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 1.6 2004/01/08 02:17:33 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, 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 */ 32 struct 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 */ 50 struct 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 // NOT USED */ 75 #define SQLITE_HASH_STRING 3 76 #define SQLITE_HASH_BINARY 4 77 78 /* 79 ** Access routines. To delete, insert a NULL pointer. 80 */ 81 void sqliteHashInit(Hash*, int keytype, int copyKey); 82 void *sqliteHashInsert(Hash*, const void *pKey, int nKey, void *pData); 83 void *sqliteHashFind(const Hash*, const void *pKey, int nKey); 84 void 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_ */ 110