Cross-Platform Retrieval of FILE* from std::fstream

Many C libraries accept std::fstream objects, while specific C library functions require a FILE* handle. This poses a challenge when attempting to use these libraries together.

Why Convert std::fstream to FILE*?

The primary reason for seeking a conversion from std::fstream to FILE* is the lack of cross-platform support for an natively available solution.

Limitations of std::fstream Implementation

Unfortunately, there is no direct method for extracting a FILE handle from an std::fstream object. This is because the implementation of std::fstream is not standardized to use FILE, leaving it at the discretion of the underlying implementation.

Alternatives to Conversion

As a result, it is not recommended to attempt a conversion between std::fstream and FILE*. Instead, consider the following alternatives:

• Use a C wrapper function: Write a wrapper function that accepts an std::fstream and provides a FILE* interface.
• Use Boost.iostreams: This library provides cross-platform support for accessing FILE* handles from various I/O objects, including std::fstream.
• Consider funopen() (non-POSIX): Although not a POSIX API, funopen() allows you to create a FILE object and specify custom file operations. You can write functions to handle read, write, seek, and close operations using your std::fstream object.

By using these alternatives, you can avoid the limitations of std::fstream's implementation and seamlessly interact with C libraries that require FILE* handles.