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Side by Side Diff: third_party/sqlite/src/hash.h

Issue 3108030: Move bundled copy of sqlite one level deeper to better separate it... (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src/
Patch Set: Created 10 years, 4 months ago
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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 1.15 2009/05/02 13:29:38 drh Exp $
16 */
17 #ifndef _SQLITE_HASH_H_
18 #define _SQLITE_HASH_H_
19
20 /* Forward declarations of structures. */
21 typedef struct Hash Hash;
22 typedef 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, some 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 **
32 ** All elements of the hash table are on a single doubly-linked list.
33 ** Hash.first points to the head of this list.
34 **
35 ** There are Hash.htsize buckets. Each bucket points to a spot in
36 ** the global doubly-linked list. The contents of the bucket are the
37 ** element pointed to plus the next _ht.count-1 elements in the list.
38 **
39 ** Hash.htsize and Hash.ht may be zero. In that case lookup is done
40 ** by a linear search of the global list. For small tables, the
41 ** Hash.ht table is never allocated because if there are few elements
42 ** in the table, it is faster to do a linear search than to manage
43 ** the hash table.
44 */
45 struct Hash {
46 unsigned int htsize; /* Number of buckets in the hash table */
47 unsigned int count; /* Number of entries in this table */
48 HashElem *first; /* The first element of the array */
49 struct _ht { /* the hash table */
50 int count; /* Number of entries with this hash */
51 HashElem *chain; /* Pointer to first entry with this hash */
52 } *ht;
53 };
54
55 /* Each element in the hash table is an instance of the following
56 ** structure. All elements are stored on a single doubly-linked list.
57 **
58 ** Again, this structure is intended to be opaque, but it can't really
59 ** be opaque because it is used by macros.
60 */
61 struct HashElem {
62 HashElem *next, *prev; /* Next and previous elements in the table */
63 void *data; /* Data associated with this element */
64 const char *pKey; int nKey; /* Key associated with this element */
65 };
66
67 /*
68 ** Access routines. To delete, insert a NULL pointer.
69 */
70 void sqlite3HashInit(Hash*);
71 void *sqlite3HashInsert(Hash*, const char *pKey, int nKey, void *pData);
72 void *sqlite3HashFind(const Hash*, const char *pKey, int nKey);
73 void sqlite3HashClear(Hash*);
74
75 /*
76 ** Macros for looping over all elements of a hash table. The idiom is
77 ** like this:
78 **
79 ** Hash h;
80 ** HashElem *p;
81 ** ...
82 ** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
83 ** SomeStructure *pData = sqliteHashData(p);
84 ** // do something with pData
85 ** }
86 */
87 #define sqliteHashFirst(H) ((H)->first)
88 #define sqliteHashNext(E) ((E)->next)
89 #define sqliteHashData(E) ((E)->data)
90 /* #define sqliteHashKey(E) ((E)->pKey) // NOT USED */
91 /* #define sqliteHashKeysize(E) ((E)->nKey) // NOT USED */
92
93 /*
94 ** Number of entries in a hash table
95 */
96 /* #define sqliteHashCount(H) ((H)->count) // NOT USED */
97
98 #endif /* _SQLITE_HASH_H_ */
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