From 4044f461408ef2ba7dffb80619268f42b0757f48 Mon Sep 17 00:00:00 2001
From: vng <viktor.govako@gmail.com>
Date: Mon, 5 Apr 2021 21:34:22 +0300
Subject: [PATCH] Fixed bug with empty files.

Signed-off-by: vng <viktor.govako@gmail.com>
---
 coding/coding_tests/file_data_test.cpp | 19 ++++++++++++++++++-
 coding/internal/file_data.cpp          | 24 +++++++++++++++++++++---
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/coding/coding_tests/file_data_test.cpp b/coding/coding_tests/file_data_test.cpp
index 4a92cd0e87..7244aec6d8 100644
--- a/coding/coding_tests/file_data_test.cpp
+++ b/coding/coding_tests/file_data_test.cpp
@@ -185,23 +185,40 @@ UNIT_TEST(EmptyFile)
   std::string const name = "test.empty";
   std::string const copy = "test.empty.copy";
 
+  // Check that both files are not exist.
+  uint64_t sz;
+  TEST(!GetFileSize(name, sz), ());
+  TEST(!GetFileSize(copy, sz), ());
+
+  // Try to copy non existing file - failed.
+  TEST(!CopyFileX(name, copy), ());
+
+  // Again, both files are not exist.
+  TEST(!GetFileSize(name, sz), ());
+  TEST(!GetFileSize(copy, sz), ());
+
   {
+    // Create empty file with zero size.
     FileData f(name, base::FileData::OP_WRITE_TRUNCATE);
   }
 
-  uint64_t sz;
+  // Check that empty file is on disk.
   TEST(GetFileSize(name, sz), ());
   TEST_EQUAL(sz, 0, ());
 
+  // Do copy.
   TEST(CopyFileX(name, copy), ());
   //TEST(!RenameFileX(name, copy), ());
 
+  // Delete copy file and rename name -> copy.
   TEST(DeleteFileX(copy), ());
   TEST(RenameFileX(name, copy), ());
 
+  // Now we don't have an initial file but have a copy.
   TEST(!GetFileSize(name, sz), ());
   TEST(GetFileSize(copy, sz), ());
   TEST_EQUAL(sz, 0, ());
 
+  // Delete copy file.
   TEST(DeleteFileX(copy), ());
 }
diff --git a/coding/internal/file_data.cpp b/coding/internal/file_data.cpp
index 28c5b10b5b..dba27edd4a 100644
--- a/coding/internal/file_data.cpp
+++ b/coding/internal/file_data.cpp
@@ -165,6 +165,7 @@ bool GetFileSize(string const & fName, uint64_t & sz)
 
 namespace
 {
+
 bool CheckFileOperationResult(int res, string const & fName)
 {
   if (!res)
@@ -181,6 +182,12 @@ bool CheckFileOperationResult(int res, string const & fName)
 
   return false;
 }
+
+bool IsEOF(ifstream & fs)
+{
+  return fs.peek() == ifstream::traits_type::eof();
+}
+
 }  // namespace
 
 bool DeleteFileX(string const & fName)
@@ -243,7 +250,7 @@ void AppendFileToFile(string const & fromFilename, string const & toFilename)
   to.open(toFilename, ios::binary | ios::app);
 
   auto * buffer = from.rdbuf();
-  if (from.peek() != ifstream::traits_type::eof())
+  if (!IsEOF(from))
     to << buffer;
 }
 
@@ -258,15 +265,26 @@ bool CopyFileX(string const & fOld, string const & fNew)
   {
     ifs.open(fOld.c_str());
     ofs.open(fNew.c_str());
+
+    // If source file is empty - make empty dest file without any errors.
+    if (IsEOF(ifs))
+      return true;
+
     ofs << ifs.rdbuf();
     ofs.flush();
     return true;
   }
-  catch (exception const & ex)
+  catch (system_error const &)
   {
-    LOG(LERROR, ("Failed to copy file from", fOld, "to", fNew, ":", strerror(errno)));
+    LOG(LWARNING, ("Failed to copy file from", fOld, "to", fNew, ":", strerror(errno)));
+  }
+  catch (exception const &)
+  {
+    LOG(LERROR, ("Unknown error when coping files:", fOld, "to", fNew, strerror(errno)));
   }
 
+  // Don't care about possible error here ..
+  (void) DeleteFileX(fNew);
   return false;
 }