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