Git 1.8.1.2
[git/jnareb-git.git] / hash.c
blob749ecfe4841a6a2af6ba4fdc6c540fd3016178f1
1 /*
2 * Some generic hashing helpers.
3 */
4 #include "cache.h"
5 #include "hash.h"
7 /*
8 * Look up a hash entry in the hash table. Return the pointer to
9 * the existing entry, or the empty slot if none existed. The caller
10 * can then look at the (*ptr) to see whether it existed or not.
12 static struct hash_table_entry *lookup_hash_entry(unsigned int hash, const struct hash_table *table)
14 unsigned int size = table->size, nr = hash % size;
15 struct hash_table_entry *array = table->array;
17 while (array[nr].ptr) {
18 if (array[nr].hash == hash)
19 break;
20 nr++;
21 if (nr >= size)
22 nr = 0;
24 return array + nr;
29 * Insert a new hash entry pointer into the table.
31 * If that hash entry already existed, return the pointer to
32 * the existing entry (and the caller can create a list of the
33 * pointers or do anything else). If it didn't exist, return
34 * NULL (and the caller knows the pointer has been inserted).
36 static void **insert_hash_entry(unsigned int hash, void *ptr, struct hash_table *table)
38 struct hash_table_entry *entry = lookup_hash_entry(hash, table);
40 if (!entry->ptr) {
41 entry->ptr = ptr;
42 entry->hash = hash;
43 table->nr++;
44 return NULL;
46 return &entry->ptr;
49 static void grow_hash_table(struct hash_table *table)
51 unsigned int i;
52 unsigned int old_size = table->size, new_size;
53 struct hash_table_entry *old_array = table->array, *new_array;
55 new_size = alloc_nr(old_size);
56 new_array = xcalloc(sizeof(struct hash_table_entry), new_size);
57 table->size = new_size;
58 table->array = new_array;
59 table->nr = 0;
60 for (i = 0; i < old_size; i++) {
61 unsigned int hash = old_array[i].hash;
62 void *ptr = old_array[i].ptr;
63 if (ptr)
64 insert_hash_entry(hash, ptr, table);
66 free(old_array);
69 void *lookup_hash(unsigned int hash, const struct hash_table *table)
71 if (!table->array)
72 return NULL;
73 return lookup_hash_entry(hash, table)->ptr;
76 void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table)
78 unsigned int nr = table->nr;
79 if (nr >= table->size/2)
80 grow_hash_table(table);
81 return insert_hash_entry(hash, ptr, table);
84 int for_each_hash(const struct hash_table *table, int (*fn)(void *, void *), void *data)
86 int sum = 0;
87 unsigned int i;
88 unsigned int size = table->size;
89 struct hash_table_entry *array = table->array;
91 for (i = 0; i < size; i++) {
92 void *ptr = array->ptr;
93 array++;
94 if (ptr) {
95 int val = fn(ptr, data);
96 if (val < 0)
97 return val;
98 sum += val;
101 return sum;
104 void free_hash(struct hash_table *table)
106 free(table->array);
107 table->array = NULL;
108 table->size = 0;
109 table->nr = 0;