/*
 * Copyright (c) 2015 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

void BV(clib_bihash_init) 
     (BVT(clib_bihash) * h, char * name, u32 nbuckets, 
     uword memory_size)
{
  void * oldheap;

  nbuckets = 1 << (max_log2 (nbuckets));

  h->name = (u8 *)name;
  h->nbuckets = nbuckets;
  h->log2_nbuckets = max_log2 (nbuckets);

  h->mheap = mheap_alloc (0 /* use VM */, memory_size);

  oldheap = clib_mem_set_heap (h->mheap);
  vec_validate_aligned (h->buckets, nbuckets - 1, CLIB_CACHE_LINE_BYTES);
  h->writer_lock = clib_mem_alloc_aligned (CLIB_CACHE_LINE_BYTES, 
                                           CLIB_CACHE_LINE_BYTES);

  clib_mem_set_heap (oldheap);
}

void BV(clib_bihash_free) (BVT(clib_bihash) * h)
{
    mheap_free (h->mheap);
    memset (h, 0, sizeof (*h));
}

static BVT(clib_bihash_value) *
BV(value_alloc) (BVT(clib_bihash) * h, u32 log2_pages)
{
    BVT(clib_bihash_value) * rv = 0;
    void * oldheap;

    ASSERT (h->writer_lock[0]);
    if (log2_pages >= vec_len (h->freelists)
        || h->freelists [log2_pages] == 0)
    {
        oldheap = clib_mem_set_heap (h->mheap);

        vec_validate (h->freelists, log2_pages);
        vec_validate_aligned (rv, (1<<log2_pages) - 1, CLIB_CACHE_LINE_BYTES);
        clib_mem_set_heap (oldheap);
        goto initialize;
    }
    rv = h->freelists[log2_pages];
    h->freelists[log2_pages] = rv->next_free;

 initialize:
    ASSERT(rv);
    ASSERT (vec_len(rv) == (1<<log2_pages));
    /* 
     * Latest gcc complains that the length arg is zero
     * if we replace (1<<log2_pages) with vec_len(rv).
     * No clue.
     */
    memset (rv, 0xff, sizeof (*rv) * (1<<log2_pages));
    return rv;
}

static void
BV(value_free) 
    (BVT(clib_bihash) * h, 
     BVT(clib_bihash_value) * v)
{
    u32 log2_pages;

    ASSERT (h->writer_lock[0]);
    
    log2_pages = min_log2(vec_len(v));

    ASSERT(vec_len (h->freelists) > log2_pages);

    v->next_free = h->freelists[log2_pages];
    h->freelists[log2_pages] = v;
}

static inline void
BV(make_working_copy) 
    (BVT(clib_bihash) * h, clib_bihash_bucket_t * b)
{
  BVT(clib_bihash_value) * v;
  clib_bihash_bucket_t working_bucket __attribute__((aligned (8)));
  void * oldheap;
  BVT(clib_bihash_value) * working_copy;
  u32 cpu_number = os_get_cpu_number();

  if (cpu_number >= vec_len (h->working_copies))
    {
      oldheap = clib_mem_set_heap (h->mheap);
      vec_validate (h->working_copies, cpu_number);
      clib_mem_set_heap (oldheap);
    }

  /* 
   * working_copies are per-cpu so that near-simultaneous
   * updates from multiple threads will not result in sporadic, spurious
   * lookup failures. 
   */
  working_copy = h->working_copies[cpu_number];

  h->saved_bucket.as_u64 = b->as_u64;
  oldheap = clib_mem_set_heap (h->mheap);

  if ((1<<b->log2_pages) > vec_len (working_copy))
    {
      vec_validate_aligned (working_copy, (1<<b->log2_pages)-1, 
                            sizeof (u64));
      h->working_copies[cpu_number] = working_copy;
    }

  _vec_len(working_copy) = 1<<b->log2_pages;
  clib_mem_set_heap (oldheap);

  v = BV(clib_bihash_get_value) (h, b->offset);

  memcpy (working_copy, v, sizeof (*v)*(1<<b->log2_pages));
  working_bucket.as_u64 = b->as_u64;
  working_bucket.offset = BV(clib_bihash_get_offset) (h, working_copy);
  CLIB_MEMORY_BARRIER();
  b->as_u64 = working_bucket.as_u64;
  h->working_copies[cpu_number] = working_copy;
}

static BVT(clib_bihash_value) *
    BV(split_and_rehash) 
    (BVT(clib_bihash) * h,
     BVT(clib_bihash_value) * old_values,
     u32 new_log2_pages)
{
  BVT(clib_bihash_value) * new_values, * v, * new_v;
  int i, j, k;

