Add custom memory management strategies to cppc4group

1 files changed, 32 insertions, 9 deletions

diff --git a/src/cppc4group.hpp b/src/cppc4group.hpp
index f11387c..d946cee 100644
--- a/src/cppc4group.hpp
+++ b/src/cppc4group.hpp
@@ -76,6 +76,35 @@ public:
 	// or an empty optional on failure
 	using TmpMemoryCallback = std::optional<TmpMemory>(*)(size_t size);
 
+	// the C++ memory management strategies work exactly the same way as in C, but with std::function instead
+	class MemoryManagement {
+	public:
+		struct MemoryManagementStrategy_t;
+		using MemoryManagementStrategy = MemoryManagementStrategy_t*;
+
+		using Start = std::function<void*(void* memory, size_t size)>;
+		using End = std::function<void(void* memory)>;
+
+	private:
+		struct Private;
+		Private* p;
+
+	public:
+		MemoryManagement(Start&& start, End&& end);
+		MemoryManagement(MemoryManagementStrategy strategy);
+
+		~MemoryManagement();
+
+		MemoryManagementStrategy operator()() const;
+
+		// this may be used as start function if it need not do anything but return the original pointer
+		static constexpr auto NoOpStart = [](void* memory, size_t) { return memory; };
+
+		static const MemoryManagement Take;
+		static const MemoryManagement Copy;
+		static const MemoryManagement Reference;
+	};
+
 	// these are equivalent to their C counterparts
 	using ReadCallback = bool(*)(const void** const data, size_t* const size, void* const arg);
 	using SetupCallback = bool(*)(void* const arg);
@@ -88,12 +117,6 @@ public:
 		Auto
 	};
 
-	enum MemoryManagement {
-		Take,
-		Copy,
-		Reference
-	};
-
 	// use this to set one of the predefined strategies
 	static void setTmpMemoryStrategy(const TmpMemoryStrategy strategy);
 
@@ -115,8 +138,8 @@ public:
 	bool openExisting(const std::string& path);
 	bool openFd(const int fd);
 	bool openFilePointer(FILE* file);
-	bool openMemory(const void* const data, const size_t size, const MemoryManagement management = Reference);
-	bool openWithReadCallback(const ReadCallback callback, void* const callbackArg, const MemoryManagement management = Take, SetupCallback initCallback = nullptr, SetupCallback deinitCallback = nullptr);
+	bool openMemory(const void* const data, const size_t size, const MemoryManagement& management = MemoryManagement::Reference);
+	bool openWithReadCallback(const ReadCallback callback, void* const callbackArg, const MemoryManagement& management = MemoryManagement::Take, SetupCallback initCallback = nullptr, SetupCallback deinitCallback = nullptr);
 
 	// save actually maps to both cc4group.save and cc4group.saveOverwrite, thanks to default arguments (yes, thats the reason why they are separate in the C-API)
 	bool save(const std::string& path, const bool overwrite = false);
@@ -148,7 +171,7 @@ public:
 
 	bool createFile(const std::string& path);
 
-	bool setEntryData(const std::string& path, const void* const data = nullptr, const size_t size = 0, const MemoryManagement management = Copy);
+	bool setEntryData(const std::string& path, const void* const data = nullptr, const size_t size = 0, const MemoryManagement& management = MemoryManagement::Copy);
 
 	// to get the child group out of the optional in case of success, construct a new CppC4Group with the move constructor: CppC4Group child{std::move(*optionalChild)};
 	std::optional<CppC4Group> openAsChild(const std::string& path);