A dir stores a magic number

src/cryfs_lib/impl/DirBlob.cpp

@@ -5,6 +5,8 @@
 //TODO Remove and replace with exception hierarchy
 #include "fspp/fuse/FuseErrnoException.h"
 
+#include "MagicNumbers.h"
+
 using std::unique_ptr;
 using std::make_unique;
 using std::vector;
@@ -22,9 +24,22 @@ DirBlob::~DirBlob() {
 }
 
 void DirBlob::InitializeEmptyDir() {
+  *magicNumber() = MagicNumbers::DIR;
   *entryCounter() = 0;
 }
 
+unsigned char *DirBlob::magicNumber() {
+  return const_cast<unsigned char*>(magicNumber(const_cast<const Blob&>(*_blob)));
+}
+
+const unsigned char *DirBlob::magicNumber(const blobstore::Blob &blob) {
+  return (unsigned char*)blob.data();
+}
+
+bool DirBlob::IsDir(const blobstore::Blob &blob) {
+  return *magicNumber(blob) == MagicNumbers::DIR;
+}
+
 unique_ptr<vector<string>> DirBlob::GetChildren() const {
   auto result = make_unique<vector<string>>();
   unsigned int entryCount = *entryCounter();
@@ -80,7 +95,7 @@ unsigned int *DirBlob::entryCounter() {
 }
 
 const unsigned int *DirBlob::entryCounter() const {
-  return (unsigned int*)(_blob->data());
+  return (unsigned int*)((char*)_blob->data() + sizeof(unsigned char));
 }
 
 char *DirBlob::entriesBegin() {
@@ -88,7 +103,7 @@ char *DirBlob::entriesBegin() {
 }
 
 const char *DirBlob::entriesBegin() const {
-  return (char *)(_blob->data())+sizeof(unsigned int);
+  return (char *)(_blob->data())+sizeof(unsigned char) + sizeof(unsigned int);
 }
 
 char *DirBlob::entriesEnd() {

src/cryfs_lib/impl/DirBlob.h

@@ -20,7 +20,11 @@ public:
   void AddChild(const std::string &name, const std::string &blobKey);
   std::string GetBlobKeyForName(const std::string &name) const;
 
+  static bool IsDir(const blobstore::Blob &blob);
+
 private:
+  unsigned char *magicNumber();
+  static const unsigned char *magicNumber(const blobstore::Blob &blob);
   unsigned int *entryCounter();
   const unsigned int *entryCounter() const;
   char *entriesBegin();

src/cryfs_lib/impl/MagicNumbers.h

@@ -0,0 +1,16 @@
+#pragma once
+#ifndef CRYFS_LIB_IMPL_MAGICNUMBERS_H_
+#define CRYFS_LIB_IMPL_MAGICNUMBERS_H_
+
+namespace cryfs {
+namespace MagicNumbers {
+
+unsigned char DIR = 0x00;
+unsigned char FILE = 0x01;
+
+}
+}
+
+
+
+#endif