// This will show a simple stream encoder where we encode from
// a []io.Reader which contain a reader for each shard.
//
// Input and output can be exchanged with files, network streams
// or what may suit your needs.
func ExampleStreamEncoder() {
dataShards := 5
parityShards := 2
// Create a StreamEncoder with the number of data and
// parity shards.
rs, err := reedsolomon.NewStream(dataShards, parityShards)
if err != nil {
log.Fatal(err)
}
shardSize := 50000
// Create input data shards.
input := make([][]byte, dataShards)
for s := range input {
input[s] = make([]byte, shardSize)
fillRandom(input[s])
}
// Convert our buffers to io.Readers
readers := make([]io.Reader, dataShards)
for i := range readers {
readers[i] = io.Reader(bytes.NewBuffer(input[i]))
}
// Create our output io.Writers
out := make([]io.Writer, parityShards)
for i := range out {
out[i] = ioutil.Discard
}
// Encode from input to output.
err = rs.Encode(readers, out)
if err != nil {
log.Fatal(err)
}
fmt.Println("ok")
// OUTPUT: ok
}
func main() {
// Parse command line parameters.
flag.Parse()
args := flag.Args()
if len(args) != 1 {
fmt.Fprintf(os.Stderr, "Error: No input filename given\n")
flag.Usage()
os.Exit(1)
}
if *dataShards > 257 {
fmt.Fprintf(os.Stderr, "Error: Too many data shards\n")
os.Exit(1)
}
fname := args[0]
// Create encoding matrix.
enc, err := reedsolomon.NewStream(*dataShards, *parShards)
checkErr(err)
fmt.Println("Opening", fname)
f, err := os.Open(fname)
checkErr(err)
instat, err := f.Stat()
checkErr(err)
shards := *dataShards + *parShards
out := make([]*os.File, shards)
// Create the resulting files.
dir, file := filepath.Split(fname)
if *outDir != "" {
dir = *outDir
}
for i := range out {
outfn := fmt.Sprintf("%s.%d", file, i)
fmt.Println("Creating", outfn)
out[i], err = os.Create(filepath.Join(dir, outfn))
checkErr(err)
}
// Split into files.
data := make([]io.Writer, *dataShards)
for i := range data {
data[i] = out[i]
}
// Do the split
err = enc.Split(f, data, instat.Size())
checkErr(err)
// Close and re-open the files.
input := make([]io.Reader, *dataShards)
for i := range data {
out[i].Close()
f, err := os.Open(out[i].Name())
checkErr(err)
input[i] = f
defer f.Close()
}
// Create parity output writers
parity := make([]io.Writer, *parShards)
for i := range parity {
parity[i] = out[*dataShards+i]
defer out[*dataShards+i].Close()
}
// Encode parity
err = enc.Encode(input, parity)
checkErr(err)
fmt.Printf("File split into %d data + %d parity shards.\n", *dataShards, *parShards)
}
func main() {
// Parse flags
flag.Parse()
args := flag.Args()
if len(args) != 1 {
fmt.Fprintf(os.Stderr, "Error: No filenames given\n")
flag.Usage()
os.Exit(1)
}
fname := args[0]
// Create matrix
enc, err := reedsolomon.NewStream(*dataShards, *parShards)
checkErr(err)
// Open the inputs
shards, size, err := openInput(*dataShards, *parShards, fname)
checkErr(err)
// Verify the shards
ok, err := enc.Verify(shards)
if ok {
fmt.Println("No reconstruction needed")
} else {
fmt.Println("Verification failed. Reconstructing data")
shards, size, err = openInput(*dataShards, *parShards, fname)
checkErr(err)
// Create out destination writers
out := make([]io.Writer, len(shards))
for i := range out {
if shards[i] == nil {
dir, _ := filepath.Split(fname)
outfn := fmt.Sprintf("%s.%d", fname, i)
fmt.Println("Creating", outfn)
out[i], err = os.Create(filepath.Join(dir, outfn))
checkErr(err)
}
}
err = enc.Reconstruct(shards, out)
if err != nil {
fmt.Println("Reconstruct failed -", err)
os.Exit(1)
}
// Close output.
for i := range out {
if out[i] != nil {
err := out[i].(*os.File).Close()
checkErr(err)
}
}
shards, size, err = openInput(*dataShards, *parShards, fname)
ok, err = enc.Verify(shards)
if !ok {
fmt.Println("Verification failed after reconstruction, data likely corrupted:", err)
os.Exit(1)
}
checkErr(err)
}
// Join the shards and write them
outfn := *outFile
if outfn == "" {
outfn = fname
}
fmt.Println("Writing data to", outfn)
f, err := os.Create(outfn)
checkErr(err)
shards, size, err = openInput(*dataShards, *parShards, fname)
checkErr(err)
// We don't know the exact filesize.
err = enc.Join(f, shards, int64(*dataShards)*size)
checkErr(err)
}