  new_values = BV(value_alloc) (h, new_log2_pages);

  v = old_values;
  for (i = 0; i < vec_len (old_values); i++)
    {
      u64 new_hash;
      
      for (j = 0; j < BIHASH_KVP_PER_PAGE; j++)
        {
          if (BV(clib_bihash_is_free)(&(v->kvp[j])) == 0)
            {
              new_hash = BV(clib_bihash_hash) (&(v->kvp[j]));
              new_hash >>= h->log2_nbuckets;
              new_hash &= (1<<new_log2_pages) - 1;

              new_v = &new_values [new_hash];

              for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
                {
                  if (BV(clib_bihash_is_free)(&(new_v->kvp[k])))
                    {
                      memcpy (&(new_v->kvp[k]), &(v->kvp[j]), 
                              sizeof (new_v->kvp[k]));
                      goto doublebreak;
                    }
                }
              /* Crap. Tell caller to try again */
              BV(value_free) (h, new_values);
              return 0;
            }
        doublebreak:
          ;
        }
      v++;
    }
  return new_values;
}

int BV(clib_bihash_add_del) 
     (BVT(clib_bihash) * h, 
      BVT(clib_bihash_kv) * add_v,
      int is_add)
{
  u32 bucket_index;
  clib_bihash_bucket_t * b, tmp_b;
  BVT(clib_bihash_value) * v, * new_v, * save_new_v, * working_copy;
  u32 value_index;
  int rv = 0;
  int i;
  u64 hash, new_hash;
  u32 new_log2_pages;
  u32 cpu_number = os_get_cpu_number();
  
  hash = BV(clib_bihash_hash) (add_v);

  bucket_index = hash & (h->nbuckets-1);
  b = &h->buckets[bucket_index];

  hash >>= h->log2_nbuckets;

  while (__sync_lock_test_and_set (h->writer_lock, 1))
    ; 

  /* First elt in the bucket? */
  if (b->offset == 0)
    {
      if (is_add == 0)
        {
          rv = -1;
          goto unlock;
        }

      v = BV(value_alloc) (h, 0);
      *v->kvp = * add_v;
      tmp_b.as_u64 = 0;
      tmp_b.offset = BV(clib_bihash_get_offset) (h, v);

      b->as_u64 = tmp_b.as_u64;
      goto unlock;
    }

  BV(make_working_copy) (h, b);

  v = BV(clib_bihash_get_value) (h, h->saved_bucket.offset);
  value_index = hash & ((1<<h->saved_bucket.log2_pages)-1);
  v += value_index;
  
  if (is_add)
    {
      /* 
       * For obvious (in hindsight) reasons, see if we're supposed to
       * replace an existing key, then look for an empty slot.
       */
      for (i = 0; i < BIHASH_KVP_PER_PAGE; i++)
        {
          if (!memcmp(&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
            {
              memcpy (&(v->kvp[i]), add_v, sizeof (*add_v));
              CLIB_MEMORY_BARRIER();
              /* Restore the previous (k,v) pairs */
              b->as_u64 = h->saved_bucket.as_u64;
              goto unlock;
            }
        }
      for (i = 0; i < BIHASH_KVP_PER_PAGE; i++)
        {
          if (BV(clib_bihash_is_free)(&(v->kvp[i])))
            {
              memcpy (&(v->kvp[i]), add_v, sizeof (*add_v));
              CLIB_MEMORY_BARRIER();
              b->as_u64 = h->saved_bucket.as_u64;
              goto unlock;
            }
        }
      /* no room at the inn... split case... */
    }
  else
    {
      for (i = 0; i < BIHASH_KVP_PER_PAGE; i++)
        {
          if (!memcmp(&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
            {
              memset (&(v->kvp[i]), 0xff, sizeof (*(add_v)));
              CLIB_MEMORY_BARRIER();
              b->as_u64 = h->saved_bucket.as_u64;
              goto unlock;
            }
        }
      rv = -3;
      b->as_u64 = h->saved_bucket.as_u64;
      goto unlock;
    }

  new_log2_pages = h->saved_bucket.log2_pages + 1;

 expand_again:
  working_copy = h->working_copies[cpu_number];
  new_v = BV(split_and_rehash) (h, working_copy, new_log2_pages);
  if (new_v == 0)
    {
      new_log2_pages++;
      goto expand_again;
    }

