Control.Concurrent.Supply

A fast unique identifier supply with local pooling and replay support.

One often has a desire to generate a bunch of integer identifiers within a single process that are unique within that process. You could use UUIDs, but they can be expensive to generate; you don't want to have your threads contending for a single external counter if the identifier is not going to be used outside the process.

concurrent-supply builds a tree-like structure which can be split; you can make smaller unique supplies and then you allocate from your supplies locally. Internally it pulls from a unique supply one block at a time as you walk into parts of the tree that haven't been explored.

Documentation

data Supply

A user managed globally unique variable supply.

Instances

Eq Supply

Ord Supply

Show Supply

Hashable Supply

Variables

newSupply :: IO Supply

Grab a new supply. Any two supplies obtained with newSupply are guaranteed to return disjoint sets of identifiers. Replaying the same sequence of operations on the same Supply will yield the same results.

freshId :: Supply -> (Int, Supply)

Obtain a fresh Id from a Supply.

splitSupply :: Supply -> (Supply, Supply)

Split a supply into two supplies that will return disjoint identifiers

Unboxed API

freshId# :: Supply -> (#Int#, Supply#)

An unboxed version of freshId

splitSupply# :: Supply -> (#Supply, Supply#)

An unboxed version of splitSupply