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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. We've modified it slightly to serve as a standalone
** hash table implementation for the full-text indexing module.
#ifndef _HASH_H_
#define _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; /* 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 */
void *(*xMalloc)(int); /* malloc() function to use */
void (*xFree)(void *); /* free() function to use */
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:
** HASH_INT nKey is used as the key and pKey is ignored.
** HASH_POINTER pKey is used as the key and nKey is ignored.
** HASH_STRING pKey points to a string that is nKey bytes long
** (including the null-terminator, if any). Case
** is respected in comparisons.
** HASH_BINARY pKey points to binary data nKey bytes long.
** memcmp() is used to compare keys.
** A copy of the key is made for HASH_STRING and HASH_BINARY
** if the copyKey parameter to HashInit is 1.
/* #define HASH_INT 1 // NOT USED */
/* #define HASH_POINTER 2 // NOT USED */
#define HASH_STRING 3
#define HASH_BINARY 4
** Access routines. To delete, insert a NULL pointer.
void HashInit(Hash*, int keytype, int copyKey);
void *HashInsert(Hash*, const void *pKey, int nKey, void *pData);
void *HashFind(const Hash*, const void *pKey, int nKey);
void HashClear(Hash*);
** Macros for looping over all elements of a hash table. The idiom is
** like this:
** Hash h;
** HashElem *p;
** ...
** for(p=HashFirst(&h); p; p=HashNext(p)){
** SomeStructure *pData = HashData(p);
** // do something with pData
** }
#define HashFirst(H) ((H)->first)
#define HashNext(E) ((E)->next)
#define HashData(E) ((E)->data)
#define HashKey(E) ((E)->pKey)
#define HashKeysize(E) ((E)->nKey)
** Number of entries in a hash table
#define HashCount(H) ((H)->count)
#endif /* _HASH_H_ */