lokinet/libutp/utp_hash.h

/*
 * Copyright (c) 2010-2013 BitTorrent, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef __UTP_HASH_H__
#define __UTP_HASH_H__

#include <string.h>  // memset
#include <stdlib.h>  // malloc

#include "utp_types.h"
#include "utp_templates.h"

// TODO: make utp_link_t a template parameter to HashTable
typedef uint32 utp_link_t;

#ifdef _MSC_VER
// Silence the warning about the C99-compliant zero-length array at the end of
// the structure
#pragma warning(disable : 4200)
#endif

#include <absl/base/attributes.h>

typedef uint32 (*utp_hash_compute_t)(const void *keyp, size_t keysize);
typedef uint (*utp_hash_equal_t)(const void *key_a, const void *key_b,
                                 size_t keysize);

// In memory the HashTable is laid out as follows:
//  ---------------------------- low
//  | hash table data members  |
//  ----------------------------  _
//  |  indices                 |  ^
//  |  .                       |  |  utp_link_t indices into the key-values.
//  |  .                       |  .
//  ----------------------------  -  <----- bep
//  |  keys and values         |     each key-value pair has size total_size
//  |  .                       |
//  |  .                       |
//  ---------------------------- high
//
// The code depends on the ability of the compiler to pad the length
// of the hash table data members structure to
// a length divisible by 32-bits with no remainder.
//
// Since the number of hash buckets (indices) should be odd, the code
// asserts this and adds one to the hash bucket count to ensure that the
// following key-value pairs array starts on a 32-bit boundary.
//
// The key-value pairs array should start on a 32-bit boundary, otherwise
// processors like the ARM will silently mangle 32-bit data in these structures
// (e.g., turning 0xABCD into 0XCDAB when moving a value from memory to register
// when the memory address is 16 bits offset from a 32-bit boundary),
// also, the value will be stored at an address two bytes lower than the address
// value would ordinarily indicate.
//
// The key-value pair is of type T. The first field in T must
// be the key, i.e., the first K bytes of T contains the key.
// total_size = sizeof(T) and thus sizeof(T) >= sizeof(K)
//
// N is the number of buckets.
//
struct utp_hash_t
{
  utp_link_t N;
  byte K;
  byte E;
  size_t count;
  utp_hash_compute_t hash_compute;
  utp_hash_equal_t hash_equal;
  utp_link_t allocated;
  utp_link_t used;
  utp_link_t free;
  utp_link_t inits[0];
};

#ifdef _MSC_VER
#pragma warning(default : 4200)
#endif

struct utp_hash_iterator_t
{
  utp_link_t bucket;
  utp_link_t elem;

  utp_hash_iterator_t() : bucket(0xffffffff), elem(0xffffffff)
  {
  }
};

uint
utp_hash_mem(const void *keyp, size_t keysize);
uint
utp_hash_comp(const void *key_a, const void *key_b, size_t keysize);

utp_hash_t *
utp_hash_create(int N, int key_size, int total_size, int initial,
                utp_hash_compute_t hashfun = utp_hash_mem,
                utp_hash_equal_t eqfun     = NULL);
void *
utp_hash_lookup(utp_hash_t *hash, const void *key);
void *
utp_hash_add(utp_hash_t **hashp, const void *key);
void *
utp_hash_del(utp_hash_t *hash, const void *key);

void *
utp_hash_iterate(utp_hash_t *hash, utp_hash_iterator_t *iter);
void
utp_hash_free_mem(utp_hash_t *hash);

/*
        This HashTable requires that T have at least
   sizeof(K)+sizeof(utp_link_t) bytes. Usually done like this:

        struct K {
                int whatever;
        };

        struct T {
                K wtf;
                utp_link_t link; // also wtf
        };
*/

template < typename K, typename T >
class utpHashTable
{
  utp_hash_t *hash;

 public:
  static uint
  compare(const void *k1, const void *k2, ABSL_ATTRIBUTE_UNUSED size_t ks)
  {
    return *((K *)k1) == *((K *)k2);
  }
  static uint32
  compute_hash(const void *k, ABSL_ATTRIBUTE_UNUSED size_t ks)
  {
    return ((K *)k)->compute_hash();
  }
  void
  Init()
  {
    hash = NULL;
  }
  bool
  Allocated()
  {
    return (hash != NULL);
  }
  void
  Free()
  {
    utp_hash_free_mem(hash);
    hash = NULL;
  }
  void
  Create(int N, int initial)
  {
    hash = utp_hash_create(N, sizeof(K), sizeof(T), initial, &compute_hash,
                           &compare);
  }
  T *
  Lookup(const K &key)
  {
    return (T *)utp_hash_lookup(hash, &key);
  }
  T *
  Add(const K &key)
  {
    return (T *)utp_hash_add(&hash, &key);
  }
  T *
  Delete(const K &key)
  {
    return (T *)utp_hash_del(hash, &key);
  }
  T *
  Iterate(utp_hash_iterator_t &iterator)
  {
    return (T *)utp_hash_iterate(hash, &iterator);
  }
  size_t
  GetCount()
  {
    return hash->count;
  }
};

#endif  //__UTP_HASH_H__