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/* hashtab.c
*
* generic hash table routines */
#include "config.h"
#include <stdio.h>
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include "common.h"
#include "hashtab.h"
#define INITIAL_TABLE_SIZE 7 /* number of buckets */
#define RESIZE_MULTIPLIER 4 /* grow table by this factor */
#define RESIZE_SIZE_MULTIPLIER 0.6 /* grow table when it's 60% full */
/* A decent string hash function */
static
unsigned long
hash (const char *s, unsigned int len, unsigned long hashsize)
{
unsigned long hashval;
for (hashval = 0; len; s++, len--)
hashval = *s + 31 * hashval;
return hashval % hashsize;
}
/* Create and return a new hash table. If NUMERIC is non-zero, items
to be hashed are numeric and shouldn't be truncated like
strings. */
struct hashtab *
hashtab_init (int numeric)
{
struct hashtab *new;
new = (struct hashtab *) xmalloc (sizeof (struct hashtab));
memset (new, 0, sizeof (struct hashtab));
new->numeric = numeric;
return new;
}
/* Return the smaller of the length of a string or the number passed
in. If 0 is passed, return the string length unconditionally. */
static
unsigned int
get_key_len (char *s, unsigned int len, int numeric)
{
if (numeric)
{
if (len == 0)
fatal ("hashtab.c (get_key_len): hashing a num with len == 0");
if (len != numeric)
fatal ("hashtab.c (get_key_len): hashing a num with len != numeric");
return len;
}
else
{
if (!len)
return strlen (s);
else
{
unsigned int i;
for (i = len; i && (*s != '\0'); s++, i--)
;
return len - i;
}
}
}
/* When the number of entries gets too big for efficient use of the
hash table, resize it. */
static
void
hashtab_resize (struct hashtab *ht)
{
unsigned long old_size, bucket;
struct hashtab_elem **old_table, *elt;
/* Save the old values. */
old_size = ht->table_size;
old_table = ht->table;
/* Resize and allocate a new table. */
ht->table_size *= RESIZE_MULTIPLIER;
ht->resize_size = ht->table_size * RESIZE_SIZE_MULTIPLIER;
ht->table = (struct hashtab_elem **)
xmalloc (sizeof (struct hashtab_elem *) * ht->table_size);
memset (ht->table, 0, sizeof (struct hashtab_elem *) * ht->table_size);
/* Step through each key in the old table, re-hashing and inserting
into the new table. We don't use the HASHTAB_FIRST and
HASHTAB_CREATE routines because we can do this more efficiently,
knowing that each element is unique (don't need check the old
ones in a bin on insert). */
for (bucket = 0; bucket < old_size; bucket++)
for (elt = old_table[bucket]; elt != NULL;)
{
struct hashtab_elem *old_next = elt->next;
elt->hashval = hash (elt->key, elt->key_len, ht->table_size);
elt->prev = NULL;
elt->next = ht->table[elt->hashval];
if (ht->table[elt->hashval])
ht->table[elt->hashval]->prev = elt;
ht->table[elt->hashval] = elt;
elt = old_next;
}
/* Remove the old table. */
free (old_table);
}
/* Create an entry for the given key. If the key already exists,
return the existing entry with the data cleared. If LEN is 0,
assume that the string is null-terminated. Otherwise, only use LEN
bytes. */
struct hashtab_elem *
hashtab_create (struct hashtab *ht, void *key, unsigned int len)
{
unsigned long hashval;
unsigned int key_len;
struct hashtab_elem *he;
if (ht->table == NULL)
{
/* Create a fresh table. */
ht->table_size = INITIAL_TABLE_SIZE;
ht->items_hashed = 0;
ht->resize_size = ht->table_size * RESIZE_SIZE_MULTIPLIER;
ht->table = (struct hashtab_elem **)
xmalloc (sizeof (struct hashtab_elem *) * ht->table_size);
memset (ht->table, 0, sizeof (struct hashtab_elem *) * ht->table_size);
}
