_sym;
  scm_t_wchar c;

  SCM_VALIDATE_STRING (1, fields);

  { /* scope */
    size_t len;
    int x;

    len = scm_i_string_length (fields);
    if (len % 2 == 1)
      SCM_MISC_ERROR ("odd length field specification: ~S", 
		      scm_list_1 (fields));

    for (x = 0; x < len; x += 2)
      {
	switch (c = scm_i_string_ref (fields, x))
	  {
	  case 'u':
	  case 'p':
	  case 's':
	    break;
	  default:
	    SCM_MISC_ERROR ("unrecognized field type: ~S", 
			    scm_list_1 (SCM_MAKE_CHAR (c)));
	  }

	switch (c = scm_i_string_ref (fields, x + 1))
	  {
	  case 'w':
	  case 'h':
	    if (scm_i_string_ref (fields, x) == 's')
	      SCM_MISC_ERROR ("self fields not writable", SCM_EOL);
	  case 'r':
	  case 'o':
	    break;
	  case 'R':
	  case 'W':
	  case 'O':
	    if (scm_i_string_ref (fields, x) == 's')
	      SCM_MISC_ERROR ("self fields not allowed in tail array", 
			      SCM_EOL);
	    if (x != len - 2)
	      SCM_MISC_ERROR ("tail array field must be last field in layout",
			      SCM_EOL);
	    break;
	  default:
	    SCM_MISC_ERROR ("unrecognized ref specification: ~S",
			    scm_list_1 (SCM_MAKE_CHAR (c)));
	  }
      }
    new_sym = scm_string_to_symbol (fields);
  }
  scm_remember_upto_here_1 (fields);
  return new_sym;
}
#undef FUNC_NAME


/* Check whether VTABLE instances have a simple layout (i.e., either
   only "pr" or only "pw" fields and no tail array) and update its flags
   accordingly.  */
static void
set_vtable_layout_flags (SCM vtable)
{
  size_t len, field;
  SCM layout;
  const char *c_layout;
  scm_t_bits flags = SCM_VTABLE_FLAG_SIMPLE;

  layout = SCM_VTABLE_LAYOUT (vtable);
  c_layout = scm_i_symbol_chars (layout);
  len = scm_i_symbol_length (layout);

  assert (len % 2 == 0);

  /* Update FLAGS according to LAYOUT.  */
  for (field = 0;
       field < len && flags & SCM_VTABLE_FLAG_SIMPLE;
       field += 2)
    {
      if (c_layout[field] != 'p')
	flags = 0;
      else
	switch (c_layout[field + 1])
	  {
	  case 'w':
	    if (field == 0)
	      flags |= SCM_VTABLE_FLAG_SIMPLE_RW;
	    break;

	  case 'r':
	    flags &= ~SCM_VTABLE_FLAG_SIMPLE_RW;
	    break;

          case 'o':
          case 'O':
            scm_c_issue_deprecation_warning
              ("Opaque struct fields are deprecated.  Struct field protection "
               "should be layered on at a higher level.");
            /* Fall through.  */

	  default:
	    flags = 0;
	  }
    }

  if (flags & SCM_VTABLE_FLAG_SIMPLE)
    {
      /* VTABLE is simple so update its flags and record the size of its
	 instances.  */
      SCM_SET_VTABLE_FLAGS (vtable, flags);
      SCM_STRUCT_DATA_SET (vtable, scm_vtable_index_size, len / 2);
    }
}

static int
scm_is_valid_vtable_layout (SCM layout)
{
  size_t len, n;
  const char *c_layout;

  c_layout = scm_i_symbol_chars (layout);
  len = scm_i_symbol_length (layout);

  if (len % 2)
    return 0;
  
  for (n = 0; n < len; n += 2)
    switch (c_layout[n])
      {
      case 'u':
      case 'p':
      case 's':
        switch (c_layout[n+1])
          {
          case 'W':
          case 'R':
          case 'O':
            if (n + 2 != len)
              return 0;
          case 'w':
          case 'h':
          case 'r':
          case 'o':
            break;
          default:
            return 0;
          }
        break;
      default:        
        return 0;
      }
  return 1;
}

static void
issue_deprecation_warning_for_self_slots (SCM vtable)
{
  SCM olayout;
  size_t idx, first_user_slot = 0;

  olayout = scm_symbol_to_string (SCM_VTABLE_LAYOUT (vtable));
  if (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_VTABLE))
    first_user_slot = scm_vtable_offset_user;

  for (idx = first_user_slot * 2; idx < scm_c_string_length (olayout); idx += 2)
    if (scm_is_eq (scm_c_string_ref (olayout, idx), SCM_MAKE_CHAR ('s')))
      scm_c_issue_deprecation_warning
        ("Vtables with \"self\" slots are deprecated.  Initialize these "
         "fields manually.");
}

