/* PSPP - computes sample statistics.
- Copyright (C) 1997-9, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1997-9, 2000, 2006 Free Software Foundation, Inc.
Written by Ben Pfaff <blp@gnu.org>.
This program is free software; you can redistribute it and/or
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
- 02111-1307, USA. */
+ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ 02110-1301, USA. */
#include <config.h>
#include "dictionary.h"
#include <stdlib.h>
+#include <ctype.h>
#include "algorithm.h"
#include "alloc.h"
#include "case.h"
+#include "cat.h"
+#include "cat-routines.h"
#include "error.h"
#include "hash.h"
#include "misc.h"
+#include "settings.h"
#include "str.h"
#include "value-labels.h"
#include "var.h"
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
/* A dictionary. */
struct dictionary
{
{
struct dictionary *d;
size_t i;
-
+
assert (s != NULL);
-
+
d = dict_create ();
- for (i = 0; i < s->var_cnt; i++)
- dict_clone_var (d, s->var[i], s->var[i]->name);
+
+ for (i = 0; i < s->var_cnt; i++)
+ {
+ struct variable *sv = s->var[i];
+ struct variable *dv = dict_clone_var_assert (d, sv, sv->name);
+ var_set_short_name (dv, sv->short_name);
+ }
+
d->next_value_idx = s->next_value_idx;
d->split_cnt = s->split_cnt;
if (d->split_cnt > 0)
{
- d->split = xmalloc (d->split_cnt * sizeof *d->split);
+ d->split = xnmalloc (d->split_cnt, sizeof *d->split);
for (i = 0; i < d->split_cnt; i++)
d->split[i] = dict_lookup_var_assert (d, s->split[i]->name);
}
dict_set_label (d, dict_get_label (s));
dict_set_documents (d, dict_get_documents (s));
+ d->vector_cnt = s->vector_cnt;
+ d->vector = xnmalloc (d->vector_cnt, sizeof *d->vector);
for (i = 0; i < s->vector_cnt; i++)
- dict_create_vector (d, s->vector[i]->name,
- s->vector[i]->var, s->vector[i]->cnt);
+ {
+ struct vector *sv = s->vector[i];
+ struct vector *dv = d->vector[i] = xmalloc (sizeof *dv);
+ int j;
+
+ dv->idx = i;
+ strcpy (dv->name, sv->name);
+ dv->cnt = sv->cnt;
+ dv->var = xnmalloc (dv->cnt, sizeof *dv->var);
+ for (j = 0; j < dv->cnt; j++)
+ dv->var[j] = d->var[sv->var[j]->index];
+ }
return d;
}
if (!(exclude_classes & (1u << dict_class_from_id (d->var[i]->name))))
count++;
- *vars = xmalloc (count * sizeof **vars);
+ *vars = xnmalloc (count, sizeof **vars);
*cnt = 0;
for (i = 0; i < d->var_cnt; i++)
if (!(exclude_classes & (1u << dict_class_from_id (d->var[i]->name))))
assert (*cnt == count);
}
+
/* Creates and returns a new variable in D with the given NAME
and WIDTH. Returns a null pointer if the given NAME would
duplicate that of an existing variable in the dictionary. */
struct variable *
-dict_create_var (struct dictionary *d, const char *name, int width)
+dict_create_var (struct dictionary *d, const char *name, int width)
{
struct variable *v;
assert (d != NULL);
assert (name != NULL);
- assert (strlen (name) >= 1 && strlen (name) <= 8);
+
assert (width >= 0 && width < 256);
+ assert (var_is_valid_name(name,0));
+
/* Make sure there's not already a variable by that name. */
if (dict_lookup_var (d, name) != NULL)
return NULL;
/* Allocate and initialize variable. */
v = xmalloc (sizeof *v);
- strncpy (v->name, name, sizeof v->name);
- v->name[8] = '\0';
- v->index = d->var_cnt;
+ str_copy_trunc (v->name, sizeof v->name, name);
v->type = width == 0 ? NUMERIC : ALPHA;
v->width = width;
v->fv = d->next_value_idx;
v->nv = width == 0 ? 1 : DIV_RND_UP (width, 8);
v->init = 1;
- v->reinit = dict_class_from_id (name) != DC_SCRATCH;
- v->miss_type = MISSING_NONE;
+ v->reinit = dict_class_from_id (v->name) != DC_SCRATCH;
