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/* go-map-index.c -- find or insert an entry in a map.
Copyright 2009 The Go Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file. */
#include <stddef.h>
#include <stdlib.h>
#include "go-alloc.h"
#include "go-assert.h"
#include "map.h"
/* Rehash MAP to a larger size. */
static void
__go_map_rehash (struct __go_map *map)
{
const struct __go_map_descriptor *descriptor;
const struct __go_type_descriptor *key_descriptor;
size_t key_offset;
size_t key_size;
size_t (*hashfn) (const void *, size_t);
size_t old_bucket_count;
void **old_buckets;
size_t new_bucket_count;
void **new_buckets;
size_t i;
descriptor = map->__descriptor;
key_descriptor = descriptor->__map_descriptor->__key_type;
key_offset = descriptor->__key_offset;
key_size = key_descriptor->__size;
hashfn = key_descriptor->__hashfn;
old_bucket_count = map->__bucket_count;
old_buckets = map->__buckets;
new_bucket_count = __go_map_next_prime (old_bucket_count * 2);
new_buckets = (void **) __go_alloc (new_bucket_count * sizeof (void *));
__builtin_memset (new_buckets, 0, new_bucket_count * sizeof (void *));
for (i = 0; i < old_bucket_count; ++i)
{
char* entry;
char* next;
for (entry = old_buckets[i]; entry != NULL; entry = next)
{
size_t key_hash;
size_t new_bucket_index;
/* We could speed up rehashing at the cost of memory space
by caching the hash code. */
key_hash = hashfn (entry + key_offset, key_size);
new_bucket_index = key_hash % new_bucket_count;
next = *(char **) entry;
*(char **) entry = new_buckets[new_bucket_index];
new_buckets[new_bucket_index] = entry;
}
}
__go_free (old_buckets);
map->__bucket_count = new_bucket_count;
map->__buckets = new_buckets;
}
/* Find KEY in MAP, return a pointer to the value. If KEY is not
present, then if INSERT is false, return NULL, and if INSERT is
true, insert a new value and zero-initialize it before returning a
pointer to it. */
void *
__go_map_index (struct __go_map *map, const void *key, _Bool insert)
{
const struct __go_map_descriptor *descriptor;
const struct __go_type_descriptor *key_descriptor;
size_t key_offset;
_Bool (*equalfn) (const void*, const void*, size_t);
size_t key_hash;
size_t key_size;
size_t bucket_index;
char *entry;
descriptor = map->__descriptor;
key_descriptor = descriptor->__map_descriptor->__key_type;
key_offset = descriptor->__key_offset;
key_size = key_descriptor->__size;
__go_assert (key_size != 0 && key_size != -1UL);
equalfn = key_descriptor->__equalfn;
key_hash = key_descriptor->__hashfn (key, key_size);
bucket_index = key_hash % map->__bucket_count;
entry = (char *) map->__buckets[bucket_index];
while (entry != NULL)
{
if (equalfn (key, entry + key_offset, key_size))
return entry + descriptor->__val_offset;
entry = *(char **) entry;
}
if (!insert)
return NULL;
if (map->__element_count >= map->__bucket_count)
{
__go_map_rehash (map);
bucket_index = key_hash % map->__bucket_count;
}
entry = (char *) __go_alloc (descriptor->__entry_size);
__builtin_memset (entry, 0, descriptor->__entry_size);
__builtin_memcpy (entry + key_offset, key, key_size);
*(char **) entry = map->__buckets[bucket_index];
map->__buckets[bucket_index] = entry;
map->__element_count += 1;
return entry + descriptor->__val_offset;
}
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