all: clean up and proerly abstract database access
This commit is contained in:
Péter Szilágyi
298
ethdb/memorydb/memorydb.go
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298
ethdb/memorydb/memorydb.go
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@ -0,0 +1,298 @@
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// Copyright 2014 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package memorydb implements the key-value database layer based on memory maps.
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package memorydb
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import (
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"errors"
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"sort"
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"strings"
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"sync"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/ethdb"
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)
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var (
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// errMemorydbClosed is returned if a memory database was already closed at the
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// invocation of a data access operation.
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errMemorydbClosed = errors.New("database closed")
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// errMemorydbNotFound is returned if a key is requested that is not found in
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// the provided memory database.
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errMemorydbNotFound = errors.New("not found")
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)
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// MemoryDatabase is an ephemeral key-value store. Apart from basic data storage
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// functionality it also supports batch writes and iterating over the keyspace in
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// binary-alphabetical order.
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type MemoryDatabase struct {
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db map[string][]byte
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lock sync.RWMutex
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}
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// New returns a wrapped map with all the required database interface methods
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// implemented.
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func New() *MemoryDatabase {
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return &MemoryDatabase{
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db: make(map[string][]byte),
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}
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}
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// NewWithCap returns a wrapped map pre-allocated to the provided capcity with
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// all the required database interface methods implemented.
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func NewWithCap(size int) *MemoryDatabase {
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return &MemoryDatabase{
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db: make(map[string][]byte, size),
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}
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}
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// Close deallocates the internal map and ensures any consecutive data access op
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// failes with an error.
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func (db *MemoryDatabase) Close() error {
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db.lock.Lock()
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defer db.lock.Unlock()
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db.db = nil
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return nil
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}
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// Has retrieves if a key is present in the key-value store.
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func (db *MemoryDatabase) Has(key []byte) (bool, error) {
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db.lock.RLock()
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defer db.lock.RUnlock()
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if db.db == nil {
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return false, errMemorydbClosed
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}
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_, ok := db.db[string(key)]
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return ok, nil
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}
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// Get retrieves the given key if it's present in the key-value store.
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func (db *MemoryDatabase) Get(key []byte) ([]byte, error) {
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db.lock.RLock()
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defer db.lock.RUnlock()
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if db.db == nil {
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return nil, errMemorydbClosed
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}
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if entry, ok := db.db[string(key)]; ok {
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return common.CopyBytes(entry), nil
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}
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return nil, errMemorydbNotFound
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}
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// Put inserts the given value into the key-value store.
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func (db *MemoryDatabase) Put(key []byte, value []byte) error {
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db.lock.Lock()
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defer db.lock.Unlock()
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if db.db == nil {
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return errMemorydbClosed
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}
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db.db[string(key)] = common.CopyBytes(value)
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return nil
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}
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// Delete removes the key from the key-value store.
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func (db *MemoryDatabase) Delete(key []byte) error {
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db.lock.Lock()
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defer db.lock.Unlock()
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if db.db == nil {
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return errMemorydbClosed
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}
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delete(db.db, string(key))
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return nil
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}
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// NewBatch creates a write-only key-value store that buffers changes to its host
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// database until a final write is called.
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func (db *MemoryDatabase) NewBatch() ethdb.Batch {
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return &memoryBatch{
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db: db,
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}
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}
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// NewIterator creates a binary-alphabetical iterator over the entire keyspace
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// contained within the memory database.
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func (db *MemoryDatabase) NewIterator() ethdb.Iterator {
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return db.NewIteratorWithPrefix(nil)
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}
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// NewIteratorWithPrefix creates a binary-alphabetical iterator over a subset
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// of database content with a particular key prefix.