  /* Try to add the new entry */
  save_new_v = new_v;
  new_hash = BV(clib_bihash_hash) (add_v);
  new_hash >>= h->log2_nbuckets;
  new_hash &= (1<<min_log2(vec_len(new_v))) - 1;
  new_v += new_hash;
  
  for (i = 0; i < BIHASH_KVP_PER_PAGE; i++)
    {
      if (BV(clib_bihash_is_free)(&(new_v->kvp[i])))
        {
          memcpy (&(new_v->kvp[i]), add_v, sizeof (*add_v));
          goto expand_ok;
        }
    }
  /* Crap. Try again */
  new_log2_pages++;
  BV(value_free) (h, save_new_v);
  goto expand_again;

 expand_ok:
  tmp_b.log2_pages = min_log2 (vec_len (save_new_v));
  tmp_b.offset = BV(clib_bihash_get_offset) (h, save_new_v);
  CLIB_MEMORY_BARRIER();
  b->as_u64 = tmp_b.as_u64;
  v = BV(clib_bihash_get_value) (h, h->saved_bucket.offset);
  BV(value_free) (h, v);

 unlock:
  CLIB_MEMORY_BARRIER();
  h->writer_lock[0] = 0;
  return rv;
}

int BV(clib_bihash_search) 
     (BVT(clib_bihash) * h, 
      BVT(clib_bihash_kv) *search_key,
      BVT(clib_bihash_kv) *valuep)
{
  u64 hash;
  u32 bucket_index;
  uword value_index;
  BVT(clib_bihash_value) * v;
  clib_bihash_bucket_t * b;
  int i;

  ASSERT(valuep);

  hash = BV(clib_bihash_hash) (search_key);

  bucket_index = hash & (h->nbuckets-1);
  b = &h->buckets[bucket_index];

  if (b->offset == 0)
    return -1;

  hash >>= h->log2_nbuckets;

  v = BV(clib_bihash_get_value) (h, b->offset);
  value_index = hash & ((1<<b->log2_pages)-1);
  v += value_index;
  
  for (i = 0; i < BIHASH_KVP_PER_PAGE; i++)
    {
      if (BV(clib_bihash_key_compare)(v->kvp[i].key, search_key->key))
        {
          *valuep = v->kvp[i];
          return 0;
        }
    }
  return -1;
}

u8 * BV(format_bihash) (u8 * s, va_list * args)
{
  BVT(clib_bihash) * h 
    = va_arg (*args, BVT(clib_bihash) *);
  int verbose = va_arg (*args, int);
  clib_bihash_bucket_t * b;
  BVT(clib_bihash_value) * v;
  int i, j, k;
  u64 active_elements = 0;

  s = format (s, "Hash table %s\n", h->name ? h->name : (u8 *) "(unnamed)");
  
  for (i = 0; i < h->nbuckets; i++)
    {
      b = &h->buckets [i];
      if (b->offset == 0)
        {
          if (verbose > 1)
            s = format (s, "[%d]: empty\n", i);
          continue;
        }

      if (verbose)
        {
          s = format (s, "[%d]: heap offset %d, len %d\n", i, 
                      b->offset, (1<<b->log2_pages));
        }

      v = BV(clib_bihash_get_value) (h, b->offset);
      for (j = 0; j < (1<<b->log2_pages); j++)
        {
          for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
            {
              if (BV(clib_bihash_is_free)(&v->kvp[k]))
                {
                  if (verbose > 1)
                    s = format (s, "    %d: empty\n", 
                                j * BIHASH_KVP_PER_PAGE + k);
                  continue;
                }
              if (verbose)
                {
                   s = format (s, "    %d: %U\n", 
                              j * BIHASH_KVP_PER_PAGE + k,
                              BV(format_bihash_kvp),
                               &(v->kvp[k]));
                }
              active_elements++;
            }
          v++;
        }
    }

  s = format (s, "    %lld active elements\n", active_elements);
  s = format (s, "    %d free lists\n", vec_len (h->freelists));
  s = format (s, "    %U\n", format_mheap, h->mheap, 1 /* verbose */);

  return s;
}

void BV(clib_bihash_foreach_key_value_pair)
    (BVT(clib_bihash) * h,
     void *callback,
     void *arg)
{
  int i, j, k;
  clib_bihash_bucket_t * b;
  BVT(clib_bihash_value) * v;
  void (*fp)(BVT(clib_bihash_kv) *, void *) = callback;
  
  for (i = 0; i < h->nbuckets; i++)
    {
      b = &h->buckets [i];
      if (b->offset == 0)
        continue;
      
      v = BV(clib_bihash_get_value) (h, b->offset);
      for (j = 0; j < (1<<b->log2_pages); j++)
        {
          for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
            {
              if (BV(clib_bihash_is_free)(&v->kvp[k]))
                continue;
                  
              (*fp)(&v->kvp[k], arg);
            }
          v++;
        }
    }
}