/* Have OBJ, a newly created vtable, inherit flags from VTABLE.  VTABLE is a
   vtable-vtable and OBJ is an instance of VTABLE.  */
void
scm_i_struct_inherit_vtable_magic (SCM vtable, SCM obj)
#define FUNC_NAME "%inherit-vtable-magic"
{
  /* Verily, what is the deal here, you ask? Basically, we need to know a couple
     of properties of structures at runtime. For example, "is this structure a
     vtable of vtables (a metaclass)?"; also, "is this structure applicable?".
     Both of these questions also imply a certain layout of the structure. So
     instead of checking the layout at runtime, what we do is pre-verify the
     layout -- so that at runtime we can just check the applicable flag and
     dispatch directly to the Scheme procedure in slot 0.  */
  SCM olayout;

  /* Verify that OBJ is a valid vtable.  */
  if (! scm_is_valid_vtable_layout (SCM_VTABLE_LAYOUT (obj)))
    SCM_MISC_ERROR ("invalid layout for new vtable: ~a",
                    scm_list_1 (SCM_VTABLE_LAYOUT (obj)));

  set_vtable_layout_flags (obj);

  /* If OBJ's vtable is compatible with the required vtable (class) layout, it
     is a metaclass.  */
  olayout = scm_symbol_to_string (SCM_VTABLE_LAYOUT (obj));
  if (scm_is_true (scm_leq_p (scm_string_length (required_vtable_fields),
                              scm_string_length (olayout)))
      && scm_is_true (scm_string_eq (olayout, required_vtable_fields,
                                     scm_from_size_t (0), 
                                     scm_string_length (required_vtable_fields),
                                     scm_from_size_t (0),
                                     scm_string_length (required_vtable_fields))))
    SCM_SET_VTABLE_FLAGS (obj, SCM_VTABLE_FLAG_VTABLE);

  /* Finally, if OBJ is an applicable class, verify that its vtable is
     compatible with the required applicable layout.  */
  if (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SETTER_VTABLE))
    {
      if (scm_is_false (scm_string_eq (olayout, required_applicable_with_setter_fields,
                                       scm_from_size_t (0), 
                                       scm_from_size_t (4), 
                                       scm_from_size_t (0),
                                       scm_from_size_t (4))))
        SCM_MISC_ERROR ("invalid applicable-with-setter struct layout",
                        scm_list_1 (olayout));
      SCM_SET_VTABLE_FLAGS (obj, SCM_VTABLE_FLAG_APPLICABLE | SCM_VTABLE_FLAG_SETTER);
    }
  else if (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_APPLICABLE_VTABLE))
    {
      if (scm_is_false (scm_string_eq (olayout, required_applicable_fields,
                                       scm_from_size_t (0), 
                                       scm_from_size_t (2), 
                                       scm_from_size_t (0),
                                       scm_from_size_t (2))))
        SCM_MISC_ERROR ("invalid applicable struct layout",
                        scm_list_1 (olayout));
      SCM_SET_VTABLE_FLAGS (obj, SCM_VTABLE_FLAG_APPLICABLE);
    }

  issue_deprecation_warning_for_self_slots (obj);

  SCM_SET_VTABLE_FLAGS (obj, SCM_VTABLE_FLAG_VALIDATED);
}
#undef FUNC_NAME


static void
scm_struct_init (SCM handle, SCM layout, size_t n_tail,
                 size_t n_inits, scm_t_bits *inits)
{
  SCM vtable;
  scm_t_bits *mem;

  vtable = SCM_STRUCT_VTABLE (handle);
  mem = SCM_STRUCT_DATA (handle);

  if (SCM_UNPACK (vtable) != 0
      && SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)
      && n_tail == 0
      && n_inits == SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size))
    /* The fast path: HANDLE has N_INITS "p" fields.  */
    memcpy (mem, inits, n_inits * sizeof (SCM));
  else
    {
      scm_t_wchar prot = 0;
      int n_fields = scm_i_symbol_length (layout) / 2;
      int tailp = 0;
      int i;
      size_t inits_idx = 0;

      i = -2;
      while (n_fields)
	{
	  if (!tailp)
	    {
	      i += 2;
	      prot = scm_i_symbol_ref (layout, i+1);
	      if (SCM_LAYOUT_TAILP (prot))
		{
		  tailp = 1;
		  prot = prot == 'R' ? 'r' : prot == 'W' ? 'w' : 'o';
		  *mem++ = (scm_t_bits)n_tail;
		  n_fields += n_tail - 1;
		  if (n_fields == 0)
		    break;
		}
	    }
	  switch (scm_i_symbol_ref (layout, i))
	    {
	    case 'u':
	      if ((prot != 'r' && prot != 'w') || inits_idx == n_inits)
		*mem = 0;
	      else
		{
		  *mem = scm_to_ulong (SCM_PACK (inits[inits_idx]));
		  inits_idx++;
		}
	      break;

