diff --git a/libguile/struct.c b/libguile/struct.c
index 321f2f199..adebe6f9f 100644
--- a/libguile/struct.c
+++ b/libguile/struct.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1996,1997,1998,1999,2000,2001, 2003, 2004, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 1996,1997,1998,1999,2000,2001, 2003, 2004, 2006, 2007, 2008, 2009, 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
@@ -22,6 +22,7 @@
 #endif
 
 #include <alloca.h>
+#include <assert.h>
 
 #include "libguile/_scm.h"
 #include "libguile/async.h"
@@ -151,6 +152,61 @@ SCM_DEFINE (scm_make_struct_layout, "make-struct-layout", 1, 0, 0,
 #undef FUNC_NAME
 
 
+/* Check whether VTABLE instances have a simple layout (i.e., either only "pr"
+   or only "pw" fields) 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':
+	  case 'W':
+	    if (!(flags & SCM_VTABLE_FLAG_SIMPLE_RW) && field > 0)
+	      /* There's a mixture of `w' and `r' flags.  */
+	      flags = 0;
+	    else
+	      flags |= SCM_VTABLE_FLAG_SIMPLE_RW;
+	    break;
+
+	  case 'r':
+	  case 'R':
+	    if (flags & SCM_VTABLE_FLAG_SIMPLE_RW)
+	      /* There's a mixture of `w' and `r' flags.  */
+	      flags = 0;
+	    break;
+
+	  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);
+    }
+}
 
 void
 scm_i_struct_inherit_vtable_magic (SCM vtable, SCM obj)
@@ -171,6 +227,8 @@ scm_i_struct_inherit_vtable_magic (SCM vtable, SCM obj)
     scm_misc_error (FUNC_NAME, "invalid layout for new vtable",
                     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));
@@ -215,60 +273,74 @@ static void
 scm_struct_init (SCM handle, SCM layout, size_t n_tail,
                  size_t n_inits, scm_t_bits *inits)
 {
-  scm_t_wchar prot = 0;
-  int n_fields = scm_i_symbol_length (layout) / 2;
-  int tailp = 0;
-  int i;
-  size_t inits_idx = 0;
-  scm_t_bits *mem = SCM_STRUCT_DATA (handle);
+  SCM vtable;
+  scm_t_bits *mem;
 
-  i = -2;
-  while (n_fields)
+  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
     {
-      if (!tailp)
+      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)
 	{
-	  i += 2;
-	  prot = scm_i_symbol_ref (layout, i+1);
-	  if (SCM_LAYOUT_TAILP (prot))
+	  if (!tailp)
 	    {
-	      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;
+	      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++;
 	}
-      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++;
     }
 }
 
@@ -627,71 +699,81 @@ SCM_DEFINE (scm_struct_ref, "struct-ref", 2, 0, 0,
 	    "integer value small enough to fit in one machine word.")
 #define FUNC_NAME s_scm_struct_ref
 {
-  SCM answer = SCM_UNDEFINED;
-  scm_t_bits * data;
-  SCM layout;
-  size_t layout_len;
+  SCM vtable, answer = SCM_UNDEFINED;
+  scm_t_bits *data;
   size_t p;
-  scm_t_bits n_fields;
-  scm_t_wchar field_type = 0;
-  
 
   SCM_VALIDATE_STRUCT (1, handle);
 
-  layout = SCM_STRUCT_LAYOUT (handle);
+  vtable = SCM_STRUCT_VTABLE (handle);
   data = SCM_STRUCT_DATA (handle);
   p = scm_to_size_t (pos);
 
-  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)
+  if (SCM_LIKELY (SCM_VTABLE_FLAG_IS_SET (vtable, SCM_VTABLE_FLAG_SIMPLE)
+  		  && p < SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size)))
     {
-      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));
-	}
+      /* The fast path: HANDLE is a struct with only "p" fields.  */
+      answer = SCM_PACK (data[p]);
     }
-  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':
-      answer = scm_from_ulong (data[p]);
-      break;
+      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':
+	  answer = scm_from_ulong (data[p]);
+	  break;
 
