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1/*
2** 2001 September 22
3**
4** The author disclaims copyright to this source code. In place of
5** a legal notice, here is a blessing:
6**
7** May you do good and not evil.
8** May you find forgiveness for yourself and forgive others.
9** May you share freely, never taking more than you give.
10**
11*************************************************************************
12** This is the header file for the generic hash-table implemenation
13** used in SQLite.
14**
15** $Id: hash.h,v 1.9 2006/02/14 10:48:39 danielk1977 Exp $
16*/
17#ifndef _SQLITE_HASH_H_
18#define _SQLITE_HASH_H_
19
20/* Forward declarations of structures. */
21typedef struct Hash Hash;
22typedef struct HashElem HashElem;
23
24/* A complete hash table is an instance of the following structure.
25** The internals of this structure are intended to be opaque -- client
26** code should not attempt to access or modify the fields of this structure
27** directly. Change this structure only by using the routines below.
28** However, many of the "procedures" and "functions" for modifying and
29** accessing this structure are really macros, so we can't really make
30** this structure opaque.
31*/
32struct Hash {
33 char keyClass; /* SQLITE_HASH_INT, _POINTER, _STRING, _BINARY */
34 char copyKey; /* True if copy of key made on insert */
35 int count; /* Number of entries in this table */
36 HashElem *first; /* The first element of the array */
37 void *(*xMalloc)(int); /* malloc() function to use */
38 void (*xFree)(void *); /* free() function to use */
39 int htsize; /* Number of buckets in the hash table */
40 struct _ht { /* the hash table */
41 int count; /* Number of entries with this hash */
42 HashElem *chain; /* Pointer to first entry with this hash */
43 } *ht;
44};
45
46/* Each element in the hash table is an instance of the following
47** structure. All elements are stored on a single doubly-linked list.
48**
49** Again, this structure is intended to be opaque, but it can't really
50** be opaque because it is used by macros.
51*/
52struct HashElem {
53 HashElem *next, *prev; /* Next and previous elements in the table */
54 void *data; /* Data associated with this element */
55 void *pKey; int nKey; /* Key associated with this element */
56};
57
58/*
59** There are 4 different modes of operation for a hash table:
60**
61** SQLITE_HASH_INT nKey is used as the key and pKey is ignored.
62**
63** SQLITE_HASH_POINTER pKey is used as the key and nKey is ignored.
64**
65** SQLITE_HASH_STRING pKey points to a string that is nKey bytes long
66** (including the null-terminator, if any). Case
67** is ignored in comparisons.
68**
69** SQLITE_HASH_BINARY pKey points to binary data nKey bytes long.
70** memcmp() is used to compare keys.
71**
72** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY
73** if the copyKey parameter to HashInit is 1.
74*/
75/* #define SQLITE_HASH_INT 1 // NOT USED */
76/* #define SQLITE_HASH_POINTER 2 // NOT USED */
77#define SQLITE_HASH_STRING 3
78#define SQLITE_HASH_BINARY 4
79
80/*
81** Access routines. To delete, insert a NULL pointer.
82*/
83void sqlite3HashInit(Hash*, int keytype, int copyKey);
84void *sqlite3HashInsert(Hash*, const void *pKey, int nKey, void *pData);
85void *sqlite3HashFind(const Hash*, const void *pKey, int nKey);
86void sqlite3HashClear(Hash*);
87
88/*
89** Macros for looping over all elements of a hash table. The idiom is
90** like this:
91**
92** Hash h;
93** HashElem *p;
94** ...
95** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
96** SomeStructure *pData = sqliteHashData(p);
97** // do something with pData
98** }
99*/
100#define sqliteHashFirst(H) ((H)->first)
101#define sqliteHashNext(E) ((E)->next)
102#define sqliteHashData(E) ((E)->data)
103#define sqliteHashKey(E) ((E)->pKey)
104#define sqliteHashKeysize(E) ((E)->nKey)
105
106/*
107** Number of entries in a hash table
108*/
109#define sqliteHashCount(H) ((H)->count)
110
111#endif /* _SQLITE_HASH_H_ */

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