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hash.h

/*      Copyright (C) 2001, 2002, 2003, 2004 Stijn van Dongen
 *
 * This file is part of MCL.  You can redistribute and/or modify MCL under the
 * terms of the GNU General Public License; either version 2 of the License or
 * (at your option) any later version.  You should have received a copy of the
 * GPL along with MCL, in the file COPYING.
*/

#ifndef util_hash_h
#define util_hash_h

/* TODO: make sort routines for keys and values by key or value criteria.
 * make interface for storing integers, preferably without objectifying them.
 *
 * make mcxHashWalk struct hidden.
*/


/*  **************************************************************************
 * *
 **            Implementation notes (a few).
 *
 *
 *    This hash interface is very powerful. It gives you more than enough
 *    rope to hang yourself and then some. It can be used as is, or wrappers
 *    can be made around it that restrict a caller's ability to err.
 *
 *    The danger lies in the fact that this interface only does retrieval
 *    and storage of pointers (both for keys and values), and does not clone
 *    anything. Anything happening with the objects pointed to during the
 *    lifetime of the hash is the responsibility of the caller.
 *
 *    What the interface cannot do currently is hash integers by value (rather
 *    than by reference). This functionality will probably be added someday.
 *    Features:
 *
 *    o  Searching, inserting, and deletion are all done by
 *       mcxHashSearch. It returns a pointer to mcxKV. When deleting, the
 *       caller must use apply mcxKVfree to it after doing whatever needs to
 *       be done with the 'val' and 'key' members.
 *
 *    o  Hashes grow automatically once the average load per bucket
 *       exceeds a settable threshold and if the hash was not declared
 *       constant.
 *
 *    o  Caller supplies both the hash function and the compare function.
 *       This interface provides several hash functions operating on a
 *       (void* base, int len) combo, where base is cast to char by the
 *       hash function. These functions can be used in creating custom hash
 *       functions for your custom objects.
 *
 *    o  You can (of course) have multiple hashes. This is not really
 *       a feature - however, since the idiotic <hsearch.h> does not offer
 *       this I thought I'd mention it.
 *
 *    o  Witness mcxHashWalkNew, mcxHashWalkStep, mcxHashWalkFree.
 * 
 *    o  There is mcxHashMerge.
 *
 *    Enjoy.
*/

#include "types.h"
#include "alloc.h"
#include "list.h"
#include "gralloc.h"


/* The hash struct is hidden. Use mcxHashGetSettings if you need
 * to peek into the interior. Or read hash.c
*/

typedef struct mcxHash mcxHash;


typedef struct
{  void*       key
;  void*       val
;
}  mcxKV       ;


typedef struct mcxHLink
{  struct mcxHLink*  next
;  mcxKV*            kv
;
}  mcxHLink          ;


mcxHash* mcxHashNew
(  int         n_buckets
,  u32         (*hash)  (const void *a)
,  int         (*cmp)   (const void *a, const void *b)
)  ;


#define MCX_HASH_OPT_DEFAULTS    0
#define MCX_HASH_OPT_CONSTANT    1
#define MCX_HASH_OPT_UNUSED      2


void mcxHashSetOpts
(  mcxHash*    hash
,  double      load
,  int         option      /* negative values will be ignored (feature) */
)  ;


typedef struct mcxHashSettings
{  int         n_buckets
;  int         n_bits
;  int         mask
;  float       load
;  int         n_entries
;  int         options
;  
}  mcxHashSettings   ;


void mcxHashGetSettings
(  mcxHash*          hash
,  mcxHashSettings*  settings
)  ;


/*  **************************************************************************
 * *
 **            mcxHashSearch
 *
 *    action               returns
 *
 *    DATUM_DELETE   ->    deleted mcxKV* or NULL if not present
 *    DATUM_INSERT   ->    new or present mcxKV*
 *    DATUM_FIND     ->    mcxKV* if present NULL otherwise.
 * 
 * usage:
 *
 *    Values have to be inserted by the caller into the returned KV struct.
 *    Make sure that keys point to objects that are constant
 *    (with respect to the cmp function) during the lifetime of the hash.
 *    YOU have to ensure the integrity of both keys and values.
 *    This enables you to do whatever suits you, such as appending to
 *    values.
 *
 *    When inserting, check whether kv->key != key (where kv is returned value)
 *    if this is the case, an identically comparing key is already present.
 *    You may want to destroy one of the two keys and decide what to do
 *    with the value.
 *
 *    When deleting, the key-value pair is removed from the hash
 *    *AND RETURNED TO CALLER* - you have to decide yourself what to do
 *    with it. If the key was not present, a value of NULL is returned.
 *
 *    When finding, life is simple. NULL if absent, matching kv otherwise.
 *
 * note:
 *
 *    memory management of keys and values is totally up to caller.
 *    If usage is clean, you can use mcxHashFree for disposal of hash.
*/

mcxKV*   mcxHashSearch
(  void*       key
,  mcxHash*    hash
,  mcxmode     ACTION
)  ;


