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/*
* Copyright 2018 Google, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Gabe Black
*/
#ifndef __BASE_FIBER_HH__
#define __BASE_FIBER_HH__
// ucontext functions (like getcontext, setcontext etc) have been marked
// as deprecated and are hence hidden in latest macOS releases.
// By defining _XOPEN_SOURCE we make them available at compilation time.
#if defined(__APPLE__) && defined(__MACH__)
#define _XOPEN_SOURCE 600
#include <ucontext.h>
#undef _XOPEN_SOURCE
#else
#include <ucontext.h>
#endif
#include <cstddef>
#include <cstdint>
/**
* This class represents a fiber, which is a light weight sort of thread which
* is cooperatively scheduled and runs sequentially with other fibers, swapping
* in and out of a single actual thread of execution.
*
* To define your own threads, create a subclass of Fiber and override its
* main() function to do what you want your fiber to do. You can start it by
* calling its run() method which will stop your execution and start the other
* fiber in your place.
*
* If your main() function ends, that fiber will automatically switch to either
* the primary fiber, or to a particular fiber you specified at construction
* time, and your fiber is considered finished.
*/
class Fiber
{
public:
const static size_t DefaultStackSize = 0x50000;
/// stack_size is the size of the stack available to this fiber.
/// link points to another fiber which will start executing when this
/// fiber's main function returns.
Fiber(size_t stack_size=DefaultStackSize);
Fiber(Fiber *link, size_t stack_size=DefaultStackSize);
virtual ~Fiber();
/// Start executing the fiber represented by this object. This function
/// will "return" when the current fiber is switched back to later on.
void run();
/// Returns whether the "main" function of this fiber has finished.
///
bool finished() const { return _finished; };
/// Get a pointer to the current running Fiber.
///
static Fiber *currentFiber();
/// Get a pointer to the primary Fiber.
/// This Fiber represents the thread of execution started by the OS, and
/// which has a Fiber attached to it after the fact.
static Fiber *primaryFiber();
protected:
/// This method is called when this fiber is first run. Override it to
/// give your fiber something to do. When main returns, the fiber will
/// mark itself as finished and switch to its link fiber.
virtual void main() = 0;
void setStarted() { started = true; }
private:
static void entryTrampoline();
void start();
ucontext_t ctx;
Fiber *link;
// The stack for this context, or a nullptr if allocated elsewhere.
uint8_t *stack;
size_t stackSize;
bool started;
bool _finished;
void createContext();
};
#endif // __BASE_FIBER_HH__
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