Opening a file then closing does not release file lock

I have some c++ code in a node.js function that opens a file like this and reads it into a buffer and then closes it.

ifstream inputFile(source.c_str(), ios::in | ios::binary);
inputFile.read(buffer, results.st_size);
inputFile.close();

Then I manipulate the file in some way and attempt to write it back to the same location. I get the following error code and message: "Text file busy". I know there is no other process touching the file. If I rename the file to some random name, and rename it back, then I am able to overwrite the file.