1 /*

     2 ** 2001 September 22

     3 **

     4 ** The author disclaims copyright to this source code.  In place of

     5 ** a legal notice, here is a blessing:

     6 **

     7 **    May you do good and not evil.

     8 **    May you find forgiveness for yourself and forgive others.

     9 **    May you share freely, never taking more than you give.

    10 **

    11 *************************************************************************

    12 ** This is the header file for the generic hash-table implemenation

    13 ** used in SQLite.  We've modified it slightly to serve as a standalone

    14 ** hash table implementation for the full-text indexing module.

    15 **

    16 */

    17 #ifndef _FTS2_HASH_H_

    18 #define _FTS2_HASH_H_

    19 

    20 /* Forward declarations of structures. */

    21 typedef struct fts2Hash fts2Hash;

    22 typedef struct fts2HashElem fts2HashElem;

    23 

    24 /* A complete hash table is an instance of the following structure.

    25 ** The internals of this structure are intended to be opaque -- client

    26 ** code should not attempt to access or modify the fields of this structure

    27 ** directly.  Change this structure only by using the routines below.

    28 ** However, many of the "procedures" and "functions" for modifying and

    29 ** accessing this structure are really macros, so we can't really make

    30 ** this structure opaque.

    31 */

    32 struct fts2Hash {

    33   char keyClass;          /* HASH_INT, _POINTER, _STRING, _BINARY */

    34   char copyKey;           /* True if copy of key made on insert */

    35   int count;              /* Number of entries in this table */

    36   fts2HashElem *first;    /* The first element of the array */

    37   int htsize;             /* Number of buckets in the hash table */

    38   struct _fts2ht {        /* the hash table */

    39     int count;               /* Number of entries with this hash */

    40     fts2HashElem *chain;     /* Pointer to first entry with this hash */

    41   } *ht;

    42 };

    43 

    44 /* Each element in the hash table is an instance of the following 

    45 ** structure.  All elements are stored on a single doubly-linked list.

    46 **

    47 ** Again, this structure is intended to be opaque, but it can't really

    48 ** be opaque because it is used by macros.

    49 */

    50 struct fts2HashElem {

    51   fts2HashElem *next, *prev; /* Next and previous elements in the table */

    52   void *data;                /* Data associated with this element */

    53   void *pKey; int nKey;      /* Key associated with this element */

    54 };

    55 

    56 /*

    57 ** There are 2 different modes of operation for a hash table:

    58 **

    59 **   FTS2_HASH_STRING        pKey points to a string that is nKey bytes long

    60 **                           (including the null-terminator, if any).  Case

    61 **                           is respected in comparisons.

    62 **

    63 **   FTS2_HASH_BINARY        pKey points to binary data nKey bytes long. 

    64 **                           memcmp() is used to compare keys.

    65 **

    66 ** A copy of the key is made if the copyKey parameter to fts2HashInit is 1.  

    67 */

    68 #define FTS2_HASH_STRING    1

    69 #define FTS2_HASH_BINARY    2

    70 

    71 /*

    72 ** Access routines.  To delete, insert a NULL pointer.

    73 */

    74 void sqlite3Fts2HashInit(fts2Hash*, int keytype, int copyKey);

    75 void *sqlite3Fts2HashInsert(fts2Hash*, const void *pKey, int nKey, void *pData);

    76 void *sqlite3Fts2HashFind(const fts2Hash*, const void *pKey, int nKey);

    77 void sqlite3Fts2HashClear(fts2Hash*);

    78 

    79 /*

    80 ** Shorthand for the functions above

    81 */

    82 #define fts2HashInit   sqlite3Fts2HashInit

    83 #define fts2HashInsert sqlite3Fts2HashInsert

    84 #define fts2HashFind   sqlite3Fts2HashFind

    85 #define fts2HashClear  sqlite3Fts2HashClear

    86 

    87 /*

    88 ** Macros for looping over all elements of a hash table.  The idiom is

    89 ** like this:

    90 **

    91 **   fts2Hash h;

    92 **   fts2HashElem *p;

    93 **   ...

    94 **   for(p=fts2HashFirst(&h); p; p=fts2HashNext(p)){

    95 **     SomeStructure *pData = fts2HashData(p);

    96 **     // do something with pData

    97 **   }

    98 */

    99 #define fts2HashFirst(H)  ((H)->first)

   100 #define fts2HashNext(E)   ((E)->next)

   101 #define fts2HashData(E)   ((E)->data)

   102 #define fts2HashKey(E)    ((E)->pKey)

   103 #define fts2HashKeysize(E) ((E)->nKey)

   104 

   105 /*

   106 ** Number of entries in a hash table

   107 */

   108 #define fts2HashCount(H)  ((H)->count)

   109 

   110 #endif /* _FTS2_HASH_H_ */