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Reindent some code, no real change (should do it for all my code once for good)
[simgrid.git] / src / gras / DataDesc / ddt_create.c
index d69fe8f..72e896f 100644 (file)
 
 /* ddt_new - creation/deletion of datatypes structs (private to this module)*/
 
-/* Authors: Olivier Aumage, Martin Quinson                                  */
-/* Copyright (C) 2003, 2004 the GRAS posse.                                 */
+/* Copyright (c) 2003 Olivier Aumage.                                       */
+/* Copyright (c) 2003, 2004 Martin Quinson.                                 */
+/* All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  under the terms of the license (GNU LGPL) which comes with this package. */
* under the terms of the license (GNU LGPL) which comes with this package. */
 
-#include "DataDesc/datadesc_private.h"
+#include "xbt/misc.h" /* min()/max() */
+#include "xbt/ex.h"
+#include "gras/DataDesc/datadesc_private.h"
 
-GRAS_LOG_NEW_DEFAULT_SUBCATEGORY(create,datadesc);
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(gras_ddt_create,gras_ddt,"Creating new datadescriptions");
 
+/*** prototypes ***/
+static gras_dd_cat_field_t
+gras_dd_find_field(gras_datadesc_type_t  type,
+               const char           *field_name);
 /**
  * gras_ddt_freev:
  *
  * gime that memory back, dude. I mean it.
  */
 void gras_ddt_freev(void *ddt) {
-  gras_datadesc_type_t *type= (gras_datadesc_type_t *)ddt;
-  
-  if (type) {
-    gras_datadesc_unref(type);
-  }
+       gras_datadesc_type_t type= (gras_datadesc_type_t)ddt;
+
+       if (type) {
+               gras_datadesc_free(&type);
+       }
 }
 
-static gras_error_t
-gras_ddt_new(const char            *name,
-            gras_datadesc_type_t **dst) {
+static gras_datadesc_type_t gras_ddt_new(const char *name) {
+       gras_datadesc_type_t res;
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
+       XBT_IN1("(%s)",name);
+       res=xbt_new0(s_gras_datadesc_type_t,1);
 
-  res=malloc(sizeof(gras_datadesc_type_t));
-  if (!res) 
-    RAISE_MALLOC;
+       res->name = (char*)strdup(name);
+       res->name_len = strlen(name);
+       res->cycle = 0;
 
-  memset(res, 0, sizeof(gras_datadesc_type_t));
-  res->name = strdup(name);
-  res->name_len = strlen(name);
-  res->refcounter = 1;
-  
-  TRY(gras_set_add(gras_datadesc_set_local,
-                  (gras_set_elm_t*)res,&gras_ddt_freev));
-    
-  *dst=res;
-  return no_error;
+       xbt_set_add(gras_datadesc_set_local,
+                       (xbt_set_elm_t)res,gras_ddt_freev);
+       XBT_OUT;
+       return res;
 }
 
+/** @brief retrieve an existing message type from its name (or NULL if it does not exist). */
+gras_datadesc_type_t gras_datadesc_by_name_or_null (const char *name) {
+       xbt_ex_t e;
+       gras_datadesc_type_t res = NULL;
+
+       TRY {
+               res = gras_datadesc_by_name(name);
+       } CATCH(e) {
+               res = NULL;
+               xbt_ex_free(e);
+       }
+       return res;
+}
 /**
- * gras_datadesc_by_name:
- *
- * Retrieve a type from its name
+ * Search the given datadesc (or raises an exception if it can't be found)
  */
-gras_datadesc_type_t *gras_datadesc_by_name(const char *name) {
-
-  gras_datadesc_type_t *type;
-
-  if (gras_set_get_by_name(gras_datadesc_set_local,
-                          name,(gras_set_elm_t**)&type) == no_error) {
-    return type;
-  } else { 
-    return NULL;
-  }
+gras_datadesc_type_t gras_datadesc_by_name(const char *name) {
+       xbt_ex_t e;
+       gras_datadesc_type_t res = NULL;
+       volatile int found = 0;
+       TRY {
+               res = (gras_datadesc_type_t)xbt_set_get_by_name(gras_datadesc_set_local,name);
+               found = 1;
+       } CATCH(e) {
+               if (e.category != not_found_error)
+                       RETHROW;
+               xbt_ex_free(e);
+       }
+       if (!found)
+               THROW1(not_found_error,0,"No registred datatype of that name: %s",name);
+
+       return res;
 }
 
 /**
- * gras_datadesc_by_id:
- *
- * Retrieve a type from its code
+ * Retrieve a type from its code (or NULL if not found)
  */
-gras_error_t gras_datadesc_by_id(long int               code,
-                                gras_datadesc_type_t **type) {
-  return gras_set_get_by_id(gras_datadesc_set_local,
-                           code,(gras_set_elm_t**)type);
+gras_datadesc_type_t gras_datadesc_by_id(long int code) {
+       xbt_ex_t e;
+       gras_datadesc_type_t res=NULL;
+       TRY {
+               res = (gras_datadesc_type_t)xbt_set_get_by_id(gras_datadesc_set_local,code);
+       } CATCH(e) {
+               if (e.category != not_found_error)
+                       RETHROW;
+               xbt_ex_free(e);
+               res = NULL;
+       }
+       return res;
 }
 
 /**
- * gras_datadesc_scalar:
- *
- * Create a new scalar and give a pointer to it 
+ * Create a new scalar and give a pointer to it
  */
-gras_error_t 
+gras_datadesc_type_t
 gras_datadesc_scalar(const char                      *name,
-                    gras_ddt_scalar_type_t           type,
-                    enum e_gras_dd_scalar_encoding   encoding,
-                    gras_datadesc_type_t           **dst) {
-
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  long int arch;
-
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
-
-  for (arch = 0; arch < gras_arch_count; arch ++) {
-    long int sz;
-    long int mask;
-    res->size[arch] = gras_arches[arch].sizeof_scalars[type];
-
-    sz = res->size[arch];
-    mask = sz;
-    
-    /* just in case you wonder, x>>1 == x/2 on all architectures when x>=0
-       and a size is always>=0 */
-    
-    /* make sure mask have all the bits under the biggest one of size set to 1
-       Example: size=000100101 => mask=0000111111 */
-    while ((sz >>= 1)) {
-      mask |= sz;
-    } 
-    
-    if (res->size[arch] & (mask >> 1)) { /* if size have bits to one beside its biggest */
-      /* size is not a power of 2 */
-      /* alignment= next power of 2 after size */
-      res->alignment[arch] = (res->size[arch] & ~(mask >> 1)) << 1;
-      gras_assert0(res->alignment[arch] != 0,
-                  "scalar type too large");
-      
-      res->aligned_size[arch] = aligned(res->size[arch], res->alignment[arch]);
-      gras_assert0 (res->aligned_size[arch] >= 0,
-                   "scalar type too large");
-      
-    } else {
-      /* size is a power of 2, life is great */
-      res->alignment[arch]       = res->size[arch];
-      res->aligned_size[arch]    = res->size[arch];
-    }
-  }
-
-  res->category_code                 = e_gras_datadesc_type_cat_scalar;
-  res->category.scalar_data.encoding = encoding;
-
-  return no_error;
+               gras_ddt_scalar_type_t           type,
+               enum e_gras_dd_scalar_encoding   encoding) {
+
+       gras_datadesc_type_t res;
+       long int arch;
+
+       XBT_IN;
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_scalar,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.scalar_data.encoding == encoding,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.scalar_data.type == type,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+               return res;
+       }
+       res = gras_ddt_new(name);
+
+       for (arch = 0; arch < gras_arch_count; arch ++) {
+               res->size[arch]         = gras_arches[arch].sizeofs[type];
+               res->alignment[arch]    = gras_arches[arch].boundaries[type];
+               res->aligned_size[arch] = ddt_aligned(res->size[arch], res->alignment[arch]);
+       }
+
+       res->category_code                 = e_gras_datadesc_type_cat_scalar;
+       res->category.scalar_data.encoding = encoding;
+       res->category.scalar_data.type     = type;
+       XBT_OUT;
+
+       return res;
 }
 
