SkThreadPool and co. are not public.

include/utils/SkThreadPool.h

-/*
- * Copyright 2012 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkThreadPool_DEFINED
-#define SkThreadPool_DEFINED
-
-#include "SkCondVar.h"
-#include "SkRunnable.h"
-#include "SkTDArray.h"
-#include "SkTInternalLList.h"
-#include "SkThreadUtils.h"
-#include "SkTypes.h"
-
-#if defined(SK_BUILD_FOR_UNIX) || defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_ANDROID)
-#    include <unistd.h>
-#endif
-
-// Returns the number of cores on this machine.
-static inline int num_cores() {
-#if defined(SK_BUILD_FOR_WIN32)
-    SYSTEM_INFO sysinfo;
-    GetSystemInfo(&sysinfo);
-    return sysinfo.dwNumberOfProcessors;
-#elif defined(SK_BUILD_FOR_UNIX) || defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_ANDROID)
-    return (int) sysconf(_SC_NPROCESSORS_ONLN);
-#else
-    return 1;
-#endif
-}
-
-template <typename T>
-class SkTThreadPool {
-public:
-    /**
-     * Create a threadpool with count threads, or one thread per core if kThreadPerCore.
-     */
-    static const int kThreadPerCore = -1;
-    explicit SkTThreadPool(int count);
-    ~SkTThreadPool();
-
-    /**
-     * Queues up an SkRunnable to run when a thread is available, or synchronously if count is 0.
-     * Does not take ownership. NULL is a safe no-op.  If T is not void, the runnable will be passed
-     * a reference to a T on the thread's local stack.
-     */
-    void add(SkTRunnable<T>*);
-
-    /**
-     * Same as add, but adds the runnable as the very next to run rather than enqueueing it.
-     */
-    void addNext(SkTRunnable<T>*);
-
-    /**
-     * Block until all added SkRunnables have completed.  Once called, calling add() is undefined.
-     */
-    void wait();
-
- private:
-    struct LinkedRunnable {
-        SkTRunnable<T>* fRunnable;  // Unowned.
-        SK_DECLARE_INTERNAL_LLIST_INTERFACE(LinkedRunnable);
-    };
-
-    enum State {
-        kRunning_State,  // Normal case.  We've been constructed and no one has called wait().
-        kWaiting_State,  // wait has been called, but there still might be work to do or being done.
-        kHalting_State,  // There's no work to do and no thread is busy.  All threads can shut down.
-    };
-
-    void addSomewhere(SkTRunnable<T>* r,
-                      void (SkTInternalLList<LinkedRunnable>::*)(LinkedRunnable*));
-
-    SkTInternalLList<LinkedRunnable> fQueue;
-    SkCondVar                        fReady;
-    SkTDArray<SkThread*>             fThreads;
-    State                            fState;
-    int                              fBusyThreads;
-
-    static void Loop(void*);  // Static because we pass in this.
-};
-
-template <typename T>
-SkTThreadPool<T>::SkTThreadPool(int count) : fState(kRunning_State), fBusyThreads(0) {
-    if (count < 0) {
-        count = num_cores();
-    }
-    // Create count threads, all running SkTThreadPool::Loop.
-    for (int i = 0; i < count; i++) {
-        SkThread* thread = SkNEW_ARGS(SkThread, (&SkTThreadPool::Loop, this));
-        *fThreads.append() = thread;
-        thread->start();
-    }
-}
-
-template <typename T>
-SkTThreadPool<T>::~SkTThreadPool() {
-    if (kRunning_State == fState) {
-        this->wait();
-    }
-}
-
-namespace SkThreadPoolPrivate {
-
-template <typename T>
-struct ThreadLocal {
-    void run(SkTRunnable<T>* r) { r->run(data); }
-    T data;
-};
-
-template <>
-struct ThreadLocal<void> {
-    void run(SkTRunnable<void>* r) { r->run(); }
-};
-
-}  // namespace SkThreadPoolPrivate
-
-template <typename T>
-void SkTThreadPool<T>::addSomewhere(SkTRunnable<T>* r,
-                                    void (SkTInternalLList<LinkedRunnable>::* f)(LinkedRunnable*)) {
-    if (r == NULL) {
-        return;
-    }
-
-    if (fThreads.isEmpty()) {
-        SkThreadPoolPrivate::ThreadLocal<T> threadLocal;
-        threadLocal.run(r);
-        return;
-    }
-
-    LinkedRunnable* linkedRunnable = SkNEW(LinkedRunnable);
-    linkedRunnable->fRunnable = r;
-    fReady.lock();
-    SkASSERT(fState != kHalting_State);  // Shouldn't be able to add work when we're halting.
-    (fQueue.*f)(linkedRunnable);
-    fReady.signal();
-    fReady.unlock();
-}
-
-template <typename T>
-void SkTThreadPool<T>::add(SkTRunnable<T>* r) {
-    this->addSomewhere(r, &SkTInternalLList<LinkedRunnable>::addToTail);
-}
-
-template <typename T>
-void SkTThreadPool<T>::addNext(SkTRunnable<T>* r) {
-    this->addSomewhere(r, &SkTInternalLList<LinkedRunnable>::addToHead);
-}
-
-
-template <typename T>
-void SkTThreadPool<T>::wait() {
-    fReady.lock();
-    fState = kWaiting_State;
-    fReady.broadcast();
-    fReady.unlock();
-
-    // Wait for all threads to stop.
-    for (int i = 0; i < fThreads.count(); i++) {
-        fThreads[i]->join();
-        SkDELETE(fThreads[i]);
-    }
-    SkASSERT(fQueue.isEmpty());
-}
-
-template <typename T>
-/*static*/ void SkTThreadPool<T>::Loop(void* arg) {
-    // The SkTThreadPool passes itself as arg to each thread as they're created.
-    SkTThreadPool<T>* pool = static_cast<SkTThreadPool<T>*>(arg);
-    SkThreadPoolPrivate::ThreadLocal<T> threadLocal;
-
-    while (true) {
-        // We have to be holding the lock to read the queue and to call wait.
-        pool->fReady.lock();
-        while(pool->fQueue.isEmpty()) {
-            // Does the client want to stop and are all the threads ready to stop?
-            // If so, we move into the halting state, and whack all the threads so they notice.
-            if (kWaiting_State == pool->fState && pool->fBusyThreads == 0) {
-                pool->fState = kHalting_State;
-                pool->fReady.broadcast();
-            }
-            // Any time we find ourselves in the halting state, it's quitting time.
-            if (kHalting_State == pool->fState) {
-                pool->fReady.unlock();
-                return;
-            }
-            // wait yields the lock while waiting, but will have it again when awoken.
-            pool->fReady.wait();
-        }
-        // We've got the lock back here, no matter if we ran wait or not.
-
-        // The queue is not empty, so we have something to run.  Claim it.
-        LinkedRunnable* r = pool->fQueue.head();
-
-        pool->fQueue.remove(r);
-
-        // Having claimed our SkRunnable, we now give up the lock while we run it.
-        // Otherwise, we'd only ever do work on one thread at a time, which rather
-        // defeats the point of this code.
-        pool->fBusyThreads++;
-        pool->fReady.unlock();
-
-        // OK, now really do the work.
-        threadLocal.run(r->fRunnable);
-        SkDELETE(r);
-
-        // Let everyone know we're not busy.
-        pool->fReady.lock();
-        pool->fBusyThreads--;
-        pool->fReady.unlock();
-    }
-
-    SkASSERT(false); // Unreachable.  The only exit happens when pool->fState is kHalting_State.
-}
-
-typedef SkTThreadPool<void> SkThreadPool;
-
-#endif