+ v->index = d->var_cnt;
+ mv_init (&v->miss, width);
if (v->type == NUMERIC)
{
- v->print.type = FMT_F;
- v->print.w = 8;
- v->print.d = 2;
+ v->print = f8_2;
+ v->alignment = ALIGN_RIGHT;
+ v->display_width = 8;
+ v->measure = MEASURE_SCALE;
}
else
{
- v->print.type = FMT_A;
- v->print.w = v->width;
- v->print.d = 0;
+ v->print = make_output_format (FMT_A, v->width, 0);
+ v->alignment = ALIGN_LEFT;
+ v->display_width = 8;
+ v->measure = MEASURE_NOMINAL;
}
v->write = v->print;
v->val_labs = val_labs_create (v->width);
v->label = NULL;
+ var_clear_short_name (v);
v->aux = NULL;
v->aux_dtor = NULL;
+ v->obs_vals = NULL;
/* Update dictionary. */
if (d->var_cnt >= d->var_cap)
{
d->var_cap = 8 + 2 * d->var_cap;
- d->var = xrealloc (d->var, d->var_cap * sizeof *d->var);
+ d->var = xnrealloc (d->var, d->var_cap, sizeof *d->var);
}
d->var[v->index] = v;
d->var_cnt++;
hsh_force_insert (d->name_tab, v);
+
d->next_value_idx += v->nv;
return v;
and WIDTH. Assert-fails if the given NAME would duplicate
that of an existing variable in the dictionary. */
struct variable *
-dict_create_var_assert (struct dictionary *d, const char *name, int width)
+dict_create_var_assert (struct dictionary *d, const char *name, int width)
{
struct variable *v = dict_create_var (d, name, width);
assert (v != NULL);
return v;
}
-/* Creates a new variable in D named NAME, as a copy of existing
- variable OV, which need not be in D or in any dictionary. */
+/* Creates and returns a new variable in D with name NAME, as a
+ copy of existing variable OV, which need not be in D or in any
+ dictionary. Returns a null pointer if the given NAME would
+ duplicate that of an existing variable in the dictionary. */
struct variable *
dict_clone_var (struct dictionary *d, const struct variable *ov,
const char *name)
assert (d != NULL);
assert (ov != NULL);
assert (name != NULL);
- assert (strlen (name) >= 1 && strlen (name) <= 8);
+
+ assert (strlen (name) >= 1);
+ assert (strlen (name) <= LONG_NAME_LEN);
nv = dict_create_var (d, name, ov->width);
if (nv == NULL)
return NULL;
+ /* Copy most members not copied via dict_create_var().
+ short_name[] is intentionally not copied, because there is
+ no reason to give a new variable with potentially a new name
+ the same short name. */
nv->init = 1;
nv->reinit = ov->reinit;
- nv->miss_type = ov->miss_type;
- memcpy (nv->missing, ov->missing, sizeof nv->missing);
+ mv_copy (&nv->miss, &ov->miss);
nv->print = ov->print;
nv->write = ov->write;
val_labs_destroy (nv->val_labs);
nv->val_labs = val_labs_copy (ov->val_labs);
if (ov->label != NULL)
nv->label = xstrdup (ov->label);
+ nv->measure = ov->measure;
+ nv->display_width = ov->display_width;
+ nv->alignment = ov->alignment;
return nv;
}
-/* Changes the name of V in D to name NEW_NAME. Assert-fails if
- a variable named NEW_NAME is already in D, except that
- NEW_NAME may be the same as V's existing name. */
-void
-dict_rename_var (struct dictionary *d, struct variable *v,
- const char *new_name)
+/* Creates and returns a new variable in D with name NAME, as a
+ copy of existing variable OV, which need not be in D or in any
+ dictionary. Assert-fails if the given NAME would duplicate
+ that of an existing variable in the dictionary. */
+struct variable *
+dict_clone_var_assert (struct dictionary *d, const struct variable *ov,
+ const char *name)
{
- assert (d != NULL);
+ struct variable *v = dict_clone_var (d, ov, name);
assert (v != NULL);
- assert (new_name != NULL);
- assert (strlen (new_name) >= 1 && strlen (new_name) <= 8);
- assert (dict_contains_var (d, v));
-