 
-/**
- * gras_dd_cat_field_free:
- *
- * Frees one struct or union field
- */
+/** Frees one struct or union field */
 void gras_dd_cat_field_free(void *f) {
-  gras_dd_cat_field_t *field = *(gras_dd_cat_field_t **)f;
-  if (field) {
-    if (field->name) 
-      free(field->name);
-    free(field);
-  }
+       gras_dd_cat_field_t field = *(gras_dd_cat_field_t *)f;
+       XBT_IN;
+       if (field) {
+               if (field->name)
+                       free(field->name);
+               free(field);
+       }
+       XBT_OUT;
 }
 
-/**
- * gras_datadesc_struct:
- *
- * Create a new struct and give a pointer to it 
- */
-gras_error_t 
-gras_datadesc_struct(const char            *name,
-                    gras_datadesc_type_t **dst) {
-
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  long int arch;
-
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+/** \brief Declare a new structure description */
+gras_datadesc_type_t
+gras_datadesc_struct(const char            *name) {
+
+       gras_datadesc_type_t res;
+       long int arch;
+
+       XBT_IN1("(%s)",name);
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               /* FIXME: Check that field redefinition matches */
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_struct,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+               return res;
+       }
+       res = gras_ddt_new(name);
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               res->size[arch] = 0;
+               res->alignment[arch] = 0;
+               res->aligned_size[arch] = 0;
+       }
+       res->category_code = e_gras_datadesc_type_cat_struct;
+       res->category.struct_data.fields =
+               xbt_dynar_new(sizeof(gras_dd_cat_field_t),
+                               gras_dd_cat_field_free);
+
+       XBT_OUT;
+       return res;
+}
 
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    res->size[arch] = 0;
-    res->alignment[arch] = 0;
-    res->aligned_size[arch] = 0;
-  }
-  res->category_code = e_gras_datadesc_type_cat_struct;
-  TRY(gras_dynar_new(&(res->category.struct_data.fields),
-                    sizeof(gras_dd_cat_field_t*),
-                    &gras_dd_cat_field_free));
+/** \brief Append a new field to a structure description */
+void
+gras_datadesc_struct_append(gras_datadesc_type_t struct_type,
+               const char          *name,
+               gras_datadesc_type_t field_type) {
+
+       gras_dd_cat_field_t field;
+       int arch;
+
+       xbt_assert2(field_type,
+                       "Cannot add the field '%s' into struct '%s': its type is NULL",
+                       name,struct_type->name);
+       XBT_IN3("(%s %s.%s;)",field_type->name,struct_type->name,name);
+       if (struct_type->category.struct_data.closed) {
+               VERB1("Ignoring request to add field to struct %s (closed. Redefinition?)",
+                               struct_type->name);
+               return;
+       }
+
+       xbt_assert1(field_type->size != 0,
+                       "Cannot add a dynamically sized field in structure %s",
+                       struct_type->name);
+
+       field=xbt_new(s_gras_dd_cat_field_t,1);
+       field->name   = (char*)strdup(name);
+
+       DEBUG0("----------------");
+       DEBUG3("PRE s={size=%ld,align=%ld,asize=%ld}",
+                       struct_type->size[GRAS_THISARCH],
+                       struct_type->alignment[GRAS_THISARCH],
+                       struct_type->aligned_size[GRAS_THISARCH]);
+
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               field->offset[arch] = ddt_aligned(struct_type->size[arch],
+                               field_type->alignment[arch]);
+
+               struct_type->size[arch] = field->offset[arch] + field_type->size[arch];
+               struct_type->alignment[arch] = max(struct_type->alignment[arch],
+                               field_type->alignment[arch]);
+               struct_type->aligned_size[arch] = ddt_aligned(struct_type->size[arch],
+                               struct_type->alignment[arch]);
+       }
+       field->type   = field_type;
+       field->send   = NULL;
+       field->recv   = NULL;
+
+       xbt_dynar_push(struct_type->category.struct_data.fields, &field);
+
+       DEBUG3("Push a %s into %s at offset %ld.",
+                       field_type->name, struct_type->name,field->offset[GRAS_THISARCH]);
+       DEBUG3("  f={size=%ld,align=%ld,asize=%ld}",
+                       field_type->size[GRAS_THISARCH],
+                       field_type->alignment[GRAS_THISARCH],
+                       field_type->aligned_size[GRAS_THISARCH]);
+       DEBUG3("  s={size=%ld,align=%ld,asize=%ld}",
+                       struct_type->size[GRAS_THISARCH],
+                       struct_type->alignment[GRAS_THISARCH],
+                       struct_type->aligned_size[GRAS_THISARCH]);
+       XBT_OUT;
+}
 
-  return no_error;
+/** \brief Close a structure description
+ *
+ * No new field can be added afterward, and it is mandatory to close the structure before using it.
+ */
+void
+gras_datadesc_struct_close(gras_datadesc_type_t struct_type) {
+       int arch;
+       XBT_IN;
+       struct_type->category.struct_data.closed = 1;
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               struct_type->size[arch] = struct_type->aligned_size[arch];
+       }
+       DEBUG4("structure %s closed. size=%ld,align=%ld,asize=%ld",
+                       struct_type->name,
+                       struct_type->size[GRAS_THISARCH],
+                       struct_type->alignment[GRAS_THISARCH],
+                       struct_type->aligned_size[GRAS_THISARCH]);
 }
 