	    case 'p':
	      if ((prot != 'r' && prot != 'w') || inits_idx == n_inits)
		*mem = SCM_UNPACK (SCM_BOOL_F);
	      else
		{
		  *mem = inits[inits_idx];
		  inits_idx++;
		}

	      break;

	    case 's':
	      *mem = SCM_UNPACK (handle);
	      break;
	    }

	  n_fields--;
	  mem++;
	}
    }
}


SCM_DEFINE (scm_struct_p, "struct?", 1, 0, 0, 
            (SCM x),
	    "Return @code{#t} iff @var{x} is a structure object, else\n"
	    "@code{#f}.")
#define FUNC_NAME s_scm_struct_p
{
  return scm_from_bool(SCM_STRUCTP (x));
}
#undef FUNC_NAME

SCM_DEFINE (scm_struct_vtable_p, "struct-vtable?", 1, 0, 0, 
            (SCM x),
	    "Return @code{#t} iff @var{x} is a vtable structure.")
#define FUNC_NAME s_scm_struct_vtable_p
{
  if (!SCM_STRUCTP (x)
      || !SCM_STRUCT_VTABLE_FLAG_IS_SET (x, SCM_VTABLE_FLAG_VTABLE))
    return SCM_BOOL_F;
  if (!SCM_VTABLE_FLAG_IS_SET (x, SCM_VTABLE_FLAG_VALIDATED))
    SCM_MISC_ERROR ("vtable has invalid layout: ~A",
                    scm_list_1 (SCM_VTABLE_LAYOUT (x)));
  return SCM_BOOL_T;
}
#undef FUNC_NAME


/* Finalization: invoke the finalizer of the struct pointed to by PTR.  */
static void
struct_finalizer_trampoline (void *ptr, void *unused_data)
{
  SCM obj = PTR2SCM (ptr);
  scm_t_struct_finalize finalize = SCM_STRUCT_FINALIZER (obj);

  if (finalize)
    finalize (obj);
}

/* All struct data must be allocated at an address whose bottom three
   bits are zero.  This is because the tag for a struct lives in the
   bottom three bits of the struct's car, and the upper bits point to
   the data of its vtable, which is a struct itself.  Thus, if the
   address of that data doesn't end in three zeros, tagging it will
   destroy the pointer.

   I suppose we should make it clear here that, the data must be 8-byte aligned,
   *within* the struct, and the struct itself should be 8-byte aligned. In
   practice we ensure this because the data starts two words into a struct.

   This function allocates an 8-byte aligned block of memory, whose first word
   points to the given vtable data, then a data pointer, then n_words of data.
 */
SCM
scm_i_alloc_struct (scm_t_bits *vtable_data, int n_words)
{
  SCM ret;

  ret = scm_words ((scm_t_bits)vtable_data | scm_tc3_struct, n_words + 2);
  SCM_SET_CELL_WORD_1 (ret, (scm_t_bits)SCM_CELL_OBJECT_LOC (ret, 2));

  /* vtable_data can be null when making a vtable vtable */
  if (vtable_data && vtable_data[scm_vtable_index_instance_finalize])
    /* Register a finalizer for the newly created instance.  */
    scm_i_set_finalizer (SCM2PTR (ret), struct_finalizer_trampoline, NULL);

  return ret;
}


SCM
scm_c_make_structv (SCM vtable, size_t n_tail, size_t n_init, scm_t_bits *init)
#define FUNC_NAME "make-struct"
{
  SCM layout;
  size_t basic_size;
  SCM obj;

  SCM_VALIDATE_VTABLE (1, vtable);

  layout = SCM_VTABLE_LAYOUT (vtable);
  basic_size = scm_i_symbol_length (layout) / 2;

  if (n_tail != 0)
    {
      SCM layout_str, last_char;
      
      if (basic_size == 0)
        {
        bad_tail: 
          SCM_MISC_ERROR ("tail array not allowed unless layout ends R, W, or O", SCM_EOL);
        }

      layout_str = scm_symbol_to_string (layout);
      last_char = scm_string_ref (layout_str,
                                  scm_from_size_t (2 * basic_size - 1));
      if (! SCM_LAYOUT_TAILP (SCM_CHAR (last_char)))
        goto bad_tail;
    }

  obj = scm_i_alloc_struct (SCM_STRUCT_DATA (vtable), basic_size + n_tail);

  scm_struct_init (obj, layout, n_tail, n_init, init);

