/**
 * Defines the given binary class name to the VM, loading the class
 * bytes from the given module.
 *
 * @return the resulting Class or {@code null} if an I/O error occurs
 */
private Class<?> defineClass(String cn, LoadedModule loadedModule) {
    ModuleReader reader = moduleReaderFor(loadedModule.mref());

    try {
        // read class file
        String rn = cn.replace('.', '/').concat(".class");
        ByteBuffer bb = reader.read(rn).orElse(null);
        if (bb == null) {
            // class not found
            return null;
        }

        try {
            return defineClass(cn, bb, loadedModule.codeSource());
        } finally {
            reader.release(bb);
        }

    } catch (IOException ioe) {
        // TBD on how I/O errors should be propagated
        return null;
    }
}
 

/**
 * Returns the ModuleReader for the given module, creating it if needed.
 */
private ModuleReader moduleReaderFor(ModuleReference mref) {
    ModuleReader reader = moduleToReader.get(mref);
    if (reader == null) {
        // avoid method reference during startup
        Function<ModuleReference, ModuleReader> create = new Function<>() {
            public ModuleReader apply(ModuleReference moduleReference) {
                try {
                    return mref.open();
                } catch (IOException e) {
                    // Return a null module reader to avoid a future class
                    // load attempting to open the module again.
                    return new NullModuleReader();
                }
            }
        };
        reader = moduleToReader.computeIfAbsent(mref, create);
    }
    return reader;
}
 

/**
 * Creates a ModuleReference to a possibly-patched module
 */
private static ModuleReference newModule(ModuleInfo.Attributes attrs,
                                         URI uri,
                                         Supplier<ModuleReader> supplier,
                                         ModulePatcher patcher,
                                         HashSupplier hasher) {
    ModuleReference mref = new ModuleReferenceImpl(attrs.descriptor(),
                                                   uri,
                                                   supplier,
                                                   null,
                                                   attrs.target(),
                                                   attrs.recordedHashes(),
                                                   hasher,
                                                   attrs.moduleResolution());
    if (patcher != null)
        mref = patcher.patchIfNeeded(mref);

    return mref;
}
 

/**
 * Constructs a new instance of this class.
 */
public ModuleReferenceImpl(ModuleDescriptor descriptor,
                           URI location,
                           Supplier<ModuleReader> readerSupplier,
                           ModulePatcher patcher,
                           ModuleTarget target,
                           ModuleHashes recordedHashes,
                           ModuleHashes.HashSupplier hasher,
                           ModuleResolution moduleResolution)
{
    super(descriptor, Objects.requireNonNull(location));
    this.location = location;
    this.readerSupplier = readerSupplier;
    this.patcher = patcher;
    this.target = target;
    this.recordedHashes = recordedHashes;
    this.hasher = hasher;
    this.moduleResolution = moduleResolution;
}
 

void add(ModuleDescriptor... descriptors) {
    for (ModuleDescriptor descriptor: descriptors) {
        String name = descriptor.name();
        if (!namesToReference.containsKey(name)) {
            //modules.add(descriptor);

            URI uri = URI.create("module:/" + descriptor.name());

            ModuleReference mref = new ModuleReference(descriptor, uri) {
                @Override
                public ModuleReader open() {
                    throw new UnsupportedOperationException();
                }
            };

            namesToReference.put(name, mref);
        }
    }
}
 

/**
 * Defines the given binary class name to the VM, loading the class
 * bytes from the given module.
 *
 * @return the resulting Class or {@code null} if an I/O error occurs
 */
private Class<?> defineClass(String cn, LoadedModule loadedModule) {
    ModuleReader reader = moduleReaderFor(loadedModule.mref());

    try {
        // read class file
        String rn = cn.replace('.', '/').concat(".class");
        ByteBuffer bb = reader.read(rn).orElse(null);
        if (bb == null) {
            // class not found
            return null;
        }

        try {
            return defineClass(cn, bb, loadedModule.codeSource());
        } finally {
            reader.release(bb);
        }

