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/** @file ha/ha0storage.cc
 Hash storage.
 Provides a data structure that stores chunks of data in
 its own storage, avoiding duplicates.

 Created September 22, 2007 Vasil Dimov
 *******************************************************/

#include "ha0storage.h"
#include "ha_prototypes.h"
#include "hash0hash.h"
#include "mem0mem.h"
#include "ut0rnd.h"

/** Retrieves a data from a storage. If it is present, a pointer to the
 stored copy of data is returned, otherwise NULL is returned. */
static const void *ha_storage_get(
    ha_storage_t *storage, /*!< in: hash storage */
    const void *data,      /*!< in: data to check for */
    ulint data_len)        /*!< in: data length */
{
  ha_storage_node_t *node;

  /* avoid repetitive calls to ut::hash_binary() in the HASH_SEARCH
  macro */
  const auto hash_value =
      ut::hash_binary(static_cast<const byte *>(data), data_len);

#define IS_FOUND \
  node->data_len == data_len &&memcmp(node->data, data, data_len) == 0

  HASH_SEARCH(next,                /* node->"next" */
              storage->hash,       /* the hash table */
              hash_value,          /* key */
              ha_storage_node_t *, /* type of node->next */
              node,                /* auxiliary variable */
              ,                    /* assertion */
              IS_FOUND);           /* search criteria */

  if (node == nullptr) {
    return (nullptr);
  }
  /* else */

  return (node->data);
}

/** Copies data into the storage and returns a pointer to the copy. If the
 same data chunk is already present, then pointer to it is returned.
 Data chunks are considered to be equal if len1 == len2 and
 memcmp(data1, data2, len1) == 0. If "data" is not present (and thus
 data_len bytes need to be allocated) and the size of storage is going to
 become more than "memlim" then "data" is not added and NULL is returned.
 To disable this behavior "memlim" can be set to 0, which stands for
 "no limit". */
const void *ha_storage_put_memlim(
    ha_storage_t *storage, /*!< in/out: hash storage */
    const void *data,      /*!< in: data to store */
    ulint data_len,        /*!< in: data length */
    ulint memlim)          /*!< in: memory limit to obey */
{
  void *raw;
  ha_storage_node_t *node;
  const void *data_copy;

  /* check if data chunk is already present */
  data_copy = ha_storage_get(storage, data, data_len);
  if (data_copy != nullptr) {
    return (data_copy);
  }

  /* not present */

  /* check if we are allowed to allocate data_len bytes */
  if (memlim > 0 && ha_storage_get_size(storage) + data_len > memlim) {
    return (nullptr);
  }

  /* we put the auxiliary node struct and the data itself in one
  continuous block */
  raw = mem_heap_alloc(storage->heap, sizeof(ha_storage_node_t) + data_len);

  node = (ha_storage_node_t *)raw;
  data_copy = (byte *)raw + sizeof(*node);

  memcpy((byte *)raw + sizeof(*node), data, data_len);

  node->data_len = data_len;
  node->data = data_copy;

  /* avoid repetitive calls to ut::hash_binary() in the HASH_INSERT
  macro */
  const auto hash_value =
      ut::hash_binary(static_cast<const byte *>(data), data_len);

  HASH_INSERT(ha_storage_node_t, /* type used in the hash chain */
              next,              /* node->"next" */
              storage->hash,     /* the hash table */
              hash_value,        /* key */
              node);             /* add this data to the hash */

  /* the output should not be changed because it will spoil the
  hash table */
  return (data_copy);
}

#ifdef UNIV_COMPILE_TEST_FUNCS

void test_ha_storage() {
  ha_storage_t *storage;
  char buf[1024];
  int i;
  const void *stored[256];
  const void *p;

  storage = ha_storage_create(0, 0);

  for (i = 0; i < 256; i++) {
    memset(buf, i, sizeof(buf));
    stored[i] = ha_storage_put(storage, buf, sizeof(buf));
  }

  // ha_storage_empty(&storage);

  for (i = 255; i >= 0; i--) {
    memset(buf, i, sizeof(buf));
    p = ha_storage_put(storage, buf, sizeof(buf));

    if (p != stored[i]) {
      ib::warn(ER_IB_MSG_523) << "ha_storage_put() returned " << p
                              << " instead of " << stored[i] << ", i=" << i;
      return;
    }
  }

  ib::info(ER_IB_MSG_524) << "all ok";

  ha_storage_free(storage);
}

#endif /* UNIV_COMPILE_TEST_FUNCS */
