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.  We've modified it slightly to serve as a standalone
14** hash table implementation for the full-text indexing module.
15**
16*/
17#ifndef _HASH_H_
18#define _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;          /* 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**   HASH_INT         nKey is used as the key and pKey is ignored.
62**
63**   HASH_POINTER     pKey is used as the key and nKey is ignored.
64**
65**   HASH_STRING      pKey points to a string that is nKey bytes long
66**                           (including the null-terminator, if any).  Case
67**                           is respected in comparisons.
68**
69**   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 HASH_STRING and HASH_BINARY
73** if the copyKey parameter to HashInit is 1.
74*/
75/* #define HASH_INT       1 // NOT USED */
76/* #define HASH_POINTER   2 // NOT USED */
77#define HASH_STRING    3
78#define HASH_BINARY    4
79
80/*
81** Access routines.  To delete, insert a NULL pointer.
82*/
83void HashInit(Hash*, int keytype, int copyKey);
84void *HashInsert(Hash*, const void *pKey, int nKey, void *pData);
85void *HashFind(const Hash*, const void *pKey, int nKey);
86void HashClear(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=HashFirst(&h); p; p=HashNext(p)){
96**     SomeStructure *pData = HashData(p);
97**     // do something with pData
98**   }
99*/
100#define HashFirst(H)  ((H)->first)
101#define HashNext(E)   ((E)->next)
102#define HashData(E)   ((E)->data)
103#define HashKey(E)    ((E)->pKey)
104#define HashKeysize(E) ((E)->nKey)
105
106/*
107** Number of entries in a hash table
108*/
109#define HashCount(H)  ((H)->count)
110
111#endif /* _HASH_H_ */
112