first commit.. all the files

Author: Manohar Akula

ClassModifier.h

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+import javassist.*; 
+
+public class ClassModifier {
+    public static void main(String[] args) {        
+        try {            
+            System.loadLibrary("jvmfaketime");
+
+            ClassPool pool = ClassPool.getDefault();
+            CtClass systemClass = pool.get("java.lang.System");
+
+			systemClass.addField(
+				CtField.make("public static long fakeTimeOffset;", systemClass)
+			);
+
+            systemClass.addMethod(
+				CtNewMethod.make(
+					"public static void resetTime() { System.fakeTimeOffset = 0L; }",
+				systemClass)
+			);
+			
+            systemClass.addMethod(
+				CtNewMethod.make(
+					"public static void moveTimeBy(long offset) { System.fakeTimeOffset += offset; }",
+				systemClass)
+			);
+
+            systemClass.addMethod(
+				CtNewMethod.make(
+					Modifier.PUBLIC | Modifier.STATIC | Modifier.NATIVE,
+					CtClass.longType,
+					"trueCurrentTimeMillis",
+					new CtClass[0],
+					new CtClass[0],
+					null,
+				systemClass)
+			);
+
+            systemClass.addMethod(
+				CtNewMethod.make(
+					Modifier.PUBLIC | Modifier.STATIC | Modifier.NATIVE,
+					CtClass.voidType,
+					"startFakingTime",
+					new CtClass[0],
+					new CtClass[0],
+					null,
+				systemClass)
+			);
+
+            systemClass.writeFile();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

ClassModifier.java

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+import java.util.*;
+import java.lang.reflect.Method;
+import static java.lang.System.*;
+
+public class Tests {
+    public static void main(String[] args) {            
+        try {
+            Method m = ClassLoader.class.getDeclaredMethod("loadLibrary", Class.class, String.class, Boolean.TYPE);
+            m.setAccessible(true);
+            m.invoke(null, java.lang.System.class, "jvmfaketime", false);
+        } catch (Exception e) {
+            System.out.println("couldn't load native library.");
+        }
+		
+        out.println("current time: " + new Date());            
+
+        startFakingTime();
+		moveTimeBy(30 * 24 * 60 * 60 * 1000l);
+        out.println("faked by 30 days: " + new Date());            
+        out.println("faked still, true time: " + new Date());            
+        resetTime();
+        out.println("defaked: " + new Date());            
+        startFakingTime();
+        moveTimeBy(1 * 24 * 60 * 60 * 1000l);
+        out.println("faked by 1 day again: " + new Date());            
+    }
+}

README.md

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+cc -I '$JAVA_HOME/include' -I '$JAVA_HOME/include/darwin' -o libjvmfaketime.dylib -dynamiclib jvmfaketime.c
+echo "compiled libjvmfaketime.so..."
+
+sudo cp libjvmfaketime.dylib $JAVA_HOME/jre/lib
+echo "installed libjvmfaketime in $JAVA_HOME/jre/lib"
+
+javac -cp javassist.jar:. ClassModifier.java
+java -cp .:javassist.jar -Djava.library.path=. ClassModifier
+jar -cf jvmfaketime.jar java/
+echo "generated jvmfaketime.jar in current directory"
+
+echo "\nexecuting fake time functions, please verify manually"
+javac -Xbootclasspath/p:jvmfaketime.jar Tests.java
+java -cp . -Xbootclasspath/p:jvmfaketime.jar Tests

Tests.java

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+cc -I "$JAVA_HOME/include" -I "$JAVA_HOME/include/darwin" -o libjvmfaketime.dylib -dynamiclib jvmfaketime.c
+echo "compiled libjvmfaketime.dylib..."
+
+sudo cp libjvmfaketime.dylib $JAVA_HOME/jre/lib
+echo "installed libjvmfaketime in $JAVA_HOME/jre/lib"
+
+javac -cp javassist.jar:. ClassModifier.java
+java -cp .:javassist.jar -Djava.library.path=. ClassModifier
+jar -cf jvmfaketime.jar java/
+echo "generated jvmfaketime.jar in current directory"
+
+echo "\nexecuting fake time functions, please verify manually"
+javac -Xbootclasspath/p:jvmfaketime.jar Tests.java
+java -cp . -Xbootclasspath/p:jvmfaketime.jar Tests

build-linux.sh

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+#include <jni.h>
+#include <sys/time.h>
+#include <stdlib.h>
+
+long long system_time() {
+	struct timeval now;
+	gettimeofday(&now, NULL);
+	return now.tv_sec * 1000LL + now.tv_usec / 1000LL;
+}
+
+JNIEXPORT jlong JNICALL Fake_CurrentTimeMillis(JNIEnv* env, jclass jc) {
+	jfieldID field = (*env)->GetStaticFieldID(env, jc, "fakeTimeOffset", "J");
+	if (field == NULL || (*env)->ExceptionCheck(env)) {
+ 		(*env)->ExceptionClear(env);		
+   		return 0;
+	}
+	jlong offset = (*env)->GetStaticLongField(env, jc, field);
+	return system_time() + offset;
+}
+
+JNIEXPORT jlong JNICALL Fake_TrueCurrentTimeMillis(JNIEnv* env, jclass jc) {
+	return system_time();
+}
+
+static JNINativeMethod fake_method[] = {
+    { "currentTimeMillis", "()J", (void*) &Fake_CurrentTimeMillis },
+    { "trueCurrentTimeMillis", "()J", (void*) &Fake_TrueCurrentTimeMillis }
+};
+
+JNIEXPORT void JNICALL Java_java_lang_System_startFakingTime(JNIEnv *env, jclass cls) {
+    (*env)->RegisterNatives(env, cls, fake_method, sizeof(fake_method) / sizeof(fake_method[0]));
+}

build-osx.sh

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+--- java6
+C_INCLUDE_PATH=/System/Library/Frameworks/JavaVM.framework/Versions/A/Headers cc jvmfaketime.c -o libjvmfaketime.dylib -dynamiclib -lcurl
+sudo cp libjvmfaketime.dylib /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Libraries
+
+javac -cp javassist.jar:. ClassModifier.java
+java -cp .:javassist.jar -Djava.library.path=. ClassModifier
+
+javac -Xbootclasspath/p:. Test.java
+java -cp . -Xbootclasspath/p:. Test
+
+--- java7
+C_INCLUDE_PATH=/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/include cc -I '/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/include/darwin' jvmfaketime.c -o libjvmfaketime.dylib -dynamiclib -lcurl
+sudo cp libjvmfaketime.dylib /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/jre/lib
+
+javac -cp javassist.jar:. ClassModifier.java
+java -cp .:javassist.jar -Djava.library.path=. ClassModifier
+
+javac -Xbootclasspath/p:. Test.java
+java -cp . -Xbootclasspath/p:. Test