  /* If we're making a vtable, validate its layout and inherit
     flags. However we allow for separation of allocation and
     initialization, to humor GOOPS, so only validate if the layout was
     passed as an initarg. */
  if (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_VTABLE)
      && scm_is_true (SCM_VTABLE_LAYOUT (obj)))
    scm_i_struct_inherit_vtable_magic (vtable, obj);

  return obj;
}
#undef FUNC_NAME

SCM
scm_c_make_struct (SCM vtable, size_t n_tail, size_t n_init, scm_t_bits init, ...)
{
  va_list foo;
  scm_t_bits *v;
  size_t i;

  v = alloca (sizeof (scm_t_bits) * n_init);

  va_start (foo, init);
  for (i = 0; i < n_init; i++)
    {
      v[i] = init;
      init = va_arg (foo, scm_t_bits);
    }
  va_end (foo);

  return scm_c_make_structv (vtable, n_tail, n_init, v);
}

SCM_DEFINE (scm_allocate_struct, "allocate-struct", 2, 0, 0,
            (SCM vtable, SCM nfields),
	    "Allocate a new structure with space for @var{nfields} fields.\n\n"
	    "@var{vtable} must be a vtable structure (@pxref{Vtables}).\n\n"
	    "@var{nfields} must be a non-negative integer.  Strictly speaking\n"
	    "@var{nfields} is redundant, as the vtable carries the size\n"
            "for its instances.  However passing it is useful as a sanity\n"
            "check, given that one module can inline a constructor in\n"
            "another.\n\n"
	    "Fields will be initialized with their default values.")
#define FUNC_NAME s_scm_allocate_struct
{
  SCM ret;
  size_t c_nfields;

  SCM_VALIDATE_VTABLE (1, vtable);
  c_nfields = scm_to_size_t (nfields);

  SCM_ASSERT (SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size) == c_nfields,
              nfields, 2, FUNC_NAME);

  ret = scm_i_alloc_struct (SCM_STRUCT_DATA (vtable), c_nfields);

  if (SCM_LIKELY (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)))
    {
      size_t n;
      for (n = 0; n < c_nfields; n++)
        SCM_STRUCT_DATA_SET (ret, n, SCM_UNPACK (SCM_BOOL_F));
    }
  else
    scm_struct_init (ret, SCM_VTABLE_LAYOUT (vtable), 0, 0, NULL);

  return ret;
}
#undef FUNC_NAME

SCM_DEFINE (scm_make_struct_no_tail, "make-struct/no-tail", 1, 0, 1, 
            (SCM vtable, SCM init),
	    "Create a new structure.\n\n"
	    "@var{vtable} must be a vtable structure (@pxref{Vtables}).\n\n"
	    "The @var{init1}, @dots{} are optional arguments describing how\n"
	    "successive fields of the structure should be initialized.\n"
            "Only fields with protection 'r' or 'w' can be initialized.\n"
            "Hidden fields (those with protection 'h') have to be manually\n"
            "set.\n\n"
	    "If fewer optional arguments than initializable fields are supplied,\n"
	    "fields of type 'p' get default value #f while fields of type 'u' are\n"
	    "initialized to 0.")
#define FUNC_NAME s_scm_make_struct_no_tail
{
  size_t i, n_init;
  long ilen;
  scm_t_bits *v;

  SCM_VALIDATE_VTABLE (1, vtable);
  ilen = scm_ilength (init);
  if (ilen < 0)
    SCM_MISC_ERROR ("Rest arguments do not form a proper list.", SCM_EOL);
  
  n_init = (size_t)ilen;

  /* best to use alloca, but init could be big, so hack to avoid a possible
     stack overflow */
  if (n_init < 64)
    v = alloca (n_init * sizeof(scm_t_bits));
  else
    v = scm_gc_malloc (n_init * sizeof(scm_t_bits), "struct");

  for (i = 0; i < n_init; i++, init = SCM_CDR (init))
    v[i] = SCM_UNPACK (SCM_CAR (init));

  return scm_c_make_structv (vtable, 0, n_init, v);
}
#undef FUNC_NAME

SCM
scm_i_make_vtable_vtable (SCM fields)
#define FUNC_NAME "make-vtable-vtable"
{
  SCM layout, obj;
  size_t basic_size;
  scm_t_bits v;