 /**
- * gras_datadesc_struct_append:
+ * gras_datadesc_cycle_set:
  *
- * Append a field to the struct
+ * Tell GRAS that the pointers of the type described by ddt may present
+ * some loop, and that the cycle detection mechanism is needed.
+ *
+ * Note that setting this option when not needed have a rather bad effect
+ * on the performance (several times slower on big data).
  */
-gras_error_t 
-gras_datadesc_struct_append(gras_datadesc_type_t  *struct_type,
-                           const char            *name,
-                           gras_datadesc_type_t  *field_type) {
-
-  gras_error_t errcode;
-  gras_dd_cat_field_t *field;
-  int arch;
-  gras_assert1(!struct_type->category.struct_data.closed,
-              "Cannot add anything to the already closed struct %s",
-              struct_type->name);
-  gras_assert1(field_type->size >= 0,
-              "Cannot add a dynamically sized field in structure %s",
-              struct_type->name);
-    
-  field=malloc(sizeof(gras_dd_cat_field_t));
-  if (!field)
-    RAISE_MALLOC;
-
-  field->name   = strdup(name);
-
-  DEBUG0("----------------");
-  DEBUG4("PRE s={size=%ld,align=%ld,asize=%ld} struct_boundary=%d",
-        struct_type->size[GRAS_THISARCH], 
-        struct_type->alignment[GRAS_THISARCH], 
-        struct_type->aligned_size[GRAS_THISARCH],
-        gras_arches[GRAS_THISARCH].struct_boundary);
-     
-     
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    field->offset[arch] = aligned(struct_type->size[arch],
-                                 min(field_type->alignment[arch],
-                                     gras_arches[arch].struct_boundary));
-
-    struct_type->size[arch] = field->offset[arch] + field_type->size[arch];
-    struct_type->alignment[arch] = max(struct_type->alignment[arch],
-                                      field_type->alignment[arch]);
-    struct_type->aligned_size[arch] = aligned(struct_type->size[arch],
-                                             struct_type->alignment[arch]);
-  }
-  field->code   = field_type->code;
-  field->pre    = NULL;
-  field->post   = NULL;
-  
-  TRY(gras_dynar_push(struct_type->category.struct_data.fields, &field));
-
-  DEBUG3("Push a %s into %s at offset %ld.",
-        field_type->name, struct_type->name,field->offset[GRAS_THISARCH]);
-  DEBUG3("  f={size=%ld,align=%ld,asize=%ld}",
-        field_type->size[GRAS_THISARCH], 
-        field_type->alignment[GRAS_THISARCH], 
-        field_type->aligned_size[GRAS_THISARCH]);
-  DEBUG3("  s={size=%ld,align=%ld,asize=%ld}",
-        struct_type->size[GRAS_THISARCH], 
-        struct_type->alignment[GRAS_THISARCH], 
-        struct_type->aligned_size[GRAS_THISARCH]);
-  return no_error;
-}
 void
-gras_datadesc_struct_close(gras_datadesc_type_t  *struct_type) {
-   struct_type->category.struct_data.closed = 1;
-   //   INFO0("FIXME: Do something in gras_datadesc_struct_close");
+gras_datadesc_cycle_set(gras_datadesc_type_t ddt) {
+       ddt->cycle = 1;
 }
 
 /**
- * gras_datadesc_union:
+ * gras_datadesc_cycle_unset:
  *
- * Create a new union and give a pointer to it 
+ * Tell GRAS that the pointers of the type described by ddt do not present
+ * any loop and that cycle detection mechanism are not needed.
+ * (default)
  */
-gras_error_t 
+void
+gras_datadesc_cycle_unset(gras_datadesc_type_t ddt) {
+       ddt->cycle = 0;
+}
+
+/** \brief Declare a new union description */
+gras_datadesc_type_t
 gras_datadesc_union(const char                   *name,
-                   gras_datadesc_type_cb_int_t   selector,
-                   gras_datadesc_type_t        **dst) {
+               gras_datadesc_type_cb_int_t   selector) {
+
+       gras_datadesc_type_t res;
+       int arch;
+
+       XBT_IN1("(%s)",name);
+       xbt_assert0(selector,
+                       "Attempt to creat an union without field_count function");
+
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               /* FIXME: Check that field redefinition matches */
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_union,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.union_data.selector == selector,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+               return res;
+       }
+
+       res = gras_ddt_new(name);
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               res->size[arch] = 0;
+               res->alignment[arch] = 0;
+               res->aligned_size[arch] = 0;
+       }
+
+       res->category_code              = e_gras_datadesc_type_cat_union;
+       res->category.union_data.fields =
+               xbt_dynar_new(sizeof(gras_dd_cat_field_t*),
+                               gras_dd_cat_field_free);
+       res->category.union_data.selector = selector;
+
+       return res;
+}
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  int arch;
+/** \brief Append a new field to an union description */
+void gras_datadesc_union_append(gras_datadesc_type_t  union_type,
+               const char           *name,
+               gras_datadesc_type_t  field_type) {
+
+       gras_dd_cat_field_t field;
+       int arch;
+
+       XBT_IN3("(%s %s.%s;)",field_type->name,union_type->name,name);
+       xbt_assert1(field_type->size != 0,
+                       "Cannot add a dynamically sized field in union %s",
+                       union_type->name);
+
+       if (union_type->category.union_data.closed) {
+               VERB1("Ignoring request to add field to union %s (closed)",
+                               union_type->name);
+               return;
+       }
+
+       field=xbt_new0(s_gras_dd_cat_field_t,1);
+
+       field->name   = (char*)strdup(name);
+       field->type   = field_type;
+       /* All offset are left to 0 in an union */
+
+       xbt_dynar_push(union_type->category.union_data.fields, &field);
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               union_type->size[arch] = max(union_type->size[arch],
+                               field_type->size[arch]);
+               union_type->alignment[arch] = max(union_type->alignment[arch],
+                               field_type->alignment[arch]);
+               union_type->aligned_size[arch] = ddt_aligned(union_type->size[arch],
+                               union_type->alignment[arch]);
+       }
+}
 
-  gras_assert0(selector,
-              "Attempt to creat an union without field_count function");
 
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+/** \brief Close an union description
+ *
+ * No new field can be added afterward, and it is mandatory to close the union before using it.
+ */
+void
+gras_datadesc_union_close(gras_datadesc_type_t union_type) {
+       union_type->category.union_data.closed = 1;
+}
 
-  for (arch=0; arch<gras_arch_count; arch ++) {
-     res->size[arch] = 0;
-     res->alignment[arch] = 0;
-     res->aligned_size[arch] = 0;
-  }
+/** \brief Copy a type under another name
+ *
+ * This may reveal useful to circumvent parsing macro limitations
+ */
+gras_datadesc_type_t
+gras_datadesc_copy(const char           *name,
+               gras_datadesc_type_t  copied) {
 
-  res->category_code           = e_gras_datadesc_type_cat_union;
-  TRY(gras_dynar_new(&(res->category.union_data.fields),
-                    sizeof(gras_dd_cat_field_t*),
-                    &gras_dd_cat_field_free));
-  res->category.union_data.selector = selector;
+       gras_datadesc_type_t res = gras_ddt_new(name);
+       char *name_cpy = res->name;
 
-  return no_error;
+       memcpy(res,copied,sizeof(s_gras_datadesc_type_t));
+       res->name = name_cpy;
+       return res;
 }
 
