| /* |
| ** 2001 September 22 |
| ** |
| ** The author disclaims copyright to this source code. In place of |
| ** a legal notice, here is a blessing: |
| ** |
| ** May you do good and not evil. |
| ** May you find forgiveness for yourself and forgive others. |
| ** May you share freely, never taking more than you give. |
| ** |
| ************************************************************************* |
| ** This is the header file for the generic hash-table implemenation |
| ** used in SQLite. |
| */ |
| #ifndef _SQLITE_HASH_H_ |
| #define _SQLITE_HASH_H_ |
| |
| /* Forward declarations of structures. */ |
| typedef struct Hash Hash; |
| typedef struct HashElem HashElem; |
| |
| /* A complete hash table is an instance of the following structure. |
| ** The internals of this structure are intended to be opaque -- client |
| ** code should not attempt to access or modify the fields of this structure |
| ** directly. Change this structure only by using the routines below. |
| ** However, some of the "procedures" and "functions" for modifying and |
| ** accessing this structure are really macros, so we can't really make |
| ** this structure opaque. |
| ** |
| ** All elements of the hash table are on a single doubly-linked list. |
| ** Hash.first points to the head of this list. |
| ** |
| ** There are Hash.htsize buckets. Each bucket points to a spot in |
| ** the global doubly-linked list. The contents of the bucket are the |
| ** element pointed to plus the next _ht.count-1 elements in the list. |
| ** |
| ** Hash.htsize and Hash.ht may be zero. In that case lookup is done |
| ** by a linear search of the global list. For small tables, the |
| ** Hash.ht table is never allocated because if there are few elements |
| ** in the table, it is faster to do a linear search than to manage |
| ** the hash table. |
| */ |
| struct Hash { |
| unsigned int htsize; /* Number of buckets in the hash table */ |
| unsigned int count; /* Number of entries in this table */ |
| HashElem *first; /* The first element of the array */ |
| struct _ht { /* the hash table */ |
| int count; /* Number of entries with this hash */ |
| HashElem *chain; /* Pointer to first entry with this hash */ |
| } *ht; |
| }; |
| |
| /* Each element in the hash table is an instance of the following |
| ** structure. All elements are stored on a single doubly-linked list. |
| ** |
| ** Again, this structure is intended to be opaque, but it can't really |
| ** be opaque because it is used by macros. |
| */ |
| struct HashElem { |
| HashElem *next, *prev; /* Next and previous elements in the table */ |
| void *data; /* Data associated with this element */ |
| const char *pKey; int nKey; /* Key associated with this element */ |
| }; |
| |
| /* |
| ** Access routines. To delete, insert a NULL pointer. |
| */ |
| void sqlite3HashInit(Hash*); |
| void *sqlite3HashInsert(Hash*, const char *pKey, int nKey, void *pData); |
| void *sqlite3HashFind(const Hash*, const char *pKey, int nKey); |
| void sqlite3HashClear(Hash*); |
| |
| /* |
| ** Macros for looping over all elements of a hash table. The idiom is |
| ** like this: |
| ** |
| ** Hash h; |
| ** HashElem *p; |
| ** ... |
| ** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){ |
| ** SomeStructure *pData = sqliteHashData(p); |
| ** // do something with pData |
| ** } |
| */ |
| #define sqliteHashFirst(H) ((H)->first) |
| #define sqliteHashNext(E) ((E)->next) |
| #define sqliteHashData(E) ((E)->data) |
| /* #define sqliteHashKey(E) ((E)->pKey) // NOT USED */ |
| /* #define sqliteHashKeysize(E) ((E)->nKey) // NOT USED */ |
| |
| /* |
| ** Number of entries in a hash table |
| */ |
| /* #define sqliteHashCount(H) ((H)->count) // NOT USED */ |
| |
| #endif /* _SQLITE_HASH_H_ */ |