the massive refactoring effort

[chaz/yoink] / src / moof / thread.hh

/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
**]  All rights reserved.
*
* vi:ts=4 sw=4 tw=75
*
* Distributable under the terms and conditions of the 2-clause BSD license;
* see the file COPYING for a complete text of the license.
*
**************************************************************************/

/**
 * \file thread.hh
 * Light C++ wrapper around the SDL threads API.
 */

#ifndef _MOOF_THREAD_HH_
#define _MOOF_THREAD_HH_

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <SDL/SDL.h>

#include <moof/math.hh>


namespace moof {


/**
 * Represents a thread which may be running.  You cannot instantiate a
 * thread object directly; new threads are created by detaching functions
 * using the detach() method.  Once a thread is detached, it will continue
 * running until the function returns.  You don't need to keep the thread
 * object you want to wait() or kill() the thread later.
 */
class thread
{
public:

        typedef boost::function<int(void)> function;


        /**
         * Construct an invalid thread object which has no association with any
         * real thread.
         */
        thread() :
                thread_(0) {}

        /**
         * Execute a function in a new thread.
         * \param function The function to execute.
         * \return The new thread, or an invalid thread if an error occurred.
         */
        static thread detach(const function& function)
        {
                thread::function* fcopy = new thread::function(function);
                SDL_Thread* thread = SDL_CreateThread(&thread::run, (void*)fcopy);
                if (thread == 0) delete fcopy;
                return moof::thread(thread);
        }


        /**
         * Wait for the thread to terminate, getting its return value.  The
         * thread will be invalidated.
         * \return The integer value returned by the detached function.
         */
        int wait()
        {
                int i;
                SDL_WaitThread(thread_, &i);
                thread_ = 0;
                return i;
        }

        /**
         * Forcefully kill the thread without giving it a chance to clean up
         * after itself.  The thread will be invalidated.  Don't use this.
         */
        void kill()
        {
                SDL_KillThread(thread_);
                thread_ = 0;
        }

        /**
         * Get whether or not the thread object is associated with a real
         * thread.
         * \return True if the thread is valid, false otherwise.
         */
        bool is_valid() const
        {
                return thread_ != 0;
        }


        /**
         * Get a unique identifier for this thread, if it is valid.
         * \return The identifier.
         */
        uint32_t identifier() const
        {
                return SDL_GetThreadID(thread_);
        }

        /**
         * Get the unique identifier of the calling thread.
         * \return The identifier.
         */
        static uint32_t current_identifier()
        {
                return SDL_ThreadID();
        }


private:

        thread(SDL_Thread* thread) :
                thread_(thread) {}

        static int run(void* arg)
        {
                int code = (*(function*)arg)();
                delete (function*)arg;
                return code;
        }


        SDL_Thread* thread_;
};


/**
 * An abstract class representing some task that is to be run
 * asynchronously.
 */
class async_task
{
public:

        /**
         * Deconstruct the task.
         */
        virtual ~async_task() {}

        /**
         * Get whether or not the task is done.
         * \return True if the task is done, false otherwise.
         */
        virtual bool is_done() const = 0;

        /**
         * Begin the task.
         */
        virtual void run() = 0;

        /**
         * Block the current thread until the task is finished.
         * \return A value representing the state of the finished task.
         */
        virtual int wait() = 0;
};

/**
 * An asynchronous task that is run to be executed in a separated thread.
 */
class threaded_task
{
public:

        /**
         * Get the thread object the task is executing in.
         * \return The thread.
         */
        const class thread& thread() const { return thread_; }

        /**
         * Block the current thread until the task thread is finished.
         * \return The integer value returned by the task function.
         */
        int wait()
        {
                return thread_.wait();
        }


protected:

        class thread thread_;
};


/**
 * A mutex to protect sensitive sections of code from threads which might
 * otherwise cause unpredictable results.
 */
class mutex
{
public:

        /**
         * Construct a mutex.
         */
    mutex() :
                mutex_(SDL_CreateMutex()) {}

        /**
         * Deconstruct a mutex.
         */
    ~mutex()
        {
                SDL_DestroyMutex(mutex_);
        }


        /**
         * Block until the calling thread can secure exclusive access to the
         * code protected by the mutex.
         * \return True if the lock was acquired, false otherwise.
         * \see lock
         */
    bool acquire_lock()
        {
                return (SDL_LockMutex(mutex_) == 0);
        }

