tvl-depot/third_party/git/hashmap.c
Vincent Ambo f4609b896f merge(3p/git): Merge git subtree at v2.29.2
This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb
2020-11-21 19:45:56 +01:00

323 lines
7.7 KiB
C

/*
* Generic implementation of hash-based key value mappings.
*/
#include "cache.h"
#include "hashmap.h"
#define FNV32_BASE ((unsigned int) 0x811c9dc5)
#define FNV32_PRIME ((unsigned int) 0x01000193)
unsigned int strhash(const char *str)
{
unsigned int c, hash = FNV32_BASE;
while ((c = (unsigned char) *str++))
hash = (hash * FNV32_PRIME) ^ c;
return hash;
}
unsigned int strihash(const char *str)
{
unsigned int c, hash = FNV32_BASE;
while ((c = (unsigned char) *str++)) {
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
unsigned int memhash(const void *buf, size_t len)
{
unsigned int hash = FNV32_BASE;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
unsigned int memihash(const void *buf, size_t len)
{
unsigned int hash = FNV32_BASE;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
/*
* Incorporate another chunk of data into a memihash
* computation.
*/
unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
{
unsigned int hash = hash_seed;
unsigned char *ucbuf = (unsigned char *) buf;
while (len--) {
unsigned int c = *ucbuf++;
if (c >= 'a' && c <= 'z')
c -= 'a' - 'A';
hash = (hash * FNV32_PRIME) ^ c;
}
return hash;
}
#define HASHMAP_INITIAL_SIZE 64
/* grow / shrink by 2^2 */
#define HASHMAP_RESIZE_BITS 2
/* load factor in percent */
#define HASHMAP_LOAD_FACTOR 80
static void alloc_table(struct hashmap *map, unsigned int size)
{
map->tablesize = size;
map->table = xcalloc(size, sizeof(struct hashmap_entry *));
/* calculate resize thresholds for new size */
map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
if (size <= HASHMAP_INITIAL_SIZE)
map->shrink_at = 0;
else
/*
* The shrink-threshold must be slightly smaller than
* (grow-threshold / resize-factor) to prevent erratic resizing,
* thus we divide by (resize-factor + 1).
*/
map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
}
static inline int entry_equals(const struct hashmap *map,
const struct hashmap_entry *e1, const struct hashmap_entry *e2,
const void *keydata)
{
return (e1 == e2) ||
(e1->hash == e2->hash &&
!map->cmpfn(map->cmpfn_data, e1, e2, keydata));
}
static inline unsigned int bucket(const struct hashmap *map,
const struct hashmap_entry *key)
{
return key->hash & (map->tablesize - 1);
}
int hashmap_bucket(const struct hashmap *map, unsigned int hash)
{
return hash & (map->tablesize - 1);
}
static void rehash(struct hashmap *map, unsigned int newsize)
{
unsigned int i, oldsize = map->tablesize;
struct hashmap_entry **oldtable = map->table;
alloc_table(map, newsize);
for (i = 0; i < oldsize; i++) {
struct hashmap_entry *e = oldtable[i];
while (e) {
struct hashmap_entry *next = e->next;
unsigned int b = bucket(map, e);
e->next = map->table[b];
map->table[b] = e;
e = next;
}
}
free(oldtable);
}
static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
const struct hashmap_entry *key, const void *keydata)
{
struct hashmap_entry **e = &map->table[bucket(map, key)];
while (*e && !entry_equals(map, *e, key, keydata))
e = &(*e)->next;
return e;
}
static int always_equal(const void *unused_cmp_data,
const struct hashmap_entry *unused1,
const struct hashmap_entry *unused2,
const void *unused_keydata)
{
return 0;
}
void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
const void *cmpfn_data, size_t initial_size)
{
unsigned int size = HASHMAP_INITIAL_SIZE;
memset(map, 0, sizeof(*map));
map->cmpfn = equals_function ? equals_function : always_equal;
map->cmpfn_data = cmpfn_data;
/* calculate initial table size and allocate the table */
initial_size = (unsigned int) ((uint64_t) initial_size * 100
/ HASHMAP_LOAD_FACTOR);
while (initial_size > size)
size <<= HASHMAP_RESIZE_BITS;
alloc_table(map, size);
/*
* Keep track of the number of items in the map and
* allow the map to automatically grow as necessary.