    } catch (IOException ioe) {
        // TBD on how I/O errors should be propagated
        return null;
    }
}
 

/**
 * Creates a ModuleReference to a possibly-patched module
 */
private static ModuleReference newModule(ModuleInfo.Attributes attrs,
                                         URI uri,
                                         Supplier<ModuleReader> supplier,
                                         ModulePatcher patcher,
                                         HashSupplier hasher) {
    ModuleReference mref = new ModuleReferenceImpl(attrs.descriptor(),
                                                   uri,
                                                   supplier,
                                                   null,
                                                   attrs.target(),
                                                   attrs.recordedHashes(),
                                                   hasher,
                                                   attrs.moduleResolution());
    if (patcher != null)
        mref = patcher.patchIfNeeded(mref);

    return mref;
}
 

/**
 * Constructs a new instance of this class.
 */
ModuleReferenceImpl(ModuleDescriptor descriptor,
                    URI location,
                    Supplier<ModuleReader> readerSupplier,
                    ModulePatcher patcher,
                    ModuleTarget target,
                    ModuleHashes recordedHashes,
                    ModuleHashes.HashSupplier hasher,
                    ModuleResolution moduleResolution)
{
    super(descriptor, Objects.requireNonNull(location));
    this.location = location;
    this.readerSupplier = readerSupplier;
    this.patcher = patcher;
    this.target = target;
    this.recordedHashes = recordedHashes;
    this.hasher = hasher;
    this.moduleResolution = moduleResolution;
}
 

public static void main(String[] args) throws Exception {
    String mn = args[0];

    ModuleReference mref = ModuleLayer.boot()
            .configuration()
            .findModule(mn)
            .map(ResolvedModule::reference)
            .orElseThrow(() -> new RuntimeException(mn + " not resolved!!"));

    try (ModuleReader reader = mref.open()) {
        reader.list().forEach(name -> {
            testFindUnchecked(name);

            // if the resource is a directory then find without trailing slash
            if (name.endsWith("/")) {
                testFindUnchecked(name.substring(0, name.length() - 1));
            }
        });
    }
}
 

/**
 * Test ModuleReader#find
 */
void testFind(ModuleReader reader, String name, byte[] expectedBytes)
    throws IOException
{
    Optional<URI> ouri = reader.find(name);
    assertTrue(ouri.isPresent());

    URL url = ouri.get().toURL();
    if (!url.getProtocol().equalsIgnoreCase("jmod")) {
        URLConnection uc = url.openConnection();
        uc.setUseCaches(false);
        try (InputStream in = uc.getInputStream()) {
            byte[] bytes = in.readAllBytes();
            assertTrue(Arrays.equals(bytes, expectedBytes));
        }
    }
}
 

/**
 * Test ModuleReader#read
 */
void testRead(ModuleReader reader, String name, byte[] expectedBytes)
    throws IOException
{
    Optional<ByteBuffer> obb = reader.read(name);
    assertTrue(obb.isPresent());

    ByteBuffer bb = obb.get();
    try {
        int rem = bb.remaining();
        assertTrue(rem == expectedBytes.length);
        byte[] bytes = new byte[rem];
        bb.get(bytes);
        assertTrue(Arrays.equals(bytes, expectedBytes));
    } finally {
        reader.release(bb);
    }
}
 

private static void scanManifest(String resource, ModuleReader reader, Map<String, Object> propertyMap) throws IOException {
  try(var input = reader.open(resource).orElseThrow(() -> new IOException("resource unavailable " + resource));
      var isr = new InputStreamReader(input, StandardCharsets.UTF_8);
      var lineReader = new BufferedReader(isr)) {

    lineReader.lines()
    .flatMap(line -> {
      int index = line.indexOf(':');
      if (index == -1) {
        return Stream.empty();
      }
      String key = line.substring(0, index);
      String value = line.substring(index + 1).trim();
      return extractManifestValue(key, value).map(object -> Map.entry(key, object)).stream();
    })
    .forEach(entry -> propertyMap.put(entry.getKey(), entry.getValue()));