-/**
- * gras_datadesc_union_append:
+/** \brief Declare a new type being a reference to the one passed in arg */
+gras_datadesc_type_t
+gras_datadesc_ref(const char           *name,
+               gras_datadesc_type_t  referenced_type) {
+
+       gras_datadesc_type_t res;
+       gras_datadesc_type_t pointer_type = gras_datadesc_by_name("data pointer");
+       int arch;
+
+       XBT_IN1("(%s)",name);
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_ref,
+                               "Redefinition of %s does not match",name);
+               xbt_assert1(res->category.ref_data.type == referenced_type,
+                               "Redefinition of %s does not match",name);
+               xbt_assert1(res->category.ref_data.selector == NULL,
+                               "Redefinition of %s does not match",name);
+               VERB1("Discarding redefinition of %s",name);
+               return res;
+       }
+
+       res = gras_ddt_new(name);
+
+       xbt_assert0(pointer_type, "Cannot get the description of data pointer");
+
+       for (arch=0; arch<gras_arch_count; arch ++){
+               res->size[arch] = pointer_type->size[arch];
+               res->alignment[arch] = pointer_type->alignment[arch];
+               res->aligned_size[arch] = pointer_type->aligned_size[arch];
+       }
+
+       res->category_code                = e_gras_datadesc_type_cat_ref;
+       res->category.ref_data.type     = referenced_type;
+       res->category.ref_data.selector = NULL;
+
+       return res;
+}
+/** \brief Declare a new type being a generic reference.
  *
- * Append a field to the union
+ * The callback passed in argument is to be used to select which type is currently used.
+ * So, when GRAS wants to send a generic reference, it passes the current data to the selector
+ * callback and expects it to return the type description to use.
  */
-gras_error_t 
-gras_datadesc_union_append(gras_datadesc_type_t  *union_type,
-                          const char            *name,
-                          gras_datadesc_type_t  *field_type) {
-
-  gras_error_t errcode;
-  gras_dd_cat_field_t *field;
-  int arch;
-
-  gras_assert1(!union_type->category.union_data.closed,
-              "Cannot add anything to the already closed union %s",
-              union_type->name);
-  gras_assert1(field_type->size >= 0,
-              "Cannot add a dynamically sized field in union %s",
-              union_type->name);
-    
-  field=malloc(sizeof(gras_dd_cat_field_t));
-  if (!field)
-    RAISE_MALLOC;
-
-  field->name   = strdup(name);
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    field->offset[arch] = 0; /* that's the purpose of union ;) */
-  }
-  field->code   = field_type->code;
-  field->pre    = NULL;
-  field->post   = NULL;
-  
-  TRY(gras_dynar_push(union_type->category.union_data.fields, &field));
-
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    union_type->size[arch] = max(union_type->size[arch],
-                                field_type->size[arch]);
-    union_type->alignment[arch] = max(union_type->alignment[arch],
-                                     field_type->alignment[arch]);
-    union_type->aligned_size[arch] = aligned(union_type->size[arch],
-                                            union_type->alignment[arch]);
-  }
-  return no_error;
+gras_datadesc_type_t
+gras_datadesc_ref_generic(const char                *name,
+               gras_datadesc_selector_t   selector) {
+
+       gras_datadesc_type_t res;
+       gras_datadesc_type_t pointer_type = gras_datadesc_by_name("data pointer");
+       int arch;
+
+       XBT_IN1("(%s)",name);
+       res = gras_datadesc_by_name_or_null(name);
+
+       if (res) {
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_ref,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.ref_data.type == NULL,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.ref_data.selector == selector,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+               return res;
+       }
+       res = gras_ddt_new(name);
+
+       xbt_assert0(pointer_type, "Cannot get the description of data pointer");
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               res->size[arch] = pointer_type->size[arch];
+               res->alignment[arch] = pointer_type->alignment[arch];
+               res->aligned_size[arch] = pointer_type->aligned_size[arch];
+       }
+
+       res->category_code              = e_gras_datadesc_type_cat_ref;
+
+       res->category.ref_data.type     = NULL;
+       res->category.ref_data.selector = selector;
+
+       return res;
 }
 
-void
-gras_datadesc_union_close(gras_datadesc_type_t  *union_type) {
-   union_type->category.union_data.closed = 1;
-   //   INFO0("FIXME: Do something in gras_datadesc_union_close");
+/** \brief Declare a new type being an array of fixed size and content */
+gras_datadesc_type_t
+gras_datadesc_array_fixed(const char           *name,
+               gras_datadesc_type_t  element_type,
+               long int              fixed_size) {
+
+       gras_datadesc_type_t res;
+       int arch;
+
+       XBT_IN1("(%s)",name);
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_array,
+                               "Redefinition of type %s does not match", name);
+
+               if (res->category.array_data.type != element_type) {
+                       ERROR1("Redefinition of type %s does not match: array elements differ", name);
+                       gras_datadesc_type_dump(res->category.array_data.type);
+                       gras_datadesc_type_dump(element_type);
+               }
+
+               xbt_assert1(res->category.array_data.fixed_size == fixed_size,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.array_data.dynamic_size == NULL,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+
+               return res;
+       }
+       res = gras_ddt_new(name);
+
+       xbt_assert1(fixed_size > 0, "'%s' is a array of null fixed size",name);
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               res->size[arch] = fixed_size * element_type->aligned_size[arch];
+               res->alignment[arch] = element_type->alignment[arch];
+               res->aligned_size[arch] = res->size[arch];
+       }
+
+       res->category_code              = e_gras_datadesc_type_cat_array;
+
+       res->category.array_data.type         = element_type;
+       res->category.array_data.fixed_size   = fixed_size;
+       res->category.array_data.dynamic_size = NULL;
+
+       return res;
 }
-/**
- * gras_datadesc_ref:
+
+/** \brief Declare a new type being an array of fixed size, but accepting several content types. */
+gras_datadesc_type_t gras_datadesc_array_dyn(const char                 *name,
+               gras_datadesc_type_t        element_type,
+               gras_datadesc_type_cb_int_t dynamic_size) {
+
+       gras_datadesc_type_t res;
+       int arch;
+
+       XBT_IN1("(%s)",name);
+       xbt_assert1(dynamic_size,
+                       "'%s' is a dynamic array without size discriminant",
+                       name);
+
+       res = gras_datadesc_by_name_or_null(name);
+       if (res) {
+               xbt_assert1(res->category_code == e_gras_datadesc_type_cat_array,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.array_data.type == element_type,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.array_data.fixed_size == 0,
+                               "Redefinition of type %s does not match", name);
+               xbt_assert1(res->category.array_data.dynamic_size == dynamic_size,
+                               "Redefinition of type %s does not match", name);
+               VERB1("Discarding redefinition of %s",name);
+
+               return res;
+       }
+
+       res = gras_ddt_new(name);
+
+       for (arch=0; arch<gras_arch_count; arch ++) {
+               res->size[arch] = 0; /* make sure it indicates "dynamic" */
+               res->alignment[arch] = element_type->alignment[arch];
+               res->aligned_size[arch] = 0; /*FIXME: That was so in GS, but looks stupid*/
+       }
+
+       res->category_code              = e_gras_datadesc_type_cat_array;
+
+       res->category.array_data.type         = element_type;
+       res->category.array_data.fixed_size   = 0;
+       res->category.array_data.dynamic_size = dynamic_size;
+
+       return res;
+}
+
+/** \brief Declare a new type being an array which size can be found with \ref gras_cbps_i_pop
+ *
+ * Most of the time, you want to include a reference in your structure which
+ * is a pointer to a dynamic array whose size is fixed by another field of
+ * your structure.
+ *
+ * This case pops up so often that this function was created to take care of
+ * this case. It creates a dynamic array type whose size is poped from the
+ * current cbps, and then create a reference to it.
+ *
+ * The name of the created datatype will be the name of the element type, with
+ * '[]*' appended to it.
+ *
+ * Then to use it, you just have to make sure that your structure pre-callback
+ * does push the size of the array in the cbps (using #gras_cbps_i_push), and
+ * you are set.
+ *
+ * But be remember that this is a stack. If you have two different pop_arr, you
+ * should push the second one first, so that the first one is on the top of the
+ * list when the first field gets transfered.
  *
- * Create a new ref to a fixed type and give a pointer to it 
  */
-gras_error_t 
-gras_datadesc_ref(const char             *name,
-                 gras_datadesc_type_t   *referenced_type,
-                 gras_datadesc_type_t  **dst) {
+gras_datadesc_type_t
+gras_datadesc_ref_pop_arr(gras_datadesc_type_t element_type) {
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  gras_datadesc_type_t *pointer_type = gras_datadesc_by_name("data pointer");
-  int arch;
+       gras_datadesc_type_t res;
+       char *name=(char*)xbt_malloc(strlen(element_type->name) + 4);
 
