/*

 ** 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.

 **

 ** $Id: hash.h,v 1.12 2008/10/10 17:41:29 drh Exp $

 */

 #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, many of the "procedures" and "functions" for modifying and

 ** accessing this structure are really macros, so we can't really make

 ** this structure opaque.

 */

 struct Hash {

   unsigned int copyKey: 1;  /* True if copy of key made on insert */

   unsigned int htsize : 31; /* 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 */

   void *pKey; int nKey;    /* Key associated with this element */

 };

 /*

 ** Access routines.  To delete, insert a NULL pointer.

 */

 void sqlite3HashInit(Hash*, int copyKey);

 void *sqlite3HashInsert(Hash*, const void *pKey, int nKey, void *pData);

 void *sqlite3HashFind(const Hash*, const void *pKey, int nKey);

 HashElem *sqlite3HashFindElem(const Hash*, const void *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)

 #define sqliteHashKeysize(E) ((E)->nKey)

 /*

 ** Number of entries in a hash table

 */

 #define sqliteHashCount(H)  ((H)->count)

 #endif /* _SQLITE_HASH_H_ */