Add SkThreadPool for managing threads.

Skia-ized from https://codereview.appspot.com/6755043/

TODO: Use SkThread and platform independent features.

Review URL: https://codereview.appspot.com/6777064

git-svn-id: http://skia.googlecode.com/svn/trunk@6217 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 147 insertions, 0 deletions

diff --git a/include/utils/SkCondVar.h b/include/utils/SkCondVar.h
new file mode 100644
index 0000000000..d2539e4b9e
--- /dev/null
+++ b/include/utils/SkCondVar.h
@@ -0,0 +1,45 @@
+/*
+ * 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 SkCondVar_DEFINED
+#define SkCondVar_DEFINED
+
+#include <pthread.h>
+
+class SkCondVar {
+public:
+    SkCondVar();
+    ~SkCondVar();
+
+    void lock();
+    void unlock();
+
+    /**
+     * Pause the calling thread. Will be awoken when signal() is called.
+     * Must be called while lock() is held (but gives it up while waiting).
+     */
+    void wait();
+
+    /**
+     * Wake one thread waiting on this condition. Must be called while lock()
+     * is held.
+     */
+    void signal();
+
+    /**
+     * Wake all threads waiting on this condition. Must be called while lock()
+     * is held.
+     */
+    void broadcast();
+
+private:
+    // FIXME: Make this independent of pthreads.
+    pthread_mutex_t  fMutex;
+    pthread_cond_t   fCond;
+};
+
+#endif
diff --git a/include/utils/SkCountdown.h b/include/utils/SkCountdown.h
new file mode 100644
index 0000000000..6bcec7d5ff
--- /dev/null
+++ b/include/utils/SkCountdown.h
@@ -0,0 +1,36 @@
+/*
+ * 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 SkCountdown_DEFINED
+#define SkCountdown_DEFINED
+
+#include "SkCondVar.h"
+#include "SkRunnable.h"
+#include "SkTypes.h"
+
+class SkCountdown : public SkRunnable {
+public:
+    explicit SkCountdown(int32_t count);
+
+    /**
+     * Resets the countdown to the count provided.
+     */
+    void reset(int32_t count);
+
+    virtual void run() SK_OVERRIDE;
+
+    /**
+     * Blocks until run() has been called count times.
+     */
+    void wait();
+
+private:
+    SkCondVar fReady;
+    int32_t   fCount;
+};
+
+#endif
diff --git a/include/utils/SkRunnable.h b/include/utils/SkRunnable.h
new file mode 100644
index 0000000000..c7bedcc979
--- /dev/null
+++ b/include/utils/SkRunnable.h
@@ -0,0 +1,16 @@
+/*
+ * 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 SkRunnable_DEFINED
+#define SkRunnable_DEFINED
+
+class SkRunnable {
+public:
+    virtual void run() = 0;
+};
+
+#endif
diff --git a/include/utils/SkThreadPool.h b/include/utils/SkThreadPool.h
new file mode 100644
index 0000000000..a96f87b275
--- /dev/null
+++ b/include/utils/SkThreadPool.h
@@ -0,0 +1,50 @@
+/*
+ * 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 "SkTDArray.h"
+#include "SkTDLinkedList.h"
+
+class SkRunnable;
+class SkThread;
+
+class SkThreadPool {
+
+public:
+    /**
+     * Create a threadpool with exactly count (>=0) threads.
+     */
+    explicit SkThreadPool(int count);
+    ~SkThreadPool();
+
+    /**
+     * Queues up an SkRunnable to run when a thread is available, or immediately if
+     * count is 0.  NULL is a safe no-op.  Does not take ownership.
+     */
+    void add(SkRunnable*);
+
+ private:
+    struct LinkedRunnable {
+        // Unowned pointer.
+        SkRunnable* fRunnable;
+
+    private:
+        SK_DEFINE_DLINKEDLIST_INTERFACE(LinkedRunnable)
+    };
+
+    SkTDLinkedList<LinkedRunnable> fQueue;
+    SkCondVar                      fReady;
+    SkTDArray<SkThread*>           fThreads;
+    bool                           fDone;
+
+    static void Loop(void*);  // Static because we pass in this.
+};
+
+#endif