 #if 0
-    case 'i':
-      answer = scm_from_long (data[p]);
-      break;
+	case 'i':
+	  answer = scm_from_long (data[p]);
+	  break;
 
-    case 'd':
-      answer = scm_make_real (*((double *)&(data[p])));
-      break;
+	case 'd':
+	  answer = scm_make_real (*((double *)&(data[p])));
+	  break;
 #endif
 
-    case 's':
-    case 'p':
-      answer = SCM_PACK (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)));
+	default:
+	  SCM_MISC_ERROR ("unrecognized field type: ~S",
+			  scm_list_1 (SCM_MAKE_CHAR (field_type)));
+	}
     }
 
   return answer;
@@ -706,65 +788,76 @@ SCM_DEFINE (scm_struct_set_x, "struct-set!", 3, 0, 0,
 	    "to.")
 #define FUNC_NAME s_scm_struct_set_x
 {
-  scm_t_bits * data;
-  SCM layout;
-  size_t layout_len;
+  SCM vtable;
+  scm_t_bits *data;
   size_t p;
-  int n_fields;
-  scm_t_wchar field_type = 0;
 
   SCM_VALIDATE_STRUCT (1, handle);
 
-  layout = SCM_STRUCT_LAYOUT (handle);
+  vtable = SCM_STRUCT_VTABLE (handle);
   data = SCM_STRUCT_DATA (handle);
   p = scm_to_size_t (pos);
 
-  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);
+  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 "p" fields.  */
+    data[p] = SCM_UNPACK (val);
   else
-    SCM_MISC_ERROR ("set! denied for field ~A", scm_list_1 (pos));
-  
-  switch (field_type)
     {
-    case 'u':
-      data[p] = SCM_NUM2ULONG (3, val);
-      break;
+      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':
+	  data[p] = SCM_NUM2ULONG (3, val);
+	  break;
 
 #if 0
-    case 'i':
-      data[p] = SCM_NUM2LONG (3, val);
-      break;
+	case 'i':
+	  data[p] = SCM_NUM2LONG (3, val);
+	  break;
 
-    case 'd':
-      *((double *)&(data[p])) = scm_num2dbl (val, (char *)SCM_ARG3);
-      break;
+	case 'd':
+	  *((double *)&(data[p])) = scm_num2dbl (val, (char *)SCM_ARG3);
+	  break;
 #endif
 
-    case 'p':
-      data[p] = SCM_UNPACK (val);
-      break;
+	case 'p':
+	  data[p] = SCM_UNPACK (val);
+	  break;
 
-    case 's':
-      SCM_MISC_ERROR ("self fields immutable", SCM_EOL);
+	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)));
+	default:
+	  SCM_MISC_ERROR ("unrecognized field type: ~S",
+			  scm_list_1 (SCM_MAKE_CHAR (field_type)));
+	}
     }
 
   return val;
diff --git a/libguile/struct.h b/libguile/struct.h
index 537ef90ed..012d9b6e7 100644
--- a/libguile/struct.h
+++ b/libguile/struct.h
@@ -3,7 +3,7 @@
 #ifndef SCM_STRUCT_H
 #define SCM_STRUCT_H
 
-/* Copyright (C) 1995,1997,1999,2000,2001, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 1995,1997,1999,2000,2001, 2006, 2007, 2008, 2009, 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
@@ -41,12 +41,12 @@
 /* All vtables have the following fields. */
 #define SCM_VTABLE_BASE_LAYOUT                                          \
   "pr" /* layout */                                                     \
-  "uh" /* flags */                                                      \
+  "uh" /* flags */							\
   "sr" /* self */                                                       \
   "uh" /* finalizer */                                                  \
   "pw" /* printer */                                                    \
   "ph" /* name (hidden from make-struct for back-compat reasons) */     \
-  "uh" /* reserved */                                                   \
+  "uh" /* size */							\
   "uh" /* reserved */
 
