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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 "runtime.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;

  uintptr_t key_offset;

  size_t key_size;

  uintptr_t (*hashfn) (const void *, uintptr_t);

  uintptr_t old_bucket_count;

  void **old_buckets;

  uintptr_t new_bucket_count;

  void **new_buckets;

  uintptr_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;

  uintptr_t key_offset;

  _Bool (*equalfn) (const void*, const void*, uintptr_t);

  size_t key_hash;

  size_t key_size;

  size_t bucket_index;

  char *entry;

  if (map == NULL)

    {

      if (insert)

        runtime_panicstring ("assignment to entry in nil map");

      return NULL;

    }

  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;

}