forked from blevesearch/bleve
/
field_cache.go
75 lines (68 loc) · 2.07 KB
/
field_cache.go
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// 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 ""
}