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d1f128b050
This is in an effort to make the source index of 'unpack_trees()' as being const, and thus making the compiler help us verify that we only access it for reading. The constification also extended to some of the hashing helpers that get called indirectly. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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