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f62d053b49
it works better (requires fewer calls to sqlite3StrICmp()) for large schemas, and uses less code space. FossilOrigin-Name: 0318b68c845c84eded757c67f820e1783551574ac9e5670be640c4bfe22a934b
98 lines
3.5 KiB
C
98 lines
3.5 KiB
C
/*
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** 2001 September 22
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This is the header file for the generic hash-table implementation
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** used in SQLite.
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*/
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#ifndef SQLITE_HASH_H
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#define SQLITE_HASH_H
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/* Forward declarations of structures. */
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typedef struct Hash Hash;
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typedef struct HashElem HashElem;
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/* A complete hash table is an instance of the following structure.
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** The internals of this structure are intended to be opaque -- client
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** code should not attempt to access or modify the fields of this structure
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** directly. Change this structure only by using the routines below.
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** However, some of the "procedures" and "functions" for modifying and
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** accessing this structure are really macros, so we can't really make
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** this structure opaque.
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**
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** All elements of the hash table are on a single doubly-linked list.
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** Hash.first points to the head of this list.
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**
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** There are Hash.htsize buckets. Each bucket points to a spot in
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** the global doubly-linked list. The contents of the bucket are the
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** element pointed to plus the next _ht.count-1 elements in the list.
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**
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** Hash.htsize and Hash.ht may be zero. In that case lookup is done
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** by a linear search of the global list. For small tables, the
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** Hash.ht table is never allocated because if there are few elements
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** in the table, it is faster to do a linear search than to manage
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** the hash table.
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*/
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struct Hash {
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unsigned int htsize; /* Number of buckets in the hash table */
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unsigned int count; /* Number of entries in this table */
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HashElem *first; /* The first element of the array */
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struct _ht { /* the hash table */
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unsigned int count; /* Number of entries with this hash */
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HashElem *chain; /* Pointer to first entry with this hash */
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} *ht;
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};
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/* Each element in the hash table is an instance of the following
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** structure. All elements are stored on a single doubly-linked list.
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**
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** Again, this structure is intended to be opaque, but it can't really
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** be opaque because it is used by macros.
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*/
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struct HashElem {
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HashElem *next, *prev; /* Next and previous elements in the table */
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void *data; /* Data associated with this element */
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const char *pKey; /* Key associated with this element */
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unsigned int h; /* hash for pKey */
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};
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/*
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** Access routines. To delete, insert a NULL pointer.
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*/
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void sqlite3HashInit(Hash*);
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void *sqlite3HashInsert(Hash*, const char *pKey, void *pData);
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void *sqlite3HashFind(const Hash*, const char *pKey);
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void sqlite3HashClear(Hash*);
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/*
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** Macros for looping over all elements of a hash table. The idiom is
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** like this:
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**
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** Hash h;
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** HashElem *p;
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** ...
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** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
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** SomeStructure *pData = sqliteHashData(p);
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** // do something with pData
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** }
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*/
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#define sqliteHashFirst(H) ((H)->first)
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#define sqliteHashNext(E) ((E)->next)
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#define sqliteHashData(E) ((E)->data)
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/* #define sqliteHashKey(E) ((E)->pKey) // NOT USED */
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/* #define sqliteHashKeysize(E) ((E)->nKey) // NOT USED */
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/*
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** Number of entries in a hash table
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*/
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#define sqliteHashCount(H) ((H)->count)
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#endif /* SQLITE_HASH_H */
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