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func (db *MemoryDatabase) NewIteratorWithPrefix(prefix []byte) ethdb.Iterator {
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db.lock.RLock()
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defer db.lock.RUnlock()
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var (
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pr = string(prefix)
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keys = make([]string, 0, len(db.db))
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values = make([][]byte, 0, len(db.db))
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)
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// Collect the keys from the memory database corresponding to the given prefix
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for key := range db.db {
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if strings.HasPrefix(key, pr) {
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keys = append(keys, key)
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}
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}
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// Sort the items and retrieve the associated values
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sort.Strings(keys)
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for _, key := range keys {
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values = append(values, db.db[key])
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}
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return &memoryIterator{
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keys: keys,
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values: values,
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}
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}
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// Stat returns a particular internal stat of the database.
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func (db *MemoryDatabase) Stat(property string) (string, error) {
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return "", errors.New("unknown property")
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}
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// Compact is not supported on a memory database.
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func (db *MemoryDatabase) Compact(start []byte, limit []byte) error {
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return errors.New("unsupported operation")
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}
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// Len returns the number of entries currently present in the memory database.
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//
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// Note, this method is only used for testing (i.e. not public in general) and
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// does not have explicit checks for closed-ness to allow simpler testing code.
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func (db *MemoryDatabase) Len() int {
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db.lock.RLock()
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defer db.lock.RUnlock()
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return len(db.db)
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}
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// keyvalue is a key-value tuple tagged with a deletion field to allow creating
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// memory-database write batches.
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type keyvalue struct {
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key []byte
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value []byte
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delete bool
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}
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// memoryBatch is a write-only memory batch that commits changes to its host
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// database when Write is called. A batch cannot be used concurrently.
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type memoryBatch struct {
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db *MemoryDatabase
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writes []keyvalue
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size int
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}
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// Put inserts the given value into the batch for later committing.
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func (b *memoryBatch) Put(key, value []byte) error {
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b.writes = append(b.writes, keyvalue{common.CopyBytes(key), common.CopyBytes(value), false})
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b.size += len(value)
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return nil
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}
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// Delete inserts the a key removal into the batch for later committing.
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func (b *memoryBatch) Delete(key []byte) error {
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b.writes = append(b.writes, keyvalue{common.CopyBytes(key), nil, true})
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b.size += 1
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return nil
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}
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// ValueSize retrieves the amount of data queued up for writing.
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func (b *memoryBatch) ValueSize() int {
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return b.size
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}
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// Write flushes any accumulated data to the memory database.
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func (b *memoryBatch) Write() error {
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b.db.lock.Lock()
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defer b.db.lock.Unlock()
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for _, keyvalue := range b.writes {
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if keyvalue.delete {
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delete(b.db.db, string(keyvalue.key))
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continue
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}
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b.db.db[string(keyvalue.key)] = keyvalue.value
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}
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return nil
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}
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// Reset resets the batch for reuse.
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func (b *memoryBatch) Reset() {
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b.writes = b.writes[:0]
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b.size = 0
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}
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// memoryIterator can walk over the (potentially partial) keyspace of a memory
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// key value store. Internally it is a deep copy of the entire iterated state,
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// sorted by keys.
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type memoryIterator struct {
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inited bool
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keys []string
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values [][]byte
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}
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// Next moves the iterator to the next key/value pair. It returns whether the
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// iterator is exhausted.
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func (it *memoryIterator) Next() bool {
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// If the iterator was not yet initialized, do it now
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if !it.inited {
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it.inited = true
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return len(it.keys) > 0
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}
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// Iterator already initialize, advance it
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if len(it.keys) > 0 {
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it.keys = it.keys[1:]
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it.values = it.values[1:]
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}
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return len(it.keys) > 0
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}
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// Error returns any accumulated error. Exhausting all the key/value pairs
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// is not considered to be an error. A memory iterator cannot encounter errors.
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func (it *memoryIterator) Error() error {
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return nil
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}
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// Key returns the key of the current key/value pair, or nil if done. The caller
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// should not modify the contents of the returned slice, and its contents may
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// change on the next call to Next.
