Updates

Former-commit-id: 8220f5660a75af69ee6358af3782416dae9aa185 [formerly 098749492c954879b5a01324076804e74947c780] [formerly 34f6dda3fafc72730b4e44d0c23ade6940bb90d4 [formerly 4b3ebca48c]]
Former-commit-id: 722e71cd19b9ecceb627cc1e65572839bd2a55c8 [formerly 23d5ac81b9ff1f39b51cc042eb2ac12d2e5da6fc]
Former-commit-id: c4e5ea0d6db7edcfdc3b551e0c43d1c77ef587c3

file.go

@@ -1,6 +1,14 @@
 package filemanager
 
 import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/hex"
+	"errors"
+	"hash"
+	"io"
 	"io/ioutil"
 	"mime"
 	"net/http"
@@ -13,6 +21,10 @@ import (
 	humanize "github.com/dustin/go-humanize"
 )
 
+var (
+	errInvalidOption = errors.New("Invalid option")
+)
+
 // fileInfo contains the information about a particular file or directory.
 type fileInfo struct {
 	// Used to store the file's content temporarily.
@@ -149,6 +161,37 @@ func (i *fileInfo) Read() error {
 	return nil
 }
 
+func (i fileInfo) Checksum(kind string) (string, error) {
+	file, err := os.Open(i.Path)
+	if err != nil {
+		return "", err
+	}
+
+	defer file.Close()
+
+	var h hash.Hash
+
+	switch kind {
+	case "md5":
+		h = md5.New()
+	case "sha1":
+		h = sha1.New()
+	case "sha256":
+		h = sha256.New()
+	case "sha512":
+		h = sha512.New()
+	default:
+		return "", errInvalidOption
+	}
+
+	_, err = io.Copy(h, file)
+	if err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
 // StringifyContent returns a string with the file content.
 func (i fileInfo) StringifyContent() string {
 	return string(i.content)