        /**
         * Unlock the mutex.  Call this after the sensitive block of code to
         * allow another thread to acquire the lock.
         * \return True if the mutex was unlocked, false otherwise.
         * \see lock
         */
    bool release_lock()
        {
                return (SDL_UnlockMutex(mutex_) == 0);
        }


        /**
         * As an alternative method for locking, objects of this class will
         * automagically release the lock if it is still locked at
         * deconstruction.  Therefore, it's generally safer to use this method
         * since it makes it much more difficult to forget to unlock a mutex.
         */
    class lock
    {
    public:

                /**
                 * Construct a lock.
                 * \param mutex The mutex.
                 */
        explicit lock(mutex& mutex) :
                        mutex_(mutex),
                        is_locked_(false) {}

                /**
                 * Deconstruct a lock.  The lock is automagically released if it is
                 * still locked.
                 */
        ~lock()
                {
                        if (is_locked_) release();
                }


                /**
                 * Try to acquire a lock on the mutex.
                 * \return True if the mutex was locked, false otherwise.
                 */
        bool acquire()
                {
                        return (is_locked_ = mutex_.acquire_lock());
                }

                /**
                 * Release the lock.
                 * \return True if the mutex was unlocked, false otherwise.
                 */
        bool release()
                {
                        bool result = mutex_.release_lock();
                        is_locked_ = false;
                        return result;
                }


                /**
                 * Get whether or not the mutex is locked.
                 * \return True if the mutex is locked, false otherwise.
                 */
        bool is_locked() const
                {
                        return is_locked_;
                }


    protected:

        mutex&  mutex_;
        bool    is_locked_;

        friend class condition;
    };

        /**
         * This type of lock tries to acquire a lock on the mutex during
         * construction and releases the lock on deconstruction.
         */
    class scoped_lock : private lock
    {
        public:

                /**
                 * Construct a lock.
                 * \param mutex The mutex.
                 */
                explicit scoped_lock(mutex& mutex) :
                        lock(mutex)
                {
                        acquire();
                }

                /**
                 * Get whether or not the mutex is locked.
                 * \return True if the mutex is locked, false otherwise.
                 */
                bool is_locked() const
                {
                        return lock::is_locked();
                }
    };


private:

    SDL_mutex* mutex_;

    friend class condition;
};


/**
 * A class representing a condition variable.
 */
class condition
{
public:

        /**
         * Construct a condition.
         */
    condition()
        {
                condition_ = SDL_CreateCond();
        }

        /**
         * Deconstruct a condition.
         */
    ~condition()
        {
                SDL_DestroyCond(condition_);
        }


        /**
         * Unlock the mutex and wait for another thread to notify the thread,
         * at which point the mutex will be re-locked and the method will
         * return.
         * \param mutex The mutex.
         * \return True if the thread was notified, false otherwise.
         */
        bool wait(mutex& mutex)
        {
        return (SDL_CondWait(condition_, mutex.mutex_) == 0);
        }

        /**
         * Unlock the mutex associated with a lock and wait for another thread
         * to notify the thread, at which point the lock will be re-locked and
         * the method will return.
         * \param lock The lock.
         * \return True if the thread was notified, false otherwise.
         */
    bool wait(mutex::lock& lock)
        {
        return (SDL_CondWait(condition_, lock.mutex_.mutex_) == 0);
    }

        /**
         * Unlock the mutex and wait for another thread to notify the thread,
         * at which point the mutex will be re-locked and the method will
         * return.  If the thread was not notified before a certain number of
         * seconds, the method will return anyway.
         * \param mutex The mutex.
         * \param timeout Number of seconds to wait.
         * \return True if the thread was notified, false otherwise.
         */
    bool wait(mutex& mutex, scalar timeout)
        {
                Uint32 ms = timeout * SCALAR(1000.0);
        return (SDL_CondWaitTimeout(condition_, mutex.mutex_, ms) == 0);
        }

        /**
         * Unlock the mutex associated with a lock and wait for another thread
         * to notify the thread, at which point the lock will be re-locked and
         * the method will return.  If the thread was not notified before a
         * certain number of seconds, the method will return anyway.
         * \param lock The lock.
         * \param timeout Number of seconds to wait.
         * \return True if the thread was notified, false otherwise.
         */
    bool wait(mutex::lock& lock, scalar timeout)
        {
                Uint32 ms = timeout * SCALAR(1000.0);
        return (SDL_CondWaitTimeout(condition_,
                                                                        lock.mutex_.mutex_, ms) == 0);
        }


