From 5df5aa394a7a237a7e7cb666dd280b3ccef804fa Mon Sep 17 00:00:00 2001
From: Meutel <meutel@meutel.net>
Date: Sat, 8 Jul 2017 12:05:03 +0200
Subject: [PATCH] SHA directory with concurrency

---
 .gitignore               |  1 +
 shadirconcurrent/main.go | 64 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 shadirconcurrent/main.go

diff --git a/.gitignore b/.gitignore
index aa04a47..d401de0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -37,3 +37,4 @@ go-financial/go-financial
 my-fnv/my-fnv
 my-md5/my-md5
 shadir/shadir
+shadirconcurrent/shadirconcurrent
diff --git a/shadirconcurrent/main.go b/shadirconcurrent/main.go
new file mode 100644
index 0000000..c304b94
--- /dev/null
+++ b/shadirconcurrent/main.go
@@ -0,0 +1,64 @@
+package main
+
+import "fmt"
+import "crypto/sha256"
+import "io"
+import "log"
+import "os"
+import "path/filepath"
+import "sync/atomic"
+
+var chan_hash chan string
+var running int32
+
+func walk(path string, info os.FileInfo, err error) error {
+	if err != nil {
+		log.Fatalln(err)
+		return err
+	}
+
+	if info.IsDir() {
+		return nil
+	} else {
+		atomic.AddInt32(&running, 1)
+		go hash(info.Name(), path)
+	}
+	return nil
+}
+
+func hash(name string, path string) {
+	h, err := sha256File(path)
+	if err != nil {
+		log.Fatalln(err)
+	}
+	chan_hash <- fmt.Sprintf("SHA256 (%s) =  %x", name, h)
+}
+
+func sha256File(path string) ([]byte, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		log.Fatalln(err)
+		return nil, err
+	}
+	defer f.Close()
+	h := sha256.New()
+	io.Copy(h, f)
+	return h.Sum(nil), nil
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		log.Fatalln("Usage shadir file")
+	}
+	chan_hash = make(chan string)
+	if err := filepath.Walk(os.Args[1], walk); err != nil {
+		panic(err)
+	}
+	for str := range chan_hash {
+		fmt.Println(str)
+		atomic.AddInt32(&running, -1)
+		if running <= 0 {
+			return
+		}
+	}
+}