initial commit

vendor/github.com/blevesearch/bleve/index/field_cache.go

@@ -0,0 +1,75 @@
+//  Copyright (c) 2015 Couchbase, Inc.
+//  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+//  except in compliance with the License. You may obtain a copy of the License at
+//    http://www.apache.org/licenses/LICENSE-2.0
+//  Unless required by applicable law or agreed to in writing, software distributed under the
+//  License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+//  either express or implied. See the License for the specific language governing permissions
+//  and limitations under the License.
+
+package index
+
+import (
+	"sync"
+)
+
+type FieldCache struct {
+	fieldIndexes   map[string]uint16
+	lastFieldIndex int
+	mutex          sync.RWMutex
+}
+
+func NewFieldCache() *FieldCache {
+	return &FieldCache{
+		fieldIndexes:   make(map[string]uint16),
+		lastFieldIndex: -1,
+	}
+}
+
+func (f *FieldCache) AddExisting(field string, index uint16) {
+	f.mutex.Lock()
+	defer f.mutex.Unlock()
+	f.fieldIndexes[field] = index
+	if int(index) > f.lastFieldIndex {
+		f.lastFieldIndex = int(index)
+	}
+}
+
+// FieldNamed returns the index of the field, and whether or not it existed
+// before this call.  if createIfMissing is true, and new field index is assigned
+// but the second return value will still be false
+func (f *FieldCache) FieldNamed(field string, createIfMissing bool) (uint16, bool) {
+	f.mutex.RLock()
+	if index, ok := f.fieldIndexes[field]; ok {
+		f.mutex.RUnlock()
+		return index, true
+	} else if !createIfMissing {
+		f.mutex.RUnlock()
+		return 0, false
+	}
+	// trade read lock for write lock
+	f.mutex.RUnlock()
+	f.mutex.Lock()
+	// need to check again with write lock
+	if index, ok := f.fieldIndexes[field]; ok {
+		f.mutex.Unlock()
+		return index, true
+	}
+	// assign next field id
+	index := uint16(f.lastFieldIndex + 1)
+	f.fieldIndexes[field] = index
+	f.lastFieldIndex = int(index)
+	f.mutex.Unlock()
+	return index, false
+}
+
+func (f *FieldCache) FieldIndexed(index uint16) string {
+	f.mutex.RLock()
+	defer f.mutex.RUnlock()
+	for fieldName, fieldIndex := range f.fieldIndexes {
+		if index == fieldIndex {
+			return fieldName
+		}
+	}
+	return ""
+}