CreatePath – Full Path Creation (wstring version)

Environment: Visual C++

This is a simple function I wrote in order to deal with creating complete (multi-level) paths.

The function works recursively, and uses std::wstring, but can actaully work on any basic_string -based string. It can deal with trailing slashes (eg. “c:temp” vs. “c:temp”), as well as network locations (eg. “\machineshared”).

You might notice the call to SetLastError(). The reason is to make it easy to verify what went wrong in case of an error – instead of handling exceptions and/or error strings, all you have to do is call GetLastError() if the function returns false.

You can use the function to make sure a directory exists before creating a file in it:

  std::wstring wsFileName;
  int pos = wsFileName.find_last_of(L"\");
  if (0 <= pos)
  {
    std::wstring wsPath = wsFileName.substr(0, pos);

    if (CreatePath(wsPath))
    {
      CreateFileW(wsFileName.c_str(), ...);
    }
    else
    {
      std::wcout << L"Error #" << GetLastError() << std::endl;
    }
  }

Here is the source code:

bool CreatePath(std::wstring &wsPath)
{
  DWORD attr;
  int pos;
  bool result = true;
  // Check for trailing slash:
  pos = wsPath.find_last_of(SLASH);
  if (wsPath.length() == pos + 1)  // last character is “”
  {
    wsPath.resize(pos);
  }
  // Look for existing object:
  attr = GetFileAttributesW(wsPath.c_str());
  if (0xFFFFFFFF == attr)  // doesn’t exist yet – create it!
  {
    pos = wsPath.find_last_of(SLASH);
    if (0 < pos)
    {
      // Create parent dirs:
      result = CreatePath(wsPath.substr(0, pos));
    }
    // Create node:
    result = result && CreateDirectoryW(wsPath.c_str(), NULL);
  }
  else if (FILE_ATTRIBUTE_DIRECTORY != attr)
  {  // object already exists, but is not a dir
    SetLastError(ERROR_FILE_EXISTS);
    result = false;
  }
  return result;
}

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