Add Backup() method

README.md

@@ -42,6 +42,9 @@ Other methods:
 ```go
 // Flush data to disk
 err = db.Flush()
+
+// Backup data to another file
+err = db.Backup("new/file/path")
 ```
 
 ## File structure
@@ -63,6 +66,6 @@ File is log stuctured list of commands:
 
 ## TODO
 
-- [ ] Implement `Copy()` method to copy store without deleted records
+- [ ] Add delete records test for `Backup()` method
 - [ ] Test [seekable zstd streams](https://github.com/SaveTheRbtz/zstd-seekable-format-go)
 - [ ] Implement optional separate index file to speedup store initialization

record.go

@@ -2,6 +2,7 @@ package zkv
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"encoding/binary"
 	"encoding/gob"
 	"io"
@@ -20,8 +21,17 @@ type Record struct {
 	ValueBytes []byte
 }
 
+func newRecordBytes(recordType RecordType, keyHash [sha256.Size224]byte, valueBytes []byte) (*Record, error) {
+	record := &Record{
+		Type:       recordType,
+		KeyHash:    keyHash,
+		ValueBytes: valueBytes}
+
+	return record, nil
+}
+
 func newRecord(recordType RecordType, key, value interface{}) (*Record, error) {
-	keyBytes, err := encode(key)
+	keyHash, err := hashInterface(key)
 	if err != nil {
 		return nil, err
 	}
@@ -31,12 +41,7 @@ func newRecord(recordType RecordType, key, value interface{}) (*Record, error) {
 		return nil, err
 	}
 
-	record := &Record{
-		Type:       recordType,
-		KeyHash:    hashBytes(keyBytes),
-		ValueBytes: valueBytes}
-
-	return record, nil
+	return newRecordBytes(recordType, keyHash, valueBytes)
 }
 
 func (r *Record) Marshal() ([]byte, error) {

zkv.go

@@ -2,6 +2,7 @@ package zkv
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"encoding/base64"
 	"fmt"
 	"io"
@@ -35,13 +36,13 @@ func OpenWithOptions(filePath string, options Options) (*Store, error) {
 	f, err := os.OpenFile(filePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
 	if err != nil {
 		f.Close()
-		return nil, fmt.Errorf("ошибка при открытии файла для записи: %v", err)
+		return nil, fmt.Errorf("open store file: %v", err)
 	}
 
 	compressor, err := zstd.NewWriter(f)
 	if err != nil {
 		f.Close()
-		return nil, fmt.Errorf("ошибка при инициализации компрессора: %v", err)
+		return nil, fmt.Errorf("compressor initialization: %v", err)
 	}
 
 	database := &Store{
@@ -59,14 +60,14 @@ func OpenWithOptions(filePath string, options Options) (*Store, error) {
 	readF, err := os.Open(filePath)
 	if err != nil {
 		f.Close()
-		return nil, fmt.Errorf("ошибка при открытии файла для чтения: %v", err)
+		return nil, fmt.Errorf("open file for indexing: %v", err)
 	}
 	defer readF.Close()
 
 	decompressor, err := zstd.NewReader(readF)
 	if err != nil {
 		f.Close()
-		return nil, fmt.Errorf("ошибка при инициализации декомпрессора: %v", err)
+		return nil, fmt.Errorf("decompressor initialization: %v", err)
 	}
 	defer decompressor.Close()
 
@@ -78,7 +79,7 @@ func OpenWithOptions(filePath string, options Options) (*Store, error) {
 		}
 		if err != nil {
 			f.Close()
-			return nil, fmt.Errorf("ошибка при чтении записи из файла: %v", err)
+			return nil, fmt.Errorf("read record error: %v", err)
 		}
 
 		switch record.Type {
@@ -157,6 +158,43 @@ func (s *Store) Flush() error {
 	return s.flush()
 }
 
+func (s *Store) BackupWithOptions(filePath string, newFileOptions Options) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	err := s.flush()
+	if err != nil {
+		return err
+	}
+
+	newStore, err := OpenWithOptions(filePath, newFileOptions)
+	if err != nil {
+		return err
+	}
+
+	for keyHashStr := range s.dataOffset {
+		var keyHash [sha256.Size224]byte
+		copy(keyHash[:], keyHashStr)
+
+		valueBytes, err := s.getGobBytes(keyHash)
+		if err != nil {
+			newStore.Close()
+			return err
+		}
+		err = newStore.setBytes(keyHash, valueBytes)
+		if err != nil {
+			newStore.Close()
+			return err
+		}
+	}
+
+	return newStore.Close()
+}
+
+func (s *Store) Backup(filePath string) error {
+	return s.BackupWithOptions(filePath, defaultOptions)
+}
+
 func (s *Store) Close() error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -174,6 +212,35 @@ func (s *Store) Close() error {
 	return s.file.Close()
 }
 
+func (s *Store) setBytes(keyHash [sha256.Size224]byte, valueBytes []byte) error {
+	record, err := newRecordBytes(RecordTypeSet, keyHash, valueBytes)
+	if err != nil {
+		return err
+	}
+
+	b, err := record.Marshal()
+	if err != nil {
+		return err
+	}
+
+	s.bufferDataOffset[string(record.KeyHash[:])] = int64(s.buffer.Len())
+
+	_, err = s.buffer.Write(b)
+	if err != nil {
+		return err
+	}
+
+	if s.buffer.Len() > s.options.BufferSize {
+		err = s.flush()
+
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (s *Store) set(key, value interface{}) error {
 	record, err := newRecord(RecordTypeSet, key, value)
 	if err != nil {
@@ -203,6 +270,64 @@ func (s *Store) set(key, value interface{}) error {
 	return nil
 }
 
+func (s *Store) getGobBytes(keyHash [sha256.Size224]byte) ([]byte, error) {
+	s.readOrderChan <- struct{}{}
+	defer func() { <-s.readOrderChan }()
+
+	offset, exists := s.bufferDataOffset[string(keyHash[:])]
+	if exists {
+		reader := bytes.NewReader(s.buffer.Bytes())
+
+		err := skip(reader, offset)
+		if err != nil {
+			return nil, err
+		}
+
+		_, record, err := readRecord(reader)
+		if err != nil {
+			return nil, err
+		}
+
+		return record.ValueBytes, nil
+	}
+
+	offset, exists = s.dataOffset[string(keyHash[:])]
+	if !exists {
+		return nil, ErrNotExists
+	}
+
+	readF, err := os.Open(s.filePath)
+	if err != nil {
+		return nil, err
+	}
+	defer readF.Close()
+
+	decompressor, err := zstd.NewReader(readF)
+	if err != nil {
+		return nil, err
+	}
+	defer decompressor.Close()
+
+	err = skip(decompressor, offset)
+	if err != nil {
+		return nil, err
+	}
+
+	_, record, err := readRecord(decompressor)
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(record.KeyHash[:], keyHash[:]) {
+		expectedHashStr := base64.StdEncoding.EncodeToString(keyHash[:])
+		gotHashStr := base64.StdEncoding.EncodeToString(record.KeyHash[:])
+		return nil, fmt.Errorf("wrong hash of offset %d: expected %s, got %s", offset, expectedHashStr, gotHashStr)
+	}
+
+	return record.ValueBytes, nil
+
+}
+
 func (s *Store) get(key, value interface{}) error {
 	s.readOrderChan <- struct{}{}
 	defer func() { <-s.readOrderChan }()
@@ -257,7 +382,9 @@ func (s *Store) get(key, value interface{}) error {
 	}
 
 	if !bytes.Equal(record.KeyHash[:], hashToFind[:]) {
-		return fmt.Errorf("wrong hash on this offset: expected %s, got %s", base64.StdEncoding.EncodeToString(hashToFind[:]), base64.StdEncoding.EncodeToString(record.KeyHash[:])) // TODO: заменить на константную ошибку
+		expectedHashStr := base64.StdEncoding.EncodeToString(hashToFind[:])
+		gotHashStr := base64.StdEncoding.EncodeToString(record.KeyHash[:])
+		return fmt.Errorf("wrong hash of offset %d: expected %s, got %s", offset, expectedHashStr, gotHashStr)
 	}
 
 	return decode(record.ValueBytes, value)

zkv_test.go

@@ -1,12 +1,40 @@
 package zkv
 
 import (
+	"bytes"
 	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
+func TestRecord(t *testing.T) {
+	buf := new(bytes.Buffer)
+
+	var records []Record
+
+	for i := 0; i < 10; i++ {
+		record, err := newRecord(RecordTypeSet, i, i)
+		assert.NoError(t, err)
+
+		records = append(records, *record)
+
+		b, err := record.Marshal()
+		assert.NoError(t, err)
+
+		_, err = buf.Write(b)
+		assert.NoError(t, err)
+	}
+
+	for i := 0; i < 10; i++ {
+		_, record, err := readRecord(buf)
+		assert.NoError(t, err)
+
+		assert.Equal(t, record.KeyHash, records[i].KeyHash)
+		assert.Equal(t, record.ValueBytes, records[i].ValueBytes)
+	}
+}
+
 func TestReadWriteBasic(t *testing.T) {
 	const filePath = "TestReadWriteBasic.zkv"
 	const recordCount = 100
@@ -207,3 +235,42 @@ func TestBufferRead(t *testing.T) {
 	assert.NoError(t, err)
 
 }
+
+func TestBackupBasic(t *testing.T) {
+	const filePath = "TestBackupBasic.zkv"
+	const newFilePath = "TestBackupBasic2.zkv"
+	const recordCount = 100
+	defer os.Remove(filePath)
+	defer os.Remove(newFilePath)
+
+	db, err := Open(filePath)
+	assert.NoError(t, err)
+
+	for i := 1; i <= recordCount; i++ {
+		err = db.Set(i, i)
+		assert.NoError(t, err)
+	}
+
+	err = db.Backup(newFilePath)
+	assert.NoError(t, err)
+
+	err = db.Close()
+	assert.NoError(t, err)
+
+	db, err = Open(newFilePath)
+	assert.NoError(t, err)
+
+	assert.Len(t, db.dataOffset, recordCount)
+
+	for i := 1; i <= recordCount; i++ {
+		var gotValue int
+
+		err = db.Get(i, &gotValue)
+		assert.NoError(t, err)
+		assert.Equal(t, i, gotValue)
+	}
+
+	err = db.Close()
+	assert.NoError(t, err)
+
+}