public:

// Formatted version of a single call stack frame.

struct FrameInfo {

// Signature of the parent class.

string class_signature;

// Generic signature of the parent class.

string class_generic;

// Method executing code at the call frame.

string method_name;

// Name of the source code file or empty string if the Java class was

// compiled without source debugging information.

string source_file_name;

// Line number of the statement in the call frame or -1 if the Java class

// was compiled without line number debugging information.

int line_number;

};

// Raw version of a single call stack frame. The purpose of the split between

// "FrameInfo" and "JvmFrame" is to separate data collection from data

// formatting. "JvmFrame" contains the necessary information to read local

// variables and points to "FrameInfo" through "frame_info_key" member.

// "JvmFrame" can only be used within the scope of JVMTI callback and should

// be discarded immediately thereafter. The formatting of the protocol message

// to the Hub service, on the other hand, is deferred to a worker thread that

// only uses data in "FrameInfo" structure.

struct JvmFrame {

// Code location at the current stack frame. If not available (for example

// for injected frames), "code_location.method" will be nullptr.

jvmtiFrameInfo code_location;

// Reference to "FrameInfo" structure. The data is obtained through

// "ResolveCallFrameKey" method.

int frame_info_key;

};

public:

virtual ~EvalCallStack() { }

// Reads call stack of a particular thread (typically that would be the

// thread that hit a breakpoint). The function returns list of call frame

// keys, which can be resolved to a more detailed information through

// "ResolveCallFrameKey" function. The call frame key stays valid even if

// the Java method has been unloaded.

virtual void Read(jthread thread, std::vector<JvmFrame>* result) = 0;

// Resolves call frame key returned in "Read" function. The data is stored

// indefinitely and the call frame key will remain valid even if JVM unloads

// the method or the class.

virtual const FrameInfo& ResolveCallFrameKey(int key) const = 0;

// Associates frame key with the specified frame. This method is used to

// inject artificial stack frames.

virtual int InjectFrame(const FrameInfo& frame_info) = 0;

// Indicates that the specified Java method is no longer valid.

virtual void JvmtiOnCompiledMethodUnload(jmethodID method) = 0;