Function cm_block_buffer_get_data_pointer 

pub unsafe extern "C" fn cm_block_buffer_get_data_pointer(
    block_buffer: *mut c_void,
    offset: usize,
    out_length_at_offset: *mut usize,
    out_total_length: *mut usize,
    out_data_pointer: *mut *mut c_void,
) -> i32

Swift bridge function cm_block_buffer_get_data_pointer for the corresponding Apple API.