  SCM_VALIDATE_STRING (1, fields);

  layout = scm_make_struct_layout (fields);
  if (!scm_is_valid_vtable_layout (layout))
    SCM_MISC_ERROR ("invalid user fields", scm_list_1 (fields));

  basic_size = scm_i_symbol_length (layout) / 2;

  obj = scm_i_alloc_struct (NULL, basic_size);
  /* Make it so that the vtable of OBJ is itself.  */
  SCM_SET_CELL_WORD_0 (obj, (scm_t_bits) SCM_STRUCT_DATA (obj) | scm_tc3_struct);

  v = SCM_UNPACK (layout);
  scm_struct_init (obj, layout, 0, 1, &v);
  SCM_SET_VTABLE_FLAGS (obj,
                        SCM_VTABLE_FLAG_VTABLE | SCM_VTABLE_FLAG_VALIDATED);

  return obj;
}
#undef FUNC_NAME

SCM_DEFINE (scm_make_vtable, "make-vtable", 1, 1, 0,
            (SCM fields, SCM printer),
	    "Create a vtable, for creating structures with the given\n"
	    "@var{fields}.\n"
	    "\n"
	    "The optional @var{printer} argument is a function to be called\n"
	    "@code{(@var{printer} struct port)} on the structures created.\n"
	    "It should look at @var{struct} and write to @var{port}.")
#define FUNC_NAME s_scm_make_vtable
{
  if (SCM_UNBNDP (printer))
    printer = SCM_BOOL_F;

  return scm_c_make_struct (scm_standard_vtable_vtable, 0, 2,
                            SCM_UNPACK (scm_make_struct_layout (fields)),
                            SCM_UNPACK (printer));
}
#undef FUNC_NAME


/* Return true if S1 and S2 are equal structures, i.e., if their vtable and
   contents are the same.  Field protections are honored.  Thus, it is an
   error to test the equality of structures that contain opaque fields.  */
SCM
scm_i_struct_equalp (SCM s1, SCM s2)
#define FUNC_NAME "scm_i_struct_equalp"
{
  SCM vtable1, vtable2, layout;
  size_t struct_size, field_num;

  SCM_VALIDATE_STRUCT (1, s1);
  SCM_VALIDATE_STRUCT (2, s2);

  vtable1 = SCM_STRUCT_VTABLE (s1);
  vtable2 = SCM_STRUCT_VTABLE (s2);

  if (!scm_is_eq (vtable1, vtable2))
    return SCM_BOOL_F;

  layout = SCM_STRUCT_LAYOUT (s1);
  struct_size = scm_i_symbol_length (layout) / 2;

  for (field_num = 0; field_num < struct_size; field_num++)
    {
      scm_t_bits field1, field2;

      field1 = SCM_STRUCT_DATA_REF (s1, field_num);
      field2 = SCM_STRUCT_DATA_REF (s2, field_num);

      if (field1 != field2) {
        switch (scm_i_symbol_ref (layout, field_num * 2))
          {
          case 'p':
            /* Having a normal field point to the object itself is a bit
               bonkers, but R6RS enums do it, so here we have a horrible
               hack.  */
            if (field1 != SCM_UNPACK (s1) && field2 != SCM_UNPACK (s2))
              {
                if (scm_is_false
                    (scm_equal_p (SCM_PACK (field1), SCM_PACK (field2))))
                  return SCM_BOOL_F;
              }
            break;
          case 's':
            /* Skip to avoid infinite recursion.  */
            break;
          case 'u':
            return SCM_BOOL_F;
          default:
            /* Don't bother inspecting tail arrays; we never did this in
               the past and in the future tail arrays are going away
               anyway.  */
            return SCM_BOOL_F;
          }
      }
    }

  /* FIXME: Tail elements should be tested for equality.  */

  return SCM_BOOL_T;
}
#undef FUNC_NAME





SCM_DEFINE (scm_struct_ref, "struct-ref", 2, 0, 0,
            (SCM handle, SCM pos),
	    "Access the @var{pos}th field of struct associated with\n"
	    "@var{handle}.\n"
	    "\n"
	    "If the field is of type 'p', then it can be set to an arbitrary\n"
	    "value.\n"
	    "\n"
	    "If the field is of type 'u', then it can only be set to a\n"
	    "non-negative integer value small enough to fit in one machine\n"
	    "word.")
#define FUNC_NAME s_scm_struct_ref
{
  SCM vtable, answer = SCM_UNDEFINED;
  scm_t_bits *data;
  size_t p;

  SCM_VALIDATE_STRUCT (1, handle);

  vtable = SCM_STRUCT_VTABLE (handle);
  data = SCM_STRUCT_DATA (handle);
  p = scm_to_size_t (pos);

  if (SCM_LIKELY (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)
  		  && p < SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size)))
    /* The fast path: HANDLE is a struct with only "p" fields.  */
    answer = SCM_PACK (data[p]);
  else
    {
      SCM layout;
      size_t layout_len, n_fields;
      scm_t_wchar field_type = 0;

      layout = SCM_STRUCT_LAYOUT (handle);
      layout_len = scm_i_symbol_length (layout);
      n_fields = layout_len / 2;

      if (SCM_LAYOUT_TAILP (scm_i_symbol_ref (layout, layout_len - 1)))
	n_fields += data[n_fields - 1];

