Question 1

How do I pass a JavaScript function as a callback to C using ffi-rs?

Accepted Answer

Use funcConstructor with createPointer to wrap the JS function, but note it creates a threadsafe function that runs asynchronously. Remember to free the pointer with freePointer after use to avoid memory leaks, as shown in the function example.

Question 2

What's the difference between ffi-rs and ffi-napi?

Accepted Answer

ffi-rs is built with Rust for better performance and maintenance, supports more types like C++ classes, and has a simpler API. However, it requires manual memory management, whereas ffi-napi might abstract some of that but is slower per benchmarks.

Question 3

How to avoid memory leaks when using ffi-rs?

Accepted Answer

Always use freePointer for External types, set freeResultMemory appropriately in load calls, and manage allocations carefully on both JavaScript and native sides, as detailed in the memory management section of the README.

Question 4

Can I use ffi-rs with TypeScript for type safety?

Accepted Answer

Yes, ffi-rs is designed with TypeScript in mind, providing comprehensive type hints and interfaces. The README recommends TypeScript development to benefit from these features.

Question 5

How to compile a C library for use with ffi-rs on Linux?

Accepted Answer

Use g++ with the -shared flag, as shown in the README example: 'g++ -shared -o libsum.so cpp/sum.cpp'. Ensure the compilation environment matches your Node.js runtime to avoid compatibility issues.

Question 6

Does ffi-rs support asynchronous FFI calls?

Accepted Answer

Yes, through the runInNewThread option, which returns a promise for non-blocking execution. Additionally, JS function callbacks are handled asynchronously via threadsafe functions.

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