1 files changed, 89 insertions, 0 deletions
diff --git a/go/tools/builders/md5sum.go b/go/tools/builders/md5sum.go
new file mode 100644
index 00000000..834eb272
--- /dev/null
+++ b/go/tools/builders/md5sum.go
@@ -0,0 +1,89 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// md5sum replicates the equivalent functionality of the unix tool of the same name.
+package main
+
+import (
+	"crypto/md5"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+)
+
+func md5SumFile(filename string) ([]byte, error) {
+	var result []byte
+	f, err := os.Open(filename)
+	if err != nil {
+		return result, err
+	}
+	defer f.Close()
+	hash := md5.New()
+	if _, err := io.Copy(hash, f); err != nil {
+		return nil, err
+	}
+	return hash.Sum(result), nil
+}
+
+func run(args []string) error {
+	// Prepare our flags
+	flags := flag.NewFlagSet("md5sum", flag.ExitOnError)
+	output := flags.String("output", "", "If set, write the results to this file, instead of stdout.")
+	if err := flags.Parse(args); err != nil {
+		return err
+	}
+	// print the outputs if we need not
+	to := os.Stdout
+	if *output != "" {
+		f, err := os.Create(*output)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		to = f
+	}
+	for _, path := range flags.Args() {
+		walkFn := func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			if info.IsDir() {
+				return nil
+			}
+
+			if b, err := md5SumFile(path); err != nil {
+				return err
+			} else {
+				fmt.Fprintf(to, "%s  %x\n", path, b)
+			}
+			return nil
+		}
+
+		if err := filepath.Walk(path, walkFn); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("GoMd5sum: ")
+	if err := run(os.Args[1:]); err != nil {
+		log.Fatal(err)
+	}
+}