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// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.
package db
import (
"encoding/json"
"io/ioutil"
"os"
"sync"
"github.com/dexon-foundation/dexon-consensus/common"
"github.com/dexon-foundation/dexon-consensus/core/types"
)
type blockSeqIterator struct {
idx int
db *MemBackedDB
}
// NextBlock implemenets BlockIterator.NextBlock method.
func (seq *blockSeqIterator) NextBlock() (types.Block, error) {
curIdx := seq.idx
seq.idx++
return seq.db.getBlockByIndex(curIdx)
}
// MemBackedDB is a memory backed DB implementation.
type MemBackedDB struct {
blocksMutex sync.RWMutex
blockHashSequence common.Hashes
blocksByHash map[common.Hash]*types.Block
persistantFilePath string
}
// NewMemBackedDB initialize a memory-backed database.
func NewMemBackedDB(persistantFilePath ...string) (
dbInst *MemBackedDB, err error) {
dbInst = &MemBackedDB{
blockHashSequence: common.Hashes{},
blocksByHash: make(map[common.Hash]*types.Block),
}
if len(persistantFilePath) == 0 || len(persistantFilePath[0]) == 0 {
return
}
dbInst.persistantFilePath = persistantFilePath[0]
buf, err := ioutil.ReadFile(dbInst.persistantFilePath)
if err != nil {
if !os.IsNotExist(err) {
// Something unexpected happened.
return
}
// It's expected behavior that file doesn't exists, we should not
// report error on it.
err = nil
return
}
// Init this instance by file content, it's a temporary way
// to export those private field for JSON encoding.
toLoad := struct {
Sequence common.Hashes
ByHash map[common.Hash]*types.Block
}{}
err = json.Unmarshal(buf, &toLoad)
if err != nil {
return
}
dbInst.blockHashSequence = toLoad.Sequence
dbInst.blocksByHash = toLoad.ByHash
return
}
// HasBlock returns wheter or not the DB has a block identified with the hash.
func (m *MemBackedDB) HasBlock(hash common.Hash) bool {
m.blocksMutex.RLock()
defer m.blocksMutex.RUnlock()
_, ok := m.blocksByHash[hash]
return ok
}
// GetBlock returns a block given a hash.
func (m *MemBackedDB) GetBlock(hash common.Hash) (types.Block, error) {
m.blocksMutex.RLock()
defer m.blocksMutex.RUnlock()
return m.internalGetBlock(hash)
}
func (m *MemBackedDB) internalGetBlock(hash common.Hash) (types.Block, error) {
b, ok := m.blocksByHash[hash]
if !ok {
return types.Block{}, ErrBlockDoesNotExist
}
return *b, nil
}
// PutBlock inserts a new block into the database.
func (m *MemBackedDB) PutBlock(block types.Block) error {
if m.HasBlock(block.Hash) {
return ErrBlockExists
}
m.blocksMutex.Lock()
defer m.blocksMutex.Unlock()
m.blockHashSequence = append(m.blockHashSequence, block.Hash)
m.blocksByHash[block.Hash] = &block
return nil
}
// UpdateBlock updates a block in the database.
func (m *MemBackedDB) UpdateBlock(block types.Block) error {
if !m.HasBlock(block.Hash) {
return ErrBlockDoesNotExist
}
m.blocksMutex.Lock()
defer m.blocksMutex.Unlock()
m.blocksByHash[block.Hash] = &block
return nil
}
// Close implement Closer interface, which would release allocated resource.
func (m *MemBackedDB) Close() (err error) {
// Save internal state to a pretty-print json file. It's a temporary way
// to dump private file via JSON encoding.
if len(m.persistantFilePath) == 0 {
return
}
m.blocksMutex.RLock()
defer m.blocksMutex.RUnlock()
toDump := struct {
Sequence common.Hashes
ByHash map[common.Hash]*types.Block
}{
Sequence: m.blockHashSequence,
ByHash: m.blocksByHash,
}
// Dump to JSON with 2-space indent.
buf, err := json.Marshal(&toDump)
if err != nil {
return
}
err = ioutil.WriteFile(m.persistantFilePath, buf, 0644)
return
}
func (m *MemBackedDB) getBlockByIndex(idx int) (types.Block, error) {
m.blocksMutex.RLock()
defer m.blocksMutex.RUnlock()
if idx >= len(m.blockHashSequence) {
return types.Block{}, ErrIterationFinished
}
hash := m.blockHashSequence[idx]
return m.internalGetBlock(hash)
}
// GetAllBlocks implement Reader.GetAllBlocks method, which allows caller
// to retrieve all blocks in DB.
func (m *MemBackedDB) GetAllBlocks() (BlockIterator, error) {
return &blockSeqIterator{db: m}, nil
}
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