      SCM_ASSERT_RANGE (1, pos, p < n_fields);

      if (p * 2 < layout_len)
	{
	  scm_t_wchar ref;
	  field_type = scm_i_symbol_ref (layout, p * 2);
	  ref = scm_i_symbol_ref (layout, p * 2 + 1);
	  if ((ref != 'r') && (ref != 'w') && (ref != 'h'))
	    {
	      if ((ref == 'R') || (ref == 'W'))
		field_type = 'u';
	      else
		SCM_MISC_ERROR ("ref denied for field ~A", scm_list_1 (pos));
	    }
	}
      else if (scm_i_symbol_ref (layout, layout_len - 1) != 'O')
	field_type = scm_i_symbol_ref(layout, layout_len - 2);
      else
	SCM_MISC_ERROR ("ref denied for field ~A", scm_list_1 (pos));

      switch (field_type)
	{
	case 'u':
          scm_c_issue_deprecation_warning
            ("Accessing unboxed struct fields with struct-ref is deprecated.  "
             "Use struct-ref/unboxed instead.");
	  answer = scm_from_ulong (data[p]);
	  break;

	case 's':
	case 'p':
	  answer = SCM_PACK (data[p]);
	break;


	default:
	  SCM_MISC_ERROR ("unrecognized field type: ~S",
			  scm_list_1 (SCM_MAKE_CHAR (field_type)));
	}
    }

  return answer;
}
#undef FUNC_NAME


SCM_DEFINE (scm_struct_set_x, "struct-set!", 3, 0, 0,
            (SCM handle, SCM pos, SCM val),
	    "Set the slot of the structure @var{handle} with index @var{pos}\n"
	    "to @var{val}.  Signal an error if the slot can not be written\n"
	    "to.")
#define FUNC_NAME s_scm_struct_set_x
{
  SCM vtable;
  scm_t_bits *data;
  size_t p;

  SCM_VALIDATE_STRUCT (1, handle);

  vtable = SCM_STRUCT_VTABLE (handle);
  data = SCM_STRUCT_DATA (handle);
  p = scm_to_size_t (pos);

  if (SCM_LIKELY (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)
  		  && SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE_RW)
  		  && p < SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size)))
    /* The fast path: HANDLE is a struct with only "pw" fields.  */
    data[p] = SCM_UNPACK (val);
  else
    {
      SCM layout;
      size_t layout_len, n_fields;
      scm_t_wchar field_type = 0;

      layout = SCM_STRUCT_LAYOUT (handle);
      layout_len = scm_i_symbol_length (layout);
      n_fields = layout_len / 2;

      if (SCM_LAYOUT_TAILP (scm_i_symbol_ref (layout, layout_len - 1)))
	n_fields += data[n_fields - 1];

      SCM_ASSERT_RANGE (1, pos, p < n_fields);

      if (p * 2 < layout_len)
	{
	  char set_x;
	  field_type = scm_i_symbol_ref (layout, p * 2);
	  set_x = scm_i_symbol_ref (layout, p * 2 + 1);
	  if (set_x != 'w' && set_x != 'h')
	    SCM_MISC_ERROR ("set! denied for field ~A", scm_list_1 (pos));
	}
      else if (scm_i_symbol_ref (layout, layout_len - 1) == 'W')
	field_type = scm_i_symbol_ref (layout, layout_len - 2);
      else
	SCM_MISC_ERROR ("set! denied for field ~A", scm_list_1 (pos));

      switch (field_type)
	{
	case 'u':
          scm_c_issue_deprecation_warning
            ("Accessing unboxed struct fields with struct-set! is deprecated.  "
             "Use struct-set!/unboxed instead.");
	  data[p] = SCM_NUM2ULONG (3, val);
	  break;

	case 'p':
	  data[p] = SCM_UNPACK (val);
	  break;

	case 's':
	  SCM_MISC_ERROR ("self fields immutable", SCM_EOL);

	default:
	  SCM_MISC_ERROR ("unrecognized field type: ~S",
			  scm_list_1 (SCM_MAKE_CHAR (field_type)));
	}
    }

  return val;
}
#undef FUNC_NAME


SCM_DEFINE (scm_struct_ref_unboxed, "struct-ref/unboxed", 2, 0, 0,
            (SCM handle, SCM pos),
	    "Access the @var{pos}th field of struct associated with\n"
	    "@var{handle}.  The field must be of type 'u'.")
#define FUNC_NAME s_scm_struct_ref_unboxed
{
  SCM vtable, layout;
  size_t layout_len, n_fields;
  size_t p;