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+       sprintf(name,"%s[]",element_type->name);
 
-  gras_assert0(pointer_type, "Cannot get the description of data pointer");
-      
-  for (arch=0; arch<gras_arch_count; arch ++){
-    res->size[arch] = pointer_type->size[arch];
-    res->alignment[arch] = pointer_type->alignment[arch];
-    res->aligned_size[arch] = pointer_type->aligned_size[arch];
-  }
+       res = gras_datadesc_array_dyn(name,element_type,
+                       gras_datadesc_cb_pop);
 
-  res->category_code           = e_gras_datadesc_type_cat_ref;
+       sprintf(name,"%s[]*",element_type->name);
+       res = gras_datadesc_ref(name,res);
 
-  res->category.ref_data.code     = referenced_type->code;
-  res->category.ref_data.selector = NULL;
+       free(name);
 
-  return no_error;
+       return res;
 }
-/**
- * gras_datadesc_ref_generic:
- *
- * Create a new ref to a type given at use time, and give a pointer to it 
+
+/*
+ *##
+ *## Constructor of container datatypes
+ *##
  */
-gras_error_t 
-gras_datadesc_ref_generic(const char                      *name,
-                         gras_datadesc_type_cb_int_t      selector,
-                         gras_datadesc_type_t           **dst) {
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  gras_datadesc_type_t *pointer_type = gras_datadesc_by_name("data pointer");
-  int arch;
+#include "xbt/dynar_private.h"
+static void gras_datadesc_dynar_cb(gras_datadesc_type_t typedesc, gras_cbps_t vars, void *data) {
+       gras_datadesc_type_t subtype;
+       xbt_dynar_t dynar=(xbt_dynar_t)data;
 
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+       memcpy(&dynar->free_f, &typedesc->extra, sizeof(dynar->free_f));
 
-  gras_assert0(pointer_type, "Cannot get the description of data pointer");
-      
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    res->size[arch] = pointer_type->size[arch];
-    res->alignment[arch] = pointer_type->alignment[arch];
-    res->aligned_size[arch] = pointer_type->aligned_size[arch];
-  }
+       /* search for the elemsize in what we have. If elements are "int", typedesc got is "int[]*" */
+       subtype = gras_dd_find_field(typedesc,"data")->type;
 
-  res->category_code           = e_gras_datadesc_type_cat_ref;
+       /* this is now a ref to array of what we're looking for */
+       subtype = subtype->category.ref_data.type;
+       subtype = subtype->category.array_data.type;
 
-  res->category.ref_data.code     = -1;
-  res->category.ref_data.selector = selector;
+       DEBUG1("subtype is %s",subtype->name);
 
-  return no_error;
+       dynar->elmsize = subtype->size[GRAS_THISARCH];
+       dynar->size = dynar->used;
+       dynar->mutex = NULL;
 }
 
-/**
- * gras_datadesc_array_fixed:
+/** \brief Declare a new type being a dynar in which each elements are of the given type
+ *
+ *  The type gets registered under the name "dynar(%s)_s", where %s is the name of the subtype.
+ *  For example, a dynar of doubles will be called "dynar(double)_s" and a dynar of dynar of
+ *  strings will be called "dynar(dynar(string)_s)_s".
  *
- * Create a new array and give a pointer to it 
+ *  \param elm_t: the datadesc of the elements
+ *  \param free_func: the function to use to free the elements when the dynar gets freed
  */
-gras_error_t 
-gras_datadesc_array_fixed(const char              *name,
-                         gras_datadesc_type_t    *element_type,
-                         long int                 fixed_size,
-                         gras_datadesc_type_t   **dst) {
+gras_datadesc_type_t
+gras_datadesc_dynar(gras_datadesc_type_t elm_t,
+               void_f_pvoid_t free_func) {
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  int arch;
+       char *buffname;
+       gras_datadesc_type_t res;
 
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+       asprintf(&buffname,"s_xbt_dynar_of_%s",elm_t->name);
 
-  gras_assert1(fixed_size > 0, "'%s' is a array of negative fixed size",name);
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    res->size[arch] = fixed_size * element_type->aligned_size[arch];
-    res->alignment[arch] = element_type->alignment[arch];
-    res->aligned_size[arch] = res->size[arch];
-  }  
+       res = gras_datadesc_struct(buffname);
 
-  res->category_code           = e_gras_datadesc_type_cat_array;
+       gras_datadesc_struct_append(res, "size",
+                       gras_datadesc_by_name("unsigned long int"));
 
-  res->category.array_data.code         = element_type->code;
-  res->category.array_data.fixed_size   = fixed_size;
-  res->category.array_data.dynamic_size = NULL;
-
-  return no_error;
-}
-/**
- * gras_datadesc_array_dyn:
- *
- * Create a new array and give a pointer to it 
- */
-gras_error_t 
-gras_datadesc_array_dyn(const char                      *name,
-                       gras_datadesc_type_t            *element_type,
-                       gras_datadesc_type_cb_int_t      dynamic_size,
-                       gras_datadesc_type_t           **dst) {
+       gras_datadesc_struct_append(res, "used",
+                       gras_datadesc_by_name("unsigned long int"));
 
