smallnest / exp

Experimental packages not in std and golang.org/exp

exp

Experimental packages not in std and golang.org/exp

packages

• sync

  • generic sync.Map: modify sync.Map to support generic
  • Phaser: a reusable synchronization barrier, similar in functionality to java.util.concurrent.Phaser
  • Notifier: implement the observer pattern via channel
  • Shard: a sharding data structure with lock-free read and write
  • Exchanger: a synchronization point at which goroutines can pair and swap elements within pairs. Each goroutine presents some object on entry to the exchange method, matches with a partner goroutine, and receives its partner's object on return. An Exchanger may be viewed as a bidirectional form of a channel.
  • atomicx: add C++ 20 atomic wait/notify feature for go std atomic
    • Pointer[T]
    • Value
    • Uintptr
    • Bool
    • Int32
    • Int64
    • Uint32
    • Uint64
  • Pool: a generic pool, forked from https://github.com/mkmik/syncpool

• container

  • heap: generic heap
  • binheap: human friendly generic heap
  • list: generic list
  • ring: generic ring
  • skiplist: generic skiplist based on mauricegit/skiplist
  • set: discussion at golang/go#47331
    • Set: generic set
    • SortedSet: generic sorted set
  • maps:
    • OrderedMap: an insert-order map. The main code is forked wk8/go-ordered-map
    • AccessOrderedMap: an access-order map.
    • BidiMap: a bidirectional map.
  • Tuple: a collection of generic tuples.

• chanx

  • Batch: batch get from channels efficiently

• io

  • MmapReader: a mmap reader which implements io.Reader, io.ReadAt, io.Closer and can ReadLine

• db

  • Rows and Row provides two helper functions to query structs from databases.
  • RowsMap and RowMap provides two helper functions to query map from databases.

exp's Issues

Conversion from unsafe.Pointer to *V violates unsafe package rules

exp/sync/sync_map.go

Line 194 in 3592a45

return e.p.CompareAndSwap((*V)(expunged), nil)

exp/sync/sync_map.go

Line 519 in 3592a45

if e.p.CompareAndSwap(nil, (*V)(expunged)) {

I got curious about this approach and talked with Go devs and community - is it safe to do so? Their answer was no - it's not. Go compiler makes no promises about not following pointer value and exploring contents in the runtime.

Per docs:

(1) Conversion of a *T1 to Pointer to *T2.

Provided that T2 is no larger than T1 and that the two share an equivalent memory layout, this conversion allows reinterpreting data of one type as data of another type. An example is the implementation of math.Float64bits:

So you can't do this technically. What you can do is use plain unsafe.Pointer instead of atomic.Pointer.

add stat.SlidingWindow and stat.TumblingWindow

add Set implementation

add SkipList implementation