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package bigcache
import "sync"
type iteratorError string
func (e iteratorError) Error() string {
return string(e)
}
// ErrInvalidIteratorState is reported when iterator is in invalid state
const ErrInvalidIteratorState = iteratorError("Iterator is in invalid state. Use SetNext() to move to next position")
// ErrCannotRetrieveEntry is reported when entry cannot be retrieved from underlying
const ErrCannotRetrieveEntry = iteratorError("Could not retrieve entry from cache")
var emptyEntryInfo = EntryInfo{}
// EntryInfo holds informations about entry in the cache
type EntryInfo struct {
timestamp uint64
hash uint64
key string
value []byte
}
// Key returns entry's underlying key
func (e EntryInfo) Key() string {
return e.key
}
// Hash returns entry's hash value
func (e EntryInfo) Hash() uint64 {
return e.hash
}
// Timestamp returns entry's timestamp (time of insertion)
func (e EntryInfo) Timestamp() uint64 {
return e.timestamp
}
// Value returns entry's underlying value
func (e EntryInfo) Value() []byte {
return e.value
}
// EntryInfoIterator allows to iterate over entries in the cache
type EntryInfoIterator struct {
mutex sync.Mutex
cache *BigCache
currentShard int
currentIndex int
elements []uint32
elementsCount int
valid bool
}
// SetNext moves to next element and returns true if it exists.
func (it *EntryInfoIterator) SetNext() bool {
it.mutex.Lock()
it.valid = false
it.currentIndex++
if it.elementsCount > it.currentIndex {
it.valid = true
it.mutex.Unlock()
return true
}
for i := it.currentShard + 1; i < it.cache.config.Shards; i++ {
it.elements, it.elementsCount = it.cache.shards[i].copyKeys()
// Non empty shard - stick with it
if it.elementsCount > 0 {
it.currentIndex = 0
it.currentShard = i
it.valid = true
it.mutex.Unlock()
return true
}
}
it.mutex.Unlock()
return false
}
func newIterator(cache *BigCache) *EntryInfoIterator {
elements, count := cache.shards[0].copyKeys()
return &EntryInfoIterator{
cache: cache,
currentShard: 0,
currentIndex: -1,
elements: elements,
elementsCount: count,
}
}
// Value returns current value from the iterator
func (it *EntryInfoIterator) Value() (EntryInfo, error) {
it.mutex.Lock()
if !it.valid {
it.mutex.Unlock()
return emptyEntryInfo, ErrInvalidIteratorState
}
entry, err := it.cache.shards[it.currentShard].getEntry(int(it.elements[it.currentIndex]))
if err != nil {
it.mutex.Unlock()
return emptyEntryInfo, ErrCannotRetrieveEntry
}
it.mutex.Unlock()
return EntryInfo{
timestamp: readTimestampFromEntry(entry),
hash: readHashFromEntry(entry),
key: readKeyFromEntry(entry),
value: readEntry(entry),
}, nil
}
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