w32threads: support for frame multithreading

Replace our incomplete w32threads implementation with x264's pthreads
w32threads wrapper.
Relicensed to LGPL with kind permission by Pegasys Inc.

Signed-off-by: Janne Grunau <janne-libav@jannau.net>

1 files changed, 207 insertions, 0 deletions

diff --git a/libavcodec/w32pthreads.h b/libavcodec/w32pthreads.h
new file mode 100644
index 0000000..7774817
--- /dev/null
+++ b/libavcodec/w32pthreads.h
@@ -0,0 +1,207 @@
+/*
+ * Copyright (C) 2010-2011 x264 project
+ *
+ * Authors: Steven Walters <kemuri9@gmail.com>
+ *          Pegasys Inc. <http://www.pegasys-inc.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * w32threads to pthreads wrapper
+ */
+
+#ifndef AVCODEC_W32PTHREADS_H
+#define AVCODEC_W32PTHREADS_H
+
+/* Build up a pthread-like API using underlying Windows API. Have only static
+ * methods so as to not conflict with a potentially linked in pthread-win32
+ * library.
+ * As most functions here are used without checking return values,
+ * only implement return values as necessary. */
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <process.h>
+
+typedef struct {
+    void *handle;
+    void *(*func)(void* arg);
+    void *arg;
+    void *ret;
+} pthread_t;
+
+/* the conditional variable api for windows 6.0+ uses critical sections and
+ * not mutexes */
+typedef CRITICAL_SECTION pthread_mutex_t;
+
+/* This is the CONDITIONAL_VARIABLE typedef for using Window's native
+ * conditional variables on kernels 6.0+.
+ * MinGW does not currently have this typedef. */
+typedef struct {
+    void *ptr;
+} pthread_cond_t;
+
+/* function pointers to conditional variable API on windows 6.0+ kernels */
+static void (WINAPI *cond_broadcast)(pthread_cond_t *cond);
+static void (WINAPI *cond_init)(pthread_cond_t *cond);
+static void (WINAPI *cond_signal)(pthread_cond_t *cond);
+static BOOL (WINAPI *cond_wait)(pthread_cond_t *cond, pthread_mutex_t *mutex,
+                                DWORD milliseconds);
+
+static unsigned __stdcall attribute_align_arg win32thread_worker(void *arg)
+{
+    pthread_t *h = arg;
+    h->ret = h->func(h->arg);
+    return 0;
+}
+
+static int pthread_create(pthread_t *thread, const void *unused_attr,
+                          void *(*start_routine)(void*), void *arg)
+{
+    thread->func   = start_routine;
+    thread->arg    = arg;
+    thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
+                                           0, NULL);
+    return !thread->handle;
+}
+
+static void pthread_join(pthread_t thread, void **value_ptr)
+{
+    DWORD ret = WaitForSingleObject(thread.handle, INFINITE);
+    if (ret != WAIT_OBJECT_0)
+        return;
+    if (value_ptr)
+        *value_ptr = thread.ret;
+    CloseHandle(thread.handle);
+}
+
+#define pthread_mutex_init(m, a) InitializeCriticalSection(m)
+#define pthread_mutex_destroy(m) DeleteCriticalSection(m)
+#define pthread_mutex_lock(m)    EnterCriticalSection(m)
+#define pthread_mutex_unlock(m)  LeaveCriticalSection(m)
+
+/* for pre-Windows 6.0 platforms we need to define and use our own condition
+ * variable and api */
+typedef struct {
+    pthread_mutex_t mtx_waiter_count;
+    volatile int waiter_count;
+    HANDLE semaphore;
+} win32_cond_t;
+
+static void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
+{
+    win32_cond_t *win32_cond = NULL;
+    if (cond_init) {
+        cond_init(cond);
+        return;
+    }
+
+    /* non native condition variables */
+    win32_cond = av_mallocz(sizeof(win32_cond_t));
+    if (!win32_cond)
+        return;
+    cond->ptr = win32_cond;
+    win32_cond->semaphore = CreateSemaphore(NULL, 0, 0x7fffffff, NULL);
+    if (!win32_cond->semaphore)
+        return;
+
+    pthread_mutex_init(&win32_cond->mtx_waiter_count, NULL);
+}
+
+static void pthread_cond_destroy(pthread_cond_t *cond)
+{
+    win32_cond_t *win32_cond = cond->ptr;
+    /* native condition variables do not destroy */
+    if (cond_init)
+        return;
+
+    /* non native condition variables */
+    CloseHandle(win32_cond->semaphore);
+    pthread_mutex_destroy(&win32_cond->mtx_waiter_count);
+    av_freep(&win32_cond);
+    cond->ptr = NULL;
+}
+
+static void pthread_cond_broadcast(pthread_cond_t *cond)
+{
+    win32_cond_t *win32_cond = cond->ptr;
+    if (cond_broadcast) {
+        cond_broadcast(cond);
+        return;
+    }
+
+    /* non native condition variables */
+    pthread_mutex_lock(&win32_cond->mtx_waiter_count);
+    if (win32_cond->waiter_count) {
+        ReleaseSemaphore(win32_cond->semaphore, win32_cond->waiter_count, NULL);
+        win32_cond->waiter_count = 0;
+    }
+    pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
+}
+
+static void pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
+{
+    win32_cond_t *win32_cond = cond->ptr;
+    if (cond_wait) {
+        cond_wait(cond, mutex, INFINITE);
+        return;
+    }
+
+    /* non native condition variables */
+    pthread_mutex_lock(&win32_cond->mtx_waiter_count);
+    win32_cond->waiter_count++;
+    pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
+
+    pthread_mutex_unlock(mutex);
+    WaitForSingleObject(win32_cond->semaphore, INFINITE);
+    pthread_mutex_lock(mutex);
+}
+
+static void pthread_cond_signal(pthread_cond_t *cond)
+{
+    win32_cond_t *win32_cond = cond->ptr;
+    if (cond_signal) {
+        cond_signal(cond);
+        return;
+    }
+
+    /* non-native condition variables */
+    pthread_mutex_lock(&win32_cond->mtx_waiter_count);
+    if (win32_cond->waiter_count) {
+        ReleaseSemaphore(win32_cond->semaphore, 1, NULL);
+        win32_cond->waiter_count--;
+    }
+    pthread_mutex_unlock(&win32_cond->mtx_waiter_count);
+}
+
+static void w32thread_init(void)
+{
+    HANDLE kernel_dll = GetModuleHandle(TEXT("kernel32.dll"));
+    /* if one is available, then they should all be available */
+    cond_init      =
+        (void*)GetProcAddress(kernel_dll, "InitializeConditionVariable");
+    cond_broadcast =
+        (void*)GetProcAddress(kernel_dll, "WakeAllConditionVariable");
+    cond_signal    =
+        (void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
+    cond_wait      =
+        (void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
+}
+
+#endif /* AVCODEC_W32PTHREADS_H */