/* Hash the key. */
key_len = get_key_len (key, len, ht->numeric);
hashval = hash (key, key_len, ht->table_size);
/* We could use HASHTAB_FIND, but then we'd have to call STRLEN
twice & etc. */
for (he = ht->table[hashval]; he != NULL; he = he->next)
{
if ((he->key_len == key_len) && (memcmp (he->key, key, key_len) == 0))
{
/* Clear the existing data and return the entry. */
he->data = NULL;
return he;
}
}
/* Create a new entry, since we didn't find one. */
he = (struct hashtab_elem *) xmalloc (sizeof (struct hashtab_elem));
he->key_len = key_len;
he->key = (char *) xmalloc (sizeof (char) * (he->key_len + 1));
memcpy (he->key, key, key_len);
/* Make sure the key is null-terminated -- this won't hurt if we're
using a numeric hash value, since the extra zero will never get
considered. */
((char *) he->key)[he->key_len] = '\0';
he->ht = ht;
he->prev = NULL;
he->hashval = hashval;
he->next = ht->table[hashval];
if (ht->table[hashval])
ht->table[hashval]->prev = he;
ht->table[hashval] = he;
ht->items_hashed++;
/* Are there too many items in the table? */
if (ht->items_hashed > ht->resize_size)
hashtab_resize (ht);
return he;
}
/* Find KEY in HT and return the entry associated with it. If LEN is
0, assume that the string is null-terminated. Otherwise, only use
LEN bytes. */
struct hashtab_elem *
hashtab_find (struct hashtab *ht, void *key, unsigned int len)
{
unsigned long hashval;
unsigned int key_len;
struct hashtab_elem *he;
if (ht->table == NULL)
return NULL;
key_len = get_key_len (key, len, ht->numeric);
hashval = hash (key, key_len, ht->table_size);
for (he = ht->table[hashval]; he != NULL; he = he->next)
if ((he->key_len == key_len) && (memcmp (he->key, key, key_len) == 0))
return he;
return NULL;
}
/* Return the key associated with HE. */
void *
hashtab_get_key (struct hashtab_elem *he)
{
return he->key;
}
/* Return the data associated with HE. */
void *
hashtab_get_value (struct hashtab_elem *he)
{
return he->data;
}
/* Set the data for HE. */
void
hashtab_set_value (struct hashtab_elem *he, void *v, unsigned int len)
{
he->data = (void *) xmalloc (len);
memcpy (he->data, v, len);
}
/* Return the first thing in the table. */
struct hashtab_elem *
hashtab_first (struct hashtab *ht, struct hashtab_order *ho)
{
ho->which = 0;
ho->elem = NULL;
ho->ht = ht;
return hashtab_next (ho);
}
/* Given HO, return the next entry in the hash table. */
struct hashtab_elem *
hashtab_next (struct hashtab_order *ho)
{
unsigned long i;
struct hashtab_elem *he;
if (ho->elem)
{
he = ho->elem;
ho->elem = he->next;
if (he->next == NULL)
ho->which++;
return he;
}
for (i = ho->which; i < ho->ht->table_size; i++)
for (he = ho->ht->table[i]; he != NULL; he = he->next)
{
ho->which = (he->next ? i : i + 1);
ho->elem = he->next;
return he;
}
return NULL; /* nothing in the table */
}
void
hashtab_dump_keys (struct hashtab *ht, FILE *out)
{
struct hashtab_order ho;
struct hashtab_elem *he;
for (he = hashtab_first (ht, &ho);
he != NULL;
he = hashtab_next (&ho))
fprintf (stddebug, "%s (%d)\n", (char *) he->key, he->key_len);
}
/* Delete the given element from the hash table. We want to be able
to call this in between calls to HASHTAB_NEXT so we can use the
obvious way to delete items from the table. */
void
hashtab_delete (struct hashtab_elem *he)
{
he->ht->items_hashed--;
if (he->prev)
he->prev->next = he->next;
else
he->ht->table[he->hashval] = he->next;
if (he->next)
he->next->prev = he->prev;
if (he->data)
free (he->data);
free (he->key);
free (he);
}
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