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/*

** 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_ */