src/data/case.h

   1 /* PSPP - a program for statistical analysis.
   2    Copyright (C) 2004, 2007, 2009, 2010, 2011 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
  16
  17 #ifndef DATA_CASE_H
  18 #define DATA_CASE_H 1
  19
  20 #include <limits.h>
  21 #include <stddef.h>
  22 #include <stdbool.h>
  23 #include <stdlib.h>
  24
  25 #include "libpspp/compiler.h"
  26 #include "libpspp/str.h"
  27 #include "data/caseproto.h"
  28
  29 struct variable;
  30
  31 /* A count of cases or the index of a case within a collection of
  32    them. */
  33 #define CASENUMBER_MAX LONG_MAX
  34 typedef long int casenumber;
  35
  36 /* Reference-counted case implementation.
  37
  38    A newly created case has a single owner (the code that created
  39    it), represented by an initial reference count of 1.  Other
  40    code that receives the case may keep a virtual copy of it by
  41    calling case_ref, which increments the case's reference count.
  42    When this is done, the case becomes shared between its
  43    original owner and each piece of code that incremented the
  44    reference count.
  45
  46    A shared case (one whose reference count is greater than 1)
  47    must not be modified, because this would make the case change
  48    in the view of every reference count holder, not just the one
  49    that intended to change the case.  Because the purpose of
  50    keeping the reference count is to make a virtual copy of the
  51    case, this is undesirable behavior.  The case_unshare function
  52    provides a solution, by making a new, unshared copy of a
  53    shared case. */
  54 struct ccase
  55   {
  56     struct caseproto *proto;    /* Case prototype. */
  57     size_t ref_cnt;             /* Reference count. */
  58     union value values[1];      /* Values. */
  59   };
  60
  61 struct ccase *case_create (const struct caseproto *) MALLOC_LIKE;
  62 struct ccase *case_try_create (const struct caseproto *) MALLOC_LIKE;
  63 struct ccase *case_clone (const struct ccase *) MALLOC_LIKE;
  64
  65 static inline struct ccase *case_unshare (struct ccase *) WARN_UNUSED_RESULT;
  66 struct ccase *case_ref (const struct ccase *) WARN_UNUSED_RESULT;
  67 static inline void case_unref (struct ccase *);
  68 static inline bool case_is_shared (const struct ccase *);
  69
  70 static inline size_t case_get_n_values (const struct ccase *);
  71 static inline const struct caseproto *case_get_proto (const struct ccase *);
  72
  73 size_t case_get_cost (const struct caseproto *);
  74
  75 struct ccase *case_resize (struct ccase *, const struct caseproto *)
  76   WARN_UNUSED_RESULT;
  77 struct ccase *case_unshare_and_resize (struct ccase *,
  78                                        const struct caseproto *)
  79   WARN_UNUSED_RESULT;
  80
  81 void case_set_missing (struct ccase *);
  82
  83 void case_copy (struct ccase *dst, size_t dst_idx,
  84                 const struct ccase *src, size_t src_idx,
  85                 size_t cnt);
  86 void case_copy_out (const struct ccase *,
  87                     size_t start_idx, union value *, size_t n_values);
  88 void case_copy_in (struct ccase *,
  89                    size_t start_idx, const union value *, size_t n_values);
  90
  91 const union value *case_data (const struct ccase *, const struct variable *);
  92 const union value *case_data_idx (const struct ccase *, size_t idx);
  93 union value *case_data_rw (struct ccase *, const struct variable *);
  94 union value *case_data_rw_idx (struct ccase *, size_t idx);
  95
  96 double case_num (const struct ccase *, const struct variable *);
  97 double case_num_idx (const struct ccase *, size_t idx);
  98 double *case_num_rw (struct ccase *, const struct variable *);
  99 double *case_num_rw_idx (struct ccase *, size_t idx);
 100
 101 const uint8_t *case_str (const struct ccase *, const struct variable *);
 102 const uint8_t *case_str_idx (const struct ccase *, size_t idx);
 103 struct substring case_ss (const struct ccase *, const struct variable *);
 104 struct substring case_ss_idx (const struct ccase *, size_t width, size_t idx);
 105 uint8_t *case_str_rw (struct ccase *, const struct variable *);
 106 uint8_t *case_str_rw_idx (struct ccase *, size_t idx);
 107
 108 int case_compare (const struct ccase *, const struct ccase *,
 109                   const struct variable *const *, size_t n_vars);
 110 int case_compare_2dict (const struct ccase *, const struct ccase *,
 111                         const struct variable *const *,
 112                         const struct variable *const *,
 113                         size_t n_vars);
 114
 115 const union value *case_data_all (const struct ccase *);
 116 union value *case_data_all_rw (struct ccase *);
 117 \f
 118 struct ccase *case_unshare__ (struct ccase *);
 119 void case_unref__ (struct ccase *);
 120
 121 /* If C is a shared case, that is, if it has a reference count
 122    greater than 1, makes a new unshared copy and returns it,
 123    decrementing C's reference count.  If C is not shared (its
 124    reference count is 1), returns C.
 125
 126    This function should be used before attempting to modify any
 127    of the data in a case that might be shared, e.g.:
 128         c = case_unshare (c);              // Make sure that C is not shared.
 129         *case_num_rw (c, myvar) = 1;       // Modify data in C.
 130 */
 131 static inline struct ccase *
 132 case_unshare (struct ccase *c)
 133 {
 134   if (case_is_shared (c))
 135     c = case_unshare__ (c);
 136   return c;
 137 }
 138
 139 /* Decrements case C's reference count.  Frees C if its
 140    reference count drops to 0.
 141
 142    If C is a null pointer, this function has no effect. */
 143 static inline void
 144 case_unref (struct ccase *c)
 145 {
 146   if (c != NULL && --c->ref_cnt == 0)
 147     case_unref__ (c);
 148 }
 149
 150 /* Returns true if case C is shared.  A case that is shared
 151    cannot be modified directly.  Instead, an unshared copy must
 152    first be made with case_unshare(). */
 153 static inline bool
 154 case_is_shared (const struct ccase *c)
 155 {
 156   return c->ref_cnt > 1;
 157 }
 158
 159 /* Returns the number of union values in C. */
 160 static inline size_t
 161 case_get_n_values (const struct ccase *c)
 162 {
 163   return caseproto_get_n_widths (c->proto);
 164 }
 165
 166 /* Returns the prototype that describes the format of case C.
 167    The caller must not unref the returned prototype. */
 168 static inline const struct caseproto *
 169 case_get_proto (const struct ccase *c)
 170 {
 171   return c->proto;
 172 }
 173
 174 #endif /* data/case.h */