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func (it *memoryIterator) Key() []byte {
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if len(it.keys) > 0 {
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return []byte(it.keys[0])
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}
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return nil
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}
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// Value returns the value of the current key/value pair, or nil if done. The
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// caller should not modify the contents of the returned slice, and its contents
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// may change on the next call to Next.
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func (it *memoryIterator) Value() []byte {
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if len(it.values) > 0 {
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return it.values[0]
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}
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return nil
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}
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// Release releases associated resources. Release should always succeed and can
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// be called multiple times without causing error.
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func (it *memoryIterator) Release() {
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it.keys, it.values = nil, nil
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}
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100
ethdb/memorydb/memorydb_test.go
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100
ethdb/memorydb/memorydb_test.go
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@ -0,0 +1,100 @@
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// Copyright 2019 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package memorydb
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import (
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"bytes"
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"testing"
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)
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// Tests that key-value iteration on top of a memory database works.
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func TestMemoryDBIterator(t *testing.T) {
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tests := []struct {
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content map[string]string
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prefix string
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order []string
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}{
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// Empty databases should be iterable
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{map[string]string{}, "", nil},
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{map[string]string{}, "non-existent-prefix", nil},
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// Single-item databases should be iterable
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{map[string]string{"key": "val"}, "", []string{"key"}},
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{map[string]string{"key": "val"}, "k", []string{"key"}},
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{map[string]string{"key": "val"}, "l", nil},
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// Multi-item databases should be fully iterable
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{
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map[string]string{"k1": "v1", "k5": "v5", "k2": "v2", "k4": "v4", "k3": "v3"},
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"",
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[]string{"k1", "k2", "k3", "k4", "k5"},
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},
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{
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map[string]string{"k1": "v1", "k5": "v5", "k2": "v2", "k4": "v4", "k3": "v3"},
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"k",
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[]string{"k1", "k2", "k3", "k4", "k5"},
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},
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{
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map[string]string{"k1": "v1", "k5": "v5", "k2": "v2", "k4": "v4", "k3": "v3"},
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"l",
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nil,
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},
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// Multi-item databases should be prefix-iterable
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{
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map[string]string{
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"ka1": "va1", "ka5": "va5", "ka2": "va2", "ka4": "va4", "ka3": "va3",
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"kb1": "vb1", "kb5": "vb5", "kb2": "vb2", "kb4": "vb4", "kb3": "vb3",
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},
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"ka",
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[]string{"ka1", "ka2", "ka3", "ka4", "ka5"},
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},
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{
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map[string]string{
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"ka1": "va1", "ka5": "va5", "ka2": "va2", "ka4": "va4", "ka3": "va3",
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"kb1": "vb1", "kb5": "vb5", "kb2": "vb2", "kb4": "vb4", "kb3": "vb3",
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},
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"kc",
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nil,
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},
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}
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for i, tt := range tests {
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// Create the key-value data store
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db := New()
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for key, val := range tt.content {
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if err := db.Put([]byte(key), []byte(val)); err != nil {
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t.Fatalf("test %d: failed to insert item %s:%s into database: %v", i, key, val, err)
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}
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}
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// Iterate over the database with the given configs and verify the results
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it, idx := db.NewIteratorWithPrefix([]byte(tt.prefix)), 0
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for it.Next() {
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if !bytes.Equal(it.Key(), []byte(tt.order[idx])) {
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t.Errorf("test %d: item %d: key mismatch: have %s, want %s", i, idx, string(it.Key()), tt.order[idx])
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}
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if !bytes.Equal(it.Value(), []byte(tt.content[tt.order[idx]])) {
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t.Errorf("test %d: item %d: value mismatch: have %s, want %s", i, idx, string(it.Value()), tt.content[tt.order[idx]])
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}
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idx++
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}
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if err := it.Error(); err != nil {
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t.Errorf("test %d: iteration failed: %v", i, err)
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}
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if idx != len(tt.order) {
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t.Errorf("test %d: iteration terminated prematurely: have %d, want %d", i, idx, len(tt.order))
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}
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}
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}
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