github.com/nutsdb/nutsdb@v1.0.4/iterator.go (about)

     1  // Copyright 2023 The nutsdb Author. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package nutsdb
    16  
    17  import (
    18  	"github.com/tidwall/btree"
    19  )
    20  
    21  type Iterator struct {
    22  	tx      *Tx
    23  	options IteratorOptions
    24  	iter    btree.IterG[*Item]
    25  }
    26  
    27  type IteratorOptions struct {
    28  	Reverse bool
    29  }
    30  
    31  func NewIterator(tx *Tx, bucket string, options IteratorOptions) *Iterator {
    32  	b, err := tx.db.bm.GetBucket(DataStructureBTree, bucket)
    33  	if err != nil {
    34  		return nil
    35  	}
    36  	iterator := &Iterator{
    37  		tx:      tx,
    38  		options: options,
    39  		iter:    tx.db.Index.bTree.getWithDefault(b.Id).btree.Iter(),
    40  	}
    41  
    42  	if options.Reverse {
    43  		iterator.iter.Last()
    44  	} else {
    45  		iterator.iter.First()
    46  	}
    47  
    48  	return iterator
    49  }
    50  
    51  func (it *Iterator) Rewind() bool {
    52  	if it.options.Reverse {
    53  		return it.iter.Last()
    54  	} else {
    55  		return it.iter.First()
    56  	}
    57  }
    58  
    59  func (it *Iterator) Seek(key []byte) bool {
    60  	return it.iter.Seek(&Item{key: key})
    61  }
    62  
    63  func (it *Iterator) Next() bool {
    64  	if it.options.Reverse {
    65  		return it.iter.Prev()
    66  	} else {
    67  		return it.iter.Next()
    68  	}
    69  }
    70  
    71  func (it *Iterator) Valid() bool {
    72  	return it.iter.Item() != nil
    73  }
    74  
    75  func (it *Iterator) Key() []byte {
    76  	return it.iter.Item().key
    77  }
    78  
    79  func (it *Iterator) Value() ([]byte, error) {
    80  	return it.tx.db.getValueByRecord(it.iter.Item().record)
    81  }