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Async load works, using exceptions for special resources.

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This commit is contained in:
William Moberg
2016-01-14 16:27:45 +01:00
parent 9f185a1e35
commit 71047b08ec
13 changed files with 160 additions and 181 deletions
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include/Engine/Core/ResourceManager.h
+83 -94
View File
@@ -12,33 +12,13 @@
/** Base Resource class.
Implement this class for every resource to be handled by the resource manager.
If it should be possible to load the resource asyncronously (on a separate thread in the background),
using LoadAsync() then any necessary OpenGL calls (Eg. glGenBuffers(), glBindBuffer(), etc.) must be
made in GlCommands() method, and not inside the constructor (see Texture.cpp for an example).
*/
class Resource
{
friend class ResourceManager;
private:
bool m_FullyConstructed;
protected:
Resource() : m_FullyConstructed(false) { }
//This method only needs to be overridden if:
// 1: a) It should be possible to load the resource with LoadAsync(), or
// b) This resource will be loaded inside the constructor of another resource that can be loaded with LoadAsync().
// c) Same as above but recursively.
// 2: a) The resource needs to make OpenGL calls, or
// b) The resource contains a resource that makes OGL calls, or
// c) The resource contains a resource that contains ... ... a resource that makes OGL calls, or
//
//If 2.a: any calls should be made in the GlCommands.
//If 2.b or 2.c: PostCtorGLCommands() should be called on the contained resource(s).
//If GlCommands needs to be overridden and GlCommands is also overridden by a baseclass then the baseclass
//implementation should be called in from the derived class implementation (see Model.cpp for an example).
virtual void GlCommands() { }
Resource() { }
public:
// Pretend that this is a pure virtual function that you have to implement
@@ -47,21 +27,30 @@ public:
virtual void Reload() { }
virtual void OnChildReloaded(Resource* child) { }
//If this resource implements GlCommands and it is loaded in another resource,
//then the containing resource must also implement GlCommands and
//call this method in it (see RawModel.cpp for an example).
void PostCtorGLCommands()
{
if (!m_FullyConstructed) {
GlCommands();
}
m_FullyConstructed = true;
}
unsigned int TypeID;
unsigned int ResourceID;
};
//Any class inheriting from this class will always be loaded on the master thread, not on a parallel worker thread.
//This is important in case some instructions must be executed on the main thread, e.g. OpenGL commands, like glBindBuffer.
//This resource can still be loaded asyncronously, but it will not be loaded in a thread, instead it's constructor will
//be called once on every ResourceManager::Load, just throw StillLoadingException in the constructor if it is not done yet.
class ThreadUnsafeResource : public Resource
{
friend class ResourceManager;
protected:
//Should be thrown in a Resource's constructor if it cannot complete because another resource is still loading.
//Not actually an error, just a message to the ResourceManager.
struct StillLoadingException : public std::exception
{
virtual const char* what() const throw()
{
return "Resource is still loading.";
}
};
};
/** Singleton resource manager to keep track of and cache any external engine assets */
class ResourceManager
{
@@ -85,24 +74,20 @@ public:
*/
// TODO: Templateify
static bool IsResourceLoaded(std::string resourceType, std::string resourceName);
/** If the resource is not in cache, starts loading the resource and returns nullptr immediately.
/** If Async is false: Hot-loads a resource and caches it for future use.
Fairly safe to assume that return value is always a valid pointer, will only return nullptr on error.
If Async is true: If the resource is not loaded yet, starts loading the resource
in the background and returns nullptr immediately.
If the resource has been loaded already, return a pointer to it.
@tparam T Resource type.
@param resourceName Fully qualified name of the resource to load.
*/
template <typename T>
static T* LoadAsync(std::string resourceName, Resource* parent = nullptr);
/** Hot-loads a resource and caches it for future use.
Fairly safe to assume that return value is a valid pointer, will only return nullptr on error.
@tparam T Resource type.
@tparam Async Set this to true if the resource should be loaded asyncronously.
@param resourceName Fully qualified name of the resource to load.
*/
template <typename T>
static T* Load(std::string resourceName, Resource* parent = nullptr);
template <typename T, bool Async = false>
static T* Load(std::string resourceName, Resource* parent = nullptr);
/** Reloads an already loaded resource, keeping its resource ID intact.
@@ -116,6 +101,22 @@ public:
static void Update();
private:
//Represents a pointer value to signify that a resource haven't failed, but is not fully loaded.
class SpecialResourcePointer
{
public:
SpecialResourcePointer()
: m_Val(new Resource())
{}
~SpecialResourcePointer()
{
delete m_Val;
}
//Make this class implicitly convertible to the Resource*.
operator Resource* const() const { return m_Val; }
private:
Resource* const m_Val;
};
//This is a haxy way to make sure that IsMainThread is run when the program starts, so the master thread id is set.
