/* PSPP - a program for statistical analysis.
Copyright (C) 2010, 2011 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
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see . */
#include
#include "libpspp/intern.h"
#include
#include
#include "libpspp/assertion.h"
#include "libpspp/cast.h"
#include "libpspp/hash-functions.h"
#include "libpspp/hmap.h"
#include "gl/xalloc.h"
/* A single interned string. */
struct interned_string
{
struct hmap_node node; /* Node in hash table. */
size_t ref_cnt; /* Reference count. */
size_t length; /* strlen(string). */
char string[1]; /* Null-terminated string. */
};
/* All interned strings. */
static struct hmap interns = HMAP_INITIALIZER (interns);
/* Searches the table of interned strings for one equal to S, which has length
LENGTH and hash value HASH. */
static struct interned_string *
intern_lookup__ (const char *s, size_t length, unsigned int hash)
{
struct interned_string *is;
HMAP_FOR_EACH_WITH_HASH (is, struct interned_string, node, hash, &interns)
if (is->length == length && !memcmp (s, is->string, length))
return is;
return NULL;
}
/* Returns an interned version of string S. Pass the returned string to
intern_unref() to release it. */
const char *
intern_new (const char *s)
{
size_t length = strlen (s);
unsigned int hash = hash_bytes (s, length, 0);
struct interned_string *is;
is = intern_lookup__ (s, length, hash);
if (is != NULL)
is->ref_cnt++;
else
{
is = xmalloc (length + sizeof *is);
hmap_insert (&interns, &is->node, hash);
is->ref_cnt = 1;
is->length = length;
memcpy (is->string, s, length + 1);
}
return is->string;
}
const char *
intern_new_if_nonnull (const char *s)
{
return s ? intern_new (s) : NULL;
}
static struct interned_string *
interned_string_from_string (const char *s_)
{
char (*s)[1] = (char (*)[1]) s_;
struct interned_string *is = UP_CAST (s, struct interned_string, string);
assert (is->ref_cnt> 0);
return is;
}
/* Increases the reference count on S, which must be an interned string
returned by intern_new(). */
const char *
intern_ref (const char *s)
{
struct interned_string *is = interned_string_from_string (s);
is->ref_cnt++;
return s;
}
const char *
intern_ref_if_nonnull (const char *s)
{
return s ? intern_ref (s) : NULL;
}
/* Decreases the reference count on S, which must be an interned string
returned by intern_new(). If the reference count reaches 0, frees the
interned string. */
void
intern_unref (const char *s)
{
if (s)
{
struct interned_string *is = interned_string_from_string (s);
if (--is->ref_cnt == 0)
{
hmap_delete (&interns, &is->node);
free (is);
}
}
}
/* Given null-terminated string S, returns true if S is an interned string
returned by intern_string_new(), false otherwise.
This is appropriate for use in debug assertions, e.g.:
assert (is_interned_string (s));
*/
bool
is_interned_string (const char *s)
{
size_t length = strlen (s);
unsigned int hash = hash_bytes (s, length, 0);
return intern_lookup__ (s, length, hash) != NULL;
}
/* Returns the length of S, which must be an interned string returned by
intern_new(). */
size_t
intern_strlen (const char *s)
{
return interned_string_from_string (s)->length;
}