ENEE150 – 0102ANDREW GOFFIN

Project 4 & Function Pointers

Project 4

Hash Table ADT A data type that points to a hash table Separate struct needed for hash table nodes themselves Hash table struct MUST contain:

Pointer to bucket array for table Function pointer to a print function for the table

Hash table struct should probably contain: Table stats (total number of records, average search, worst

search) Hash table NODE structs must contain:

Self-referring next pointer (like a linked list) Generic “data” pointer String key

Goffin – ENEE150

Project 4 Continued

Hash Table Operations Phash_table new_hash(int size, void (*print_func)(void *)): constructor

Takes function pointer to set the hash table’s print function void free_hash(Phash_table table): destructor void insert_hash(Phash_table table, char *key, void *data)

“constructor” for hash table node: uses hash function to insert into table void *find_hash(Phash_table table, char *key)

Returns pointer to node with key or NULL if no node with key exists void stat_hash(Phash_table table, int *total, float *average_search, int

*worst_search) Modifies variables total, average_search, and worse_search by reference

void dump_hash(Phash_table table) Uses function pointer to print table contents

void resize_hash(Phash_table table, int size) Changes number of buckets to “size” – you must re-hash all the entries!

Goffin – ENEE150

Other Project 4 ADT Notes

You can use other fields or private methods! As long as the public methods work as stated, you’re

good

Hash function Due to potential bit overflow, use unsigned int

variables to store intermediate valuesSearch stats based on number of records

traversed to get to the one you’re looking for Typically, more buckets = more efficient searching

Goffin – ENEE150

Project 4: Implementations

parse.c Parsing words in a dictionary and inserting them into the

hash table In this case, the word is both the key and part of the

data See handout #14 for an earlier implementation of this

performance-test.c Code is provided: simply shows how increasing buckets

improves performance Also shows benefit of separating use and implementation

Yeung didn’t need your ADT implementation to write this module!

Goffin – ENEE150

Function Pointers

Sometimes different users may want slightly different results from an ADT Ex: Printing the hash table in project 4 Someone may want to print int data, others char data,

etc.Can make functions generic using function

pointers Further supports polymorphism for ADTs

Goffin – ENEE150

Function Pointer Declaration

Must specify return type and parametersvoid (*func)(int, float) The above can only be a function pointer for a

function with the same interface Can assign a function to the function pointer by

simply sayingfunc = foo;

where foo is a function with the same interface as func

(*func)(10, 3.14); The above passes 10 and 3.14 into foo

Goffin – ENEE150