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/* Linear probe hash table.
*
* Simple hashtable with open adressing linear probe.
* Does not manage memory of key/value pointers.
* Does not support deleting entries.
*/
#include "fitz.h"
#include "muxps.h"
static const unsigned primes[] =
{
61, 127, 251, 509, 1021, 2039, 4093, 8191, 16381, 32749, 65521,
131071, 262139, 524287, 1048573, 2097143, 4194301, 8388593, 0
};
typedef struct xps_hash_entry_s xps_hash_entry;
struct xps_hash_entry_s
{
char *key;
void *value;
};
struct xps_hash_table_s
{
void *ctx;
unsigned int size;
unsigned int load;
xps_hash_entry *entries;
};
static inline int
xps_tolower(int c)
{
if (c >= 'A' && c <= 'Z')
return c + 32;
return c;
}
static unsigned int
xps_hash(char *s)
{
unsigned int h = 0;
while (*s)
h = xps_tolower(*s++) + (h << 6) + (h << 16) - h;
return h;
}
xps_hash_table *
xps_hash_new(void)
{
xps_hash_table *table;
table = fz_malloc(sizeof(xps_hash_table));
table->size = primes[0];
table->load = 0;
table->entries = fz_calloc(table->size, sizeof(xps_hash_entry));
memset(table->entries, 0, table->size * sizeof(xps_hash_entry));
return table;
}
static int
xps_hash_double(xps_hash_table *table)
{
xps_hash_entry *old_entries;
xps_hash_entry *new_entries;
unsigned int old_size = table->size;
unsigned int new_size = table->size * 2;
int i;
for (i = 0; primes[i] != 0; i++)
{
if (primes[i] > old_size)
{
new_size = primes[i];
break;
}
}
old_entries = table->entries;
new_entries = fz_calloc(new_size, sizeof(xps_hash_entry));
table->size = new_size;
table->entries = new_entries;
table->load = 0;
memset(table->entries, 0, table->size * sizeof(xps_hash_entry));
for (i = 0; i < old_size; i++)
if (old_entries[i].value)
xps_hash_insert(table, old_entries[i].key, old_entries[i].value);
fz_free(old_entries);
return 0;
}
void
xps_hash_free(xps_hash_table *table,
void (*free_key)(void *),
void (*free_value)(void *))
{
int i;
for (i = 0; i < table->size; i++)
{
if (table->entries[i].key && free_key)
free_key(table->entries[i].key);
if (table->entries[i].value && free_value)
free_value(table->entries[i].value);
}
fz_free(table->entries);
fz_free(table);
}
void *
xps_hash_lookup(xps_hash_table *table, char *key)
{
xps_hash_entry *entries = table->entries;
unsigned int size = table->size;
unsigned int pos = xps_hash(key) % size;
while (1)
{
if (!entries[pos].value)
return NULL;
if (xps_strcasecmp(key, entries[pos].key) == 0)
return entries[pos].value;
pos = (pos + 1) % size;
}
}
int
xps_hash_insert(xps_hash_table *table, char *key, void *value)
{
xps_hash_entry *entries;
unsigned int size, pos;
/* Grow the table at 80% load */
if (table->load > table->size * 8 / 10)
{
if (xps_hash_double(table) < 0)
return fz_rethrow(-1, "cannot grow hash table");
}
entries = table->entries;
size = table->size;
pos = xps_hash(key) % size;
while (1)
{
if (!entries[pos].value)
{
entries[pos].key = key;
entries[pos].value = value;
table->load ++;
return 0;
}
if (xps_strcasecmp(key, entries[pos].key) == 0)
{
return 0;
}
pos = (pos + 1) % size;
}
}
void
xps_hash_debug(xps_hash_table *table)
{
int i;
printf("hash table load %d / %d\n", table->load, table->size);
for (i = 0; i < table->size; i++)
{
if (!table->entries[i].value)
printf("table % 4d: empty\n", i);
else
printf("table % 4d: key=%s value=%p\n", i,
table->entries[i].key, table->entries[i].value);
}
}
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