Add ability for logger to change output streams

Author: Nikita Nazarov

src/agent.cpp

@@ -56,17 +56,17 @@ static jboolean setAllocationSamplingMode(jvmtiEventMode mode) {
 }
 
 JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
-    handleOptions(options);
+    logger::handleOptions(options);
 
-    debug("on agent load");
+    logger::debug("on agent load");
     jvmtiEnv *jvmti = nullptr;
     jint result = jvm->GetEnv((void **) &jvmti, JVMTI_VERSION_1_0);
     if (result != JNI_OK || jvmti == nullptr) {
         std::cerr << "ERROR: Unable to access JVMTI!" << std::endl;
         return result;
     }
 
-    debug("set capabilities");
+    logger::debug("set capabilities");
     jvmtiCapabilities capabilities;
     setRequiredCapabilities(jvmti, capabilities);
     jvmtiError error = jvmti->AddCapabilities(&capabilities);
@@ -83,15 +83,15 @@ JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved)
         }
     }
 
-    debug("set callbacks");
+    logger::debug("set callbacks");
     jvmtiEventCallbacks callbacks;
     std::memset(&callbacks, 0, sizeof(jvmtiEventCallbacks));
     callbacks.SampledObjectAlloc = SampledObjectAlloc;
     jvmti->SetEventCallbacks(&callbacks, sizeof(jvmtiEventCallbacks));
 
     gdata = new GlobalAgentData();
     gdata->jvmti = jvmti;
-    debug("initializing done");
+    logger::debug("initializing done");
     return JNI_OK;
 }
 

src/log.cpp

@@ -2,6 +2,7 @@
 
 #include <string>
 #include <iostream>
+#include <fstream>
 #include "log.h"
 
 namespace logger {
@@ -16,34 +17,45 @@ namespace logger {
 
     LogLevel LEVEL = ERROR;
     std::chrono::steady_clock::time_point timePoint;
+    std::ostream *out = &std::cout;
+
+    void open(const char *fileName) {
+        out = new std::ofstream(fileName);
+    }
+
+    void close() {
+        if (out != &std::cout) {
+            delete out;
+        }
+    }
 
     void fatal(const char *msg) {
         if (LEVEL >= FATAL) {
-            std::cerr << "MEMORY_AGENT::FATAL " << msg << std::endl;
+            *out << "MEMORY_AGENT::FATAL " << msg << std::endl;
         }
     }
 
     void error(const char *msg) {
         if (LEVEL >= ERROR) {
-            std::cerr << "MEMORY_AGENT::ERROR " << msg << std::endl;
+            *out << "MEMORY_AGENT::ERROR " << msg << std::endl;
         }
     }
 
     void warn(const char *msg) {
         if (LEVEL >= WARN) {
-            std::cout << "MEMORY_AGENT::WARN " << msg << std::endl;
+            *out << "MEMORY_AGENT::WARN " << msg << std::endl;
         }
     }
 
     void info(const char *msg) {
         if (LEVEL >= INFO) {
-            std::cout << "MEMORY_AGENT::INFO " << msg << std::endl;
+            *out  << "MEMORY_AGENT::INFO " << msg << std::endl;
         }
     }
 
     void debug(const char *msg) {
         if (LEVEL >= DEBUG) {
-            std::cout << "MEMORY_AGENT::DEBUG " << msg << std::endl;
+            *out << "MEMORY_AGENT::DEBUG " << msg << std::endl;
         }
     }
 
@@ -56,7 +68,7 @@ namespace logger {
             long long passedTime = std::__1::chrono::duration_cast<std::chrono::milliseconds>(
                     std::chrono::steady_clock::now() - timePoint
             ).count();
-            std::cout << "MEMORY_AGENT::TIME_MS" << passedTime << std::endl;
+            *out << "MEMORY_AGENT::TIME_MS " << passedTime << std::endl;
         }
     }
 

src/log.h

@@ -19,6 +19,10 @@ namespace logger {
     void logPassedTime();
 
     void handleOptions(const char *options);
+
+    void open(const char *fileName);
+
+    void close();
 }
 
 #endif //MEMORY_AGENT_LOG_H