Add Agent concept

CMakeLists.txt

@@ -1,5 +1,8 @@
 cmake_minimum_required(VERSION 3.1)
 
+set (CMAKE_BUILD_TYPE Debug)
+set (CMAKE_CXX_STANDARD 14)
+
 # Add JNI headers to `include` path
 include_directories(include)
 add_subdirectory(jni)

README.md

@@ -14,7 +14,7 @@ JNI without the JVM
 - Interceptors support
 - Threading support
 - GC utilities
-- Reflection
+- Reflection support
 
 ##### Licensing
 

example/example.cpp

@@ -3,7 +3,8 @@
 #include <unistd.h>
 #include <iostream>
 
-#include "fake_jvm.h"
+#include "fake_jni.h"
+#include "agent.h"
 
 using std::string;
 
@@ -12,19 +13,8 @@ string GetCurrentPath() {
    return (getcwd(buf, sizeof(buf)) ? buf : "");
 }
 
-static jint (*JNI_OnLoad_)(JavaVM *vm, void *reserved);
-static void (*JNI_OnUnload_)(JavaVM *vm, void *reserved);
-
 int main(int argc, char* argv[]) {
-    void *exampleJniAgent = dlopen((GetCurrentPath() + "/libexample_jni_agent.so").c_str(), RTLD_LAZY);
-
-    (void*&) JNI_OnLoad_ = dlsym(exampleJniAgent, "JNI_OnLoad");
-    (void*&) JNI_OnUnload_ = dlsym(exampleJniAgent, "JNI_OnUnload");
-
-    JavaVM* vm = FakeJVM::instance.GetFakeJVM();
-    JNI_OnLoad_(vm, nullptr);
-    JNI_OnUnload_(vm, nullptr);
-
-    dlclose(exampleJniAgent);
+    Agent agent (GetCurrentPath() + "/libexample_jni_agent.so", { &dlopen, &dlsym, &dlclose });
+    FakeJVM::instance.close();
     return 0;
 }

include/agent.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "jni.h"
+
+#include <dlfcn.h>
+
+#include <string>
+#include <stdexcept>
+
+// TODO(meme) make this not gross
+struct AgentOptions {
+    void* (*dlopen_)(const char *filename, int flags);
+    void* (*dlsym_)(void *handle, const char *symbol);
+    int (*dlclose_)(void *handle);
+
+    AgentOptions(void* (*dlopen_)(const char*, int), void* (*dlsym_)(void*, const char*), int (*dlclose_)(void*))
+        : dlopen_(dlopen_), dlsym_(dlsym_), dlclose_(dlclose_) { }
+};
+
+class Agent {
+private:
+    std::string path_;
+    AgentOptions const& options_;
+
+    void *handle_;
+    jint (*JNI_OnLoad_)(JavaVM *vm, void *reserved);
+    void (*JNI_OnUnload_)(JavaVM *vm, void *reserved);
+
+public:
+    Agent(std::string path, AgentOptions const& options);
+
+    bool open();
+
+    bool close();
+};

include/fake_jni.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "jni.h"
+#include "agent.h"
+
+#include <vector>
+
+class FakeJVM {
+private:
+    JavaVM vm_;
+    std::vector<Agent*> agents_;
+
+public:
+    static FakeJVM instance;
+
+    FakeJVM();
+
+    JavaVM* getFakeJVM() { return &vm_; }
+
+    void addAgent(Agent* agent) {
+        agents_.push_back(agent);
+        agent->open();
+    }
+
+    void close() {
+        for (auto& agent : agents_) {
+            agent->close();
+        }
+    }
+};

jni/CMakeLists.txt

@@ -1,4 +1,5 @@
 # All sources for the JNI target (only STATIC is supported)
 add_library(jni STATIC
-    fake_jvm.cpp
+    fake_jni.cpp
+    agent.cpp
 )

jni/agent.cpp

@@ -0,0 +1,30 @@
+#include "agent.h"
+#include "fake_jni.h"
+
+#include <iostream>
+
+Agent::Agent(std::string path, AgentOptions const& options) : path_(path), options_(options) {
+    FakeJVM::instance.addAgent(this);
+}
+
+bool Agent::open() {
+    handle_ = options_.dlopen_(path_.c_str(), RTLD_LAZY);
+
+    if (!handle_) {
+        throw std::runtime_error("Agent failed to load using `dlopen`");
+    }
+
+    (void*&) JNI_OnLoad_ = options_.dlsym_(handle_, "JNI_OnLoad");
+    (void*&) JNI_OnUnload_ = options_.dlsym_(handle_, "JNI_OnUnload");
+
+    if (!JNI_OnLoad_ || !JNI_OnUnload_) {
+        throw std::runtime_error("JNI_OnLoad or JNI_OnUnload not found");
+    }
+
+    return JNI_OnLoad_(FakeJVM::instance.getFakeJVM(), nullptr) > JNI_VERSION_1_8;
+}
+
+bool Agent::close() {
+    JNI_OnUnload_(FakeJVM::instance.getFakeJVM(), nullptr);
+    return options_.dlclose_(handle_) ? false : true;
+}

jni/fake_jvm.cpp → jni/fake_jni.cpp

@@ -1,4 +1,4 @@
-#include "fake_jvm.h"
+#include "fake_jni.h"
 
 FakeJVM FakeJVM::instance;