psigen / flexure

Flexure is a lightweight middleware mechanism for fast real-time communication.

Flexure

A prototype of a low-overhead middleware layer for fast configuration and IPC in real-time.

This is only a prototype. Do not use this in production code.

Examples

Different ways of getting and setting values into /apple/orange:

flex = new Flexure("/");
*flex["apple"]["orange"] = 2.0;
*flex["apple/orange"] = 2.1;
*flex["apple//orange"] = 2.2;
*flex["/apple/orange"] = 2.3;
*(new Flexure("/apple"))["orange"] = 2.4;
*(new Flexure("apple"))["orange"] = 2.5;

int orange = *flex["apple"]["orange"];
std::cout << "Orange is '"
          << orange << "'" << std::endl;
// Prints "Orange is '2.5'"

Remapping namespaces at runtime:

flex = new Flexure("apple");
flex.remap("orange", "/pear");
*flex["orange"] = 2.0; // Sets /pear = 2.0
*flex["/orange"] = 2.0; // Sets /orange = 2.0
*flex["mango"] = 2.0; // Sets apple/mango = 2.0

Registering a callback when a node changes values:

void callback(Flexure f, value) {
  std::cout << "Changed to '" 
            << new_val << "'" << std::endl;
}

flex = new Flexure("/");
*flex["apple"]["orange"] = 1.0;

flex["apple"]["orange"].Observe(callback);
*flex["apple"]["orange"] = 2.0;
// Prints "Changed to '2.0'"

flex["apple"]["orange"].Unobserve(callback);
*flex["apple"]["orange"] = 0.0;
// No output

Locking a hierarchy for read persistence:

Flexure f = flex["apple"];
Flexure f2 = flex["apple"];
*f = 2.0;

f.Lock();

int apple = *f;
std::cout << "Apple is '"
          << apple << "'" << std::endl;
// Prints "Apple is '2.0'"

*f = 2.5;
*f2 = 3.0;

int apple = *f;
std::cout << "Apple is '"
          << apple << "'" << std::endl;
// Prints "Apple is '2.5'"

f.Unlock();

int apple = *f;
std::cout << "Apple is '"
          << apple << "'" << std::endl;
// Prints "Apple is '3.0'" OR "Apple is '2.5'"

Transacting a hierarchy for atomic updates:

Flexure f = flex["apple"];
f.BeginTransaction();
*f = 2.0;
*f["apple"] = false;
*f["pear"] = "Pear";
f.EndTransaction();

Philosophy

• IPC metadata will be read in YAML and sent in JSON to maximize compatibility.
• Customizable serialization/deserialization templates can be added.
• It should be possible to change transports completely without changing the backing store.
• It should be possible to change front-end APIs entirely without changing the backing store.
• Only one special value in the YAML schema:
• Use native data formats or interfaces in any native language implementation.
• Don't require Boost, but be compatible with Boost.