  SCM_VALIDATE_STRUCT (1, handle);

  vtable = SCM_STRUCT_VTABLE (handle);
  p = scm_to_size_t (pos);

  layout = SCM_VTABLE_LAYOUT (vtable);
  layout_len = scm_i_symbol_length (layout);
  n_fields = layout_len / 2;

  SCM_ASSERT_RANGE (1, pos, p < n_fields);

  /* Only 'u' fields, no tail arrays.  */
  SCM_ASSERT (scm_i_symbol_ref (layout, p * 2) == 'u',
              layout, 0, FUNC_NAME);

  /* Don't support opaque fields.  */
  SCM_ASSERT (scm_i_symbol_ref (layout, p * 2 + 1) != 'o',
              layout, 0, FUNC_NAME);

  return scm_from_uintptr_t (SCM_STRUCT_DATA_REF (handle, p));
}
#undef FUNC_NAME


SCM_DEFINE (scm_struct_set_x_unboxed, "struct-set!/unboxed", 3, 0, 0,
            (SCM handle, SCM pos, SCM val),
	    "Set the slot of the structure @var{handle} with index @var{pos}\n"
	    "to @var{val}.  Signal an error if the slot can not be written\n"
	    "to.")
#define FUNC_NAME s_scm_struct_set_x_unboxed
{
  SCM vtable, layout;
  size_t layout_len, n_fields;
  size_t p;

  SCM_VALIDATE_STRUCT (1, handle);

  vtable = SCM_STRUCT_VTABLE (handle);
  p = scm_to_size_t (pos);

  layout = SCM_VTABLE_LAYOUT (vtable);
  layout_len = scm_i_symbol_length (layout);
  n_fields = layout_len / 2;

  SCM_ASSERT_RANGE (1, pos, p < n_fields);

  /* Only 'u' fields, no tail arrays.  */
  SCM_ASSERT (scm_i_symbol_ref (layout, p * 2) == 'u',
              layout, 0, FUNC_NAME);

  /* Don't support opaque fields.  */
  SCM_ASSERT (scm_i_symbol_ref (layout, p * 2 + 1) != 'o',
              layout, 0, FUNC_NAME);

  if (scm_i_symbol_ref (layout, p * 2 + 1) == 'r')
    SCM_MISC_ERROR ("set! denied for field ~A", scm_list_1 (pos));

  SCM_STRUCT_DATA_SET (handle, p, scm_to_uintptr_t (val));

  return val;
}
#undef FUNC_NAME


SCM_DEFINE (scm_struct_vtable, "struct-vtable", 1, 0, 0, 
            (SCM handle),
	    "Return the vtable structure that describes the type of struct\n"
	    "associated with @var{handle}.")
#define FUNC_NAME s_scm_struct_vtable
{
  SCM_VALIDATE_STRUCT (1, handle);
  return SCM_STRUCT_VTABLE (handle);
}
#undef FUNC_NAME


/* {Associating names and classes with vtables}
 *
 * The name of a vtable should probably be stored as a slot.  This is
 * a backward compatible solution until agreement has been achieved on
 * how to associate names with vtables.
 */

unsigned long
scm_struct_ihashq (SCM obj, unsigned long n, void *closure)
{
  /* The length of the hash table should be a relative prime it's not
     necessary to shift down the address.  */
  return SCM_UNPACK (obj) % n;
}

SCM_DEFINE (scm_struct_vtable_name, "struct-vtable-name", 1, 0, 0, 
            (SCM vtable),
	    "Return the name of the vtable @var{vtable}.")
#define FUNC_NAME s_scm_struct_vtable_name
{
  SCM_VALIDATE_VTABLE (1, vtable);
  return SCM_VTABLE_NAME (vtable);
}
#undef FUNC_NAME

SCM_DEFINE (scm_set_struct_vtable_name_x, "set-struct-vtable-name!", 2, 0, 0, 
            (SCM vtable, SCM name),
	    "Set the name of the vtable @var{vtable} to @var{name}.")
#define FUNC_NAME s_scm_set_struct_vtable_name_x
{
  SCM_VALIDATE_VTABLE (1, vtable);
  SCM_VALIDATE_SYMBOL (2, name);
  SCM_SET_VTABLE_NAME (vtable, name);
  /* FIXME: remove this, and implement proper struct classes instead.
     (Vtables *are* classes.)  */
  scm_i_define_class_for_vtable (vtable);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME




