os/persistentdata/persistentstorage/sqlite3api/SQLite/fts3_hash.h
author sl@SLION-WIN7.fritz.box
Fri, 15 Jun 2012 03:10:57 +0200
changeset 0 bde4ae8d615e
permissions -rw-r--r--
First public contribution.
     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*, int keytype, int 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 
    79 /*
    80 ** Shorthand for the functions above
    81 */
    82 #define fts3HashInit   sqlite3Fts3HashInit
    83 #define fts3HashInsert sqlite3Fts3HashInsert
    84 #define fts3HashFind   sqlite3Fts3HashFind
    85 #define fts3HashClear  sqlite3Fts3HashClear
    86 
    87 /*
    88 ** Macros for looping over all elements of a hash table.  The idiom is
    89 ** like this:
    90 **
    91 **   fts3Hash h;
    92 **   fts3HashElem *p;
    93 **   ...
    94 **   for(p=fts3HashFirst(&h); p; p=fts3HashNext(p)){
    95 **     SomeStructure *pData = fts3HashData(p);
    96 **     // do something with pData
    97 **   }
    98 */
    99 #define fts3HashFirst(H)  ((H)->first)
   100 #define fts3HashNext(E)   ((E)->next)
   101 #define fts3HashData(E)   ((E)->data)
   102 #define fts3HashKey(E)    ((E)->pKey)
   103 #define fts3HashKeysize(E) ((E)->nKey)
   104 
   105 /*
   106 ** Number of entries in a hash table
   107 */
   108 #define fts3HashCount(H)  ((H)->count)
   109 
   110 #endif /* _FTS3_HASH_H_ */