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/* RCSid: $Id: lookup.h,v 1.10 2003/02/28 20:11:29 greg Exp $ */ |
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/* |
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* Header file for general associative table lookup routines |
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*/ |
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#ifndef _MGF_LOOKUP_H_ |
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#define _MGF_LOOKUP_H_ |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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|
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|
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typedef struct { |
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char *key; /* key name */ |
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long hval; /* key hash value (for efficiency) */ |
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char *data; /* pointer to client data */ |
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} LUENT; |
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|
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typedef struct { |
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unsigned long (*hashf)(char *); /* key hash function */ |
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int (*keycmp)(const char *, const char *); /* key comparison function */ |
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void (*freek)(char *); /* free a key */ |
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void (*freed)(char *); /* free the data */ |
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int tsiz; /* current table size */ |
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LUENT *tabl; /* table, if allocated */ |
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int ndel; /* number of deleted entries */ |
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} LUTAB; |
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|
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#define LU_SINIT(fk,fd) {lu_shash,strcmp,(void (*)())(fk),\ |
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(void (*)())(fd),0,NULL,0} |
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|
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/* |
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* The lu_init routine is called to initialize a table. The number of |
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* elements passed is not a limiting factor, as a table can grow to |
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* any size permitted by memory. However, access will be more efficient |
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* if this number strikes a reasonable balance between default memory use |
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* and the expected (minimum) table size. The value returned is the |
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* actual allocated table size (or zero if there was insufficient memory). |
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* |
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* The hashf, keycmp, freek and freed member functions must be assigned |
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* separately. If the hash value is sufficient to guarantee equality |
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* between keys, then the keycmp pointer may be NULL. Otherwise, it |
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* should return 0 if the two passed keys match. If it is not necessary |
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* (or possible) to free the key and/or data values, then the freek and/or |
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* freed member functions may be NULL. |
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* |
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* It isn't fully necessary to call lu_init to initialize the LUTAB structure. |
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* If tsiz is 0, then the first call to lu_find will allocate a minimal table. |
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* The LU_SINIT macro provides a convenient static declaration for character |
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* string keys. |
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* |
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* The lu_find routine returns the entry corresponding to the given |
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* key. If the entry does not exist, the corresponding key field will |
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* be NULL. If the entry has been previously deleted but not yet freed, |
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* then only the data field will be NULL. It is the caller's |
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* responsibility to (allocate and) assign the key and data fields when |
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* creating a new entry. The only case where lu_find returns NULL is when |
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* the system has run out of memory. |
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* |
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* The lu_delete routine frees an entry's data (if any) by calling |
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* the freed member function, but does not free the key field. This |
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* will be freed later during (or instead of) table reallocation. |
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* It is therefore an error to reuse or do anything with the key |
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* field after calling lu_delete. |
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* |
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* The lu_done routine calls the given free function once for each |
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* assigned table entry (i.e. each entry with an assigned key value). |
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* The user must define these routines to free the key and the data |
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* in the LU_TAB structure. The final action of lu_done is to free the |
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* allocated table itself. |
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*/ |
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|
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extern int lu_init(LUTAB *, int); |
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extern LUENT *lu_find(LUTAB *, char *); |
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extern void lu_delete(LUTAB *, char *); |
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extern void lu_done(LUTAB *); |
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extern unsigned long lu_shash(char *); |
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|
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|
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#ifdef __cplusplus |
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} |
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#endif |
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#endif /* _MGF_LOOKUP_H_ */ |
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