go.blog: pipelines and cancellation.

R=adg, r, rsc, ken, bcmills
CC=adonovan, campoy, david.crawshaw, gmlewis, golang-codereviews
https://golang.org/cl/71070047

1 files changed, 53 insertions, 0 deletions

diff --git a/content/pipelines/serial.go b/content/pipelines/serial.go
new file mode 100644
index 0000000..7a44ca1
--- /dev/null
+++ b/content/pipelines/serial.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+)
+
+// MD5All reads all the files in the file tree rooted at root and returns a map
+// from file path to the MD5 sum of the file's contents.  If the directory walk
+// fails or any read operation fails, MD5All returns an error.
+func MD5All(root string) (map[string][md5.Size]byte, error) {
+	m := make(map[string][md5.Size]byte)
+	err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error { // HL
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+		data, err := ioutil.ReadFile(path) // HL
+		if err != nil {
+			return err
+		}
+		m[path] = md5.Sum(data) // HL
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+func main() {
+	// Calculate the MD5 sum of all files under the specified directory,
+	// then print the results sorted by path name.
+	m, err := MD5All(os.Args[1]) // HL
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	var paths []string
+	for path := range m {
+		paths = append(paths, path)
+	}
+	sort.Strings(paths) // HL
+	for _, path := range paths {
+		fmt.Printf("%x  %s\n", m[path], path)
+	}
+}