public:

// Keep the dictionary of objects in a hash table that maps hash code to

// list of objects with that hash code. The usage of std::unordered_map and

// std::list is important: "Find" returns pointer to the stored data and

// these two data structures don't relocate the data when they grow (unlike

// std::vector).

// We could use hash table from jobject to TData and override hash function

// and equality operations to go to JNI. Benchmark showed no significant

// difference in performance between the two approaches.

typedef std::unordered_map<int32, std::list<std::pair<jobject, TData>>> Map;

public:

// Default constructor (no explicit cleanup of element values on removal).

JobjectMap() { }

~JobjectMap() {

RemoveAll();

}

// Enables cleanup of element values on removal.

explicit JobjectMap(

std::function<void(jobject, TData*)> cleanup_routine)

: cleanup_routine_(cleanup_routine) {

}

// Checks whether the specified Java object is already contained in the map.

bool Contains(jobject obj) const;

// Looks up for the data corresponding to the specified Java object. Returns

// nullptr if object is not in the dictionary or if error occurs.

TData* Find(jobject obj);

const TData* Find(jobject obj) const;

// Inserts a new entry to the map. If the object is already present in the

// map, the function returns false and the data structure is not changed.

// If an error occurs taking ref, the function also returns false.

// "inserted" is set to the actual object and data pair stored in the map.

bool Insert(jobject obj, TData data, std::pair<jobject, TData>** inserted);

bool Insert(jobject obj, TData data);

// Removes the specified object from the dictionary (releasing the ref).

// Returns true if the object was actually removed.

bool Remove(jobject obj);

// Removes all entries from the dictionary (releasing the refs). This

// function doesn't have to be called on Agent_OnUnload because JVM discards

// all the references on shutdown.

void RemoveAll();

private:

// Operation to invoke upon removal of an entry from the dictionary.

std::function<void(jobject, TData*)> cleanup_routine_;

// Hash table of Java objects

Map map_;

DISALLOW_COPY_AND_ASSIGN(JobjectMap);

public:

static jobject Create(jobject obj) {

return jni()->NewWeakGlobalRef(obj);

}

static void Delete(jobject obj) {

jni()->DeleteWeakGlobalRef(obj);

}

public:

static jobject Create(jobject obj) {

return jni()->NewGlobalRef(obj);

}

static void Delete(jobject obj) {

jni()->DeleteGlobalRef(obj);

}

public:

static jobject Create(jobject obj) {

return obj;

}

static void Delete(jobject obj) { }