- if (!strcmp (v->name, new_name))
- return;
-
- assert (dict_lookup_var (d, new_name) == NULL);
-
- hsh_force_delete (d->name_tab, v);
- strncpy (v->name, new_name, sizeof v->name);
- v->name[8] = '\0';
- hsh_force_insert (d->name_tab, v);
+ return v;
}
/* Returns the variable named NAME in D, or a null pointer if no
assert (d != NULL);
assert (name != NULL);
- assert (strlen (name) >= 1 && strlen (name) <= 8);
-
- strncpy (v.name, name, sizeof v.name);
- v.name[8] = '\0';
+ str_copy_trunc (v.name, sizeof v.name, name);
return hsh_find (d->name_tab, &v);
}
return v;
}
-/* Returns nonzero if variable V is in dictionary D. */
-int
+/* Returns true if variable V is in dictionary D,
+ false otherwise. */
+bool
dict_contains_var (const struct dictionary *d, const struct variable *v)
{
assert (d != NULL);
assert (d != NULL);
assert (v != NULL);
assert (dict_contains_var (d, v));
- assert (d->var[v->index] == v);
/* Delete aux data. */
var_clear_aux (v);
dict_clear_vectors (d);
/* Remove V from var array. */
+ remove_element (d->var, d->var_cnt, sizeof *d->var, v->index);
d->var_cnt--;
- memmove (d->var + v->index, d->var + v->index + 1,
- (d->var_cnt - v->index) * sizeof *d->var);
/* Update index. */
for (i = v->index; i < d->var_cnt; i++)
/* Free memory. */
val_labs_destroy (v->val_labs);
+ cat_stored_values_destroy (v);
free (v->label);
free (v);
}
dict_delete_var (d, *vars++);
}
+/* Deletes scratch variables from dictionary D. */
+void
+dict_delete_scratch_vars (struct dictionary *d)
+{
+ int i;
+
+ /* FIXME: this can be done in O(count) time, but this algorithm
+ is O(count**2). */
+ assert (d != NULL);
+
+ for (i = 0; i < d->var_cnt; )
+ if (dict_class_from_id (d->var[i]->name) == DC_SCRATCH)
+ dict_delete_var (d, d->var[i]);
+ else
+ i++;
+}
+
+/* Moves V to 0-based position IDX in D. Other variables in D,
+ if any, retain their relative positions. Runs in time linear
+ in the distance moved. */
+void
+dict_reorder_var (struct dictionary *d, struct variable *v,
+ size_t new_index)
+{
+ size_t min_idx, max_idx;
+ size_t i;
+
+ assert (d != NULL);
+ assert (v != NULL);
+ assert (dict_contains_var (d, v));
+ assert (new_index < d->var_cnt);
+
+ move_element (d->var, d->var_cnt, sizeof *d->var, v->index, new_index);
+
+ min_idx = min (v->index, new_index);
+ max_idx = max (v->index, new_index);
+ for (i = min_idx; i <= max_idx; i++)
+ d->var[i]->index = i;
+}
+
/* Reorders the variables in D, placing the COUNT variables
listed in ORDER in that order at the beginning of D. The
other variables in D, if any, retain their relative
assert (count == 0 || order != NULL);
assert (count <= d->var_cnt);
- new_var = xmalloc (d->var_cnt * sizeof *new_var);
+ new_var = xnmalloc (d->var_cnt, sizeof *new_var);
memcpy (new_var, order, count * sizeof *new_var);
for (i = 0; i < count; i++)
{
d->var = new_var;
}
+/* Changes the name of V in D to name NEW_NAME. Assert-fails if
+ a variable named NEW_NAME is already in D, except that
+ NEW_NAME may be the same as V's existing name. */
+void
+dict_rename_var (struct dictionary *d, struct variable *v,
+ const char *new_name)
+{
+ assert (d != NULL);
+ assert (v != NULL);
+ assert (new_name != NULL);
+ assert (var_is_valid_name (new_name, false));
+ assert (dict_contains_var (d, v));
+ assert (!compare_var_names (v->name, new_name, NULL)
+ || dict_lookup_var (d, new_name) == NULL);
+
+ hsh_force_delete (d->name_tab, v);
+ str_copy_trunc (v->name, sizeof v->name, new_name);
+ hsh_force_insert (d->name_tab, v);
+
+ if (get_algorithm () == ENHANCED)
+ var_clear_short_name (v);
+}
+