  }
}
 

private static void scanJavaClass(String resource, ModuleReader reader, Set<String> requirePackages, Set<String> exports, Set<String> uses) throws IOException {
try(var input = reader.open(resource).orElseThrow(() -> new IOException("resource unavailable " + resource))) {
  var classReader = new ClassReader(input);
  var className = classReader.getClassName();
  if (className.equals("module-info")) {
    return;  // skip module-info
  }
  var packageName = packageOf(className);
  exports.add(packageName);

  classReader.accept(new ClassRemapper(EmptyClassVisitor.getInstance(), new Remapper() {
    @Override
    public String map(String typeName) {
      String packageName = packageOf(typeName);
      requirePackages.add(packageName);
      return typeName;
    }
  }) {
    String owner;
 

/**
 * Creates a ModuleReader for the given module.
 */
private ModuleReader createModuleReader(ModuleReference mref) {
    try {
        return mref.open();
    } catch (IOException e) {
        // Return a null module reader to avoid a future class load
        // attempting to open the module again.
        return new NullModuleReader();
    }
}
 

/**
 * Creates a ModuleReference to a possibly-patched module in a modular JAR.
 */
static ModuleReference newJarModule(ModuleInfo.Attributes attrs,
                                    ModulePatcher patcher,
                                    Path file) {
    URI uri = file.toUri();
    Supplier<ModuleReader> supplier = () -> new JarModuleReader(file, uri);
    HashSupplier hasher = (a) -> ModuleHashes.computeHash(file, a);
    return newModule(attrs, uri, supplier, patcher, hasher);
}
 

/**
 * Creates a ModuleReference to a module in a JMOD file.
 */
static ModuleReference newJModModule(ModuleInfo.Attributes attrs, Path file) {
    URI uri = file.toUri();
    Supplier<ModuleReader> supplier = () -> new JModModuleReader(file, uri);
    HashSupplier hasher = (a) -> ModuleHashes.computeHash(file, a);
    return newModule(attrs, uri, supplier, null, hasher);
}
 

/**
 * Creates a ModuleReference to a possibly-patched exploded module.
 */
static ModuleReference newExplodedModule(ModuleInfo.Attributes attrs,
                                         ModulePatcher patcher,
                                         Path dir) {
    Supplier<ModuleReader> supplier = () -> new ExplodedModuleReader(dir);
    return newModule(attrs, dir.toUri(), supplier, patcher, null);
}
 

@Override
public ModuleReader open() throws IOException {
    try {
        return readerSupplier.get();
    } catch (UncheckedIOException e) {
        throw e.getCause();
    }
}
 

/**
 * Creates a ModuleReference to the system module.
 */
static ModuleReference toModuleReference(ModuleDescriptor descriptor,
                                         ModuleTarget target,
                                         ModuleHashes recordedHashes,
                                         HashSupplier hasher,
                                         ModuleResolution mres) {
    String mn = descriptor.name();
    URI uri = JNUA.create("jrt", "/".concat(mn));

    Supplier<ModuleReader> readerSupplier = new Supplier<>() {
        @Override
        public ModuleReader get() {
            return new SystemModuleReader(mn, uri);
        }
    };

    ModuleReference mref = new ModuleReferenceImpl(descriptor,
                                                   uri,
                                                   readerSupplier,
                                                   null,
                                                   target,
                                                   recordedHashes,
                                                   hasher,
                                                   mres);

    // may need a reference to a patched module if --patch-module specified
    mref = ModuleBootstrap.patcher().patchIfNeeded(mref);

    return mref;
}
 

/**
 * Returns the ModuleReader to delegate to when the resource is not
 * found in a patch location.
 */
private ModuleReader delegate() throws IOException {
    ModuleReader r = delegate;
    if (r == null) {
        synchronized (this) {
            r = delegate;
            if (r == null) {
                delegate = r = mref.open();
            }
        }
    }
    return r;
}
 

