316 lines
8.4 KiB
Go
316 lines
8.4 KiB
Go
// Copyright 2018 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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// Database 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 Database 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() *Database {
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return &Database{
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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) *Database {
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return &Database{
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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 *Database) 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 *Database) 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 *Database) 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 *Database) 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 *Database) 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 *Database) NewBatch() ethdb.Batch {
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return &batch{
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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 a subset
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// of database content with a particular key prefix, starting at a particular
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// initial key (or after, if it does not exist).
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func (db *Database) NewIterator(prefix []byte, start []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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st = string(append(prefix, start...))
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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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// and start
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for key := range db.db {
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if !strings.HasPrefix(key, pr) {
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continue
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}
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if key >= st {
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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 &iterator{
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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 *Database) 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, but there's no need either as
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// a memory database doesn't waste space anyway.
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func (db *Database) Compact(start []byte, limit []byte) error {
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return nil
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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 *Database) 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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// batch 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 batch struct {
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db *Database
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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 *batch) 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(key) + 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 *batch) 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 += len(key)
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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 *batch) 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 *batch) 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 *batch) 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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// Replay replays the batch contents.
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func (b *batch) Replay(w ethdb.KeyValueWriter) error {
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for _, keyvalue := range b.writes {
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if keyvalue.delete {
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if err := w.Delete(keyvalue.key); err != nil {
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return err
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}
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continue
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}
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if err := w.Put(keyvalue.key, keyvalue.value); err != nil {
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return err
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}
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}
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return nil
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}
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// iterator can walk over the (potentially partial) keyspace of a memory key
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// 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 iterator 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 *iterator) 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 *iterator) 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 *iterator) 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 *iterator) 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 *iterator) Release() {
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it.keys, it.values = nil, nil
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}
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