Add LICENSE and README.md. Set default concurrency to the number of

CPUs, and read stdin if no input files are specified.

LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2020 Gregory Pomerantz
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

@@ -0,0 +1,16 @@
+# b3sum
+
+A golang port of b3sum
+
+This is a simple `b3sum` command using `github.com/zeebo/blake3`.
+
+Usage:
+  b3sum [flags] [file]...
+  -h	Prints help information
+  -l int
+    	The number of output bytes, prior to hex encoding (default 32)
+  -p int
+    	The maximum concurrency (defaults to the number of CPUs)
+
+If no input files are specified, `b3sum` reads `stdin`.
+

main.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime"
 	"sync"
 
 	"github.com/zeebo/blake3"
@@ -14,27 +15,17 @@ import (
 var (
 	help = flag.Bool("h", false, "Prints help information")
 	length = flag.Int("l", 32,  "The number of output bytes, prior to hex encoding")
-	par = flag.Int("p", 4, "The maximum concurrency")
+	par = flag.Int("p", runtime.NumCPU(), "The maximum concurrency")
 )
 
 func main() {
 	flag.Parse()
-	if *help || len(flag.Args()) == 0 || *par < 1 {
+	if *help || *par < 1 {
 		flag.Usage()
 		os.Exit(0)
 	}
-	q := make(chan struct{}, *par)
-	wg := &sync.WaitGroup{}
-
-	for _, name := range flag.Args() {
-		q <- struct{}{}
-		wg.Add(1)
-		go func(name string) {
+	sum := func(file io.ReadCloser) string {
 		buf := [65536]byte{}
-			file, err := os.Open(name)
-			if err != nil {
-				panic(err)
-			}
 		hasher := blake3.NewSized(*length)
 		for {
 			n, err := file.Read(buf[:])
@@ -47,7 +38,24 @@ func main() {
 		}
 		file.Close()
 		hash := hasher.Sum([]byte{})
-			fmt.Print(hex.EncodeToString(hash))
+		return hex.EncodeToString(hash)
+	}
+
+	if len(flag.Args()) == 0 {
+		fmt.Println(sum(os.Stdin))
+	} else {
+		q := make(chan struct{}, *par)
+		wg := &sync.WaitGroup{}
+
+		for _, name := range flag.Args() {
+			q <- struct{}{}
+			wg.Add(1)
+			go func(name string) {
+				file, err := os.Open(name)
+				if err != nil {
+					panic(err)
+				}
+				fmt.Print(sum(file))
 				fmt.Print("  ")
 				fmt.Println(name)
 				<- q
@@ -56,3 +64,4 @@ func main() {
 		}
 		wg.Wait()
 	}
+}