Trivial Description
hashtable_remove appears to call the hash function in consecutive lines. As hash functions are generally cpu intensive, using the hashvalue returned from the first call will result in a performance improvement.
void * /* returns value associated with key */
hashtable_remove(struct hashtable *h, void *k)
...
unsigned int hashvalue, index;
hashvalue = hash(h,k);
index = indexFor(h->tablelength,hash(h,k));
pE = &(h->table[index]);
e = *pE;