vp9/decoder: add thread worker

vp9/decoder/vp9_thread.[hc]
Original source:
 http://git.chromium.org/webm/libwebp.git
 100644 blob b1615d0fb8d311666b2fa4561076c62d72c2e3ff  src/utils/thread.c
 100644 blob 13a61a4c84194c3374080cbf03d881d3cd6af40d  src/utils/thread.h

Local modifications:
 - s/WebP/VP9/g
 - camelcase functions -> lower with _'s

Change-Id: Ib6932640ee34f8b4782c6fbd15864a59d5d4c5fe

vp9/decoder/vp9_thread.h

@@ -0,0 +1,93 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Multi-threaded worker
+//
+// Original source:
+//  http://git.chromium.org/webm/libwebp.git
+//  100644 blob 13a61a4c84194c3374080cbf03d881d3cd6af40d  src/utils/thread.h
+
+
+#ifndef VP9_DECODER_VP9_THREAD_H_
+#define VP9_DECODER_VP9_THREAD_H_
+
+#include "vpx_config.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#if CONFIG_MULTITHREAD
+
+#if defined(_WIN32)
+
+#include <windows.h>
+typedef HANDLE pthread_t;
+typedef CRITICAL_SECTION pthread_mutex_t;
+typedef struct {
+  HANDLE waiting_sem_;
+  HANDLE received_sem_;
+  HANDLE signal_event_;
+} pthread_cond_t;
+
+#else
+
+#include <pthread.h>
+
+#endif    /* _WIN32 */
+#endif    /* CONFIG_MULTITHREAD */
+
+// State of the worker thread object
+typedef enum {
+  NOT_OK = 0,   // object is unusable
+  OK,           // ready to work
+  WORK          // busy finishing the current task
+} VP9WorkerStatus;
+
+// Function to be called by the worker thread. Takes two opaque pointers as
+// arguments (data1 and data2), and should return false in case of error.
+typedef int (*VP9WorkerHook)(void*, void*);
+
+// Synchronize object used to launch job in the worker thread
+typedef struct {
+#if CONFIG_MULTITHREAD
+  pthread_mutex_t mutex_;
+  pthread_cond_t  condition_;
+  pthread_t       thread_;
+#endif
+  VP9WorkerStatus status_;
+  VP9WorkerHook hook;     // hook to call
+  void* data1;            // first argument passed to 'hook'
+  void* data2;            // second argument passed to 'hook'
+  int had_error;          // return value of the last call to 'hook'
+} VP9Worker;
+
+// Must be called first, before any other method.
+void vp9_worker_init(VP9Worker* const worker);
+// Must be called to initialize the object and spawn the thread. Re-entrant.
+// Will potentially launch the thread. Returns false in case of error.
+int vp9_worker_reset(VP9Worker* const worker);
+// Makes sure the previous work is finished. Returns true if worker->had_error
+// was not set and no error condition was triggered by the working thread.
+int vp9_worker_sync(VP9Worker* const worker);
+// Triggers the thread to call hook() with data1 and data2 argument. These
+// hook/data1/data2 can be changed at any time before calling this function,
+// but not be changed afterward until the next call to vp9_worker_sync().
+void vp9_worker_launch(VP9Worker* const worker);
+// Kill the thread and terminate the object. To use the object again, one
+// must call vp9_worker_reset() again.
+void vp9_worker_end(VP9Worker* const worker);
+
+//------------------------------------------------------------------------------
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif
+
+#endif  /* VP9_DECODER_VP9_THREAD_H_ */