-  gras_error_t errcode;
-  gras_datadesc_type_t *res;
-  int arch;
+       gras_datadesc_struct_append(res, "elmsize",
+                       gras_datadesc_by_name("unsigned long int"));
 
-  gras_assert1(dynamic_size,
-              "'%s' is a dynamic array without size discriminant",
-              name);
+       gras_datadesc_struct_append(res, "data",
+                       gras_datadesc_ref_pop_arr (elm_t));
 
-  TRY(gras_ddt_new(name,dst));
-  res=*dst;
+       gras_datadesc_struct_append(res, "free_f",
+                       gras_datadesc_by_name("function pointer"));
+       memcpy(res->extra,&free_func,sizeof(free_func));
 
-  for (arch=0; arch<gras_arch_count; arch ++) {
-    res->size[arch] = -1; /* make sure it indicates "dynamic" */
-    res->alignment[arch] = element_type->alignment[arch];
-    res->aligned_size[arch] = -1; /*FIXME: That was so in GS, but looks stupid*/
-  }
+       gras_datadesc_struct_append(res, "mutex",
+                       gras_datadesc_by_name("data pointer"));
 
-  res->category_code           = e_gras_datadesc_type_cat_array;
+       gras_datadesc_struct_close(res);
 
-  res->category.array_data.code         = element_type->code;
-  res->category.array_data.fixed_size   = -1;
-  res->category.array_data.dynamic_size = dynamic_size;
+       gras_datadesc_cb_field_push(res, "used");
+       gras_datadesc_cb_recv(res,  &gras_datadesc_dynar_cb);
 
-  return no_error;
+       /* build a ref to it */
+       free(buffname);
+       asprintf(&buffname,"xbt_dynar_of_%s",elm_t->name);
+       res=gras_datadesc_ref(buffname,res);
+       free(buffname);
+       return res;
 }
 
-/**
- * gras_datadesc_ref_pop_arr:
- *
- * Most of the time, you want to include a reference in your structure which
- * is a pointer to a dynamic array whose size is fixed by another field of 
- * your structure.
- *
- * This case pops up so often that this function was created to take care of
- * this case. It creates a dynamic array type whose size is poped from the 
- * current cbps, and then create a reference to it.
- *
- * The name of the created datatype will be the name of the element type, with
- * '[]*' appended to it.
- *
- * Then to use it, you just have to make sure that your structure pre-callback
- * does push the size of the array in the cbps (using #gras_cbps_i_push), and 
- * you are set. 
- *
- * But be remember that this is a stack. If you have two different pop_arr, you
- * should push the second one first, so that the first one is on the top of the 
- * list when the first field gets transfered.
- *
- */
-gras_error_t 
-gras_datadesc_ref_pop_arr(gras_datadesc_type_t  *element_type,
-                         gras_datadesc_type_t **dst) {
-  gras_error_t errcode;
-  char *name=malloc(strlen(element_type->name) + 4);
+#include "xbt/matrix.h"
+static void gras_datadesc_matrix_cb(gras_datadesc_type_t typedesc, gras_cbps_t vars, void *data) {
+       gras_datadesc_type_t subtype;
+       xbt_matrix_t matrix=(xbt_matrix_t)data;
 
-  sprintf(name,"%s[]",element_type->name);
+       memcpy(&matrix->free_f, &typedesc->extra, sizeof(matrix->free_f));
 
-  TRY(gras_datadesc_array_dyn(name,element_type,
-                                     gras_datadesc_cb_pop, dst));
+       /* search for the elemsize in what we have. If elements are "int", typedesc got is "int[]*" */
+       subtype = gras_dd_find_field(typedesc,"data")->type;
 
-  sprintf(name,"%s[]*",element_type->name);
-  TRY(gras_datadesc_ref(name,*dst,dst));
+       /* this is now a ref to array of what we're looking for */
+       subtype = subtype->category.ref_data.type;
+       subtype = subtype->category.array_data.type;
 
-  free(name);
+       DEBUG1("subtype is %s",subtype->name);
 
-  return no_error;
+       matrix->elmsize = subtype->size[GRAS_THISARCH];
+}
+gras_datadesc_type_t
+gras_datadesc_matrix(gras_datadesc_type_t elm_t,
+               void_f_pvoid_t const free_f) {
+       char *buffname;
+       gras_datadesc_type_t res;
+
+       asprintf(&buffname,"s_xbt_matrix_t(%s)",elm_t->name);
+       res = gras_datadesc_struct(buffname);
+
+       gras_datadesc_struct_append(res, "lines",
+                       gras_datadesc_by_name("unsigned int"));
+       gras_datadesc_struct_append(res, "rows",
+                       gras_datadesc_by_name("unsigned int"));
+
+       gras_datadesc_struct_append(res, "elmsize",
+                       gras_datadesc_by_name("unsigned long int"));
+
+       gras_datadesc_struct_append(res, "data",
+                       gras_datadesc_ref_pop_arr (elm_t));
+       gras_datadesc_struct_append(res, "free_f",
+                       gras_datadesc_by_name("function pointer"));
+       gras_datadesc_struct_close(res);
+
+       gras_datadesc_cb_field_push(res, "lines");
+       gras_datadesc_cb_field_push_multiplier(res, "rows");
+
+       gras_datadesc_cb_recv(res,  &gras_datadesc_matrix_cb);
+       memcpy(res->extra,&free_f,sizeof(free_f));
+
+       /* build a ref to it */
+       free(buffname);
+       asprintf(&buffname,"xbt_matrix_t(%s)",elm_t->name);
+       res=gras_datadesc_ref(buffname,res);
+       free(buffname);
+       return res;
 }
-gras_error_t
+
+gras_datadesc_type_t
 gras_datadesc_import_nws(const char           *name,
-                        const DataDescriptor *desc,
-                        size_t                howmany,
-                        gras_datadesc_type_t **dst) {
-  RAISE_UNIMPLEMENTED;
+               const DataDescriptor *desc,
+               unsigned long         howmany) {
+       THROW_UNIMPLEMENTED;
 }
 
