README.md

Inter process communication in Linux based on shared memory and lockless data structures

Header only. Link with -lrt for mmap.

Build

mkdir build
cd build
cmake ..
make

Install

make install

Build examples

make examples

Minimal Demo

Full demo in examples/cpp_ipc_demo/.

Writer

#include "ipc/ipc.h"
...
ipc_writer<my_struct> writer("my_topic");

while (1)
{
  // create / obtain entry
  my_struct entry = { .field = 1 };

  writer.write(entry);
}

Reader

#include "ipc/ipc.h"
...
ipc_reader<my_struct> reader("my_topic");

while (1)
{
  my_struct entry;

  if (reader.read(entry) == 0)
  {
    // use entry
    int field = entry.field;
  }
}

Note on ring queues

When using the ring queue-based data structure exposed through ipc_reader_rq, the reader should read all available elements to avoid exhaustion in case the writer is quicker than the reader.

This can be achieved simply by changing the if statement above to a while loop:

#include "ipc/ipc.h"
...
ipc_reader_rq<my_struct> reader("my_topic");

while (1)
{
  my_struct entry;

  while (reader.read(entry) == 0)
  {
    // use entry
    int field = entry.field;
  }
}

Even more minimal example

This example uses the helper methods ipc_write / ipc_read, which contain static declared instances of the ipc objects, so that the shared memory is allocated / mapped on the first call of ipc_write / ipc_read with a new entry type or id. Full demo in examples/cpp_ipc_brief_demo/.

Writer

#include "ipc/ipc.h"
...
while (1)
{
  // create / obtain entry
  my_struct entry = { .field = 1 };

  ipc_write(entry, "my_topic");
}

Reader

#include "ipc/ipc.h"
...
while (1)
{
  my_struct entry;

  if (ipc_read(entry, "my_topic") == 0)
  {
    // use entry
    int field = entry.field;
  }
}

Debug output

A debugging interface is exposed in include/ipc/debug.h . It is used internally, but output is off by default.

Configure the debugging output by defining debug_stdout and debug_stderr to the wanted file descriptors before including ipc.h:

#define debug_stdout stdout
#define debug_stderr stderr
#include "ipc/ipc.h"