Add concurrency.

main.go

@@ -6,23 +6,31 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sync"
 
 	"github.com/zeebo/blake3"
 )
 
 var (
 	help = flag.Bool("h", false, "Prints help information")
-	length = flag.Int("l", 32,  "The number of output bytes, prior to hex encoding (default 32)")
+	length = flag.Int("l", 32,  "The number of output bytes, prior to hex encoding")
+	par = flag.Int("p", 4, "The maximum concurrency")
 )
 
 func main() {
 	flag.Parse()
-	if *help || len(flag.Args()) == 0 {
+	if *help || len(flag.Args()) == 0 || *par < 1 {
 		flag.Usage()
 		os.Exit(0)
 	}
-	buf := [65536]byte{}
+	q := make(chan struct{}, *par)
+	wg := &sync.WaitGroup{}
+
 	for _, name := range flag.Args() {
+		q <- struct{}{}
+		wg.Add(1)
+		go func(name string) {
+			buf := [65536]byte{}
 			file, err := os.Open(name)
 			if err != nil {
 				panic(err)
@@ -42,5 +50,9 @@ func main() {
 			fmt.Print(hex.EncodeToString(hash))
 			fmt.Print("  ")
 			fmt.Println(name)
+			<- q
+			wg.Done()
+		}(name)
 	}
+	wg.Wait()
 }