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iterator.go
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/
iterator.go
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package baradb
import (
"bytes"
"github.com/saint-yellow/baradb/index"
)
// Iterator an iterator of DB
type Iterator struct {
indexIterator index.Iterator // iterator of an index
db *DB // DB engine
options index.IteratorOptions // options of an iterator of an index
}
// NewItrerator initializes an iterator of DB engine
func (db *DB) NewItrerator(options index.IteratorOptions) *Iterator {
iterator := &Iterator{
indexIterator: db.index.Iterator(options.Reverse),
db: db,
options: options,
}
return iterator
}
func (it *Iterator) Rewind() {
it.indexIterator.Rewind()
it.skipToNext()
}
func (it *Iterator) Seek(key []byte) {
it.indexIterator.Seek(key)
it.skipToNext()
}
func (it *Iterator) Next() {
it.indexIterator.Next()
it.skipToNext()
}
func (it *Iterator) Valid() bool {
return it.indexIterator.Valid()
}
func (it *Iterator) Key() []byte {
return it.indexIterator.Key()
}
func (it *Iterator) Value() ([]byte, error) {
lrp := it.indexIterator.Value()
it.db.mu.RLock()
defer it.db.mu.RUnlock()
return it.db.getValueByPosition(lrp)
}
func (it *Iterator) Close() {
it.indexIterator.Close()
}
// skipToNext skips keys if Prefix of IteratorOptions is not nil
func (it *Iterator) skipToNext() {
prefixLength := len(it.options.Prefix)
if prefixLength == 0 {
return
}
for ; it.indexIterator.Valid(); it.indexIterator.Next() {
key := it.indexIterator.Key()
if prefixLength <= len(key) && bytes.Equal(it.options.Prefix, key[:prefixLength]) {
break
}
}
}