/* Renames COUNT variables specified in VARS to the names given
in NEW_NAMES within dictionary D. If the renaming would
- result in a duplicate variable name, returns zero and stores a
+ result in a duplicate variable name, returns false and stores a
name that would be duplicated into *ERR_NAME (if ERR_NAME is
- non-null). Otherwise, the renaming is successful, and nonzero
+ non-null). Otherwise, the renaming is successful, and true
is returned. */
-int
+bool
dict_rename_vars (struct dictionary *d,
struct variable **vars, char **new_names,
size_t count, char **err_name)
{
char **old_names;
size_t i;
- int success = 1;
+ bool success = true;
assert (d != NULL);
assert (count == 0 || vars != NULL);
assert (count == 0 || new_names != NULL);
- old_names = xmalloc (count * sizeof *old_names);
+ /* Remove the variables to be renamed from the name hash,
+ save their names, and rename them. */
+ old_names = xnmalloc (count, sizeof *old_names);
for (i = 0; i < count; i++)
{
assert (d->var[vars[i]->index] == vars[i]);
+ assert (var_is_valid_name (new_names[i], false));
hsh_force_delete (d->name_tab, vars[i]);
old_names[i] = xstrdup (vars[i]->name);
+ strcpy (vars[i]->name, new_names[i]);
}
-
+
+ /* Add the renamed variables back into the name hash,
+ checking for conflicts. */
for (i = 0; i < count; i++)
{
assert (new_names[i] != NULL);
assert (*new_names[i] != '\0');
- assert (strlen (new_names[i]) < 9);
- strcpy (vars[i]->name, new_names[i]);
- if (hsh_insert (d->name_tab, vars[i]) != NULL)
+ assert (strlen (new_names[i]) >= 1);
+ assert (strlen (new_names[i]) <= LONG_NAME_LEN);
+
+ if (hsh_insert (d->name_tab, vars[i]) != NULL)
{
+ /* There is a name conflict.
+ Back out all the name changes that have already
+ taken place, and indicate failure. */
size_t fail_idx = i;
if (err_name != NULL)
*err_name = new_names[i];
hsh_force_insert (d->name_tab, vars[i]);
}
- success = 0;
- break;
+ success = false;
+ goto done;
}
}
+ /* Clear short names. */
+ if (get_algorithm () == ENHANCED)
+ for (i = 0; i < count; i++)
+ var_clear_short_name (vars[i]);
+
+ done:
+ /* Free the old names we kept around. */
for (i = 0; i < count; i++)
free (old_names[i]);
free (old_names);
else
{
double w = case_num (c, d->weight->fv);
- if ( w < 0.0 || w == SYSMIS || is_num_user_missing(w, d->weight) )
+ if (w < 0.0 || mv_is_num_missing (&d->weight->miss, w))
w = 0.0;
if ( w == 0.0 && *warn_on_invalid ) {
*warn_on_invalid = 0;
i++;
}
else
- dict_delete_var (default_dict, v);
- }
-}
-
-/* Copies values from SRC, which represents a case arranged
- according to dictionary D, to DST, which represents a case
- arranged according to the dictionary that will be produced by
- dict_compact_values(D). */
-void
-dict_compact_case (const struct dictionary *d,
- struct ccase *dst, const struct ccase *src)
-{
- size_t i;
- size_t value_idx;
-
- value_idx = 0;
- for (i = 0; i < d->var_cnt; i++)
- {
- struct variable *v = d->var[i];
-
- if (dict_class_from_id (v->name) != DC_SCRATCH)
- {
- case_copy (dst, value_idx, src, v->fv, v->nv);
- value_idx += v->nv;
- }
+ dict_delete_var (d, v);
}
}
size_t next_value_idx;
int *idx_to_fv;
- idx_to_fv = xmalloc (d->var_cnt * sizeof *idx_to_fv);
+ idx_to_fv = xnmalloc (d->var_cnt, sizeof *idx_to_fv);
next_value_idx = 0;
for (i = 0; i < d->var_cnt; i++)
{
return idx_to_fv;
}
+/* Returns true if a case for dictionary D would be smaller after
+ compaction, false otherwise. Compacting a case eliminates
+ "holes" between values and after the last value. Holes are
+ created by deleting variables (or by scratch variables).
