Diffusion
Diffusion is a C++ library for efficient message-based data distribution from one writer process to multiple reader processes. Currently Diffusion supports three transport types: to/from file, through shared memory, through network. Design of diffusion focuses on simplicity and efficiency.
Getting Started
Diffusion uses CMake to generate building and installation scripts. Default installation is static; only headers and static debug and release libraries will be installed to the system library. So the resulting object files will not be dependent to Diffusion on target machine. User can specify to use dynamic libraries instead.
How to install on GNU/Linux?
After Diffusion is copied, and present working directory is set to directory diffusion. We set up a temporary directory for out-of-source build.
mkdir build
cd build
If we want to install in the default /usr/local directory, we can simply use
cmake ..
We can also specify the directory where headers and library files will be installed
cmake .. -DCMAKE_INSTALL_PREFIX=../some_directory_you_like
Then Makefile is generated, we can use
make
to build the library. Or to build and install the library to previously specified location.
sudo make install
if we wish to install into the default /usr/local directory or other system directory.
How to generate documentation?
Diffusion uses Doxygen to generate documentation for the library. Under leanfix directory, use
doxygen
to generate documentation into doc/ subdirectory. HTML version of the documentation can be then accessed by loading doc/html/index.html into the browser.
Reference
File
File form Diffusion writes to and read from a file format called diffusion file. It can be used to store message-based data, and later load them while preserving the message boundary.
Diffusion file
Diffusion file starts with a four-byte header of magic string DFSN, followed by a sequence of messages. Each message has a four-byte header of little-endian signed integer representing the payload size, and a payload. This implementation detail only matters when user wish to use diffusion file directly.
Shared Memory
Shared memory form Diffusion writer can write to a shared memory area, and let multiple shared memory readers read it concurrently without additional synchronization. It has very low latency, and is suitable for efficient data distribution between processes. The typical round trip latency for sending and receiving a 500-byte message is around 680 nanoseconds on a laptop with i5-3210M cpu, and the throughput for 500-byte message is around 8 million messages per second. The test program can be found in test directory.
Network
Network form Diffusion writer is a server waiting for network form Diffusion reader to connect. It has higher latency then shared memory, but can be used across network.