1 files changed, 120 insertions, 0 deletions
diff --git a/src/fiber.cpp b/src/fiber.cpp
new file mode 100644
index 0000000..7208ced
--- /dev/null
+++ b/src/fiber.cpp
@@ -0,0 +1,120 @@
+#include <stdlib.h>
+#include <QtCore/QtGlobal>
+
+#include "fiber.h"
+
+/*!
+  \class Fiber
+  \brief The Fiber class provides cooperatively scheduled stacks of execution.
+
+  Fibers, also known as coroutines, allow managing multiple stacks in the same
+  thread.
+
+  To create a fiber, subclass Fiber and override the run() method. To run it,
+  call cont(). This will execute the code in run() until it calls Fiber::yield().
+  At that point, the call to cont() returns. Subsequent calls to cont() will
+  continue execution of the fiber just after the yield().
+
+  Example:
+  class MyFiber : public Fiber
+  {
+      virtual void run()
+      {
+          qDebug() << "1";
+          Fiber::yield();
+          qDebug() << "2";
+      }
+  }
+
+  MyFiber fib;
+  qDebug() << "0.5";
+  fib.cont(); // prints 1
+  qDebug() << "1.5";
+  fib.cont(); // prints 2
+*/
+
+#ifdef Q_OS_MAC
+extern "C" void switchStackInternal(void* to, void** from);
+void initializeStack(void *data, int size, void (*entry)(), void **stackPointer);
+void switchStack(void* to, void** from) { switchStackInternal(to, from); }
+#else
+extern "C" void _switchStackInternal(void* to, void** from);
+void initializeStack(void *data, int size, void (*entry)(), void **stackPointer);
+void switchStack(void* to, void** from) { _switchStackInternal(to, from); }
+#endif
+
+Fiber *Fiber::_currentFiber = 0;
+
+Fiber::Fiber(int stackSize)
+    : _stackData(0)
+    , _stackPointer(0)
+    , _previousFiber(0)
+    , _status(NotStarted)
+{
+    // establish starting fiber context if necessary
+    currentFiber();
+    
+    _stackData = malloc(stackSize);
+    initializeStack(_stackData, stackSize, &entryPoint, &_stackPointer);
+}
+
+Fiber::Fiber(bool)
+    : _stackData(0)
+    , _stackPointer(0)
+    , _previousFiber(0)
+    , _status(Running)
+{
+}
+
+Fiber::~Fiber()
+{
+    if (_stackData)
+        free(_stackData);
+}
+
+Fiber *Fiber::currentFiber()
+{
+    // establish a context for the starting fiber
+    if (!_currentFiber)
+        _currentFiber = new Fiber(true);
+    
+    return _currentFiber;
+}
+
+void Fiber::entryPoint()
+{
+    _currentFiber->run();
+    yieldHelper(Terminated);
+    Q_ASSERT(0); // unreachable
+}
+
+// returns whether it can be continued again
+bool Fiber::cont()
+{    
+    Q_ASSERT(_status == NotStarted || _status == Stopped);
+    Q_ASSERT(!_previousFiber);
+    
+    _previousFiber = _currentFiber;
+    _currentFiber = this;
+    _status = Running;
+    switchStack(_stackPointer, &_previousFiber->_stackPointer);
+    return _status != Terminated;
+}
+
+void Fiber::yield()
+{
+    yieldHelper(Stopped);
+}
+
+void Fiber::yieldHelper(Status stopStatus)
+{
+    Fiber *stoppingFiber = _currentFiber;
+    Q_ASSERT(stoppingFiber);
+    Q_ASSERT(stoppingFiber->_previousFiber);
+    Q_ASSERT(stoppingFiber->_status == Running);
+
+    _currentFiber = stoppingFiber->_previousFiber;
+    stoppingFiber->_previousFiber = 0;
+    stoppingFiber->_status = stopStatus;
+    switchStack(_currentFiber->_stackPointer, &stoppingFiber->_stackPointer);
+}