Handling interrupts

This page applies to Harlequin v13.1r0 and later; and to Harlequin MultiRIP but not Harlequin Core

If a device function takes a while to do some processing, it should periodically check to see if the Harlequin MultiRIP has been interrupted.

This is done by calling the Harlequin MultiRIP function SwOften() . This function normally returns 0 and nothing needs to be done, but if this function returns -1 the device routine should abort and should return DeviceInterrupted on the next call to the device's last_error() function. It is expected that existing code that calls SwOften() should not need to be changed to support this method of handling interrupts.

For example, if a device routine needs to write a large amount of data, it should not be written in one operation, but should use code something like this:

    {
      int32 bytes_written = 0; while (len > 0)
      {
        int32 this_size; int32 result;
        this_size = (len > CHUNK) CHUNK : len;
        result = underlying_write(desc, buff, this_size); bytes_written += result;
        buff += result; len -= result;
        if (SwOften() == -1)
          {
            error = Device Interrupted; return -1;
          }
        }
      return bytes_written;
    }

In this example code listing error handling has been omitted for clarity.