 /**
- * gras_datadesc_cb_send:
- *
- * Add a pre-send callback to this datadexc.
  * (useful to push the sizes of the upcoming arrays, for example)
  */
-void gras_datadesc_cb_send (gras_datadesc_type_t         *type,
-                           gras_datadesc_type_cb_void_t  send) {
-  type->send = send;
+void gras_datadesc_cb_send (gras_datadesc_type_t          type,
+               gras_datadesc_type_cb_void_t  send) {
+       type->send = send;
 }
 /**
- * gras_datadesc_cb_recv:
- *
- * Add a post-receive callback to this datadesc.
  * (useful to put the function pointers to the rigth value, for example)
  */
-void gras_datadesc_cb_recv(gras_datadesc_type_t         *type,
-                          gras_datadesc_type_cb_void_t  recv) {
-  type->recv = recv;
+void gras_datadesc_cb_recv(gras_datadesc_type_t          type,
+               gras_datadesc_type_cb_void_t  recv) {
+       type->recv = recv;
+}
+/*
+ * gras_dd_find_field:
+ *
+ * Returns the type descriptor of the given field. Abort on error.
+ */
+static gras_dd_cat_field_t
+gras_dd_find_field(gras_datadesc_type_t  type,
+               const char           *field_name) {
+       xbt_dynar_t         field_array;
+
+       gras_dd_cat_field_t  field=NULL;
+       unsigned int         field_num;
+
+       if (type->category_code == e_gras_datadesc_type_cat_union) {
+               field_array = type->category.union_data.fields;
+       } else if (type->category_code == e_gras_datadesc_type_cat_struct) {
+               field_array = type->category.struct_data.fields;
+       } else {
+               ERROR2("%s (%p) is not a struct nor an union. There is no field.", type->name,(void*)type);
+               xbt_abort();
+       }
+       xbt_dynar_foreach(field_array,field_num,field) {
+               if (!strcmp(field_name,field->name)) {
+                       return field;
+               }
+       }
+       ERROR2("No field named '%s' in '%s'",field_name,type->name);
+       xbt_abort();
+
+}
+
+/**
+ * The given datadesc must be a struct or union (abort if not).
+ * (useful to push the sizes of the upcoming arrays, for example)
+ */
+void gras_datadesc_cb_field_send (gras_datadesc_type_t          type,
+               const char                   *field_name,
+               gras_datadesc_type_cb_void_t  send) {
+
+       gras_dd_cat_field_t field=gras_dd_find_field(type,field_name);
+       field->send = send;
 }
 
+
 /**
- * gras_datadesc_addref:
+ * The value, which must be an int, unsigned int, long int or unsigned long int
+ * is pushed to the stacks of sizes and can then be retrieved with
+ * \ref gras_datadesc_ref_pop_arr or directly with \ref gras_cbps_i_pop.
+ */
+void gras_datadesc_cb_field_push (gras_datadesc_type_t  type,
+               const char           *field_name) {
+
+       gras_dd_cat_field_t  field=gras_dd_find_field(type,field_name);
+       gras_datadesc_type_t sub_type=field->type;
+
+       DEBUG3("add a PUSHy cb to '%s' field (type '%s') of '%s'",
+                       field_name,sub_type->name,type->name);
+       if (!strcmp("int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_int;
+       } else if (!strcmp("unsigned int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_uint;
+       } else if (!strcmp("long int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_lint;
+       } else if (!strcmp("unsigned long int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_ulint;
+       } else {
+               ERROR1("Field %s is not an int, unsigned int, long int neither unsigned long int",
+                               sub_type->name);
+               xbt_abort();
+       }
+}
+
+/**
+ * Any previously pushed value is poped and the field value is multiplied to
+ * it. The result is then pushed back into the stack of sizes. It can then be
+ * retrieved with \ref gras_datadesc_ref_pop_arr or directly with \ref
+ * gras_cbps_i_pop.
  *
- * Adds a reference to the datastruct. 
- * ddt will be freed only when the refcount becomes 0.
+ * The field must be an int, unsigned int, long int or unsigned long int.
  */
-void gras_datadesc_addref(gras_datadesc_type_t *type) {
-  type->refcounter ++;
+void gras_datadesc_cb_field_push_multiplier (gras_datadesc_type_t  type,
+               const char         *field_name) {
+
+       gras_dd_cat_field_t  field=gras_dd_find_field(type,field_name);
+       gras_datadesc_type_t sub_type=field->type;
+
+       DEBUG3("add a MPUSHy cb to '%s' field (type '%s') of '%s'",
+                       field_name,sub_type->name,type->name);
+       if (!strcmp("int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_int_mult;
+       } else if (!strcmp("unsigned int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_uint_mult;
+       } else if (!strcmp("long int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_lint_mult;
+       } else if (!strcmp("unsigned long int",sub_type->name)) {
+               field->send = gras_datadesc_cb_push_ulint_mult;
+       } else {
+               ERROR1("Field %s is not an int, unsigned int, long int neither unsigned long int",
+                               sub_type->name);
+               xbt_abort();
+       }
 }
 
