neo-go/pkg/consensus/cache.go

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package consensus
import (
"container/list"
"sync"
"github.com/CityOfZion/neo-go/pkg/util"
)
// relayCache is a payload cache which is used to store
// last consensus payloads.
type relayCache struct {
*sync.RWMutex
maxCap int
elems map[util.Uint256]*list.Element
queue *list.List
}
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// hashable is a type of items which can be stored in the relayCache.
type hashable interface {
Hash() util.Uint256
}
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func newFIFOCache(capacity int) *relayCache {
return &relayCache{
RWMutex: new(sync.RWMutex),
maxCap: capacity,
elems: make(map[util.Uint256]*list.Element),
queue: list.New(),
}
}
// Add adds payload into a cache if it doesn't already exist.
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func (c *relayCache) Add(p hashable) {
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c.Lock()
defer c.Unlock()
h := p.Hash()
if c.elems[h] != nil {
return
}
if c.queue.Len() >= c.maxCap {
first := c.queue.Front()
c.queue.Remove(first)
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delete(c.elems, first.Value.(hashable).Hash())
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}
e := c.queue.PushBack(p)
c.elems[h] = e
}
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// Has checks if an item is already in cache.
func (c *relayCache) Has(h util.Uint256) bool {
c.RLock()
defer c.RUnlock()
return c.elems[h] != nil
}
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// Get returns payload with the specified hash from cache.
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func (c *relayCache) Get(h util.Uint256) hashable {
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c.RLock()
defer c.RUnlock()
e, ok := c.elems[h]
if !ok {
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return hashable(nil)
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}
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return e.Value.(hashable)
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}