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Midas C++ API - rb_xxx functions

This page contains the full API reference for the rb_xxx ring buffer functions. Ring buffers pass events between threads within a single program, for example from a readout thread to the thread that sends them on; the mfe frontend framework uses them for multi-threaded readout.

Ring Buffer Functions (rb_xxx)

Functions

rb_create 

int rb_create(int size, int max_event_size, int *ring_buffer_handle)

Create a ring buffer with a given size

Provide an inter-thread buffer scheme for handling front-end events. This code allows concurrent data acquisition, calibration and network transfer on a multi-CPU machine. One thread reads out the data, passes it via the ring buffer functions to another thread running on the other CPU, which can then calibrate and/or send the data over the network.

Parameters:

  • size (int) –
    Size of ring buffer, must be larger than 2*max_event_size
  • max_event_size (int) –
    Maximum event size to be placed into
  • ring_buffer_handle (int *)

Returns:

Declared in include/msystem.h:690, defined in src/midas.cxx:18869

rb_delete 

int rb_delete(int ring_buffer_handle)

Delete a ring buffer

Parameters:

  • ring_buffer_handle (int) –
    Handle of the ring buffer

Returns:

Declared in include/msystem.h:691, defined in src/midas.cxx:18924

rb_get_buffer_level 

int rb_get_buffer_level(int handle, int * n_bytes)

Return number of bytes in a ring buffer

Parameters:

  • handle (int) –
    Handle of the buffer to get the info
  • n_bytes (int *)

Returns:

Declared in include/msystem.h:696, defined in src/midas.cxx:19219

rb_get_rp 

int rb_get_rp(int handle, void **p, int millisec)

Obtain the current read pointer at which new data is available with optional timeout

                         available data. If p == NULL, only
                         return status.

Parameters:

  • handle (int) –
    Ring buffer handle
  • p (void **)
  • millisec (int) –
    Optional timeout in milliseconds if buffer is full. Zero to not wait at all (non-blocking)

Returns:

Declared in include/msystem.h:694, defined in src/midas.cxx:19102

rb_get_wp 

int rb_get_wp(int handle, void **p, int millisec)

Retrieve write pointer where new data can be written

Parameters:

  • handle (int) –
    Ring buffer handle
  • p (void **)
  • millisec (int) –
    Optional timeout in milliseconds if buffer is full. Zero to not wait at all (non-blocking)

Returns:

Declared in include/msystem.h:692, defined in src/midas.cxx:18961

rb_increment_rp 

int rb_increment_rp(int handle, int size)

Increment current read pointer, freeing up space for the writing thread.

Parameters:

  • handle (int) –
    Ring buffer handle
  • size (int) –
    Number of bytes to free up at current read pointer

Returns:

Declared in include/msystem.h:695, defined in src/midas.cxx:19164

rb_increment_wp 

int rb_increment_wp(int handle, int size)

rb_increment_wp

Increment current write pointer, making the data at the write pointer available to the receiving thread

Parameters:

  • handle (int) –
    Ring buffer handle
  • size (int) –
    Number of bytes placed at the WP

Returns:

Declared in include/msystem.h:693, defined in src/midas.cxx:19036

rb_set_nonblocking 

int rb_set_nonblocking()

Set all rb_get_xx to nonblocking. Needed in multi-thread environments for stopping all theads without deadlock

Returns:

Declared in include/msystem.h:689, defined in src/midas.cxx:18828