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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 implementation | |
| 13 ** used in SQLite. | |
| 14 */ | |
| 15 #ifndef _SQLITE_HASH_H_ | |
| 16 #define _SQLITE_HASH_H_ | |
| 17 | |
| 18 /* Forward declarations of structures. */ | |
| 19 typedef struct Hash Hash; | |
| 20 typedef struct HashElem HashElem; | |
| 21 | |
| 22 /* A complete hash table is an instance of the following structure. | |
| 23 ** The internals of this structure are intended to be opaque -- client | |
| 24 ** code should not attempt to access or modify the fields of this structure | |
| 25 ** directly. Change this structure only by using the routines below. | |
| 26 ** However, some of the "procedures" and "functions" for modifying and | |
| 27 ** accessing this structure are really macros, so we can't really make | |
| 28 ** this structure opaque. | |
| 29 ** | |
| 30 ** All elements of the hash table are on a single doubly-linked list. | |
| 31 ** Hash.first points to the head of this list. | |
| 32 ** | |
| 33 ** There are Hash.htsize buckets. Each bucket points to a spot in | |
| 34 ** the global doubly-linked list. The contents of the bucket are the | |
| 35 ** element pointed to plus the next _ht.count-1 elements in the list. | |
| 36 ** | |
| 37 ** Hash.htsize and Hash.ht may be zero. In that case lookup is done | |
| 38 ** by a linear search of the global list. For small tables, the | |
| 39 ** Hash.ht table is never allocated because if there are few elements | |
| 40 ** in the table, it is faster to do a linear search than to manage | |
| 41 ** the hash table. | |
| 42 */ | |
| 43 struct Hash { | |
| 44 unsigned int htsize; /* Number of buckets in the hash table */ | |
| 45 unsigned int count; /* Number of entries in this table */ | |
| 46 HashElem *first; /* The first element of the array */ | |
| 47 struct _ht { /* the hash table */ | |
| 48 int count; /* Number of entries with this hash */ | |
| 49 HashElem *chain; /* Pointer to first entry with this hash */ | |
| 50 } *ht; | |
| 51 }; | |
| 52 | |
| 53 /* Each element in the hash table is an instance of the following | |
| 54 ** structure. All elements are stored on a single doubly-linked list. | |
| 55 ** | |
| 56 ** Again, this structure is intended to be opaque, but it can't really | |
| 57 ** be opaque because it is used by macros. | |
| 58 */ | |
| 59 struct HashElem { | |
| 60 HashElem *next, *prev; /* Next and previous elements in the table */ | |
| 61 void *data; /* Data associated with this element */ | |
| 62 const char *pKey; /* Key associated with this element */ | |
| 63 }; | |
| 64 | |
| 65 /* | |
| 66 ** Access routines. To delete, insert a NULL pointer. | |
| 67 */ | |
| 68 void sqlite3HashInit(Hash*); | |
| 69 void *sqlite3HashInsert(Hash*, const char *pKey, void *pData); | |
| 70 void *sqlite3HashFind(const Hash*, const char *pKey); | |
| 71 void sqlite3HashClear(Hash*); | |
| 72 | |
| 73 /* | |
| 74 ** Macros for looping over all elements of a hash table. The idiom is | |
| 75 ** like this: | |
| 76 ** | |
| 77 ** Hash h; | |
| 78 ** HashElem *p; | |
| 79 ** ... | |
| 80 ** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){ | |
| 81 ** SomeStructure *pData = sqliteHashData(p); | |
| 82 ** // do something with pData | |
| 83 ** } | |
| 84 */ | |
| 85 #define sqliteHashFirst(H) ((H)->first) | |
| 86 #define sqliteHashNext(E) ((E)->next) | |
| 87 #define sqliteHashData(E) ((E)->data) | |
| 88 /* #define sqliteHashKey(E) ((E)->pKey) // NOT USED */ | |
| 89 /* #define sqliteHashKeysize(E) ((E)->nKey) // NOT USED */ | |
| 90 | |
| 91 /* | |
| 92 ** Number of entries in a hash table | |
| 93 */ | |
| 94 /* #define sqliteHashCount(H) ((H)->count) // NOT USED */ | |
| 95 | |
| 96 #endif /* _SQLITE_HASH_H_ */ | |
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Chromium Code Reviews
Issue 2846743003:
[sql] Remove SQLite 3.10.2 reference directory. (Closed)
