size_t samples = file.file_size / 4;
size_t ir_samples = sizeof(ir) / 4;
for (size_t i = 0; i < samples; ++i)
{
    for (size_t j = 0; j < ir_samples && i >= j; ++j) 
    {
        file.out_file_data[i] += file.in_file_data[i - j] * ir[j];
    }
}