ext/fts1/ft_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 _HASH_H_
  18 #define _HASH_H_
  19
  20 /* Forward declarations of structures. */
  21 typedef struct Hash Hash;
  22 typedef struct HashElem HashElem;
  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 Hash {
  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   HashElem *first;        /* The first element of the array */
  37   void *(*xMalloc)(int);  /* malloc() function to use */
  38   void (*xFree)(void *);  /* free() function to use */
  39   int htsize;             /* Number of buckets in the hash table */
  40   struct _ht {            /* the hash table */
  41     int count;               /* Number of entries with this hash */
  42     HashElem *chain;         /* Pointer to first entry with this hash */
  43   } *ht;
  44 };
  45
  46 /* Each element in the hash table is an instance of the following
  47 ** structure.  All elements are stored on a single doubly-linked list.
  48 **
  49 ** Again, this structure is intended to be opaque, but it can't really
  50 ** be opaque because it is used by macros.
  51 */
  52 struct HashElem {
  53   HashElem *next, *prev;   /* Next and previous elements in the table */
  54   void *data;              /* Data associated with this element */
  55   void *pKey; int nKey;    /* Key associated with this element */
  56 };
  57
  58 /*
  59 ** There are 4 different modes of operation for a hash table:
  60 **
  61 **   HASH_INT         nKey is used as the key and pKey is ignored.
  62 **
  63 **   HASH_POINTER     pKey is used as the key and nKey is ignored.
  64 **
  65 **   HASH_STRING      pKey points to a string that is nKey bytes long
  66 **                           (including the null-terminator, if any).  Case
  67 **                           is respected in comparisons.
  68 **
  69 **   HASH_BINARY      pKey points to binary data nKey bytes long.
  70 **                           memcmp() is used to compare keys.
  71 **
  72 ** A copy of the key is made for HASH_STRING and HASH_BINARY
  73 ** if the copyKey parameter to HashInit is 1.
  74 */
  75 /* #define HASH_INT       1 // NOT USED */
  76 /* #define HASH_POINTER   2 // NOT USED */
  77 #define HASH_STRING    3
  78 #define HASH_BINARY    4
  79
  80 /*
  81 ** Access routines.  To delete, insert a NULL pointer.
  82 */
  83 void HashInit(Hash*, int keytype, int copyKey);
  84 void *HashInsert(Hash*, const void *pKey, int nKey, void *pData);
  85 void *HashFind(const Hash*, const void *pKey, int nKey);
  86 void HashClear(Hash*);
  87
  88 /*
  89 ** Macros for looping over all elements of a hash table.  The idiom is
  90 ** like this:
  91 **
  92 **   Hash h;
  93 **   HashElem *p;
  94 **   ...
  95 **   for(p=HashFirst(&h); p; p=HashNext(p)){
  96 **     SomeStructure *pData = HashData(p);
  97 **     // do something with pData
  98 **   }
  99 */
 100 #define HashFirst(H)  ((H)->first)
 101 #define HashNext(E)   ((E)->next)
 102 #define HashData(E)   ((E)->data)
 103 #define HashKey(E)    ((E)->pKey)
 104 #define HashKeysize(E) ((E)->nKey)
 105
 106 /*
 107 ** Number of entries in a hash table
 108 */
 109 #define HashCount(H)  ((H)->count)
 110
 111 #endif /* _HASH_H_ */