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minio/cmd/erasure-demo/decode.go

91 lines
1.9 KiB

package main
import (
"io/ioutil"
"log"
"os"
"strconv"
"github.com/codegangsta/cli"
"github.com/minio-io/minio/pkgs/erasure"
)
func decode(c *cli.Context) {
// check if minio-encode called without parameters
if len(c.Args()) != 1 {
cli.ShowCommandHelp(c, "decode")
return
}
config, err := parseInput(c)
if err != nil {
log.Fatal(err)
}
k := config.k
m := config.m
// check if output file exists, fail if so
if _, err := os.Stat(config.output); !os.IsNotExist(err) {
log.Fatal("Output file exists")
}
// get list of files
var inputFiles []string
if _, err := os.Stat(config.input + ".length"); os.IsNotExist(err) {
err = nil
chunkCount := 0
for !os.IsNotExist(err) {
_, err = os.Stat(config.input + "." + strconv.Itoa(chunkCount) + ".length")
chunkCount += 1
}
chunkCount = chunkCount - 1
inputFiles = make([]string, chunkCount)
for i := 0; i < chunkCount; i++ {
inputFiles[i] = config.input + "." + strconv.Itoa(i)
}
} else {
inputFiles = []string{config.input}
}
// open file to write
outputFile, err := os.OpenFile(config.output, os.O_CREATE|os.O_WRONLY, 0600)
defer outputFile.Close()
if err != nil {
log.Fatal(err)
}
for _, inputFile := range inputFiles {
// get chunks
chunks := make([][]byte, k+m)
for i := 0; i < k+m; i++ {
chunks[i], _ = ioutil.ReadFile(inputFile + "." + strconv.Itoa(i))
}
// get length
lengthBytes, err := ioutil.ReadFile(inputFile + ".length")
if err != nil {
log.Fatal(err)
}
lengthString := string(lengthBytes)
length, err := strconv.Atoi(lengthString)
if err != nil {
log.Fatal(err)
}
// set up encoder
erasureParameters, _ := erasure.ParseEncoderParams(k, m, erasure.CAUCHY)
// decode data
decodedData, err := erasure.Decode(chunks, erasureParameters, length)
if err != nil {
log.Fatal(err)
}
// append decoded data
length, err = outputFile.Write(decodedData)
if err != nil {
log.Fatal(err)
}
}
}