* Do not pre-allocate all buckets based on requested table size. This
defeats the point of a dynamic hash table which adjusts it's memory
usage depending upon the number of items it holds. Pre-allocation
also runs afoul of the table contraction logic, if the table is
pre-allocated to a large size it will subsequently try to compact it
negating the pre-allocation. Now the initial allocation is
restricted to one directory segment (i.e. table->segment_count == 1)
* If the caller did not specify the directory_bits and segment_bits
then compute them from the requested table size. The directory_size
and segment_size must be powers of 2 to accmodate fast
arithmetic. An optimal maximum number of buckets would be equal to
the anticipated table size. If there were no collisions that would
mean each item would be located in it's own bucket whose chain
length is 1, the item would be immediatly found upon indexing into
the bucket table.
* There is a requirment there be at least one directory
segment, however contract_table() failed to enforce this
requirement. Add a check to enforce the requirement.
* If hash_create() or hash_create_ex() failed it left the tbl
parameter uninitialized but returned an error code. Now upon failure
tbl is initialized to NULL as well as returning an error code.
* Clean up how the directory and segment sizes were computed. It had
been using a loop and shifting 1 bit at a time, now it shifts all
the bits in one operation and assures at least one directory and
segment are allocated.
* In the event of an early exit from hash_create_ex() due to an error
make sure all previously allocated resources are cleaned up by
calling hash_destroy(). There was only one place this was
missing. hash_destroy() blindly assumed the table had a directory,
normally it would unless hash_destroy was called due to an early
exit in hash_create_ex(). Modify hash_destroy() to check for the
existence of the directory before cleaning up the directory
contents.
* Update the function documentation in dhash.h to explain each
parameter of hash_create() and hash_create_ex().
* Enhance dhash_test.c
- To output the random seed used to intialize the random number
generator and add command line option to set the random seed. This
permits recreating a failed test run.
- Add command line parameter to set the initial table size.
- Use proper string to long conversion routines when reading command
line parameters (e.g. strtoul() instead of atoi())
- Add logic to make sure each test value is unique.
* Add additional information to the debug output to show the computed
directory_bits, segment_bits, sizes, etc.
* Adjust the debug_level conditionals to be less verbose.