+
+ The return value may differ from whether compacting a case
+ from dictionary D would *change* the case: compaction could
+ rearrange values even if it didn't reduce space
+ requirements. */
+bool
+dict_needs_compaction (const struct dictionary *d)
+{
+ return dict_get_compacted_value_cnt (d) < dict_get_next_value_idx (d);
+}
+\f
+/* How to copy a contiguous range of values between cases. */
+struct copy_map
+ {
+ size_t src_idx; /* Starting value index in source case. */
+ size_t dst_idx; /* Starting value index in target case. */
+ size_t cnt; /* Number of values. */
+ };
+
+/* How to compact a case. */
+struct dict_compactor
+ {
+ struct copy_map *maps; /* Array of mappings. */
+ size_t map_cnt; /* Number of mappings. */
+ };
+
+/* Creates and returns a dict_compactor that can be used to
+ compact cases for dictionary D.
+
+ Compacting a case eliminates "holes" between values and after
+ the last value. Holes are created by deleting variables (or
+ by scratch variables). */
+struct dict_compactor *
+dict_make_compactor (const struct dictionary *d)
+{
+ struct dict_compactor *compactor;
+ struct copy_map *map;
+ size_t map_allocated;
+ size_t value_idx;
+ size_t i;
+
+ compactor = xmalloc (sizeof *compactor);
+ compactor->maps = NULL;
+ compactor->map_cnt = 0;
+ map_allocated = 0;
+
+ value_idx = 0;
+ map = NULL;
+ for (i = 0; i < d->var_cnt; i++)
+ {
+ struct variable *v = d->var[i];
+
+ if (dict_class_from_id (v->name) == DC_SCRATCH)
+ continue;
+ if (map != NULL && map->src_idx + map->cnt == v->fv)
+ map->cnt += v->nv;
+ else
+ {
+ if (compactor->map_cnt == map_allocated)
+ compactor->maps = x2nrealloc (compactor->maps, &map_allocated,
+ sizeof *compactor->maps);
+ map = &compactor->maps[compactor->map_cnt++];
+ map->src_idx = v->fv;
+ map->dst_idx = value_idx;
+ map->cnt = v->nv;
+ }
+ value_idx += v->nv;
+ }
+
+ return compactor;
+}
+
+/* Compacts SRC by copying it to DST according to the scheme in
+ COMPACTOR.
+
+ Compacting a case eliminates "holes" between values and after
+ the last value. Holes are created by deleting variables (or
+ by scratch variables). */
+void
+dict_compactor_compact (const struct dict_compactor *compactor,
+ struct ccase *dst, const struct ccase *src)
+{
+ size_t i;
+
+ for (i = 0; i < compactor->map_cnt; i++)
+ {
+ const struct copy_map *map = &compactor->maps[i];
+ case_copy (dst, map->dst_idx, src, map->src_idx, map->cnt);
+ }
+}
+
+/* Destroys COMPACTOR. */
+void
+dict_compactor_destroy (struct dict_compactor *compactor)
+{
+ if (compactor != NULL)
+ {
+ free (compactor->maps);
+ free (compactor);
+ }
+}
+
/* Returns the SPLIT FILE vars (see cmd_split_file()). Call
dict_get_split_cnt() to determine how many SPLIT FILE vars
there are. Returns a null pointer if and only if there are no
assert (cnt == 0 || split != NULL);
d->split_cnt = cnt;
- d->split = xrealloc (d->split, cnt * sizeof *d->split);
+ d->split = xnrealloc (d->split, cnt, sizeof *d->split);
memcpy (d->split, split, cnt * sizeof *d->split);
}
}
/* Creates in D a vector named NAME that contains CNT variables
- VAR (see cmd_vector()). Returns nonzero if successful, or
- zero if a vector named NAME already exists in D. */
-int
+ VAR (see cmd_vector()). Returns true if successful, or
+ false if a vector named NAME already exists in D. */
+bool
dict_create_vector (struct dictionary *d,
const char *name,
