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/* Copyright (C) 2021 Nicolas Peugnet <n.peugnet@free.fr>
This file is part of dna-backup.
dna-backup is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
dna-backup is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with dna-backup. If not, see <https://www.gnu.org/licenses/>. */
package dna
import (
"bytes"
"encoding/gob"
"fmt"
"io"
"os"
"path/filepath"
"github.com/n-peugnet/dna-backup/export"
"github.com/n-peugnet/dna-backup/logger"
)
type Direction int
const (
Forward Direction = iota
Backward
)
type DnaDrive struct {
poolCount int
trackSize int
tracksPerPool int
pools []Pool
}
type Pool struct {
Data io.ReadWriteCloser
TrackCount int
}
type Header struct {
Chunks uint64
Recipe uint64
Files uint64
}
func New(
destination string,
poolCount int,
trackSize int,
tracksPerPool int,
) *DnaDrive {
pools := make([]Pool, poolCount)
os.MkdirAll(destination, 0755)
for i := range pools {
path := filepath.Join(destination, fmt.Sprintf("%02d", i))
file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
logger.Panic(err)
}
stat, err := file.Stat()
if err != nil {
logger.Panic(err)
}
pools[i] = Pool{file, int(stat.Size()) / trackSize}
}
return &DnaDrive{
poolCount: poolCount,
trackSize: trackSize,
tracksPerPool: tracksPerPool,
pools: pools,
}
}
func (d *DnaDrive) ExportVersion(end chan<- bool) export.Input {
rChunks, wChunks := io.Pipe()
rRecipe, wRecipe := io.Pipe()
rFiles, wFiles := io.Pipe()
version := export.Version{
Input: export.Input{
Chunks: wChunks,
Recipe: wRecipe,
Files: wFiles,
},
Output: export.Output{
Chunks: rChunks,
Recipe: rRecipe,
Files: rFiles,
},
}
go d.writeVersion(version.Output, end)
return version.Input
}
func (d *DnaDrive) writeVersion(output export.Output, end chan<- bool) {
var err error
var recipe, files, version bytes.Buffer
n := write(output.Chunks, d.pools[1:], d.trackSize, d.tracksPerPool, Forward)
_, err = io.Copy(&recipe, output.Recipe)
if err != nil {
logger.Error("dna export recipe ", err)
}
_, err = io.Copy(&files, output.Files)
if err != nil {
logger.Error("dna export files ", err)
}
header := Header{
uint64(n),
uint64(recipe.Len()),
uint64(files.Len()),
}
e := gob.NewEncoder(&version)
err = e.Encode(header)
if err != nil {
logger.Error("dna export version header: ", err)
}
logger.Debugf("version len %d", version.Len())
rest := int64(d.trackSize - version.Len())
logger.Debugf("version rest %d", rest)
n, err = io.CopyN(&version, &recipe, rest)
logger.Debugf("recipe copied in version %d", n)
rest -= n
logger.Debugf("version rest %d", rest)
if err == io.EOF && rest > 0 { // recipe is written to version but there is space left
n, err = io.CopyN(&version, &files, rest)
logger.Debugf("files copied in version %d", n)
rest -= n
logger.Debugf("version rest %d", rest)
if err == io.EOF && rest > 0 { // files is writtent to version but there is space left
// version.Write(make([]byte, rest))
} else if err != nil { // another error than EOF happened
logger.Error("dna export files: ", err)
} else { // files has not been fully written so we write what is left to pools
write(&files, d.pools[1:], d.trackSize, d.tracksPerPool, Backward)
}
} else if err != nil { // another error than EOF happened
logger.Error("dna export recipe: ", err)
} else { // recipe has not been fully written so we concat with files and write what is left to pools
io.Copy(&recipe, &files)
write(&recipe, d.pools[1:], d.trackSize, d.tracksPerPool, Backward)
}
write(&version, d.pools[:1], d.trackSize, d.tracksPerPool, Forward)
end <- true
}
func write(r io.Reader, pools []Pool, trackSize int, tracksPerPool int, direction Direction) int64 {
var err error
var i, n int
var count int64
if direction == Backward {
i = len(pools) - 1
}
for err != io.ErrUnexpectedEOF && err != io.EOF {
if pools[i].TrackCount == tracksPerPool {
if direction == Backward {
i--
} else {
i++
}
if i < 0 || i >= len(pools) {
logger.Panic("dna export: no space left")
}
continue
}
buf := make([]byte, trackSize)
n, err = io.ReadFull(r, buf)
if err == io.EOF {
break
}
logger.Debug("written track:", n, err)
count += int64(n)
n, errw := pools[i].Data.Write(buf)
if errw != nil {
logger.Error("dna export: pool %d: %d/%d bytes written: %s", i, n, len(buf), errw)
}
pools[i].TrackCount++
}
return count
}
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