1 /* PSPP - a program for statistical analysis.
2 Copyright (C) 2010 Free Software Foundation, Inc.
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.
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.
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/>. */
19 #include "libpspp/intern.h"
24 #include "libpspp/assertion.h"
25 #include "libpspp/hash-functions.h"
26 #include "libpspp/hmap.h"
28 #include "gl/xalloc.h"
30 /* A single interned string. */
31 struct interned_string
33 struct hmap_node node; /* Node in hash table. */
34 size_t ref_cnt; /* Reference count. */
35 char string[1]; /* Null-terminated string. */
38 /* All interned strings. */
39 static struct hmap interns = HMAP_INITIALIZER (interns);
41 /* Searches the table of interned string for */
42 static struct interned_string *
43 intern_lookup__ (const char *s, size_t length, unsigned int hash)
45 struct interned_string *is;
47 HMAP_FOR_EACH_WITH_HASH (is, struct interned_string, node, hash, &interns)
48 if (!memcmp (s, is->string, length + 1))
54 /* Returns an interned version of string S. Pass the returned string to
55 intern_unref() to release it. */
57 intern_new (const char *s)
59 size_t length = strlen (s);
60 unsigned int hash = hash_bytes (s, length, 0);
61 struct interned_string *is;
63 is = intern_lookup__ (s, length, hash);
68 is = xmalloc (length + sizeof *is);
69 hmap_insert (&interns, &is->node, hash);
71 memcpy (is->string, s, length + 1);
76 static struct interned_string *
77 interned_string_from_string (const char *s)
79 const size_t ofs = offsetof (struct interned_string, string);
80 struct interned_string *is = (struct interned_string *) (s - ofs);
81 assert (is->ref_cnt > 0);
85 /* Increases the reference count on S, which must be an interned string
86 returned by intern_new(). */
88 intern_ref (const char *s)
90 struct interned_string *is = interned_string_from_string (s);
95 /* Decreases the reference count on S, which must be an interned string
96 returned by intern_new(). If the reference count reaches 0, frees the
99 intern_unref (const char *s)
101 struct interned_string *is = interned_string_from_string (s);
102 if (--is->ref_cnt == 0)
104 hmap_delete (&interns, &is->node);
109 /* Given null-terminated string S, returns true if S is an interned string
110 returned by intern_string_new(), false otherwise.
112 This is appropriate for use in debug assertions, e.g.:
113 assert (is_interned_string (s));
116 is_interned_string (const char *s)
118 size_t length = strlen (s);
119 unsigned int hash = hash_bytes (s, length, 0);
120 return intern_lookup__ (s, length, hash) != NULL;