*/
map->do_count_items = 1;
}
void hashmap_free_(struct hashmap *map, ssize_t entry_offset)
{
if (!map || !map->table)
return;
if (entry_offset >= 0) { /* called by hashmap_free_entries */
struct hashmap_iter iter;
struct hashmap_entry *e;
hashmap_iter_init(map, &iter);
while ((e = hashmap_iter_next(&iter)))
/*
* like container_of, but using caller-calculated
* offset (caller being hashmap_free_entries)
*/
free((char *)e - entry_offset);
}
free(map->table);
memset(map, 0, sizeof(*map));
}
struct hashmap_entry *hashmap_get(const struct hashmap *map,
const struct hashmap_entry *key,
const void *keydata)
{
return *find_entry_ptr(map, key, keydata);
}
struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
const struct hashmap_entry *entry)
{
struct hashmap_entry *e = entry->next;
for (; e; e = e->next)
if (entry_equals(map, entry, e, NULL))
return e;
return NULL;
}
void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
{
unsigned int b = bucket(map, entry);
/* add entry */
entry->next = map->table[b];
map->table[b] = entry;
/* fix size and rehash if appropriate */
if (map->do_count_items) {
map->private_size++;
if (map->private_size > map->grow_at)
rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
}
}
struct hashmap_entry *hashmap_remove(struct hashmap *map,
const struct hashmap_entry *key,
const void *keydata)
{
struct hashmap_entry *old;
struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
if (!*e)
return NULL;
/* remove existing entry */
old = *e;
*e = old->next;
old->next = NULL;
/* fix size and rehash if appropriate */
if (map->do_count_items) {
map->private_size--;
if (map->private_size < map->shrink_at)
rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
}
return old;
}
struct hashmap_entry *hashmap_put(struct hashmap *map,
struct hashmap_entry *entry)
{
struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
hashmap_add(map, entry);
return old;
}
void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
{
iter->map = map;
iter->tablepos = 0;
iter->next = NULL;
}
struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
{
struct hashmap_entry *current = iter->next;
for (;;) {
if (current) {
iter->next = current->next;
return current;
}
if (iter->tablepos >= iter->map->tablesize)
return NULL;
current = iter->map->table[iter->tablepos++];
}
}
struct pool_entry {
struct hashmap_entry ent;
size_t len;
unsigned char data[FLEX_ARRAY];
};
static int pool_entry_cmp(const void *unused_cmp_data,
const struct hashmap_entry *eptr,
const struct hashmap_entry *entry_or_key,
const void *keydata)
{
const struct pool_entry *e1, *e2;
e1 = container_of(eptr, const struct pool_entry, ent);
e2 = container_of(entry_or_key, const struct pool_entry, ent);
return e1->data != keydata &&
(e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
}
const void *memintern(const void *data, size_t len)
{
static struct hashmap map;
struct pool_entry key, *e;
/* initialize string pool hashmap */
if (!map.tablesize)
hashmap_init(&map, pool_entry_cmp, NULL, 0);
/* lookup interned string in pool */
hashmap_entry_init(&key.ent, memhash(data, len));
key.len = len;
e = hashmap_get_entry(&map, &key, ent, data);
if (!e) {
/* not found: create it */
FLEX_ALLOC_MEM(e, data, data, len);
hashmap_entry_init(&e->ent, key.ent.hash);
e->len = len;
hashmap_add(&map, &e->ent);
}
return e->data;
}