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Annotation of embedaddon/sqlite3/src/hash.h, revision 1.1.1.1

1.1       misho       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.
                     14: */
                     15: #ifndef _SQLITE_HASH_H_
                     16: #define _SQLITE_HASH_H_
                     17: 
                     18: /* Forward declarations of structures. */
                     19: typedef struct Hash Hash;
                     20: typedef struct HashElem HashElem;
                     21: 
                     22: /* A complete hash table is an instance of the following structure.
                     23: ** The internals of this structure are intended to be opaque -- client
                     24: ** code should not attempt to access or modify the fields of this structure
                     25: ** directly.  Change this structure only by using the routines below.
                     26: ** However, some of the "procedures" and "functions" for modifying and
                     27: ** accessing this structure are really macros, so we can't really make
                     28: ** this structure opaque.
                     29: **
                     30: ** All elements of the hash table are on a single doubly-linked list.
                     31: ** Hash.first points to the head of this list.
                     32: **
                     33: ** There are Hash.htsize buckets.  Each bucket points to a spot in
                     34: ** the global doubly-linked list.  The contents of the bucket are the
                     35: ** element pointed to plus the next _ht.count-1 elements in the list.
                     36: **
                     37: ** Hash.htsize and Hash.ht may be zero.  In that case lookup is done
                     38: ** by a linear search of the global list.  For small tables, the 
                     39: ** Hash.ht table is never allocated because if there are few elements
                     40: ** in the table, it is faster to do a linear search than to manage
                     41: ** the hash table.
                     42: */
                     43: struct Hash {
                     44:   unsigned int htsize;      /* Number of buckets in the hash table */
                     45:   unsigned int count;       /* Number of entries in this table */
                     46:   HashElem *first;          /* The first element of the array */
                     47:   struct _ht {              /* the hash table */
                     48:     int count;                 /* Number of entries with this hash */
                     49:     HashElem *chain;           /* Pointer to first entry with this hash */
                     50:   } *ht;
                     51: };
                     52: 
                     53: /* Each element in the hash table is an instance of the following 
                     54: ** structure.  All elements are stored on a single doubly-linked list.
                     55: **
                     56: ** Again, this structure is intended to be opaque, but it can't really
                     57: ** be opaque because it is used by macros.
                     58: */
                     59: struct HashElem {
                     60:   HashElem *next, *prev;       /* Next and previous elements in the table */
                     61:   void *data;                  /* Data associated with this element */
                     62:   const char *pKey; int nKey;  /* Key associated with this element */
                     63: };
                     64: 
                     65: /*
                     66: ** Access routines.  To delete, insert a NULL pointer.
                     67: */
                     68: void sqlite3HashInit(Hash*);
                     69: void *sqlite3HashInsert(Hash*, const char *pKey, int nKey, void *pData);
                     70: void *sqlite3HashFind(const Hash*, const char *pKey, int nKey);
                     71: void sqlite3HashClear(Hash*);
                     72: 
                     73: /*
                     74: ** Macros for looping over all elements of a hash table.  The idiom is
                     75: ** like this:
                     76: **
                     77: **   Hash h;
                     78: **   HashElem *p;
                     79: **   ...
                     80: **   for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
                     81: **     SomeStructure *pData = sqliteHashData(p);
                     82: **     // do something with pData
                     83: **   }
                     84: */
                     85: #define sqliteHashFirst(H)  ((H)->first)
                     86: #define sqliteHashNext(E)   ((E)->next)
                     87: #define sqliteHashData(E)   ((E)->data)
                     88: /* #define sqliteHashKey(E)    ((E)->pKey) // NOT USED */
                     89: /* #define sqliteHashKeysize(E) ((E)->nKey)  // NOT USED */
                     90: 
                     91: /*
                     92: ** Number of entries in a hash table
                     93: */
                     94: /* #define sqliteHashCount(H)  ((H)->count) // NOT USED */
                     95: 
                     96: #endif /* _SQLITE_HASH_H_ */