cmd, core, eth, light, trie: add trie read caching layer

vendor/github.com/allegro/bigcache/iterator.go

@@ -0,0 +1,122 @@
+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
+}