/*  **************************************************************************
 * *
 **            mcxHashMerge
 *
 *    this one COPIES OBJECT POINTERS and DOES NOT CLONE.
 *    so after the merge, hash1 and hash2 keys and values should not be freed.
 *    In case there are equivalent keys in hash1 and hash2, this may
 *    cause trouble when the caller wants to do cleaning afterwards.
 *    This interface is still under development.
 *
 *    hashd may be equal to hash1 or hash2, and it may also be NULL.
*/

mcxHash* mcxHashMerge
(  mcxHash*    hash1
,  mcxHash*    hash2
,  mcxHash*    hashd
,  void*       merge(void* val1, void* val2)
)  ;


/*  **************************************************************************
 * *
 **            mcxHashFree
 *
*     This one is tricky, especially in the kind of free routines it expects.
 *    The free routines must cast the keypp and valpp to type (type**) which
 *    must correspond with the address of a variable. They will be applied
 *    as, for instance, keyfree(&(kv->key)). keyfree and valfree are expected
 *    to check whether their argument points to a NULL variable (this is nice
 *    for the caller who does not have to worry), and after freeing they are
 *    expected to set the pointee to NULL (this is not strictly necessary
 *    though).
 *
 *    It only works of course if all keys are of the same type and all values
 *    are of the same type, and if your objects were created as expected by
 *    the free routines (presumably malloced heap memory) - be careful with
 *    constant objects like constant strings.
 *
 *    Both freekey and freeval may be NULL.
*/

void mcxHashFree
(  mcxHash**   hashpp
,  void        freekey(void* keypp)    /* (yourtype1** keypp)     */
,  void        freeval(void* valpp)    /* (yourtype2** valpp)     */
)  ;


/*
 **   Prints some information to stdout.
*/

void mcxHashStats
(  FILE*       fp
,  mcxHash*    hash
)  ;


typedef struct
{  mcxHash*    hash
;  int         i_bucket
;  mcxLink*    link
;
}  mcxHashWalk ;


mcxHashWalk* mcxHashWalkNew
(  mcxHash  *hash
)  ;


mcxKV* mcxHashWalkStep
(  mcxHashWalk* walk
)  ;


void mcxHashWalkFree
(  mcxHashWalk  **walkpp
)  ;

                        /* UNIX ELF hash */
                        /* POOR! */
u32 mcxELFhash
(  const void *key
,  u32 len
)  ;

                        /* created by Bob Jenkins     */
u32 mcxBJhash
(  const void* key
,  u32         len
)  ;

                        /* One at a time hash, Bob Jenkins/Colin Plumb */
u32 mcxOAThash
(  const void *key
,  u32        len
)  ;

                        /* created by Daniel Phillips */
u32 mcxDPhash
(  const void* key
,  u32         len
)  ;

                        /* "Berkely Database" hash (from Ozan Yigit's page) */
                        /* POOR! */
u32 mcxBDBhash
(  const void *key
,  u32        len
)  ;

                        /* Dan Bernstein hash (from Ozan Yigit's page) */
u32 mcxDJBhash
(  const void *key
,  u32        len
)  ;

                        /* created by Chris Torek */
u32 mcxCThash
(  const void* key
,  u32         len
)  ;

                        /* "GNU Emacs" hash (from m4) */
                        /* not among the best */
u32 mcxGEhash
(  const void* key
,  u32         len
)  ;

                        /* All experimental with weak points. */
u32   mcxSvDhash
(  const void        *key
,  u32               len
)  ;
u32   mcxSvD2hash
(  const void        *key
,  u32               len
)  ;
u32   mcxSvD1hash
(  const void        *key
,  u32               len
)  ;

                        /* uses mcxDPhash             */
u32 mcxStrHash
(  const void* s
)  ;


#endif


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