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 "hash.h"
-#include <assert.h>
+#include "error.h"
+#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include "algorithm.h"
#include "misc.h"
#include "str.h"
-/* Hash table. */
-struct hsh_table
- {
- size_t used; /* Number of filled entries. */
- size_t size; /* Number of entries (a power of 2). */
- void **entries; /* Hash table proper. */
-
- void *aux; /* Auxiliary data for comparison functions. */
- hsh_compare_func *compare;
- hsh_hash_func *hash;
- hsh_free_func *free;
- };
-
/* Note for constructing hash functions:
You can store the hash values in the records, then compare hash
return hash;
}
+/* Fowler-Noll-Vo 32-bit hash, for case-insensitive strings. */
+unsigned
+hsh_hash_case_string (const char *s_)
+{
+ const unsigned char *s = s_;
+ unsigned hash;
+
+ assert (s != NULL);
+
+ hash = FNV_32_BASIS;
+ while (*s != '\0')
+ hash = (hash * FNV_32_PRIME) ^ toupper (*s++);
+
+ return hash;
+}
+
/* Hash for ints. */
unsigned
hsh_hash_int (int i)
\f
/* Hash tables. */
+/* Hash table. */
+struct hsh_table
+ {
+ size_t used; /* Number of filled entries. */
+ size_t size; /* Number of entries (a power of 2). */
+ void **entries; /* Hash table proper. */
+
+ void *aux; /* Auxiliary data for comparison functions. */
+ hsh_compare_func *compare;
+ hsh_hash_func *hash;
+ hsh_free_func *free;
+ };
+
/* Creates a hash table with at least M entries. COMPARE is a
function that compares two entries and returns 0 if they are
identical, nonzero otherwise; HASH returns a nonnegative hash value
struct hsh_table *h;
int i;
- assert (size > 0);
+ if ( size == 0 )
+ return NULL;
+
assert (compare != NULL);
assert (hash != NULL);
for (i = 0; i < h->size; i++)
h->entries[i] = NULL;
+
+ h->used = 0;
}
/* Destroys table H and all its contents. */
}
}
+/* Locates an entry matching TARGET. Returns a pointer to the
+ entry, or a null pointer on failure. */
+static inline unsigned
+locate_matching_entry (struct hsh_table *h, const void *target)
+{
+ unsigned i = h->hash (target, h->aux);
+
+ for (;;)
+ {
+ void *entry;
+ i &= h->size - 1;
+ entry = h->entries[i];
+ if (entry == NULL || !h->compare (entry, target, h->aux))
+ return i;
+ i--;
+ }
+}
+
/* Changes the capacity of H to NEW_SIZE. */
static void
hsh_rehash (struct hsh_table *h, size_t new_size)
h->entries = xmalloc (sizeof *h->entries * h->size);
for (i = 0; i < h->size; i++)
h->entries[i] = NULL;
- for (table_p = begin; table_p < end; table_p++)
+ for (table_p = begin; table_p < end; table_p++)
{
- void **entry;
-
- if (*table_p == NULL)
- continue;
- entry = &h->entries[h->hash (*table_p, h->aux) & (h->size - 1)];
- while (*entry)
- if (--entry < h->entries)
- entry = &h->entries[h->size - 1];
- *entry = *table_p;
+ void *entry = *table_p;
+ if (entry != NULL)
+ h->entries[locate_matching_entry (h, entry)] = entry;
}
free (begin);
}
void *const *b = b_;
struct hsh_table *h = h_;
+ assert(a);
+ assert(b);
+
return h->compare (*a, *b, h->aux);
}
inline void **
hsh_probe (struct hsh_table *h, const void *target)
{
- void **entry;
-
+ unsigned i;
+
assert (h != NULL);
assert (target != NULL);
- /* Order of these statements is important! */
if (h->used > h->size / 2)
hsh_rehash (h, h->size * 2);
- entry = &h->entries[h->hash (target, h->aux) & (h->size - 1)];
-
- while (*entry)
- {
- if (!h->compare (*entry, target, h->aux))
- return entry;
- if (--entry < h->entries)
- entry = &h->entries[h->size - 1];
- }
- h->used++;
- return entry;
+ i = locate_matching_entry (h, target);
+ if (h->entries[i] == NULL)
+ h->used++;
+ return &h->entries[i];
}
/* Searches hash table H for TARGET. If not found, inserts
return old;
}
-/* Locates an entry matching TARGET. Returns a pointer to the
- entry, or a null pointer on failure. */
-static inline void **
-locate_matching_entry (struct hsh_table *h, const void *target)
-{
- void **entry = &h->entries[h->hash (target, h->aux) & (h->size - 1)];
-
- while (*entry)
- {
- if (!h->compare (*entry, target, h->aux))
- return entry;
- if (--entry < h->entries)
- entry = &h->entries[h->size - 1];
- }
- return NULL;
-}
-
/* Returns the entry in hash table H that matches TARGET, or NULL
if there is none. */
void *
hsh_find (struct hsh_table *h, const void *target)
{
- void **entry = locate_matching_entry (h, target);
- return entry != NULL ? *entry : NULL;
+ return h->entries[locate_matching_entry (h, target)];
}
/* Deletes the entry in hash table H that matches TARGET.
Returns nonzero if an entry was deleted.
- Note: this function is very slow because it rehashes the
- entire table. Don't use this hash table implementation if
- deletion is a common operation. */
+ Uses Knuth's Algorithm 6.4R (Deletion with linear probing).
+ Because our load factor is at most 1/2, the average number of
+ moves that this algorithm makes should be at most 2 - ln 2 ~=
+ 1.65. */
int
hsh_delete (struct hsh_table *h, const void *target)
{
- void **entry = locate_matching_entry (h, target);
- if (entry != NULL)
+ unsigned i = locate_matching_entry (h, target);
+ if (h->entries[i] != NULL)
{
+ h->used--;
if (h->free != NULL)
- h->free (*entry, h->aux);
- *entry = 0;
- hsh_rehash (h, h->size);
- return 1;
+ h->free (h->entries[i], h->aux);
+
+ for (;;)
+ {
+ unsigned r;
+ ptrdiff_t j;
+
+ h->entries[i] = NULL;
+ j = i;
+ do
+ {
+ i = (i - 1) & (h->size - 1);
+ if (h->entries[i] == NULL)
+ return 1;
+
+ r = h->hash (h->entries[i], h->aux) & (h->size - 1);
+ }
+ while ((i <= r && r < j) || (r < j && j < i) || (j < i && i <= r));
+ h->entries[j] = h->entries[i];
+ }
}
else
return 0;
#if GLOBAL_DEBUGGING
#undef NDEBUG
-#include <assert.h>
+#include "error.h"
#include <stdio.h>
/* Displays contents of hash table H on stdout. */
projects / pspp-builds.git / blobdiff