void
scm_print_struct (SCM exp, SCM port, scm_print_state *pstate)
{
  if (scm_is_true (scm_procedure_p (SCM_STRUCT_PRINTER (exp))))
    scm_printer_apply (SCM_STRUCT_PRINTER (exp), exp, port, pstate);
  else
    {
      SCM vtable = SCM_STRUCT_VTABLE (exp);
      SCM name = scm_struct_vtable_name (vtable);
      scm_puts ("#<", port);
      if (scm_is_true (name))
	{
          scm_display (name, port);
          scm_putc (' ', port);
        }
      else
	{
          if (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_VTABLE))
            scm_puts ("vtable:", port);
          else
            scm_puts ("struct:", port);
          scm_uintprint (SCM_UNPACK (vtable), 16, port);
          scm_putc (' ', port);
          scm_write (SCM_VTABLE_LAYOUT (vtable), port);
          scm_putc (' ', port);
        }
      scm_uintprint (SCM_UNPACK (exp), 16, port);
      /* hackety hack */
      if (SCM_STRUCT_APPLICABLE_P (exp))
        {
          if (scm_is_true (SCM_STRUCT_PROCEDURE (exp)))
            {
              scm_puts (" proc: ", port);
              if (scm_is_true (scm_procedure_p (SCM_STRUCT_PROCEDURE (exp))))
                scm_write (SCM_STRUCT_PROCEDURE (exp), port);
              else
                scm_puts ("(not a procedure?)", port);
            }
          if (SCM_STRUCT_SETTER_P (exp))
            {
              scm_puts (" setter: ", port);
              scm_write (SCM_STRUCT_SETTER (exp), port);
            }
        }
      scm_putc ('>', port);
    }
}

void
scm_init_struct ()
{
  SCM name;

  /* The first word of a struct is equal to `SCM_STRUCT_DATA (vtable) +
     scm_tc3_struct', and `SCM_STRUCT_DATA (vtable)' is 2 words after VTABLE by
     default.  */
  GC_REGISTER_DISPLACEMENT (2 * sizeof (scm_t_bits) + scm_tc3_struct);

  /* In the general case, `SCM_STRUCT_DATA (obj)' points 2 words after the
     beginning of a GC-allocated region; that region is different from that of
     OBJ once OBJ has undergone class redefinition.  */
  GC_REGISTER_DISPLACEMENT (2 * sizeof (scm_t_bits));

  required_vtable_fields = scm_from_latin1_string (SCM_VTABLE_BASE_LAYOUT);
  scm_c_define ("standard-vtable-fields", required_vtable_fields);
  required_applicable_fields = scm_from_latin1_string (SCM_APPLICABLE_BASE_LAYOUT);
  required_applicable_with_setter_fields = scm_from_latin1_string (SCM_APPLICABLE_WITH_SETTER_BASE_LAYOUT);

  scm_standard_vtable_vtable =
    scm_i_make_vtable_vtable (required_vtable_fields);
  name = scm_from_utf8_symbol ("<standard-vtable>");
  scm_set_struct_vtable_name_x (scm_standard_vtable_vtable, name);
  scm_define (name, scm_standard_vtable_vtable);

  scm_applicable_struct_vtable_vtable =
    scm_c_make_struct (scm_standard_vtable_vtable, 0, 1,
                       SCM_UNPACK (scm_make_struct_layout (required_vtable_fields)));
  name = scm_from_utf8_symbol ("<applicable-struct-vtable>");
  SCM_SET_VTABLE_FLAGS (scm_applicable_struct_vtable_vtable,
                        SCM_VTABLE_FLAG_APPLICABLE_VTABLE);
  scm_set_struct_vtable_name_x (scm_applicable_struct_vtable_vtable, name);
  scm_define (name, scm_applicable_struct_vtable_vtable);

  scm_applicable_struct_with_setter_vtable_vtable =
    scm_c_make_struct (scm_standard_vtable_vtable, 0, 1,
                       SCM_UNPACK (scm_make_struct_layout (required_vtable_fields)));
  name = scm_from_utf8_symbol ("<applicable-struct-with-setter-vtable>");
  scm_set_struct_vtable_name_x (scm_applicable_struct_with_setter_vtable_vtable, name);
  SCM_SET_VTABLE_FLAGS (scm_applicable_struct_with_setter_vtable_vtable,
                        SCM_VTABLE_FLAG_APPLICABLE_VTABLE | SCM_VTABLE_FLAG_SETTER_VTABLE);
  scm_define (name, scm_applicable_struct_with_setter_vtable_vtable);

  scm_c_define ("vtable-index-layout", scm_from_int (scm_vtable_index_layout));
  scm_c_define ("vtable-index-printer",
		scm_from_int (scm_vtable_index_instance_printer));
  scm_c_define ("vtable-offset-user", scm_from_int (scm_vtable_offset_user));
#include "libguile/struct.x"
}

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