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      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 _FTS3_HASH_H_
     18 #define _FTS3_HASH_H_
     19 
     20 /* Forward declarations of structures. */
     21 typedef struct Fts3Hash Fts3Hash;
     22 typedef struct Fts3HashElem Fts3HashElem;
     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 Fts3Hash {
     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   Fts3HashElem *first;    /* The first element of the array */
     37   int htsize;             /* Number of buckets in the hash table */
     38   struct _fts3ht {        /* the hash table */
     39     int count;               /* Number of entries with this hash */
     40     Fts3HashElem *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 Fts3HashElem {
     51   Fts3HashElem *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 **   FTS3_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 **   FTS3_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 fts3HashInit is 1.
     67 */
     68 #define FTS3_HASH_STRING    1
     69 #define FTS3_HASH_BINARY    2
     70 
     71 /*
     72 ** Access routines.  To delete, insert a NULL pointer.
     73 */
     74 void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey);
     75 void *sqlite3Fts3HashInsert(Fts3Hash*, const void *pKey, int nKey, void *pData);
     76 void *sqlite3Fts3HashFind(const Fts3Hash*, const void *pKey, int nKey);
     77 void sqlite3Fts3HashClear(Fts3Hash*);
     78 Fts3HashElem *sqlite3Fts3HashFindElem(const Fts3Hash *, const void *, int);
     79 
     80 /*
     81 ** Shorthand for the functions above
     82 */
     83 #define fts3HashInit     sqlite3Fts3HashInit
     84 #define fts3HashInsert   sqlite3Fts3HashInsert
     85 #define fts3HashFind     sqlite3Fts3HashFind
     86 #define fts3HashClear    sqlite3Fts3HashClear
     87 #define fts3HashFindElem sqlite3Fts3HashFindElem
     88 
     89 /*
     90 ** Macros for looping over all elements of a hash table.  The idiom is
     91 ** like this:
     92 **
     93 **   Fts3Hash h;
     94 **   Fts3HashElem *p;
     95 **   ...
     96 **   for(p=fts3HashFirst(&h); p; p=fts3HashNext(p)){
     97 **     SomeStructure *pData = fts3HashData(p);
     98 **     // do something with pData
     99 **   }
    100 */
    101 #define fts3HashFirst(H)  ((H)->first)
    102 #define fts3HashNext(E)   ((E)->next)
    103 #define fts3HashData(E)   ((E)->data)
    104 #define fts3HashKey(E)    ((E)->pKey)
    105 #define fts3HashKeysize(E) ((E)->nKey)
    106 
    107 /*
    108 ** Number of entries in a hash table
    109 */
    110 #define fts3HashCount(H)  ((H)->count)
    111 
    112 #endif /* _FTS3_HASH_H_ */
    113