ketama.h

/*
 * Copyright (c) 2017, Emory University, All rights reserved.
 * Juncheng Yang <jason.yang.china@outlook.com>
 *
 * Modify for libCacheSim based on original version
 * also add const modifier for compiler optimizations
 *
 */

/*
 * Copyright (c) 2007, Last.fm, All rights reserved.
 * Richard Jones <rj@last.fm>
 * Christian Muehlhaeuser <muesli@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Last.fm Limited nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY Last.fm ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL Last.fm BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef KETAMA_LIBKETAMA_KETAMA_H__
#define KETAMA_LIBKETAMA_KETAMA_H__

#include <sys/sem.h> /* semaphore functions and structs. */

#define MC_SHMSIZE 524288  // 512KB should be ample.

#ifdef __cplusplus /* If this is a C++ compiler, use C linkage */
extern "C" {
#endif

#ifndef __APPLE__
union semun {
  int val;              /* used for SETVAL only */
  struct semid_ds *buf; /* for IPC_STAT and IPC_SET */
  ushort *array;        /* used for GETALL and SETALL */
};
#endif

typedef int (*compfn)(const void *, const void *);

typedef struct {
  unsigned int point;  // point on circle
  char ip[22];
} mcs;

typedef struct {
  char addr[22];
  unsigned long memory;  // in CDNSimulator, this is used as weight
} serverinfo;

typedef struct {
  int numpoints;
  void *modtime;
  void *array;  // array of mcs structs
} continuum;

typedef continuum *ketama_continuum;

/** build a consistent hashing ring
 * given the number of servers and the weight of each server.
 * if weight is NULL, then each server has equal weight.
 * key_identifier is just a number for identifying shared memory */
int ketama_build_hashring(ketama_continuum *const contptr,
                          const unsigned int num_servers,
                          const unsigned long *const weight,
                          const int key_identifier);

int ketama_get_server_index(const ketama_continuum cont, const char *const key);

void ketama_get_server_indexes(const ketama_continuum cont,
                               const char *const key, unsigned int n,
                               int *indexes);

/** \brief Get a continuum struct that contains a reference to the server list.
 * \param contptr The value of this pointer will contain the retrieved
 * continuum.
 * \param filename The server-definition file which defines our continuum.
 * \return 0 on failure, 1 on success. */
int ketama_roll(ketama_continuum *contptr, char *filename);

/** \brief Frees any allocated memory.
 * \param contptr The continuum that you want to be destroy. */
void ketama_smoke(ketama_continuum contptr);

/** \brief Maps a key onto a server in the continuum.
 * \param key The key that you want to map to a specific server.
 * \param cont Pointer to the continuum in which we will search.
 * \return The mcs struct that the given key maps to. */
mcs *ketama_get_server(char *key, ketama_continuum cont);

/** \brief Print the server list of a continuum to stdout.
 * \param c The continuum to print. */
void ketama_print_continuum(ketama_continuum c);

/** \brief Compare two server entries in the circle.
 * \param a The first entry.
 * \param b The second entry.
 * \return -1 if b greater a, +1 if a greater b or 0 if both are equal. */
int ketama_compare(mcs *a, mcs *b);

/** \brief Hashing function, converting a string to an unsigned int by using
 * MD5.
 * \param inString The string that you want to hash.
 * \return The resulting hash. */
unsigned int ketama_hashi(const char *const inString);

/** \brief Hashing function to 16 bytes char array using MD5.
 * \param inString The string that you want to hash.
 * \param md5pword The resulting hash. */
void ketama_md5_digest(const char *const inString, unsigned char md5pword[16]);

/** \brief Error method for error checking.
 * \return The latest error that occurred. */
char *ketama_error();

#ifdef __cplusplus /* If this is a C++ compiler, end C linkage */
}
#endif

#endif  // KETAMA_LIBKETAMA_KETAMA_H__