Request Review: JDK-6479237 (cl) Add support for classloader names

[Mandy Chung]

> On Oct 31, 2016, at 6:51 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
>> 
>> if (VM.isModuleSystemInited() && !HashedModules.contains(m)) {
> Looks okay, an alternative would be to move that that check to L439.


What do you think about this? 
   http://cr.openjdk.java.net/~mchung/jdk9/webrevs/6479237/webrev.03/

/**
 * Returns true if the module is hashed with java.base.
 * <p>
 * This method returns false when running on the exploded image
 * since JDK modules are not hashed. They have no Version attribute
 * and so "@<version>" part will be omitted anyway.
 */
private static boolean isHashedInJavaBase(Module m) {
    // return true if module system is not initialized as the code
    // must be in java.base
    if (!VM.isModuleSystemInited())
        return true;

    return Layer.boot() == m.getLayer() && HashedModules.contains(m);
}

/*
 * Finds JDK non-upgradeable modules, i.e. the modules that are
 * included in the hashes in java.base.
 */
private static class HashedModules {
    static Set<String> HASHED_MODULES = hashedModules();

    static Set<String> hashedModules() {
        Module javaBase = Layer.boot().findModule("java.base").get();
        Optional<ModuleHashes> ohashes =
            SharedSecrets.getJavaLangModuleAccess()
                .hashes(javaBase.getDescriptor());

        if (ohashes.isPresent()) {
            Set<String> names = new HashSet<>(ohashes.get().names());
            names.add("java.base");
            return names;
        }

        return Set.of();
    }

    static boolean contains(Module m) {
        return HASHED_MODULES.contains(m.getName());
    }
}