/*

** 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.

**

** $Id$

*/

#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 {

  char keyClass;          /* SQLITE_HASH_INT, _POINTER, _STRING, _BINARY */

  char copyKey;           /* True if copy of key made on insert */

  int count;              /* Number of entries in this table */

  int htsize;             /* Number of buckets in the hash 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 */

};

/*

** There are 4 different modes of operation for a hash table:

**

**   SQLITE_HASH_INT         nKey is used as the key and pKey is ignored.

**

**   SQLITE_HASH_POINTER     pKey is used as the key and nKey is ignored.

**

**   SQLITE_HASH_STRING      pKey points to a string that is nKey bytes long

**                           (including the null-terminator, if any).  Case

**                           is ignored in comparisons.

**

**   SQLITE_HASH_BINARY      pKey points to binary data nKey bytes long. 

**                           memcmp() is used to compare keys.

**

** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY

** if the copyKey parameter to HashInit is 1.  

*/

/* #define SQLITE_HASH_INT       1 // NOT USED */

/* #define SQLITE_HASH_POINTER   2 // NOT USED */

#define SQLITE_HASH_STRING    3

#define SQLITE_HASH_BINARY    4

/*

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

*/

void sqlite3HashInit(Hash*, int keytype, 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_ */