Add string hashmap

This commit is contained in:
Rui Ueyama 2020-09-02 01:30:29 +09:00
parent f0c98e0d59
commit 0aad326f35
4 changed files with 197 additions and 0 deletions

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@ -409,6 +409,30 @@ bool is_ident1(uint32_t c);
bool is_ident2(uint32_t c);
int display_width(char *p, int len);
//
// hashmap.c
//
typedef struct {
char *key;
int keylen;
void *val;
} HashEntry;
typedef struct {
HashEntry *buckets;
int capacity;
int used;
} HashMap;
void *hashmap_get(HashMap *map, char *key);
void *hashmap_get2(HashMap *map, char *key, int keylen);
void hashmap_put(HashMap *map, char *key, void *val);
void hashmap_put2(HashMap *map, char *key, int keylen, void *val);
void hashmap_delete(HashMap *map, char *key);
void hashmap_delete2(HashMap *map, char *key, int keylen);
void hashmap_test(void);
//
// main.c
//

165
hashmap.c Normal file
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@ -0,0 +1,165 @@
// This is an implementation of the open-addressing hash table.
#include "chibicc.h"
// Initial hash bucket size
#define INIT_SIZE 16
// Rehash if the usage exceeds 70%.
#define HIGH_WATERMARK 70
// We'll keep the usage below 50% after rehashing.
#define LOW_WATERMARK 50
// Represents a deleted hash entry
#define TOMBSTONE ((void *)-1)
static uint64_t fnv_hash(char *s, int len) {
uint64_t hash = 0xcbf29ce484222325;
for (int i = 0; i < len; i++) {
hash *= 0x100000001b3;
hash ^= (unsigned char)s[i];
}
return hash;
}
// Make room for new entires in a given hashmap by removing
// tombstones and possibly extending the bucket size.
static void rehash(HashMap *map) {
// Compute the size of the new hashmap.
int nkeys = 0;
for (int i = 0; i < map->capacity; i++)
if (map->buckets[i].key && map->buckets[i].key != TOMBSTONE)
nkeys++;
int cap = map->capacity;
while ((nkeys * 100) / cap >= LOW_WATERMARK)
cap = cap * 2;
assert(cap > 0);
// Create a new hashmap and copy all key-values.
HashMap map2 = {};
map2.buckets = calloc(cap, sizeof(HashEntry));
map2.capacity = cap;
for (int i = 0; i < map->capacity; i++) {
HashEntry *ent = &map->buckets[i];
if (ent->key && ent->key != TOMBSTONE)
hashmap_put2(&map2, ent->key, ent->keylen, ent->val);
}
assert(map2.used == nkeys);
*map = map2;
}
static bool match(HashEntry *ent, char *key, int keylen) {
return ent->key && ent->key != TOMBSTONE &&
ent->keylen == keylen && memcmp(ent->key, key, keylen) == 0;
}
static HashEntry *get_entry(HashMap *map, char *key, int keylen) {
if (!map->buckets)
return NULL;
uint64_t hash = fnv_hash(key, keylen);
for (int i = 0; i < map->capacity; i++) {
HashEntry *ent = &map->buckets[(hash + i) % map->capacity];
if (match(ent, key, keylen))
return ent;
if (ent->key == NULL)
return NULL;
}
unreachable();
}
static HashEntry *get_or_insert_entry(HashMap *map, char *key, int keylen) {
if (!map->buckets) {
map->buckets = calloc(INIT_SIZE, sizeof(HashEntry));
map->capacity = INIT_SIZE;
} else if ((map->used * 100) / map->capacity >= HIGH_WATERMARK) {
rehash(map);
}
uint64_t hash = fnv_hash(key, keylen);
for (int i = 0; i < map->capacity; i++) {
HashEntry *ent = &map->buckets[(hash + i) % map->capacity];
if (match(ent, key, keylen))
return ent;
if (ent->key == TOMBSTONE) {
ent->key = key;
ent->keylen = keylen;
return ent;
}
if (ent->key == NULL) {
ent->key = key;
ent->keylen = keylen;
map->used++;
return ent;
}
}
unreachable();
}
void *hashmap_get(HashMap *map, char *key) {
return hashmap_get2(map, key, strlen(key));
}
void *hashmap_get2(HashMap *map, char *key, int keylen) {
HashEntry *ent = get_entry(map, key, keylen);
return ent ? ent->val : NULL;
}
void hashmap_put(HashMap *map, char *key, void *val) {
hashmap_put2(map, key, strlen(key), val);
}
void hashmap_put2(HashMap *map, char *key, int keylen, void *val) {
HashEntry *ent = get_or_insert_entry(map, key, keylen);
ent->val = val;
}
void hashmap_delete(HashMap *map, char *key) {
hashmap_delete2(map, key, strlen(key));
}
void hashmap_delete2(HashMap *map, char *key, int keylen) {
HashEntry *ent = get_entry(map, key, keylen);
if (ent)
ent->key = TOMBSTONE;
}
void hashmap_test(void) {
HashMap *map = calloc(1, sizeof(HashMap));
for (int i = 0; i < 5000; i++)
hashmap_put(map, format("key %d", i), (void *)(size_t)i);
for (int i = 1000; i < 2000; i++)
hashmap_delete(map, format("key %d", i));
for (int i = 1500; i < 1600; i++)
hashmap_put(map, format("key %d", i), (void *)(size_t)i);
for (int i = 6000; i < 7000; i++)
hashmap_put(map, format("key %d", i), (void *)(size_t)i);
for (int i = 0; i < 1000; i++)
assert((size_t)hashmap_get(map, format("key %d", i)) == i);
for (int i = 1000; i < 1500; i++)
assert(hashmap_get(map, "no such key") == NULL);
for (int i = 1500; i < 1600; i++)
assert((size_t)hashmap_get(map, format("key %d", i)) == i);
for (int i = 1600; i < 2000; i++)
assert(hashmap_get(map, "no such key") == NULL);
for (int i = 2000; i < 5000; i++)
assert((size_t)hashmap_get(map, format("key %d", i)) == i);
for (int i = 5000; i < 6000; i++)
assert(hashmap_get(map, "no such key") == NULL);
for (int i = 6000; i < 7000; i++)
hashmap_put(map, format("key %d", i), (void *)(size_t)i);
assert(hashmap_get(map, "no such key") == NULL);
printf("OK\n");
}

5
main.c
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@ -191,6 +191,11 @@ static void parse_args(int argc, char **argv) {
continue;
}
if (!strcmp(argv[i], "-hashmap-test")) {
hashmap_test();
exit(0);
}
// These options are ignored for now.
if (!strncmp(argv[i], "-O", 2) ||
!strncmp(argv[i], "-W", 2) ||

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@ -218,4 +218,7 @@ echo 'void foo(); void bar(); int main() { foo(); bar(); }' > $tmp/main.c
$chibicc -o $tmp/foo $tmp/main.c $tmp/foo.so
check '.so'
$chibicc -hashmap-test
check 'hashmap'
echo OK