github.com/turingchain2020/turingchain@v1.1.21/common/db/mvcc_iter.go (about)

     1  // Copyright Turing Corp. 2018 All Rights Reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package db
     6  
     7  import (
     8  	"bytes"
     9  
    10  	"github.com/turingchain2020/turingchain/types"
    11  )
    12  
    13  //MVCCIter mvcc迭代器版本
    14  //支持db 原生迭代器接口
    15  //为了支持快速迭代，我这里采用了复制数据的做法
    16  type MVCCIter struct {
    17  	*MVCCHelper
    18  }
    19  
    20  //NewMVCCIter new
    21  func NewMVCCIter(db DB) *MVCCIter {
    22  	return &MVCCIter{MVCCHelper: NewMVCC(db)}
    23  }
    24  
    25  //AddMVCC add
    26  func (m *MVCCIter) AddMVCC(kvs []*types.KeyValue, hash []byte, prevHash []byte, version int64) ([]*types.KeyValue, error) {
    27  	kvlist, err := m.MVCCHelper.AddMVCC(kvs, hash, prevHash, version)
    28  	if err != nil {
    29  		return nil, err
    30  	}
    31  	//添加last
    32  	for _, v := range kvs {
    33  		last := getLastKey(v.Key)
    34  		kv := &types.KeyValue{Key: last, Value: v.Value}
    35  		kvlist = append(kvlist, kv)
    36  	}
    37  	return kvlist, nil
    38  }
    39  
    40  //DelMVCC del
    41  func (m *MVCCIter) DelMVCC(hash []byte, version int64, strict bool) ([]*types.KeyValue, error) {
    42  	kvs, err := m.GetDelKVList(version)
    43  	if err != nil {
    44  		return nil, err
    45  	}
    46  	kvlist, err := m.MVCCHelper.delMVCC(kvs, hash, version, strict)
    47  	if err != nil {
    48  		return nil, err
    49  	}
    50  	//更新last, 读取上次版本的 lastv值，更新last
    51  	for _, v := range kvs {
    52  		if version > 0 {
    53  			lastv, err := m.GetV(v.Key, version-1)
    54  			if err == types.ErrNotFound {
    55  				kvlist = append(kvlist, &types.KeyValue{Key: getLastKey(v.Key)})
    56  				continue
    57  			}
    58  			if err != nil {
    59  				return nil, err
    60  			}
    61  			kvlist = append(kvlist, &types.KeyValue{Key: getLastKey(v.Key), Value: lastv})
    62  		}
    63  	}
    64  	return kvlist, nil
    65  }
    66  
    67  //Iterator 迭代
    68  func (m *MVCCIter) Iterator(start, end []byte, reserver bool) Iterator {
    69  	if start == nil {
    70  		start = mvccLast
    71  	} else {
    72  		start = getLastKey(start)
    73  	}
    74  	if end != nil {
    75  		end = getLastKey(end)
    76  	} else {
    77  		end = bytesPrefix(start)
    78  	}
    79  	return &mvccIt{m.db.Iterator(start, end, reserver)}
    80  }
    81  
    82  type mvccIt struct {
    83  	Iterator
    84  }
    85  
    86  //Prefix 前缀
    87  func (dbit *mvccIt) Prefix() []byte {
    88  	return mvccLast
    89  }
    90  
    91  //Key key
    92  func (dbit *mvccIt) Key() []byte {
    93  	key := dbit.Iterator.Key()
    94  	if bytes.HasPrefix(key, dbit.Prefix()) {
    95  		return key[len(dbit.Prefix()):]
    96  	}
    97  	return nil
    98  }
    99  
   100  //Valid 检查合法性
   101  func (dbit *mvccIt) Valid() bool {
   102  	if !dbit.Iterator.Valid() {
   103  		return false
   104  	}
   105  	return dbit.Key() != nil
   106  }