/* PSPP - a program for statistical analysis.
- Copyright (C) 2004, 2007 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2007, 2009 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <limits.h>
#include <stddef.h>
#include <stdbool.h>
+#include <stdlib.h>
+#include <libpspp/compiler.h>
#include "value.h"
struct variable;
#define CASENUMBER_MAX LONG_MAX
typedef long int casenumber;
-/* Opaque structure that represents a case. Use accessor
- functions instead of accessing any members directly. Use
- case_move() or case_clone() instead of copying. */
+/* Reference-counted case implementation.
+
+ A newly created case has a single owner (the code that created
+ it), represented by an initial reference count of 1. Other
+ code that receives the case may keep a virtual copy of it by
+ calling case_ref, which increments the case's reference count.
+ When this is done, the case becomes shared between its
+ original owner and each piece of code that incremented the
+ reference count.
+
+ A shared case (one whose reference count is greater than 1)
+ must not be modified, because this would make the case change
+ in the view of every reference count holder, not just the one
+ that intended to change the case. Because the purpose of
+ keeping the reference count is to make a virtual copy of the
+ case, this is undesirable behavior. The case_unshare function
+ provides a solution, by making a new, unshared copy of a
+ shared case. */
struct ccase
{
- struct case_data *case_data; /* Actual data. */
+ size_t n_values; /* Number of values. */
+ size_t ref_cnt; /* Reference count. */
+ union value values[1]; /* Values. */
};
-void case_nullify (struct ccase *);
-bool case_is_null (const struct ccase *);
+struct ccase *case_create (size_t n_values) MALLOC_LIKE;
+struct ccase *case_try_create (size_t n_values) MALLOC_LIKE;
-void case_create (struct ccase *, size_t value_cnt);
-void case_clone (struct ccase *, const struct ccase *);
-void case_move (struct ccase *, struct ccase *);
-void case_destroy (struct ccase *);
+static inline struct ccase *case_unshare (struct ccase *) WARN_UNUSED_RESULT;
+static inline struct ccase *case_ref (const struct ccase *);
+static inline void case_unref (struct ccase *);
+static inline bool case_is_shared (const struct ccase *);
-size_t case_get_value_cnt (const struct ccase *);
+static inline size_t case_get_value_cnt (const struct ccase *);
-void case_resize (struct ccase *, size_t new_cnt);
-void case_swap (struct ccase *, struct ccase *);
-
-bool case_try_create (struct ccase *, size_t value_cnt);
-bool case_try_clone (struct ccase *, const struct ccase *);
+struct ccase *case_resize (struct ccase *, size_t new_cnt) WARN_UNUSED_RESULT;
+struct ccase *case_unshare_and_resize (struct ccase *, size_t new_cnt)
+ WARN_UNUSED_RESULT;
void case_copy (struct ccase *dst, size_t dst_idx,
const struct ccase *src, size_t src_idx,
size_t cnt);
void case_copy_out (const struct ccase *,
- size_t start_idx, union value *, size_t value_cnt);
+ size_t start_idx, union value *, size_t n_values);
void case_copy_in (struct ccase *,
- size_t start_idx, const union value *, size_t value_cnt);
+ size_t start_idx, const union value *, size_t n_values);
const union value *case_data (const struct ccase *, const struct variable *);
-double case_num (const struct ccase *, const struct variable *);
-const char *case_str (const struct ccase *, const struct variable *);
+const union value *case_data_idx (const struct ccase *, size_t idx);
union value *case_data_rw (struct ccase *, const struct variable *);
+union value *case_data_rw_idx (struct ccase *, size_t idx);
-const union value *case_data_idx (const struct ccase *, size_t idx);
+double case_num (const struct ccase *, const struct variable *);
double case_num_idx (const struct ccase *, size_t idx);
+
+const char *case_str (const struct ccase *, const struct variable *);
const char *case_str_idx (const struct ccase *, size_t idx);
-union value *case_data_rw_idx (struct ccase *, size_t idx);
int case_compare (const struct ccase *, const struct ccase *,
- const struct variable *const *, size_t var_cnt);
+ const struct variable *const *, size_t n_vars);
int case_compare_2dict (const struct ccase *, const struct ccase *,
const struct variable *const *,
const struct variable *const *,
- size_t var_cnt);
+ size_t n_vars);
const union value *case_data_all (const struct ccase *);
union value *case_data_all_rw (struct ccase *);
+\f
+struct ccase *case_unshare__ (struct ccase *);
+
+/* If C is a shared case, that is, if it has a reference count
+ greater than 1, makes a new unshared copy and returns it,
+ decrementing C's reference count. If C is not shared (its
+ reference count is 1), returns C.
+
+ This function should be used before attempting to modify any
+ of the data in a case that might be shared, e.g.:
+ c = case_unshare (c); // Make sure that C is not shared.
+ case_data_rw (c, myvar)->f = 1; // Modify data in C.
+*/
+static inline struct ccase *
+case_unshare (struct ccase *c)
+{
+ if (case_is_shared (c))
+ c = case_unshare__ (c);
+ return c;
+}
+
+/* Increments case C's reference count and returns C. Afterward,
+ case C is shared among its reference count holders. */
+static inline struct ccase *
+case_ref (const struct ccase *c_)
+{
+ struct ccase *c = (struct ccase *) c_;
+ c->ref_cnt++;
+ return c;
+}
+
+/* Decrements case C's reference count. Frees C if its
+ reference count drops to 0.
+
+ If C is a null pointer, this function has no effect. */
+static inline void
+case_unref (struct ccase *c)
+{
+ if (c != NULL && !--c->ref_cnt)
+ free (c);
+}
+
+/* Returns true if case C is shared. A case that is shared
+ cannot be modified directly. Instead, an unshared copy must
+ first be made with case_unshare(). */
+static inline bool
+case_is_shared (const struct ccase *c)
+{
+ return c->ref_cnt > 1;
+}
+
+/* Returns the number of union values in C. */
+static inline size_t
+case_get_value_cnt (const struct ccase *c)
+{
+ return c->n_values;
+}
#endif /* data/case.h */
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