0.3.0 (#13)

* Fix double free bug, some interface redesign (#10)

* fix double free, change insert_or_modify interface

fixing the double free was surprisingly subtle, and involved a few small
changes to the algorithm to bring it more in line with Cliff Click's
2007 lockfree hash table.

first, it is no longer possible for multiple rehashing operations to be
in flight at once. this is primarily for simplicity's sake, but Click
claims it's faster this way. next, bucket pointers that have been copied
from an old table are marked with a tag bit. this prevents writes on the
old table from overwriting writes on the new table. finally, removal and
no longer requires the key to be cloned. instead, the value is destroyed
via MaybeUninit shenanigans and a tombstone bit is set on the bucket
pointer. the benefit here is that we are able to remove elements without
forcing a memory allocation on the user.

the interface of the insert_or_modify family of functions was changed to
require a function that has both key and value parameters. imo there was
never a solid reason not to do that, but this allows arbitrary data to
be accessed from the old key before disposing of it.

additionally, the Bucket/BucketArray classes were completely rewritten
and moved into a module of their own. i am more satisfied with the
amount of code duplication now, but i believe there is more work to be
done to unify the implementations of get, insert, and remove. in the
future, i hope to use this separate module to create a striped hash
table similar to Java 7's ConcurrentHashMap. this should significantly
increase write performance.

note that this commit includes an internal remove_if interface, which is
intended to address #7.

* move map tests into crate::map::tests

* add bucket key/value destructor tests

ensure that destructors are called for keys and values in a timely
manner

* correct growth policy to grow by a factor of 2

previous behavior would result in growing by a factor of 4 (!)

* Add remove_if family of functions (#11)

* add remove_if family of functions

`remove_if` and friends accept a condition function, which is
`impl FnMut(&K, &V) -> bool`. If the condition returns true immediately
before attempting to CAS the bucket pointer, the bucket is swapped.
Otherwise, `None` is returned.

* rewrite drivers to reduce number of function calls

this way the backtraces will have one less function call listed

* document remove_if functions

* bump version to 0.3.0

A few breaking changes were made with the `modify` and
`insert_or_modify` functions, so the next release requires a minor
version bump (since we're in pre-1.0.0 territory)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cht"
-version = "0.2.0"
+version = "0.3.0"
 authors = ["Gregory Meyer <[email protected]>"]
 edition = "2018"
 description = "Lockfree resizeable concurrent hash table."

README.md

@@ -12,7 +12,7 @@ and deletions.
 In your `Cargo.toml`:
 
 ```toml
-cht = "^0.2.0"
+cht = "^0.3.0"
 ```
 
 Then in your code: