Code review. Fix data loss.

2 files changed, 29 insertions, 2 deletions

diff --git a/coding/internal/file_data.cpp b/coding/internal/file_data.cpp
index c02650f47e..316a399285 100644
--- a/coding/internal/file_data.cpp
+++ b/coding/internal/file_data.cpp
@@ -6,12 +6,14 @@
 
 #include "base/exception.hpp"
 #include "base/logging.hpp"
+#include "base/string_utils.hpp"
 
 #include "std/cerrno.hpp"
 #include "std/cstring.hpp"
 #include "std/exception.hpp"
 #include "std/fstream.hpp"
 #include "std/target_os.hpp"
+#include "std/thread.hpp"
 
 #ifdef OMIM_OS_WINDOWS
   #include <io.h>
@@ -267,6 +269,25 @@ bool RenameFileX(string const & fOld, string const & fNew)
   return CheckFileOperationResult(res, fOld);
 }
 
+bool WriteToTempAndRenameToFile(string const & dest, function<bool(string const &)> const & write,
+                                string const & tmp)
+{
+  string const tmpFileName =
+      tmp.empty() ? dest + ".tmp" + strings::to_string(this_thread::get_id()) : tmp;
+  if (!write(tmpFileName))
+  {
+    LOG(LERROR, ("Can't write to", tmpFileName));
+    return false;
+  }
+  if (!RenameFileX(tmpFileName, dest))
+  {
+    LOG(LERROR, ("Can't rename file", tmpFileName, "to", dest));
+    DeleteFileX(tmpFileName);
+    return false;
+  }
+  return true;
+}
+
 bool CopyFileX(string const & fOld, string const & fNew)
 {
   try
diff --git a/coding/internal/file_data.hpp b/coding/internal/file_data.hpp
index ce118bb8c5..2bd4514d98 100644
--- a/coding/internal/file_data.hpp
+++ b/coding/internal/file_data.hpp
@@ -3,9 +3,10 @@
 
 #include "base/base.hpp"
 
+#include "std/functional.hpp"
+#include "std/noncopyable.hpp"
 #include "std/string.hpp"
 #include "std/target_os.hpp"
-#include "std/noncopyable.hpp"
 
 #ifdef OMIM_OS_TIZEN
 namespace Tizen
@@ -58,8 +59,13 @@ private:
 bool GetFileSize(string const & fName, uint64_t & sz);
 bool DeleteFileX(string const & fName);
 bool RenameFileX(string const & fOld, string const & fNew);
+
+/// Write to temp file and rename it to dest. Delete temp on failure.
+/// @param write function that writes to file with a given name, returns true on success.
+bool WriteToTempAndRenameToFile(string const & dest, function<bool(string const &)> const & write,
+                                string const & tmp = "");
+
 /// @return false if copy fails. DO NOT THROWS exceptions
 bool CopyFileX(string const & fOld, string const & fNew);
 bool IsEqualFiles(string const & firstFile, string const & secondFile);
-
 }