set.h

/*
Copyright (c) 2003, Keir Fraser All rights reserved.

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 Keir Fraser
    * 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 THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"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 THE COPYRIGHT
OWNER OR CONTRIBUTORS 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 __SET_H__
#define __SET_H__


typedef unsigned long setkey_t;
typedef void         *setval_t;


#ifdef __SET_IMPLEMENTATION__

/*************************************
 * INTERNAL DEFINITIONS
 */

/* Fine for 2^NUM_LEVELS nodes. */
#define NUM_LEVELS 20


/* Internal key values with special meanings. */
#define INVALID_FIELD   (0)    /* Uninitialised field value.     */
#define SENTINEL_KEYMIN ( 1UL) /* Key value of first dummy node. */
#define SENTINEL_KEYMAX (~0UL) /* Key value of last dummy node.  */


/*
 * Used internally be set access functions, so that callers can use
 * key values 0 and 1, without knowing these have special meanings.
 */
#define CALLER_TO_INTERNAL_KEY(_k) ((_k) + 2)


/*
 * SUPPORT FOR WEAK ORDERING OF MEMORY ACCESSES
 */

#ifdef WEAK_MEM_ORDER

/* Read field @_f into variable @_x. */
#define READ_FIELD(_x,_f)                                       \
do {                                                            \
    (_x) = (_f);                                                \
    if ( (_x) == INVALID_FIELD ) { RMB(); (_x) = (_f); }        \
    assert((_x) != INVALID_FIELD);                              \
} while ( 0 )

#else

/* Read field @_f into variable @_x. */
#define READ_FIELD(_x,_f) ((_x) = (_f))

#endif


#else

/*************************************
 * PUBLIC DEFINITIONS
 */

/*
 * Key range accepted by set functions.
 * We lose three values (conveniently at top end of key space).
 *  - Known invalid value to which all fields are initialised.
 *  - Sentinel key values for up to two dummy nodes.
 */
#define KEY_MIN  ( 0U)
#define KEY_MAX  ((~0U) - 3)

typedef void set_t; /* opaque */

void _init_set_subsystem(void);

/*
 * Allocate an empty set.
 */
set_t *set_alloc(void);

/*
 * Add mapping (@k -> @v) into set @s. Return previous mapped value if
 * one existed, or NULL if no previous mapping for @k existed.
 *
 * If @overwrite is FALSE, then if a mapping already exists it is not
 * modified, and the existing value is returned unchanged. It is possible
 * to see if the value was changed by observing if the return value is NULL.
 */
setval_t set_update(set_t *s, setkey_t k, setval_t v, int overwrite);

/*
 * Remove mapping for key @k from set @s. Return value associated with
 * removed mapping, or NULL is there was no mapping to delete.
 */
setval_t set_remove(set_t *s, setkey_t k);

/*
 * Look up mapping for key @k in set @s. Return value if found, else NULL.
 */
setval_t set_lookup(set_t *s, setkey_t k);

#endif /* __SET_IMPLEMENTATION__ */


#endif /* __SET_H__ */