struct MasterThreadChecker
{
@@ -124,7 +125,8 @@ private:
ResourceManager::IsMainThread();
}
};
static MasterThreadChecker m_Checker;
const static SpecialResourcePointer m_StillLoading;
const static MasterThreadChecker m_Checker;
static std::unordered_map<std::string, std::string> m_CompilerTypenameToResourceType;
static std::unordered_map<std::string, std::function<Resource*(std::string)>> m_FactoryFunctions; // type -> factory function
@@ -151,23 +153,8 @@ private:
static Resource* createResource(std::string resourceType, std::string resourceName, Resource* parent);
static bool IsMainThread();
template <bool Async>
static Resource* Load(std::string resourceType, std::string resourceName, Resource* parent = nullptr);
};
template <typename T>
T* ResourceManager::Load(std::string resourceName, Resource* parent /* = nullptr */)
{
auto resourceTypename = typeid(T).name();
auto it = m_CompilerTypenameToResourceType.find(resourceTypename);
if (it == m_CompilerTypenameToResourceType.end()) {
LOG_ERROR("Failed to load resource \"%s\" of type \"%s\": type not registered", resourceName.c_str(), resourceTypename);
return nullptr;
}
return static_cast<T*>(Load<false>(it->second, resourceName, parent));
}
template <typename T>
void ResourceManager::RegisterType(std::string typeName)
{
@@ -175,28 +162,29 @@ void ResourceManager::RegisterType(std::string typeName)
m_FactoryFunctions[typeName] = [](std::string resourceName) { return new T(resourceName); };
}
template <typename T>
T* ResourceManager::LoadAsync(std::string resourceName, Resource* parent /* = nullptr */)
template <typename T, bool async>
static T* ResourceManager::Load(std::string resourceName, Resource* parent /* = nullptr */)
{
auto resourceTypename = typeid(T).name();
auto it = m_CompilerTypenameToResourceType.find(resourceTypename);
if (it == m_CompilerTypenameToResourceType.end()) {
LOG_ERROR("Failed to load resource \"%s\" of type \"%s\": type not registered", resourceName.c_str(), resourceTypename);
return nullptr;
}
auto resourceTypename = typeid(T).name();
auto iter = m_CompilerTypenameToResourceType.find(resourceTypename);
if (iter == m_CompilerTypenameToResourceType.end()) {
LOG_ERROR("Failed to load resource \"%s\" of type \"%s\": type not registered", resourceName.c_str(), resourceTypename);
return nullptr;
}
return static_cast<T*>(Load<true>(it->second, resourceName, parent));
}
std::string resourceType = iter->second;
constexpr bool mustNotLoadInThread = std::is_base_of<ThreadUnsafeResource, T>::value;
if (mustNotLoadInThread && !IsMainThread()) {
LOG_ERROR("Failed to Load \"%s\": ThreadUnsafeResource type \"%s\" load in the constructor of another resource that is loaded asyncronously.", resourceName.c_str(), iter->second.c_str());
return nullptr;
}
template <bool Async>
static Resource* ResourceManager::Load(std::string resourceType, std::string resourceName, Resource* parent /* = nullptr */)
{
auto cacheKey = std::make_pair(resourceType, resourceName);
decltype(m_ResourceCache)::iterator it;
//If a thread has already been launched to load this resource.
auto tIt = m_LoadingThreads.find(cacheKey);
if (tIt != m_LoadingThreads.end()) {
if (Async) {
if (async) {
//Return null if the thread is still working.
if (!tIt->second.try_join_for(boost::chrono::nanoseconds(1))) {
return nullptr;
@@ -211,38 +199,39 @@ static Resource* ResourceManager::Load(std::string resourceType, std::string res
//Find the resource that the thread loaded.
it = m_ResourceCache.find(cacheKey);
if (it != m_ResourceCache.end()) {
//At this point the resource may not be completely
//done since the worker threads cannot do opengl commands.
if (IsMainThread()) {
//Do the gl commands to complete the resource if we are not a worker thread.
it->second->PostCtorGLCommands();
}
return it->second;
//Threads should not be able to throw StillLoadingException, so no check should be needed.
return static_cast<T*>(it->second);
} else {
//If resource is still null at cacheKey after thread finishes, it failed.
//If cacheKey does not exist after thread finishes, it failed.
return nullptr;
}
}
//If resource has already been loaded and cached.
//If resource has already been cached and completely loaded.
it = m_ResourceCache.find(cacheKey);
if (it != m_ResourceCache.end()) {
return it->second;
if (it != m_ResourceCache.end() && it->second != m_StillLoading) {
return static_cast<T*>(it->second);
}
Resource* res = nullptr;
//If resource is not cached..
if (Async) {
//Create a thread that loads the resource into cache.
m_LoadingThreads[cacheKey] = boost::thread(createResource, resourceType, resourceName, parent);
if (async) {
if (mustNotLoadInThread) {
res = createResource(resourceType, resourceName, parent);
if (res != m_StillLoading) {
return static_cast<T*>(res);
}
} else {
//Create a thread that loads the resource into cache.
m_LoadingThreads[cacheKey] = boost::thread(createResource, resourceType, resourceName, parent);
}
return nullptr;
} else {
//load and return the resource.
Resource* res = createResource(resourceType, resourceName, parent);
if (IsMainThread() && res != nullptr) {
//Do the gl commands to complete the resource if we are not a worker thread.
res->PostCtorGLCommands();
}
return res;
do {
res = createResource(resourceType, resourceName, parent);
} while (res == m_StillLoading);
return static_cast<T*>(res);
}
}