package main import ( "crypto/md5" "crypto/sha1" "crypto/sha256" "crypto/sha512" "flag" "fmt" "hash" "io" "os" "runtime" "sync" ) var algo = flag.String("a", "sha1", "algorithm to use") var mode = flag.Bool("c", false, "check") var ngo = flag.Int("n", runtime.NumCPU(), "number of goroutines") func main() { flag.Parse() files := flag.Args() switch *mode { case true: ec := 0 for err := range check(files) { ec++ fmt.Fprintf(os.Stderr, "%v\n", err) } if ec > 0 { os.Exit(1) } case false: ec := 0 for res := range hsh(files) { if res.err != nil { ec++ fmt.Fprintf(os.Stderr, "%v\n", res.err) } else { fmt.Printf("%v\n", res.msg) } } if ec > 0 { os.Exit(1) } } } type hashr func() hash.Hash func hsh(files []string) chan result { var h hashr switch *algo { case "sha1", "1": h = sha1.New case "sha256", "256": h = sha256.New case "sha512", "512": h = sha512.New case "md5": h = md5.New default: r := make(chan result) go func() { r <- result{err: fmt.Errorf("unsupported algorithm: %v", *algo)} }() return r } if len(files) == 0 { hsh := h() _, err := io.Copy(hsh, os.Stdin) if err != nil { fmt.Fprintf(os.Stderr, "%v\n", err) os.Exit(1) } fmt.Printf("%x -\n", hsh.Sum(nil)) return nil } jobs := make(chan work) go func() { for _, name := range files { jobs <- work{cs: checksum{filename: name}} } close(jobs) }() res := []<-chan result{} for w := 0; w < *ngo; w++ { res = append(res, compute(h, jobs)) } return rmerge(res) } type result struct { msg string err error } func compute(h hashr, jobs chan work) chan result { hsh := h() r := make(chan result) go func() { for job := range jobs { f, err := os.Open(job.cs.filename) if err != nil { r <- result{err: err} continue } hsh.Reset() _, err = io.Copy(hsh, f) f.Close() if err != nil { r <- result{err: err} continue } r <- result{msg: fmt.Sprintf("%x %s", hsh.Sum(nil), job.cs.filename)} } close(r) }() return r } func rmerge(cs []<-chan result) chan result { out := make(chan result) var wg sync.WaitGroup output := func(c <-chan result) { for n := range c { out <- n } wg.Done() } wg.Add(len(cs)) for _, c := range cs { go output(c) } go func() { wg.Wait() close(out) }() return out }