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/*
Manage a deduplicated versionned backups repository.
Sample repository:
```
repo/
├── 00000/
│ ├── chunks/
│ │ ├── 000000000000000
│ │ ├── 000000000000001
│ │ ├── 000000000000002
│ │ ├── 000000000000003
│ ├── files
│ └── recipe
└── 00001/
├── chunks/
│ ├── 000000000000000
│ ├── 000000000000001
├── files
└── recipe
```
*/
package main
import (
"encoding/gob"
"fmt"
"hash"
"io"
"io/fs"
"log"
"os"
"path"
"path/filepath"
"github.com/chmduquesne/rollinghash/rabinkarp64"
)
var chunkSize = 8 << 10
type File struct {
Path string
Size int64
}
type ChunkId struct {
Ver int
Idx uint64
}
type Chunk struct {
Id ChunkId
Value []byte
}
func Commit(source string, repo string) {
versions := LoadVersions(repo)
newVersion := len(versions)
newPath := path.Join(repo, fmt.Sprintf("%05d", newVersion))
newChunkPath := path.Join(newPath, "chunks")
// newFilesPath := path.Join(newPath, "files")
os.Mkdir(newPath, 0775)
os.Mkdir(newChunkPath, 0775)
newChunks := make(chan []byte, 16)
oldChunks := make(chan Chunk, 16)
files := ListFiles(source)
go LoadChunks(versions, oldChunks)
go ReadFiles(files, newChunks)
hashes := HashChunks(oldChunks)
MatchChunks(newChunks, hashes)
// StoreChunks(newChunkPath, newChunks)
// StoreFiles(newFilesPath, files)
fmt.Println(files)
}
func LoadVersions(repo string) []string {
versions := make([]string, 0)
files, err := os.ReadDir(repo)
if err != nil {
log.Fatalln(err)
}
for _, f := range files {
if !f.IsDir() {
continue
}
versions = append(versions, path.Join(repo, f.Name()))
}
return versions
}
func ListFiles(path string) []File {
var files []File
err := filepath.Walk(path,
func(p string, i fs.FileInfo, err error) error {
if err != nil {
log.Println(err)
return err
}
if i.IsDir() {
return nil
}
files = append(files, File{p, i.Size()})
return nil
})
if err != nil {
log.Println(err)
}
return files
}
func ReadFiles(files []File, chunks chan<- []byte) {
var buff []byte
var prev, read = chunkSize, 0
for _, f := range files {
file, err := os.Open(f.Path)
if err != nil {
log.Println(err)
continue
}
for err != io.EOF {
if prev == chunkSize {
buff = make([]byte, chunkSize)
prev, err = file.Read(buff)
} else {
read, err = file.Read(buff[prev:])
prev += read
}
if err != nil && err != io.EOF {
log.Println(err)
}
if prev == chunkSize {
chunks <- buff
}
}
}
chunks <- buff
close(chunks)
}
func StoreFiles(dest string, files []File) {
err := writeFile(dest, files)
if err != nil {
log.Println(err)
}
}
func LoadFiles(path string) []File {
files := make([]File, 0)
err := readFile(path, &files)
if err != nil {
log.Println(err)
}
return files
}
func PrintChunks(chunks <-chan []byte) {
for c := range chunks {
fmt.Println(c)
}
}
func StoreChunks(dest string, chunks <-chan []byte) {
i := 0
for c := range chunks {
path := path.Join(dest, fmt.Sprintf("%015d", i))
err := os.WriteFile(path, c, 0664)
if err != nil {
log.Println(err)
}
i++
}
}
func LoadChunks(versions []string, chunks chan<- Chunk) {
for i, v := range versions {
p := path.Join(v, "chunks")
entries, err := os.ReadDir(p)
if err != nil {
log.Printf("Error reading version '%05d' in '%s' chunks: %s", i, v, err)
}
for j, e := range entries {
if e.IsDir() {
continue
}
f := path.Join(p, e.Name())
buff, err := os.ReadFile(f)
if err != nil {
log.Printf("Error reading chunk '%s': %s", f, err.Error())
}
c := Chunk{
Id: ChunkId{
Ver: i,
Idx: uint64(j),
},
Value: buff,
}
chunks <- c
}
}
close(chunks)
}
func HashChunks(chunks <-chan Chunk) map[uint64]ChunkId {
hashes := make(map[uint64]ChunkId)
hasher := hash.Hash64(rabinkarp64.New())
for c := range chunks {
hasher.Reset()
hasher.Write(c.Value)
h := hasher.Sum64()
hashes[h] = c.Id
}
return hashes
}
func MatchChunks(chunks <-chan []byte, hashes map[uint64]ChunkId) {
hasher := rabinkarp64.New()
hasher.Write(<-chunks)
var i uint64
var offset int
var prefill int
var postfill int
for c := range chunks {
// Pre fill the window with the rest of the previous chunk
for prefill = 0; prefill < offset; prefill++ {
hasher.Roll(c[prefill])
}
// Fill the window with the current chunk and match hash byte by byte
for ; offset < len(c); offset++ {
h := hasher.Sum64()
chunk, exists := hashes[h]
if exists {
fmt.Printf("Found existing chunk: New{id:%d, offset:%d} Old%d\n", i, offset, chunk)
break
}
hasher.Roll(c[offset])
}
// Fill the window with the rest of the current chunk if it matched early
for postfill = offset; postfill < len(c); postfill++ {
hasher.Roll(c[postfill])
}
offset %= chunkSize
i++
}
}
func writeFile(filePath string, object interface{}) error {
file, err := os.Create(filePath)
if err == nil {
encoder := gob.NewEncoder(file)
encoder.Encode(object)
}
file.Close()
return err
}
func readFile(filePath string, object interface{}) error {
file, err := os.Open(filePath)
if err == nil {
decoder := gob.NewDecoder(file)
err = decoder.Decode(object)
}
file.Close()
return err
}
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