 #define scm_vtable_index_layout            0 /* A symbol describing the physical arrangement of this type. */
@@ -55,7 +55,7 @@
 #define scm_vtable_index_instance_finalize 3 /* Finalizer for instances of this struct type. */
 #define scm_vtable_index_instance_printer  4 /* A printer for this struct type. */
 #define scm_vtable_index_name              5 /* Name of this vtable. */
-#define scm_vtable_index_reserved_6        6
+#define scm_vtable_index_size              6 /* Number of fields, for simple structs.  */
 #define scm_vtable_index_reserved_7        7
 #define scm_vtable_offset_user             8 /* Where do user fields start in the vtable? */
 
@@ -79,8 +79,8 @@
 #define SCM_VTABLE_FLAG_APPLICABLE (1L << 2) /* instances of this vtable are applicable? */
 #define SCM_VTABLE_FLAG_SETTER_VTABLE (1L << 3) /* instances of this vtable are applicable-with-setter vtables? */
 #define SCM_VTABLE_FLAG_SETTER (1L << 4) /* instances of this vtable are applicable-with-setters? */
-#define SCM_VTABLE_FLAG_RESERVED_0 (1L << 5)
-#define SCM_VTABLE_FLAG_RESERVED_1 (1L << 6)
+#define SCM_VTABLE_FLAG_SIMPLE (1L << 5) /* instances of this vtable have only "pr" fields */
+#define SCM_VTABLE_FLAG_SIMPLE_RW (1L << 6) /* instances of this vtable have only "pw" fields */
 #define SCM_VTABLE_FLAG_SMOB_0 (1L << 7)
 #define SCM_VTABLE_FLAG_GOOPS_0 (1L << 8)
 #define SCM_VTABLE_FLAG_GOOPS_1 (1L << 9)
diff --git a/test-suite/tests/structs.test b/test-suite/tests/structs.test
index 2c2ca0c9c..55e08075b 100644
--- a/test-suite/tests/structs.test
+++ b/test-suite/tests/structs.test
@@ -1,7 +1,7 @@
-;;;; structs.test --- Test suite for Guile's structures.   -*- Scheme -*-
-;;;; Ludovic Courtès <ludovic.courtes@laas.fr>, 2006-06-12.
+;;;; structs.test --- Structures.      -*- mode: scheme; coding: utf-8; -*-
+;;;; Ludovic Courtès <ludo@gnu.org>, 2006-06-12.
 ;;;;
-;;;; Copyright (C) 2006, 2007, 2009 Free Software Foundation, Inc.
+;;;; Copyright (C) 2006, 2007, 2009, 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
@@ -80,9 +80,33 @@
   (pass-if "struct-set!"
      (let ((ball (make-ball green "Bob")))
        (set-owner! ball "Bill")
-       (string=? (owner ball) "Bill"))))
+       (string=? (owner ball) "Bill")))
 
+  (pass-if "struct-ref"
+     (let ((ball (make-ball red "Alice")))
+       (equal? (struct-ref ball 0) "Alice")))
 
+  (pass-if "struct-set!"
+     (let* ((v (make-vtable "pw"))
+            (s (make-struct v 0))
+            (r (struct-set! s 0 'a)))
+       (eq? r
+            (struct-ref s 0)
+            'a)))
+
+  (pass-if-exception "struct-ref out-of-range"
+     exception:out-of-range
+     (let* ((v (make-vtable "prpr"))
+            (s (make-struct v 0 'a 'b)))
+       (struct-ref s 2)))
+
+  (pass-if-exception "struct-set! out-of-range"
+     exception:out-of-range
+     (let* ((v (make-vtable "pwpw"))
+            (s (make-struct v 0 'a 'b)))
+       (struct-set! s 2 'c))))
+
+
 (with-test-prefix "equal?"
 
   (pass-if "simple structs"
@@ -153,8 +177,3 @@
 		      (lambda (port)
 			(display struct port)))))
 	 (equal? str "hello")))))
-
-
-;;; Local Variables:
-;;; coding: latin-1
-;;; End: