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db_file.go
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db_file.go
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package storage
import (
"errors"
"fmt"
"github.com/edsrzf/mmap-go"
"hash/crc32"
"io/ioutil"
"os"
"sort"
"strconv"
"strings"
)
const (
// FilePerm 默认的创建文件权限 permission
FilePerm = 0644
// DBFileFormatName default数据文件名称格式化
DBFileFormatName = "%09d.data"
//PathSeparator the default path separator
PathSeparator = string(os.PathSeparator)
)
var (
// ErrEmptyEntry the entry is empty
ErrEmptyEntry = errors.New("storage/db_file: entry or the Key of entry is empty")
)
//FileRWMethod 文件数据读写方式
type FileRWMethod uint8
const (
// FileIO 表示文件数据读写使用系统标准IO
FileIO FileRWMethod = iota
// MMap 表示文件数据读写使用Mmap
// MMap 指的是将文件或其他设备映射至内存 via https://en.wikipedia.org/wiki/Mmap
MMap
)
type DBFile struct {
Id uint32
path string
File *os.File
mmap mmap.MMap
Offset int64
method FileRWMethod
}
// NewDBFile 新建一个数据读写文件,如果是MMap,则需要Truncate文件并进行加载
func NewDBFile(path string, fileId uint32, method FileRWMethod, blockSize int64) (*DBFile, error) {
filePath := path + PathSeparator + fmt.Sprintf(DBFileFormatName, fileId)
file, err := os.OpenFile(filePath, os.O_CREATE|os.O_RDWR, FilePerm)
if err != nil {
return nil, err
}
df := &DBFile{Id: fileId, path: path, Offset: 0, method: method}
if method == FileIO {
df.File = file
} else {
if err = file.Truncate(blockSize); err != nil {
return nil, err
}
m, err := mmap.Map(file, os.O_RDWR, 0)
if err != nil {
return nil, err
}
df.mmap = m
}
return df, nil
}
// Read 从数据文件读数据, offset是读的起始位置
func (df *DBFile) Read(offset int64) (e *Entry, err error) {
var buf []byte
if buf, err = df.readBuf(offset, int64(entryHeaderSize)); err != nil {
return
}
if e, err = Decode(buf); err != nil {
return
}
offset += entryHeaderSize
if e.Meta.KeySize > 0 {
var key []byte
if key, err = df.readBuf(offset, int64(e.Meta.KeySize)); err != nil {
return
}
e.Meta.Key = key
}
offset += int64(e.Meta.KeySize)
if e.Meta.ValueSize > 0 {
var val []byte
if val, err = df.readBuf(offset, int64(e.Meta.ValueSize)); err != nil {
return
}
e.Meta.Value = val
}
offset += int64(e.Meta.ValueSize)
if e.Meta.ExtraSize > 0 {
var val []byte
if val, err = df.readBuf(offset, int64(e.Meta.ExtraSize)); err != nil {
return
}
e.Meta.Extra = val
}
checkCrc := crc32.ChecksumIEEE(e.Meta.Value)
if checkCrc != e.crc32 {
return nil, ErrInvalidCrc
}
return
}
func (df *DBFile) readBuf(offset int64, n int64) ([]byte, error) {
buf := make([]byte, n)
if df.method == FileIO {
_, err := df.File.ReadAt(buf, offset)
if err != nil {
return nil, err
}
}
if df.method == MMap && offset <= int64(len(df.mmap)) {
copy(buf, df.mmap[offset:])
}
return buf, nil
}
// Write 从文件的offset处开始写数据
func (df *DBFile) Write(e *Entry) error {
if e == nil || e.Meta.KeySize == 0 {
return ErrEmptyEntry
}
method := df.method
writeOff := df.Offset
encVal, err := e.Encode()
if err != nil {
return err
}
if method == FileIO {
if _, err := df.File.WriteAt(encVal, writeOff); err != nil {
return err
}
}
if method == MMap {
copy(df.mmap[writeOff:], encVal)
}
df.Offset += int64(e.Size())
return nil
}
// Close 读写后进行关闭擦偶走
// sync 关闭前是否持久化数据
func (df *DBFile) Close(sync bool) (err error) {
if sync {
err = df.Sync()
}
if df.File != nil {
err = df.File.Close()
}
if df.mmap != nil {
err = df.mmap.Unmap()
}
return
}
//Sync 数据持久化
func (df *DBFile) Sync() (err error) {
if df.File != nil {
err = df.File.Sync()
}
if df.mmap != nil {
err = df.mmap.Flush()
}
return
}
//Build 加载数据文件
func Build(path string, method FileRWMethod, blockSize int64) (map[uint32]*DBFile, uint32, error) {
dir, err := ioutil.ReadDir(path)
if err != nil {
return nil, 0, err
}
var fileIDs []int
for _, d := range dir {
if strings.HasSuffix(d.Name(), "data") {
splitNames := strings.Split(d.Name(), ".")
id, _ := strconv.Atoi(splitNames[0])
fileIDs = append(fileIDs, id)
}
}
sort.Ints(fileIDs)
var activeFileId uint32 = 0
archFiles := make(map[uint32]*DBFile)
if len(fileIDs) > 0 {
activeFileId = uint32(fileIDs[len(fileIDs)-1])
for i := 0; i < len(fileIDs)-1; i++ {
id := fileIDs[i]
file, err := NewDBFile(path, uint32(id), method, blockSize)
if err != nil {
return nil, activeFileId, err
}
archFiles[uint32(id)] = file
}
}
return archFiles, activeFileId, nil
}