ENH: Re-implemented cmGeneratedFileStream to look like a real stream and replace the destination file atomically. This will avoid problems with the process being terminated while generating a file.

1 files changed, 140 insertions, 0 deletions

diff --git a/Source/cmGeneratedFileStream.cxx b/Source/cmGeneratedFileStream.cxx
new file mode 100644
index 0000000..6fe889d
--- /dev/null
+++ b/Source/cmGeneratedFileStream.cxx
@@ -0,0 +1,140 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#include "cmGeneratedFileStream.h"
+
+#include "cmSystemTools.h"
+
+// Includes needed for implementation of RenameFile.  This is not in
+// system tools because it is not implemented robustly enough to move
+// files across directories.
+#ifdef _WIN32
+# include <windows.h>
+# include <sys/stat.h>
+#endif
+
+//----------------------------------------------------------------------------
+cmGeneratedFileStream::cmGeneratedFileStream(const char* name,
+                                             bool copy_if_different,
+                                             bool quiet):
+  cmGeneratedFileStreamBase(name, copy_if_different),
+  std::ofstream(m_TempName.c_str())
+{
+  // Check if the file opened.
+  if(!*this && !quiet)
+    {
+    cmSystemTools::Error("Cannot open file for write: ", m_TempName.c_str());
+    cmSystemTools::ReportLastSystemError("");
+    }
+}
+
+//----------------------------------------------------------------------------
+cmGeneratedFileStream::~cmGeneratedFileStream()
+{
+  // This is the first destructor called.  Check the status of the
+  // stream and give the information to the private base.  Next the
+  // stream will be destroyed which will close the temporary file.
+  // Finally the base destructor will be called to replace the
+  // destination file.
+  m_Okay = *this;
+}
+
+//----------------------------------------------------------------------------
+cmGeneratedFileStreamBase::cmGeneratedFileStreamBase(const char* name,
+                                                     bool copy_if_different):
+  m_Name(name),
+  m_TempName(name),
+  m_CopyIfDifferent(copy_if_different),
+  m_Okay(false)
+{
+  // Create the name of the temporary file.
+  m_TempName += ".tmp";
+
+  // Make sure the temporary file that will be used is not present.
+  cmSystemTools::RemoveFile(m_TempName.c_str());
+}
+
+//----------------------------------------------------------------------------
+cmGeneratedFileStreamBase::~cmGeneratedFileStreamBase()
+{
+  // Only consider replacing the destination file if no error
+  // occurred.
+  if(m_Okay &&
+     (!m_CopyIfDifferent ||
+      cmSystemTools::FilesDiffer(m_TempName.c_str(), m_Name.c_str())))
+    {
+    // The destination is to be replaced.  Rename the temporary to the
+    // destination atomically.
+    this->RenameFile(m_TempName.c_str(), m_Name.c_str());
+    }
+  else
+    {
+    // The destination was not replaced.  Just delete the temporary
+    // file.
+    cmSystemTools::RemoveFile(m_TempName.c_str());
+    }
+}
+
+//----------------------------------------------------------------------------
+int cmGeneratedFileStreamBase::RenameFile(const char* oldname,
+                                          const char* newname)
+{
+#ifdef _WIN32
+  /* On Windows the move functions will not replace existing files.
+     Check if the destination exists.  */
+  struct stat newFile;
+  if(stat(newname, &newFile) == 0)
+    {
+    /* The destination exists.  We have to replace it carefully.  The
+       MoveFileEx function does what we need but is not available on
+       Win9x.  */
+    OSVERSIONINFO osv;
+    DWORD attrs;
+
+    /* Make sure the destination is not read only.  */
+    attrs = GetFileAttributes(newname);
+    if(attrs & FILE_ATTRIBUTE_READONLY)
+      {
+      SetFileAttributes(newname, attrs & ~FILE_ATTRIBUTE_READONLY);
+      }
+
+    /* Check the windows version number.  */
+    osv.dwOSVersionInfoSize = sizeof(osv);
+    GetVersionEx(&osv);
+    if(osv.dwPlatformId == VER_PLATFORM_WIN32_WINDOWS)
+      {
+      /* This is Win9x.  There is no MoveFileEx implementation.  We
+         cannot quite rename the file atomically.  Just delete the
+         destination and then move the file.  */
+      DeleteFile(newname);
+      return MoveFile(oldname, newname);
+      }
+    else
+      {
+      /* This is not Win9x.  Use the MoveFileEx implementation.  */
+      return MoveFileEx(oldname, newname, MOVEFILE_REPLACE_EXISTING);
+      }
+    }
+  else
+    {
+    /* The destination does not exist.  Just move the file.  */
+    return MoveFile(oldname, newname);
+    }
+#else
+  /* On UNIX we have an OS-provided call to do this atomically.  */
+  return rename(oldname, newname) == 0;
+#endif
+}