Remove dependency to libmediadrm from drm HAL

drm HAL has been using libmediadrm for android::SharedLibrary class and
android::PluginLoader class. This is a Treble violation since
libmediadrm is a framework-only library that is not available to
vendors.

To solve the problem, the two classes are copied into this directory
to form a small static library android.hardware.drm@1.0-helper.a.

Bug: 38302533
Test: mm under /hardware/interfaces/drm/1.0/default and
/hardware/interfaces/drm/1.0/vts/functional

Change-Id: I7b4e5cdb3bc815e971e0c3b7ec99ea86042e13eb
diff --git a/drm/1.0/default/include/PluginLoader.h b/drm/1.0/default/include/PluginLoader.h
new file mode 100644
index 0000000..f387b3c
--- /dev/null
+++ b/drm/1.0/default/include/PluginLoader.h
@@ -0,0 +1,107 @@
+/**
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef PLUGIN_LOADER_H_
+#define PLUGIN_LOADER_H_
+
+#include "SharedLibrary.h"
+#include <utils/Log.h>
+#include <utils/String8.h>
+#include <utils/Vector.h>
+
+namespace android {
+namespace hardware {
+namespace drm {
+namespace V1_0 {
+namespace helper {
+
+template <class T>
+class PluginLoader {
+
+  public:
+    PluginLoader(const char *dir, const char *entry) {
+        /**
+         * scan all plugins in the plugin directory and add them to the
+         * factories list.
+         */
+        String8 pluginDir(dir);
+
+        DIR* pDir = opendir(pluginDir.string());
+        if (pDir == NULL) {
+            ALOGE("Failed to find plugin directory %s", pluginDir.string());
+        } else {
+            struct dirent* pEntry;
+            while ((pEntry = readdir(pDir))) {
+                String8 file(pEntry->d_name);
+                if (file.getPathExtension() == ".so") {
+                    String8 path = pluginDir + "/" + pEntry->d_name;
+                    T *plugin = loadOne(path, entry);
+                    if (plugin) {
+                        factories.push(plugin);
+                    }
+                }
+            }
+            closedir(pDir);
+        }
+    }
+
+    ~PluginLoader() {
+        for (size_t i = 0; i < factories.size(); i++) {
+            delete factories[i];
+        }
+    }
+
+    T *getFactory(size_t i) const {
+        return factories[i];
+    }
+
+    size_t factoryCount() const {return factories.size();}
+
+  private:
+    T* loadOne(const char *path, const char *entry) {
+        sp<SharedLibrary> library = new SharedLibrary(String8(path));
+        if (!library.get()) {
+            ALOGE("Failed to open plugin library %s: %s", path,
+                    library->lastError());
+        } else {
+            typedef T *(*CreateFactoryFunc)();
+            CreateFactoryFunc createFactoryFunc =
+                    (CreateFactoryFunc)library->lookup(entry);
+            if (createFactoryFunc) {
+                ALOGV("Found plugin factory entry %s in %s", entry, path);
+                libraries.push(library);
+                T* result = createFactoryFunc();
+                return  result;
+           }
+        }
+        return NULL;
+    }
+
+    Vector<T *> factories;
+    Vector<sp<SharedLibrary> > libraries;
+
+    PluginLoader(const PluginLoader &) = delete;
+    void operator=(const PluginLoader &) = delete;
+};
+
+}
+}
+}
+}
+} // namespace android
+
+#endif // PLUGIN_LOADER_H_
+