struct variable **var, size_t cnt)
{
struct vector *vector;
+ size_t i;
assert (d != NULL);
assert (name != NULL);
- assert (strlen (name) > 0 && strlen (name) < 9);
+ assert (var_is_valid_name (name, false));
assert (var != NULL);
assert (cnt > 0);
if (dict_lookup_vector (d, name) != NULL)
- return 0;
+ return false;
- d->vector = xrealloc (d->vector, (d->vector_cnt + 1) * sizeof *d->vector);
+ d->vector = xnrealloc (d->vector, d->vector_cnt + 1, sizeof *d->vector);
vector = d->vector[d->vector_cnt] = xmalloc (sizeof *vector);
vector->idx = d->vector_cnt++;
- strncpy (vector->name, name, 8);
- vector->name[8] = '\0';
- vector->var = xmalloc (cnt * sizeof *var);
- memcpy (vector->var, var, cnt * sizeof *var);
+ str_copy_trunc (vector->name, sizeof vector->name, name);
+ vector->var = xnmalloc (cnt, sizeof *var);
+ for (i = 0; i < cnt; i++)
+ {
+ assert (dict_contains_var (d, var[i]));
+ vector->var[i] = var[i];
+ }
vector->cnt = cnt;
- return 1;
+ return true;
}
/* Returns the vector in D with index IDX, which must be less
assert (name != NULL);
for (i = 0; i < d->vector_cnt; i++)
- if (!strcmp (d->vector[i]->name, name))
+ if (!strcasecmp (d->vector[i]->name, name))
return d->vector[i];
return NULL;
}
d->vector = NULL;
d->vector_cnt = 0;
}
+
+/* Compares two strings. */
+static int
+compare_strings (const void *a, const void *b, void *aux UNUSED)
+{
+ return strcmp (a, b);
+}
+
+/* Hashes a string. */
+static unsigned
+hash_string (const void *s, void *aux UNUSED)
+{
+ return hsh_hash_string (s);
+}
+
+/* Assigns a valid, unique short_name[] to each variable in D.
+ Each variable whose actual name is short has highest priority
+ for that short name. Otherwise, variables with an existing
+ short_name[] have the next highest priority for a given short
+ name; if it is already taken, then the variable is treated as
+ if short_name[] had been empty. Otherwise, long names are
+ truncated to form short names. If that causes conflicts,
+ variables are renamed as PREFIX_A, PREFIX_B, and so on. */
+void
+dict_assign_short_names (struct dictionary *d)
+{
+ struct hsh_table *short_names;
+ size_t i;
+
+ /* Give variables whose names are short the corresponding short
+ names, and clear short_names[] that conflict with a variable
+ name. */
+ for (i = 0; i < d->var_cnt; i++)
+ {
+ struct variable *v = d->var[i];
+ if (strlen (v->name) <= SHORT_NAME_LEN)
+ var_set_short_name (v, v->name);
+ else if (dict_lookup_var (d, v->short_name) != NULL)
+ var_clear_short_name (v);
+ }
+
+ /* Each variable with an assigned short_name[] now gets it
+ unless there is a conflict. */
+ short_names = hsh_create (d->var_cnt, compare_strings, hash_string,
+ NULL, NULL);
+ for (i = 0; i < d->var_cnt; i++)
+ {
+ struct variable *v = d->var[i];
+ if (v->short_name[0] && hsh_insert (short_names, v->short_name) != NULL)
+ var_clear_short_name (v);
+ }
+
+ /* Now assign short names to remaining variables. */
+ for (i = 0; i < d->var_cnt; i++)
+ {
+ struct variable *v = d->var[i];
+ if (v->short_name[0] == '\0')
+ {
+ int sfx;
+
+ /* Form initial short_name. */
+ var_set_short_name (v, v->name);
+
+ /* Try _A, _B, ... _AA, _AB, etc., if needed. */
+ for (sfx = 0; hsh_insert (short_names, v->short_name) != NULL; sfx++)
+ var_set_short_name_suffix (v, v->name, sfx);
+ }
+ }
+
+ /* Get rid of hash table. */
+ hsh_destroy (short_names);
+}
projects / pspp-builds.git / blobdiff