 /**
- * gras_datadesc_unref:
+ * The given datadesc must be a struct or union (abort if not).
+ * (useful to put the function pointers to the right value, for example)
+ */
+void gras_datadesc_cb_field_recv(gras_datadesc_type_t          type,
+               const char                   *field_name,
+               gras_datadesc_type_cb_void_t  recv) {
+
+       gras_dd_cat_field_t field=gras_dd_find_field(type,field_name);
+       field->recv = recv;
+}
+
+/*
+ * Free a datadesc. Should only be called at xbt_exit.
+ */
+void gras_datadesc_free(gras_datadesc_type_t *type) {
+
+       DEBUG1("Let's free ddt %s",(*type)->name);
+
+       switch ((*type)->category_code) {
+       case e_gras_datadesc_type_cat_scalar:
+       case e_gras_datadesc_type_cat_ref:
+       case e_gras_datadesc_type_cat_array:
+               /* nothing to free in there */
+               break;
+
+       case e_gras_datadesc_type_cat_struct:
+               xbt_dynar_free(&( (*type)->category.struct_data.fields ));
+               break;
+
+       case e_gras_datadesc_type_cat_union:
+               xbt_dynar_free(&( (*type)->category.union_data.fields ));
+               break;
+
+       default:
+               /* datadesc was invalid. Killing it is like euthanasy, I guess */
+               break;
+       }
+       free((*type)->name);
+       free(*type);
+       type=NULL;
+}
+
+/**
+ * gras_datadesc_type_cmp:
+ *
+ * Compares two datadesc types with the same semantic than strcmp.
  *
- * Removes a reference to the datastruct. 
- * ddt will be freed only when the refcount becomes 0.
+ * This comparison does not take the set headers into account (name and ID),
+ * but only the payload (actual type description).
  */
-void gras_datadesc_unref(gras_datadesc_type_t *type) {
-  type->refcounter--;
-  if (!type->refcounter) {
-    /* even the set of ddt released that type. Let's free it */
-    DEBUG1("Let's free ddt %s",type->name);
-
-    free(type->name);
-    switch (type->category_code) {
-    case e_gras_datadesc_type_cat_scalar:
-    case e_gras_datadesc_type_cat_ref:
-    case e_gras_datadesc_type_cat_array:
-      /* nothing to free in there */
-      break;
-
-    case e_gras_datadesc_type_cat_ignored:
-      if (type->category.ignored_data.free_func) {
-       type->category.ignored_data.free_func
-         (type->category.ignored_data.default_value);
-      }
-      break;
-
-    case e_gras_datadesc_type_cat_struct:
-      gras_dynar_free(type->category.struct_data.fields);
-      break;
-
-    case e_gras_datadesc_type_cat_union:
-      gras_dynar_free(type->category.union_data.fields);
-      break;
-      
-    default:
-      /* datadesc was invalid. Killing it is like euthanasy, I guess */
-      break;
-    }
-    free(type);
-  }
+int gras_datadesc_type_cmp(const gras_datadesc_type_t d1,
+               const gras_datadesc_type_t d2) {
+       int ret;
+       unsigned int cpt;
+       gras_dd_cat_field_t field1,field2;
+       gras_datadesc_type_t field_desc_1,field_desc_2;
+
+       if (d1 == d2) return 0; /* easy optimization */
+
+       if (!d1 && d2) {
+               DEBUG0("ddt_cmp: !d1 && d2 => 1");
+               return 1;
+       }
+       if (!d1 && !d2) {
+               DEBUG0("ddt_cmp: !d1 && !d2 => 0");
+               return 0;
+       }
+       if ( d1 && !d2) {
+               DEBUG0("ddt_cmp: d1 && !d2 => -1");
+               return -1;
+       }
+
+       for (cpt=0; cpt<gras_arch_count; cpt++) {
+               if (d1->size[cpt] != d2->size[cpt]) {
+                       DEBUG5("ddt_cmp: %s->size=%ld  !=  %s->size=%ld (on %s)",
+                                       d1->name,d1->size[cpt],d2->name,d2->size[cpt],
+                                       gras_arches[cpt].name);
+                       return d1->size[cpt] >  d2->size[cpt] ? 1 : -1;
+               }
+
+               if (d1->alignment[cpt] != d2->alignment[cpt]) {
+                       DEBUG5("ddt_cmp: %s->alignment=%ld  !=  %s->alignment=%ld (on %s)",
+                                       d1->name,d1->alignment[cpt],d2->name,d2->alignment[cpt],
+                                       gras_arches[cpt].name);
+                       return d1->alignment[cpt] > d2->alignment[cpt] ? 1 : -1;
+               }
+
+               if (d1->aligned_size[cpt] != d2->aligned_size[cpt]) {
+                       DEBUG5("ddt_cmp: %s->aligned_size=%ld  !=  %s->aligned_size=%ld (on %s)",
+                                       d1->name,d1->aligned_size[cpt],d2->name,d2->aligned_size[cpt],
+                                       gras_arches[cpt].name);
+                       return d1->aligned_size[cpt] > d2->aligned_size[cpt] ? 1 : -1;
+               }
+       }
+
+       if (d1->category_code != d2->category_code) {
+               DEBUG4("ddt_cmp: %s->cat=%s  !=  %s->cat=%s",
+                               d1->name,gras_datadesc_cat_names[d1->category_code],
+                               d2->name,gras_datadesc_cat_names[d2->category_code]);
+               return d1->category_code > d2->category_code ? 1 : -1;
+       }
+
+       if (d1->send != d2->send) {
+               DEBUG4("ddt_cmp: %s->send=%p  !=  %s->send=%p",
+                               d1->name,(void*)d1->send, d2->name,(void*)d2->send);
+               return 1; /* ISO C forbids ordered comparisons of pointers to functions */
+       }
+
+       if (d1->recv != d2->recv) {
+               DEBUG4("ddt_cmp: %s->recv=%p  !=  %s->recv=%p",
+                               d1->name,(void*)d1->recv, d2->name,(void*)d2->recv);
+               return 1; /* ISO C forbids ordered comparisons of pointers to functions */
+       }
+
+       switch (d1->category_code) {
+       case e_gras_datadesc_type_cat_scalar:
+               if (d1->category.scalar_data.encoding != d2->category.scalar_data.encoding)
+                       return d1->category.scalar_data.encoding > d2->category.scalar_data.encoding ? 1 : -1 ;
+                       break;
+
+       case e_gras_datadesc_type_cat_struct:
+               if (xbt_dynar_length(d1->category.struct_data.fields) !=
+                       xbt_dynar_length(d2->category.struct_data.fields)) {
+                       DEBUG4("ddt_cmp: %s (having %lu fields) !=  %s (having %lu fields)",
+                                       d1->name, xbt_dynar_length(d1->category.struct_data.fields),
+                                       d2->name, xbt_dynar_length(d2->category.struct_data.fields));
+
+                       return xbt_dynar_length(d1->category.struct_data.fields) >
+                       xbt_dynar_length(d2->category.struct_data.fields) ?
+                                       1 : -1;
+               }
+               xbt_dynar_foreach(d1->category.struct_data.fields, cpt, field1) {
+
+                       field2 = xbt_dynar_get_as(d2->category.struct_data.fields, cpt, gras_dd_cat_field_t);
+                       field_desc_1 = field1->type;
+                       field_desc_2 = field2->type;
+                       ret = gras_datadesc_type_cmp(field_desc_1,field_desc_2);
+                       if (ret) {
+                               DEBUG6("%s->field[%d]=%s != %s->field[%d]=%s",
+                                               d1->name,cpt,field1->name,
+                                               d2->name,cpt,field2->name);
+                               return ret;
+                       }
+
+               }
+               break;
+
+       case e_gras_datadesc_type_cat_union:
+               if (d1->category.union_data.selector != d2->category.union_data.selector)
+                       return 1;  /* ISO C forbids ordered comparisons of pointers to functions */
+
+               if (xbt_dynar_length(d1->category.union_data.fields) !=
+                       xbt_dynar_length(d2->category.union_data.fields))
+                       return xbt_dynar_length(d1->category.union_data.fields) >
+               xbt_dynar_length(d2->category.union_data.fields) ?
+                               1 : -1;
+
+               xbt_dynar_foreach(d1->category.union_data.fields, cpt, field1) {
+
+                       field2 = xbt_dynar_get_as(d2->category.union_data.fields, cpt, gras_dd_cat_field_t);
+                       field_desc_1 = field1->type;
+                       field_desc_2 = field2->type;
+                       ret = gras_datadesc_type_cmp(field_desc_1,field_desc_2);
+                       if (ret)
+                               return ret;
+
+               }
+               break;
+
+
+       case e_gras_datadesc_type_cat_ref:
+               if (d1->category.ref_data.selector != d2->category.ref_data.selector)
+                       return 1; /* ISO C forbids ordered comparisons of pointers to functions */
+
+               if (d1->category.ref_data.type != d2->category.ref_data.type)
+                       return d1->category.ref_data.type > d2->category.ref_data.type ? 1 : -1;
+                       break;
+
+       case e_gras_datadesc_type_cat_array:
+               if (d1->category.array_data.type != d2->category.array_data.type)
+                       return d1->category.array_data.type > d2->category.array_data.type ? 1 : -1;
+
+                       if (d1->category.array_data.fixed_size != d2->category.array_data.fixed_size)
+                               return d1->category.array_data.fixed_size > d2->category.array_data.fixed_size ? 1 : -1;
+
+                               if (d1->category.array_data.dynamic_size != d2->category.array_data.dynamic_size)
+                                       return 1; /* ISO C forbids ordered comparisons of pointers to functions */
+
+                               break;
+
+       default:
+               /* two stupidly created ddt are equally stupid ;) */
+               break;
+       }
+       return 0;
+
 }