/**
 * Creates a ModuleReader for the given module.
 */
private ModuleReader createModuleReader(ModuleReference mref) {
    try {
        return mref.open();
    } catch (IOException e) {
        // Return a null module reader to avoid a future class load
        // attempting to open the module again.
        return new NullModuleReader();
    }
}
 

/**
 * Creates a ModuleReader for the given module.
 */
private static ModuleReader createModuleReader(ModuleReference mref) {
    try {
        return mref.open();
    } catch (IOException e) {
        // Return a null module reader to avoid a future class load
        // attempting to open the module again.
        return new NullModuleReader();
    }
}
 

private ModuleReference toModuleReference(ModuleDescriptor md,
                                          ModuleTarget target,
                                          ModuleHashes recordedHashes,
                                          HashSupplier hasher,
                                          ModuleResolution mres) {
    String mn = md.name();
    URI uri = JNUA.create("jrt", "/".concat(mn));

    Supplier<ModuleReader> readerSupplier = new Supplier<>() {
        @Override
        public ModuleReader get() {
            return new ImageModuleReader(mn, uri);
        }
    };

    ModuleReference mref = new ModuleReferenceImpl(md,
                                                   uri,
                                                   readerSupplier,
                                                   null,
                                                   target,
                                                   recordedHashes,
                                                   hasher,
                                                   mres);

    // may need a reference to a patched module if --patch-module specified
    mref = ModuleBootstrap.patcher().patchIfNeeded(mref);

    return mref;
}
 

/**
 * Creates a ModuleReference to a possibly-patched module in a modular JAR.
 */
static ModuleReference newJarModule(ModuleInfo.Attributes attrs,
                                    ModulePatcher patcher,
                                    Path file) {
    URI uri = file.toUri();
    Supplier<ModuleReader> supplier = () -> new JarModuleReader(file, uri);
    HashSupplier hasher = (a) -> ModuleHashes.computeHash(file, a);
    return newModule(attrs, uri, supplier, patcher, hasher);
}
 

/**
 * Creates a ModuleReference to a module in a JMOD file.
 */
static ModuleReference newJModModule(ModuleInfo.Attributes attrs, Path file) {
    URI uri = file.toUri();
    Supplier<ModuleReader> supplier = () -> new JModModuleReader(file, uri);
    HashSupplier hasher = (a) -> ModuleHashes.computeHash(file, a);
    return newModule(attrs, uri, supplier, null, hasher);
}
 

/**
 * Creates a ModuleReference to a possibly-patched exploded module.
 */
static ModuleReference newExplodedModule(ModuleInfo.Attributes attrs,
                                         ModulePatcher patcher,
                                         Path dir) {
    Supplier<ModuleReader> supplier = () -> new ExplodedModuleReader(dir);
    return newModule(attrs, dir.toUri(), supplier, patcher, null);
}
 

@Override
public ModuleReader open() throws IOException {
    try {
        return readerSupplier.get();
    } catch (UncheckedIOException e) {
        throw e.getCause();
    }
}
 

/**
 * Returns the ModuleReader to delegate to when the resource is not
 * found in a patch location.
 */
private ModuleReader delegate() throws IOException {
    ModuleReader r = delegate;
    if (r == null) {
        synchronized (this) {
            r = delegate;
            if (r == null) {
                delegate = r = mref.open();
            }
        }
    }
    return r;
}
 

private static ModuleReference moduleReference(ModuleDescriptor desc) {
    return new ModuleReference(desc, null) {
        @Override
        public ModuleReader open() {
            throw new UnsupportedOperationException();
        }
    };
}
 

/**
 * Test ModuleReader#open
 */
void testOpen(ModuleReader reader, String name, byte[] expectedBytes)
    throws IOException
{
    Optional<InputStream> oin = reader.open(name);
    assertTrue(oin.isPresent());

    InputStream in = oin.get();
    try (in) {
        byte[] bytes = in.readAllBytes();
        assertTrue(Arrays.equals(bytes, expectedBytes));
    }
}