Java classes inlined into object file, plus loader

fragment of java.cpp

// This function calls the JNI routine DefineClass for each class in the
// in-memory class table (see java-classes.h). The class loader parameter passed
// to define class is the result of calling ClassLoader.getSystemClassLoader().
jthrowable java_load_classes()
{
    JNIEnv              *environment;
    jclass              class_loader;
    jmethodID           get_system_loader;
    jobject             system_loader;
    jthrowable          exception;
    jint                jni_result;

    // Get the JNI environment structure for the current thread.
    jni_result = virtual_machine->GetEnv((void**)&environment, JNI_REQUIRED);
    if(jni_result != JNI_OK)
        return false;

    // Find the standard ClassLoader class.
    class_loader = environment->FindClass("java/lang/ClassLoader");
    if(class_loader == NULL)
    {
        java_record_exception(environment, exception);
        return exception;
    }

    // Get the system class loader. The classes loaded from memory will be
    // marked as having been loaded using this class loader.
    get_system_loader =
        environment->GetStaticMethodID(class_loader, "getSystemClassLoader",
                                       "()Ljava/lang/ClassLoader;");
    if(get_system_loader == NULL)
    {
        java_record_exception(environment, exception);
        return exception;
    }

    system_loader =
        environment->CallStaticObjectMethod(class_loader, get_system_loader);

    // Iterate through the in-memory class table. For each entry, load the
    // corresponding class.
    for(int class_index = 0; class_index < class_count; ++class_index)
    {
        if(environment->DefineClass(classes[class_index].name, system_loader,
                                    (const jbyte*)classes[class_index].body,
                                    classes[class_index].body_length) == NULL)
        {
            java_record_exception(environment, exception);
            return exception;
        }
    }

    return NULL;
}

fragment of java.h

/** @brief Causes the virtual machine to load Java classes stored in the program
           image.

    To avoid the need to distribute a <code>.jar</code> file or a directory tree
    with several <code>.class</code> files together with the native portion of
    the FUSE driver, the Java classes necessary for the FUSE driver are stored
    inline in the native program image. They are therefore available in memory
    by the time the image has been loaded and the driver started.

    This function commands the virtual machine to load these classes. After
    this, the native code may freely call any of the Java code in the classes.

    The classes that are loaded are those listed in the table found in the
    generated file <code>java-classes.c</code>. The table itself is declared in
    the file <code>java-classes.h</code>. <code>java-classes.c</code> is
    typically generated by running the Java program
    <code>build.MakeClassesImage</code> with the appropriate arguments from the
    <code>Makefile</code>.

    @return <code>NULL</code> if the classes are loaded successfully. If there
            is an error, a Java exception object descriptive of the error is
            returned instead.
 */
jthrowable java_load_classes(void);

java-classes.h

/** @file java-classes.h
    @brief Definition of the inline Java class table.

    The inline Java class table contains pointers to a series of complete class
    files, and the corresponding Java modified UTF-8-encoded class names. Each
    class file is stored directly within the native binary image, and loaded by
    the driver at startup. This removes the need to distribute the classes
    separately from the native driver in a JAR file, and therefore the need to
    somehow communicate the path to the JAR file to the native binary.
 */

#ifndef _JAVA_CLASSES_H_
#define _JAVA_CLASSES_H_

/// Class table entry.
struct class_info
{
    /// Class name, encoded in Java modified UTF-8.
    const char          *name;
    /// Class body. This is the quoted contents of the .class file for the
    /// class.
    const char          *body;
    /// Length, in bytes, of the class body.
    const size_t        body_length;
};

/// Number of classes in the class table.
extern const int        class_count;
/// The class table itself.
extern const class_info classes[];

#endif // #ifndef _JAVA_CLASSES_H_