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1 /* |
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2 ** 2001 September 22 |
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3 ** |
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4 ** The author disclaims copyright to this source code. In place of |
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5 ** a legal notice, here is a blessing: |
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6 ** |
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7 ** May you do good and not evil. |
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8 ** May you find forgiveness for yourself and forgive others. |
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9 ** May you share freely, never taking more than you give. |
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10 ** |
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11 ************************************************************************* |
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12 ** This is the header file for the generic hash-table implemenation |
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13 ** used in SQLite. |
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14 ** |
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15 ** $Id: hash.h 1282 2008-11-13 09:31:33Z LarsPson $ |
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16 */ |
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17 #ifndef _SQLITE_HASH_H_ |
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18 #define _SQLITE_HASH_H_ |
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19 |
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20 /* Forward declarations of structures. */ |
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21 typedef struct Hash Hash; |
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22 typedef struct HashElem HashElem; |
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23 |
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24 /* A complete hash table is an instance of the following structure. |
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25 ** The internals of this structure are intended to be opaque -- client |
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26 ** code should not attempt to access or modify the fields of this structure |
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27 ** directly. Change this structure only by using the routines below. |
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28 ** However, many of the "procedures" and "functions" for modifying and |
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29 ** accessing this structure are really macros, so we can't really make |
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30 ** this structure opaque. |
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31 */ |
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32 struct Hash { |
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33 char keyClass; /* SQLITE_HASH_INT, _POINTER, _STRING, _BINARY */ |
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34 char copyKey; /* True if copy of key made on insert */ |
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35 int count; /* Number of entries in this table */ |
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36 int htsize; /* Number of buckets in the hash table */ |
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37 HashElem *first; /* The first element of the array */ |
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38 struct _ht { /* the hash table */ |
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39 int count; /* Number of entries with this hash */ |
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40 HashElem *chain; /* Pointer to first entry with this hash */ |
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41 } *ht; |
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42 }; |
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43 |
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44 /* Each element in the hash table is an instance of the following |
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45 ** structure. All elements are stored on a single doubly-linked list. |
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46 ** |
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47 ** Again, this structure is intended to be opaque, but it can't really |
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48 ** be opaque because it is used by macros. |
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49 */ |
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50 struct HashElem { |
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51 HashElem *next, *prev; /* Next and previous elements in the table */ |
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52 void *data; /* Data associated with this element */ |
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53 void *pKey; int nKey; /* Key associated with this element */ |
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54 }; |
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55 |
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56 /* |
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57 ** There are 4 different modes of operation for a hash table: |
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58 ** |
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59 ** SQLITE_HASH_INT nKey is used as the key and pKey is ignored. |
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60 ** |
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61 ** SQLITE_HASH_POINTER pKey is used as the key and nKey is ignored. |
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62 ** |
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63 ** SQLITE_HASH_STRING pKey points to a string that is nKey bytes long |
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64 ** (including the null-terminator, if any). Case |
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65 ** is ignored in comparisons. |
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66 ** |
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67 ** SQLITE_HASH_BINARY pKey points to binary data nKey bytes long. |
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68 ** memcmp() is used to compare keys. |
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69 ** |
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70 ** A copy of the key is made for SQLITE_HASH_STRING and SQLITE_HASH_BINARY |
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71 ** if the copyKey parameter to HashInit is 1. |
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72 */ |
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73 /* #define SQLITE_HASH_INT 1 // NOT USED */ |
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74 /* #define SQLITE_HASH_POINTER 2 // NOT USED */ |
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75 #define SQLITE_HASH_STRING 3 |
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76 #define SQLITE_HASH_BINARY 4 |
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77 |
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78 /* |
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79 ** Access routines. To delete, insert a NULL pointer. |
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80 */ |
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81 void sqlite3HashInit(Hash*, int keytype, int copyKey); |
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82 void *sqlite3HashInsert(Hash*, const void *pKey, int nKey, void *pData); |
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83 void *sqlite3HashFind(const Hash*, const void *pKey, int nKey); |
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84 HashElem *sqlite3HashFindElem(const Hash*, const void *pKey, int nKey); |
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85 void sqlite3HashClear(Hash*); |
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86 |
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87 /* |
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88 ** Macros for looping over all elements of a hash table. The idiom is |
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89 ** like this: |
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90 ** |
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91 ** Hash h; |
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92 ** HashElem *p; |
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93 ** ... |
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94 ** for(p=sqliteHashFirst(&h); p; p=sqliteHashNext(p)){ |
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95 ** SomeStructure *pData = sqliteHashData(p); |
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96 ** // do something with pData |
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97 ** } |
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98 */ |
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99 #define sqliteHashFirst(H) ((H)->first) |
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100 #define sqliteHashNext(E) ((E)->next) |
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101 #define sqliteHashData(E) ((E)->data) |
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102 #define sqliteHashKey(E) ((E)->pKey) |
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103 #define sqliteHashKeysize(E) ((E)->nKey) |
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104 |
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105 /* |
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106 ** Number of entries in a hash table |
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107 */ |
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108 #define sqliteHashCount(H) ((H)->count) |
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109 |
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110 #endif /* _SQLITE_HASH_H_ */ |