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110 lines
3.8 KiB
110 lines
3.8 KiB
13 years ago
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/*
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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 implemenation
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** used in SQLite.
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**
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** $Id: hash.h,v 1.6 2004/01/08 02:17:33 drh Exp $
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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, many 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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struct Hash {
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char keyClass; /* SQLITE_HASH_INT, _POINTER, _STRING, _BINARY */
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char copyKey; /* True if copy of key made on insert */
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int count; /* Number of entries in this table */
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HashElem *first; /* The first element of the array */
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int htsize; /* Number of buckets in the hash table */
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struct _ht { /* the hash table */
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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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void *pKey; int nKey; /* Key associated with this element */
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};
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/*
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** There are 4 different modes of operation for a hash table:
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**
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** SQLITE_HASH_INT nKey is used as the key and pKey is ignored.
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**
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** SQLITE_HASH_POINTER pKey is used as the key and nKey is ignored.
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**
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** SQLITE_HASH_STRING pKey points to a string that is nKey bytes long
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** (including the null-terminator, if any). Case
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** is ignored in comparisons.
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**
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** SQLITE_HASH_BINARY pKey points to binary data nKey bytes long.
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** memcmp() is used to compare keys.
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**
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** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY
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** if the copyKey parameter to HashInit is 1.
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*/
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#define SQLITE_HASH_INT 1
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/* #define SQLITE_HASH_POINTER 2 // NOT USED */
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#define SQLITE_HASH_STRING 3
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#define SQLITE_HASH_BINARY 4
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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 sqliteHashInit(Hash*, int keytype, int copyKey);
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void *sqliteHashInsert(Hash*, const void *pKey, int nKey, void *pData);
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void *sqliteHashFind(const Hash*, const void *pKey, int nKey);
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void sqliteHashClear(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)
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#define sqliteHashKeysize(E) ((E)->nKey)
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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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