97 lines
3.4 KiB
C
97 lines
3.4 KiB
C
/*
|
|
** 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_ */
|