path: root/blockdb/level-db.go

// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core 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-core 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-core library. If not, see
// <http://www.gnu.org/licenses/>.

package blockdb

import (
    "encoding/json"

    "github.com/syndtr/goleveldb/leveldb"
    "github.com/syndtr/goleveldb/leveldb/opt"

    "github.com/dexon-foundation/dexon-consensus-core/common"
    "github.com/dexon-foundation/dexon-consensus-core/core/types"
)

// LevelDBBackedBlockDB is a leveldb backed BlockDB implementation.
type LevelDBBackedBlockDB struct {
    db *leveldb.DB
}

// NewLevelDBBackedBlockDB initialize a leveldb-backed block database.
func NewLevelDBBackedBlockDB(
    path string) (lvl *LevelDBBackedBlockDB, err error) {

    db, err := leveldb.OpenFile(path, nil)
    if err != nil {
        return
    }
    lvl = &LevelDBBackedBlockDB{db: db}
    return
}

// Close implement Closer interface, which would release allocated resource.
func (lvl *LevelDBBackedBlockDB) Close() error {
    return lvl.db.Close()
}

// Has implements the Reader.Has method.
func (lvl *LevelDBBackedBlockDB) Has(hash common.Hash) bool {
    exists, err := lvl.db.Has([]byte(hash[:]), nil)
    if err != nil {
        // TODO(missionliao): Modify the interface to return error.
        panic(err)
    }
    return exists
}

// Get implements the Reader.Get method.
func (lvl *LevelDBBackedBlockDB) Get(
    hash common.Hash) (block types.Block, err error) {

    queried, err := lvl.db.Get([]byte(hash[:]), nil)
    if err != nil {
        if err == leveldb.ErrNotFound {
            err = ErrBlockDoesNotExist
        }
        return
    }
    err = json.Unmarshal(queried, &block)
    if err != nil {
        return
    }
    return
}

// Update implements the Writer.Update method.
func (lvl *LevelDBBackedBlockDB) Update(block types.Block) (err error) {
    // NOTE: we didn't handle changes of block hash (and it
    //       should not happen).
    marshaled, err := json.Marshal(&block)
    if err != nil {
        return
    }

    if !lvl.Has(block.Hash) {
        err = ErrBlockDoesNotExist
        return
    }
    err = lvl.db.Put(
        []byte(block.Hash[:]),
        marshaled,
        &opt.WriteOptions{
            Sync: true,
        })
    if err != nil {
        return
    }
    return
}

// Put implements the Writer.Put method.
func (lvl *LevelDBBackedBlockDB) Put(block types.Block) (err error) {
    marshaled, err := json.Marshal(&block)
    if err != nil {
        return
    }
    if lvl.Has(block.Hash) {
        err = ErrBlockExists
        return
    }
    syncedOpt := &opt.WriteOptions{
        // We should force to sync for each write, it's safer
        // from crash.
        Sync: true,
    }
    err = lvl.db.Put(
        []byte(block.Hash[:]),
        marshaled,
        syncedOpt)
    if err != nil {
        return
    }
    return
}

// GetAll implements Reader.GetAll method, which allows callers
// to retrieve all blocks in DB.
func (lvl *LevelDBBackedBlockDB) GetAll() (BlockIterator, error) {
    // TODO (mission): Implement this part via goleveldb's iterator.
    return nil, ErrNotImplemented
}