ext/fts3/fts3_hash.h

   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 implementation
  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_ */