Implement proper Size() handling in custom rwops

SDL2pp/ContainerRWops.hh

@@ -82,6 +82,19 @@ public:
 	ContainerRWops(C& container) : container_(container), position_(0) {
 	}
 
+	////////////////////////////////////////////////////////////
+	/// \brief Get the size of the data stream
+	///
+	/// \returns Size of the data stream on success, -1 if unknown
+	///
+	/// \see SDL2pp::RWops::Size
+	/// \see http://wiki.libsdl.org/SDL_RWsize
+	///
+	////////////////////////////////////////////////////////////
+	virtual Sint64 Size() override {
+		return static_cast<Sint64>(container_.size());
+	}
+
 	////////////////////////////////////////////////////////////
 	/// \brief Seek within the container
 	///

SDL2pp/RWops.cc

@@ -26,6 +26,13 @@
 
 namespace SDL2pp {
 
+Sint64 RWops::StdSizeFuncWrapper(SDL_RWops* context) {
+	assert(context != nullptr);
+	SDL_RWops* sdl_rwops = reinterpret_cast<SDL_RWops*>(context->hidden.unknown.data1);
+	assert(sdl_rwops != nullptr);
+	return sdl_rwops->size(sdl_rwops);
+}
+
 Sint64 RWops::StdSeekFuncWrapper(SDL_RWops* context, Sint64 offset, int whence) {
 	assert(context != nullptr);
 	SDL_RWops* sdl_rwops = reinterpret_cast<SDL_RWops*>(context->hidden.unknown.data1);
@@ -63,6 +70,13 @@ int RWops::StdCloseFuncWrapper(SDL_RWops* context) {
 	return ret;
 }
 
+Sint64 RWops::CustomSizeFuncWrapper(SDL_RWops* context) {
+	assert(context != nullptr);
+	CustomRWops* custom_rwops = reinterpret_cast<CustomRWops*>(context->hidden.unknown.data1);
+	assert(custom_rwops != nullptr);
+	return custom_rwops->Size();
+}
+
 Sint64 RWops::CustomSeekFuncWrapper(SDL_RWops* context, Sint64 offset, int whence) {
 	assert(context != nullptr);
 	CustomRWops* custom_rwops = reinterpret_cast<CustomRWops*>(context->hidden.unknown.data1);
@@ -136,6 +150,7 @@ RWops::RWops(SDL_RWops* rwops) {
 	if (rwops_ == nullptr)
 		throw Exception("SDL_AllocRW");
 
+	rwops_->size = StdSizeFuncWrapper;
 	rwops_->seek = StdSeekFuncWrapper;
 	rwops_->read = StdReadFuncWrapper;
 	rwops_->write = StdWriteFuncWrapper;

SDL2pp/RWops.hh

@@ -53,6 +53,16 @@ public:
 	////////////////////////////////////////////////////////////
 	virtual ~CustomRWops() {}
 
+	////////////////////////////////////////////////////////////
+	/// \brief Get the size of the data stream
+	///
+	/// \returns Size of the data stream on success, -1 if unknown
+	///
+	/// \see http://wiki.libsdl.org/SDL_RWsize
+	///
+	////////////////////////////////////////////////////////////
+	virtual Sint64 Size() = 0;
+
 	////////////////////////////////////////////////////////////
 	/// \brief Seek within the data stream
 	///
@@ -148,11 +158,13 @@ protected:
 	SDL_RWops* rwops_; ///< Managed SDL_RWops object
 
 private:
+	static Sint64 StdSizeFuncWrapper(SDL_RWops* context);
 	static Sint64 StdSeekFuncWrapper(SDL_RWops* context, Sint64 offset, int whence);
 	static size_t StdReadFuncWrapper(SDL_RWops* context, void *ptr, size_t size, size_t maxnum);
 	static size_t StdWriteFuncWrapper(SDL_RWops* context, const void *ptr, size_t size, size_t maxnum);
 	static int StdCloseFuncWrapper(SDL_RWops* context);
 
+	static Sint64 CustomSizeFuncWrapper(SDL_RWops* context);
 	static Sint64 CustomSeekFuncWrapper(SDL_RWops* context, Sint64 offset, int whence);
 	static size_t CustomReadFuncWrapper(SDL_RWops* context, void *ptr, size_t size, size_t maxnum);
 	static size_t CustomWriteFuncWrapper(SDL_RWops* context, const void *ptr, size_t size, size_t maxnum);
@@ -272,6 +284,7 @@ public:
 		if (rwops_ == nullptr)
 			throw Exception("SDL_AllocRW");
 
+		rwops_->size = CustomSizeFuncWrapper;
 		rwops_->seek = CustomSeekFuncWrapper;
 		rwops_->read = CustomReadFuncWrapper;
 		rwops_->write = CustomWriteFuncWrapper;

SDL2pp/StreamRWops.hh

@@ -24,6 +24,7 @@
 
 #include <SDL2pp/RWops.hh>
 
+#include <cassert>
 #include <stdexcept>
 #include <iostream>
 #include <type_traits>
@@ -147,6 +148,26 @@ public:
 	StreamRWops(S& stream) : stream_(stream) {
 	}
 
+	////////////////////////////////////////////////////////////
+	/// \brief Get the size of the data stream
+	///
+	/// \returns Size of the data stream on success, -1 if unknown
+	///
+	/// \see SDL2pp::RWops::Size
+	/// \see http://wiki.libsdl.org/SDL_RWsize
+	///
+	////////////////////////////////////////////////////////////
+	virtual Sint64 Size() override {
+		Sint64 old_pos = TellHelper<S>();
+		if (old_pos == -1) // not seekable?
+			return -1;
+		SeekHelper<S>(0, std::ios_base::end);
+		Sint64 size = TellHelper<S>();
+		SeekHelper<S>(old_pos, std::ios_base::beg);
+		assert(TellHelper<S>() == old_pos); // make sure we're back to where we were
+		return size;
+	}
+
 	////////////////////////////////////////////////////////////
 	/// \brief Seek within the stream
 	///