xref: /titanic_41/usr/src/lib/libsqlite/src/hash.h (revision c5c4113dfcabb1eed3d4bdf7609de5170027a794)
1 
2 #pragma ident	"%Z%%M%	%I%	%E% SMI"
3 
4 /*
5 ** 2001 September 22
6 **
7 ** The author disclaims copyright to this source code.  In place of
8 ** a legal notice, here is a blessing:
9 **
10 **    May you do good and not evil.
11 **    May you find forgiveness for yourself and forgive others.
12 **    May you share freely, never taking more than you give.
13 **
14 *************************************************************************
15 ** This is the header file for the generic hash-table implemenation
16 ** used in SQLite.
17 **
18 ** $Id: hash.h,v 1.6 2004/01/08 02:17:33 drh Exp $
19 */
20 #ifndef _SQLITE_HASH_H_
21 #define _SQLITE_HASH_H_
22 
23 /* Forward declarations of structures. */
24 typedef struct Hash Hash;
25 typedef struct HashElem HashElem;
26 
27 /* A complete hash table is an instance of the following structure.
28 ** The internals of this structure are intended to be opaque -- client
29 ** code should not attempt to access or modify the fields of this structure
30 ** directly.  Change this structure only by using the routines below.
31 ** However, many of the "procedures" and "functions" for modifying and
32 ** accessing this structure are really macros, so we can't really make
33 ** this structure opaque.
34 */
35 struct Hash {
36   char keyClass;          /* SQLITE_HASH_INT, _POINTER, _STRING, _BINARY */
37   char copyKey;           /* True if copy of key made on insert */
38   int count;              /* Number of entries in this table */
39   HashElem *first;        /* The first element of the array */
40   int htsize;             /* Number of buckets in the hash table */
41   struct _ht {            /* the hash table */
42     int count;               /* Number of entries with this hash */
43     HashElem *chain;         /* Pointer to first entry with this hash */
44   } *ht;
45 };
46 
47 /* Each element in the hash table is an instance of the following
48 ** structure.  All elements are stored on a single doubly-linked list.
49 **
50 ** Again, this structure is intended to be opaque, but it can't really
51 ** be opaque because it is used by macros.
52 */
53 struct HashElem {
54   HashElem *next, *prev;   /* Next and previous elements in the table */
55   void *data;              /* Data associated with this element */
56   void *pKey; int nKey;    /* Key associated with this element */
57 };
58 
59 /*
60 ** There are 4 different modes of operation for a hash table:
61 **
62 **   SQLITE_HASH_INT         nKey is used as the key and pKey is ignored.
63 **
64 **   SQLITE_HASH_POINTER     pKey is used as the key and nKey is ignored.
65 **
66 **   SQLITE_HASH_STRING      pKey points to a string that is nKey bytes long
67 **                           (including the null-terminator, if any).  Case
68 **                           is ignored in comparisons.
69 **
70 **   SQLITE_HASH_BINARY      pKey points to binary data nKey bytes long.
71 **                           memcmp() is used to compare keys.
72 **
73 ** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY
74 ** if the copyKey parameter to HashInit is 1.
75 */
76 #define SQLITE_HASH_INT       1
77 /* #define SQLITE_HASH_POINTER   2 // NOT USED */
78 #define SQLITE_HASH_STRING    3
79 #define SQLITE_HASH_BINARY    4
80 
81 /*
82 ** Access routines.  To delete, insert a NULL pointer.
83 */
84 void sqliteHashInit(Hash*, int keytype, int copyKey);
85 void *sqliteHashInsert(Hash*, const void *pKey, int nKey, void *pData);
86 void *sqliteHashFind(const Hash*, const void *pKey, int nKey);
87 void sqliteHashClear(Hash*);
88 
89 /*
90 ** Macros for looping over all elements of a hash table.  The idiom is
91 ** like this:
92 **
93 **   Hash h;
94 **   HashElem *p;
95 **   ...
96 **   for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){
97 **     SomeStructure *pData = sqliteHashData(p);
98 **     // do something with pData
99 **   }
100 */
101 #define sqliteHashFirst(H)  ((H)->first)
102 #define sqliteHashNext(E)   ((E)->next)
103 #define sqliteHashData(E)   ((E)->data)
104 #define sqliteHashKey(E)    ((E)->pKey)
105 #define sqliteHashKeysize(E) ((E)->nKey)
106 
107 /*
108 ** Number of entries in a hash table
109 */
110 #define sqliteHashCount(H)  ((H)->count)
111 
112 #endif /* _SQLITE_HASH_H_ */
113