        /**
         * Notify one other thread that is waiting on the condition.
         * \return True on success, false otherwise.
         */
    bool notify()
        {
                return (SDL_CondSignal(condition_) == 0);
        }

        /**
         * Notify all other threads that are waiting on the condition.
         * \return True on success, false otherwise.
         */
    bool notify_all()
        {
                return (SDL_CondBroadcast(condition_) == 0);
        }


private:

    SDL_cond* condition_;
};


/**
 * A semaphore class.
 */
class semaphore
{
public:

        /**
         * Construct a semaphore.
         * \param value The initial value of the semaphore.
         */
    explicit semaphore(uint32_t value)
        {
                semaphore_ = SDL_CreateSemaphore(value);
        }

        /**
         * Deconstruct a semaphore.
         */
    ~semaphore()
        {
                SDL_DestroySemaphore(semaphore_);
        }


        /**
         * Block until the calling thread can secure exclusive access to the
         * code protected by the semaphore.
         * \return True if the lock was acquired, false otherwise.
         * \see lock
         */
    bool acquire_lock()
        {
                return (SDL_SemWait(semaphore_) == 0);
        }

        /**
         * Block until the calling thread can secure exclusive access to the
         * code protected by the semaphore, or until the timeout expires.
         * \param timeout Number of seconds to try.
         * \return True if the lock was acquired, false otherwise.
         */
        bool acquire_lock(scalar timeout)
        {
                Uint32 ms = timeout * SCALAR(1000.0);
                return (SDL_SemWaitTimeout(semaphore_, ms) == 0);
        }

        /**
         * Unlock the semaphore.  Call this after the sensitive block of code
         * to allow another thread to acquire the lock.
         * \return True if the semaphore was unlocked, false otherwise.
         * \see lock
         */
    bool release_lock()
        {
                return (SDL_SemPost(semaphore_) == 0);
        }

        /**
         * Try to lock the semaphore, but don't block if the lock is not
         * immediately available.
         * \return True if the semaphore was locked, false otherwise.
         */
    bool try_lock()
        {
                return (SDL_SemTryWait(semaphore_) == 0);
        }

        /**
         * As an alternative method for locking, objects of this class will
         * automagically release the lock if it is still locked at
         * deconstruction.  Therefore, it's generally safer to use this method
         * since it makes it much more difficult to forget to unlock a
         * semaphore.
         */
    class lock
    {
    public:

                /**
                 * Construct a lock.
                 * \param semaphore The semaphore.
                 */
        explicit lock(semaphore& semaphore) :
                        semaphore_(semaphore),
                        is_locked_(false) {}

                /**
                 * Deconstruct a lock.  The lock is automagically released if it is
                 * still locked.
                 */
        ~lock()
                {
                        if (is_locked_) release();
                }
        

                /**
                 * Try to acquire a lock on the semaphore.
                 * \return True if the semaphore was locked, false otherwise.
                 */
        bool acquire()
                {
                        return (is_locked_ = semaphore_.acquire_lock());
                }

                /**
                 * Release the lock.
                 * \return True if the semaphore was unlocked, false otherwise.
                 */
        bool release()
                {
                        bool result = semaphore_.release_lock();
                        is_locked_ = false;
                        return result;
                }

                /**
                 * Get whether or not the semaphore is locked.
                 * \return True if the semaphore is locked, false otherwise.
                 */
        bool is_locked() const
                {
                        return is_locked_;
                }
        

    protected:

        semaphore&      semaphore_;
        bool            is_locked_;
    };
    
        /**
         * This type of lock tries to acquire a lock on the semaphore during
         * construction and releases the lock on deconstruction.
         */
    class scoped_lock : private lock
    {
    public:

                /**
                 * Construct a lock.
                 * \param semaphore The semaphore.
                 */
        explicit scoped_lock(semaphore& semaphore) :
                        lock(semaphore)
                {
                        acquire();
                }

                /**
                 * Get whether or not the semaphore is locked.
                 * \return True if the semaphore is locked, false otherwise.
                 */
                bool is_locked() const
                {
                        return lock::is_locked();
                }
    };


private:

    SDL_sem* semaphore_;
};


} // namespace moof

#endif // _MOOF_THREAD_HH_