saved

frontend/cookie/cookie.go

@@ -0,0 +1,47 @@
+package cookie
+
+import (
+	"encoding/base64"
+	"errors"
+	"net/http"
+)
+
+var (
+	ErrValueTooLong = errors.New("cookie value too long")
+	ErrInvalidValue = errors.New("invalid cookie value")
+)
+
+func Write(w http.ResponseWriter, cookie http.Cookie) error {
+	// Encode the cookie value using base64.
+	cookie.Value = base64.URLEncoding.EncodeToString([]byte(cookie.Value))
+
+	// Check the total length of the cookie contents. Return the ErrValueTooLong
+	// error if it's more than 4096 bytes.
+	if len(cookie.String()) > 4096 {
+		return ErrValueTooLong
+	}
+
+	// Write the cookie as normal.
+	http.SetCookie(w, &cookie)
+
+	return nil
+}
+
+func Read(r *http.Request, name string) (string, error) {
+	// Read the cookie as normal.
+	cookie, err := r.Cookie(name)
+	if err != nil {
+		return "", err
+	}
+
+	// Decode the base64-encoded cookie value. If the cookie didn't contain a
+	// valid base64-encoded value, this operation will fail and we return an
+	// ErrInvalidValue error.
+	value, err := base64.URLEncoding.DecodeString(cookie.Value)
+	if err != nil {
+		return "", ErrInvalidValue
+	}
+
+	// Return the decoded cookie value.
+	return string(value), nil
+}