github.com/decred/dcrd/blockchain/stake

tickettreap

Package tickettreap implements a treap data structure that is used to hold live tickets ordered by their key along with some associated data using a combination of binary search tree and heap semantics. It is a self-organizing and randomized data structure that doesn't require complex operations to maintain balance. Search, insert, and delete operations are all O(log n). Both mutable and immutable variants are provided.

The mutable variant is typically faster since it is able to simply update the treap when modifications are made. However, a mutable treap is not safe for concurrent access without careful use of locking by the caller and care must be taken when iterating since it can change out from under the iterator.

The immutable variant works by creating a new version of the treap for all mutations by replacing modified nodes with new nodes that have updated values while sharing all unmodified nodes with the previous version. This is extremely useful in concurrent applications since the caller only has to atomically replace the treap pointer with the newly returned version after performing any mutations. All readers can simply use their existing pointer as a snapshot since the treap it points to is immutable. This effectively provides O(1) snapshot capability with efficient memory usage characteristics since the old nodes only remain allocated until there are no longer any references to them.

Usage

This package is only used internally in the stake code and as such is not available for use outside of it.

License

Package tickettreap is licensed under the copyfree ISC License.