111 lines
2.5 KiB
C
111 lines
2.5 KiB
C
/*
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* Some generic hashing helpers.
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*/
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#include "cache.h"
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#include "hash.h"
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/*
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* Look up a hash entry in the hash table. Return the pointer to
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* the existing entry, or the empty slot if none existed. The caller
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* can then look at the (*ptr) to see whether it existed or not.
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*/
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static struct hash_table_entry *lookup_hash_entry(unsigned int hash, const struct hash_table *table)
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{
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unsigned int size = table->size, nr = hash % size;
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struct hash_table_entry *array = table->array;
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while (array[nr].ptr) {
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if (array[nr].hash == hash)
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break;
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nr++;
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if (nr >= size)
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nr = 0;
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}
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return array + nr;
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}
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/*
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* Insert a new hash entry pointer into the table.
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*
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* If that hash entry already existed, return the pointer to
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* the existing entry (and the caller can create a list of the
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* pointers or do anything else). If it didn't exist, return
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* NULL (and the caller knows the pointer has been inserted).
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*/
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static void **insert_hash_entry(unsigned int hash, void *ptr, struct hash_table *table)
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{
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struct hash_table_entry *entry = lookup_hash_entry(hash, table);
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if (!entry->ptr) {
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entry->ptr = ptr;
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entry->hash = hash;
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table->nr++;
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return NULL;
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}
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return &entry->ptr;
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}
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static void grow_hash_table(struct hash_table *table)
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{
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unsigned int i;
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unsigned int old_size = table->size, new_size;
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struct hash_table_entry *old_array = table->array, *new_array;
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new_size = alloc_nr(old_size);
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new_array = xcalloc(sizeof(struct hash_table_entry), new_size);
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table->size = new_size;
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table->array = new_array;
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table->nr = 0;
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for (i = 0; i < old_size; i++) {
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unsigned int hash = old_array[i].hash;
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void *ptr = old_array[i].ptr;
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if (ptr)
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insert_hash_entry(hash, ptr, table);
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}
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free(old_array);
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}
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void *lookup_hash(unsigned int hash, const struct hash_table *table)
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{
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if (!table->array)
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return NULL;
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return lookup_hash_entry(hash, table)->ptr;
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}
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void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table)
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{
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unsigned int nr = table->nr;
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if (nr >= table->size/2)
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grow_hash_table(table);
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return insert_hash_entry(hash, ptr, table);
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}
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int for_each_hash(const struct hash_table *table, int (*fn)(void *))
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{
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int sum = 0;
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unsigned int i;
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unsigned int size = table->size;
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struct hash_table_entry *array = table->array;
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for (i = 0; i < size; i++) {
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void *ptr = array->ptr;
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array++;
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if (ptr) {
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int val = fn(ptr);
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if (val < 0)
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return val;
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sum += val;
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}
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}
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return sum;
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}
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void free_hash(struct hash_table *table)
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{
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free(table->array);
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table->array = NULL;
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table->size = 0;
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table->nr = 0;
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}
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