/*** 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 1.8 2004/08/20 14:08:51 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 {  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 */  HashElem *first;        /* The first element of the array */  int htsize;             /* Number of buckets in the hash table */  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);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_ */