lnd.xprv/channeldb/migration_01_to_11/reject_cache.go
Joost Jager 6e463c1634
channeldb: make copy for migrations
This commit is a direct copy of the complete channeldb package. It only
changes the package declaration at the top of every file. We make this
full copy so that review can be focused on the actual changes made.
Otherwise changes may drown in all the file moves.

Linting for the new package is disabled, as it contains lots of
pre-existing issues.
2019-10-24 12:49:38 +02:00

96 lines
2.9 KiB
Go

package migration_01_to_11
// rejectFlags is a compact representation of various metadata stored by the
// reject cache about a particular channel.
type rejectFlags uint8
const (
// rejectFlagExists is a flag indicating whether the channel exists,
// i.e. the channel is open and has a recent channel update. If this
// flag is not set, the channel is either a zombie or unknown.
rejectFlagExists rejectFlags = 1 << iota
// rejectFlagZombie is a flag indicating whether the channel is a
// zombie, i.e. the channel is open but has no recent channel updates.
rejectFlagZombie
)
// packRejectFlags computes the rejectFlags corresponding to the passed boolean
// values indicating whether the edge exists or is a zombie.
func packRejectFlags(exists, isZombie bool) rejectFlags {
var flags rejectFlags
if exists {
flags |= rejectFlagExists
}
if isZombie {
flags |= rejectFlagZombie
}
return flags
}
// unpack returns the booleans packed into the rejectFlags. The first indicates
// if the edge exists in our graph, the second indicates if the edge is a
// zombie.
func (f rejectFlags) unpack() (bool, bool) {
return f&rejectFlagExists == rejectFlagExists,
f&rejectFlagZombie == rejectFlagZombie
}
// rejectCacheEntry caches frequently accessed information about a channel,
// including the timestamps of its latest edge policies and whether or not the
// channel exists in the graph.
type rejectCacheEntry struct {
upd1Time int64
upd2Time int64
flags rejectFlags
}
// rejectCache is an in-memory cache used to improve the performance of
// HasChannelEdge. It caches information about the whether or channel exists, as
// well as the most recent timestamps for each policy (if they exists).
type rejectCache struct {
n int
edges map[uint64]rejectCacheEntry
}
// newRejectCache creates a new rejectCache with maximum capacity of n entries.
func newRejectCache(n int) *rejectCache {
return &rejectCache{
n: n,
edges: make(map[uint64]rejectCacheEntry, n),
}
}
// get returns the entry from the cache for chanid, if it exists.
func (c *rejectCache) get(chanid uint64) (rejectCacheEntry, bool) {
entry, ok := c.edges[chanid]
return entry, ok
}
// insert adds the entry to the reject cache. If an entry for chanid already
// exists, it will be replaced with the new entry. If the entry doesn't exists,
// it will be inserted to the cache, performing a random eviction if the cache
// is at capacity.
func (c *rejectCache) insert(chanid uint64, entry rejectCacheEntry) {
// If entry exists, replace it.
if _, ok := c.edges[chanid]; ok {
c.edges[chanid] = entry
return
}
// Otherwise, evict an entry at random and insert.
if len(c.edges) == c.n {
for id := range c.edges {
delete(c.edges, id)
break
}
}
c.edges[chanid] = entry
}
// remove deletes an entry for chanid from the cache, if it exists.
func (c *rejectCache) remove(chanid uint64) {
delete(c.edges, chanid)
}