Type Alias jpegxl_rs::parallel::RunnerFn

source · 
pub type RunnerFn = unsafe extern "C" fn(runner_opaque: *mut c_void, jpegxl_opaque: *mut c_void, init_func: InitFn, run_func: RunFn, start_range: u32, end_range: u32) -> JxlParallelRetCode;
Expand description

FFI runner function.

A parallel runner implementation can be provided by a JPEG XL caller to allow running computations in multiple threads. This function must call the initialization function init_func in the same thread that called it and then call the passed run_func once for every number in the range [start_range, end_range) (including start_rangege but not including end_range) possibly from different multiple threads in parallel.

The JxlParallelRunner function does not need to be re-entrant. This means that the same JxlParallelRunner function with the same runner_opaque provided parameter will not be called from the library from either init_func or run_func in the same decoder or encoder instance. However, a single decoding or encoding instance may call the provided JxlParallelRunner multiple times for different parts of the decoding or encoding process.

§Returns

  • 0: if the @p init call succeeded (returned 0) and no other error occurred in the runner code.
  • JXL_PARALLEL_RET_RUNNER_ERROR if an error occurred in the runner code, for example, setting up the threads.
  • Return the return value of init_func if non-zero.