Function blosc2_set_threads_callback 

pub unsafe extern "C" fn blosc2_set_threads_callback(
    callback: blosc_threads_callback,
    callback_data: *mut c_void,
)

Set the threading backend for parallel compression/decompression to use callback to execute work instead of using the Blosc-managed threads. This function is not thread-safe and should be called before any other Blosc function: it affects all Blosc contexts. Passing NULL uses the default Blosc threading backend. The callback_data argument is passed through to the callback.