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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 1.1 2003/08/05 23:03:07 graydon 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 int htsize; /* Number of buckets in the hash table */
38 struct _ht { /* the hash table */
39 int count; /* Number of entries with this hash */
40 HashElem *chain; /* Pointer to first entry with this hash */
41 } *ht;
42};
43
44/* Each element in the hash table is an instance of the following
45** structure. All elements are stored on a single doubly-linked list.
46**
47** Again, this structure is intended to be opaque, but it can't really
48** be opaque because it is used by macros.
49*/
50struct HashElem {
51 HashElem *next, *prev; /* Next and previous elements in the table */
52 void *data; /* Data associated with this element */
53 void *pKey; int nKey; /* Key associated with this element */
54};
55
56/*
57** There are 4 different modes of operation for a hash table:
58**
59** SQLITE_HASH_INT nKey is used as the key and pKey is ignored.
60**
61** SQLITE_HASH_POINTER pKey is used as the key and nKey is ignored.
62**
63** SQLITE_HASH_STRING pKey points to a string that is nKey bytes long
64** (including the null-terminator, if any). Case
65** is ignored in comparisons.
66**
67** SQLITE_HASH_BINARY pKey points to binary data nKey bytes long.
68** memcmp() is used to compare keys.
69**
70** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY
71** if the copyKey parameter to HashInit is 1.
72*/
73#define SQLITE_HASH_INT 1
74#define SQLITE_HASH_POINTER 2
75#define SQLITE_HASH_STRING 3
76#define SQLITE_HASH_BINARY 4
77
78/*
79** Access routines. To delete, insert a NULL pointer.
80*/
81void sqliteHashInit(Hash*, int keytype, int copyKey);
82void *sqliteHashInsert(Hash*, const void *pKey, int nKey, void *pData);
83void *sqliteHashFind(const Hash*, const void *pKey, int nKey);
84void sqliteHashClear(Hash*);
85
86/*
87** Macros for looping over all elements of a hash table. The idiom is
88** like this:
89**
90** Hash h;
91** HashElem *p;
92** ...
93** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
94** SomeStructure *pData = sqliteHashData(p);
95** // do something with pData
96** }
97*/
98#define sqliteHashFirst(H) ((H)->first)
99#define sqliteHashNext(E) ((E)->next)
100#define sqliteHashData(E) ((E)->data)
101#define sqliteHashKey(E) ((E)->pKey)
102#define sqliteHashKeysize(E) ((E)->nKey)
103
104/*
105** Number of entries in a hash table
106*/
107#define sqliteHashCount(H) ((H)->count)
108
109#endif /* _SQLITE_HASH_H_ */

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