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