Add rsha256 - remote sha256 utility.

cmd/rsha256/main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"crypto/sha256"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"path/filepath"
+
+	"github.com/kisom/goutils/lib"
+)
+
+func fetch(remote string) ([]byte, error) {
+	resp, err := http.Get(remote)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return body, nil
+}
+
+func main() {
+	flag.Parse()
+
+	for _, remote := range flag.Args() {
+		u, err := url.Parse(remote)
+		if err != nil {
+			lib.Warn(err, "parsing %s", remote)
+			continue
+		}
+
+		name := filepath.Base(u.Path)
+		if name == "" {
+			lib.Warnx("source URL doesn't appear to name a file")
+			continue
+		}
+
+		body, err := fetch(remote)
+		if err != nil {
+			lib.Warn(err, "fetching %s", remote)
+			continue
+		}
+
+		h := sha256.Sum256(body)
+		fmt.Printf("%s: sha256=%x\n", name, h)
+	}
+}