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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * accompanied this code).
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package jdk.internal.loader;

import jdk.internal.misc.VM;
import jdk.internal.ref.CleanerFactory;
import jdk.internal.util.StaticProperty;

import java.io.File;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.Objects;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

Native libraries are loaded via System.loadLibrary(String), System.load(String), Runtime.loadLibrary(String) and Runtime.load(String). They are caller-sensitive. Each class loader has a NativeLibraries instance to register all of its loaded native libraries. System::loadLibrary (and other APIs) only allows a native library to be loaded by one class loader, i.e. one NativeLibraries instance. Any attempt to load a native library that has already been loaded by a class loader with another class loader will fail. /**
 * Native libraries are loaded via {@link System#loadLibrary(String)},
 * {@link System#load(String)}, {@link Runtime#loadLibrary(String)} and
 * {@link Runtime#load(String)}.  They are caller-sensitive.
 *
 * Each class loader has a NativeLibraries instance to register all of its
 * loaded native libraries.  System::loadLibrary (and other APIs) only
 * allows a native library to be loaded by one class loader, i.e. one
 * NativeLibraries instance.  Any attempt to load a native library that
 * has already been loaded by a class loader with another class loader
 * will fail.
 */
public final class NativeLibraries {

    private final Map<String, NativeLibraryImpl> libraries = new ConcurrentHashMap<>();
    private final ClassLoader loader;
    // caller, if non-null, is the fromClass parameter for NativeLibraries::loadLibrary
    // unless specified
    private final Class<?> caller;      // may be null
    private final boolean searchJavaLibraryPath;
    // loading JNI native libraries
    private final boolean isJNI;

    
Creates a NativeLibraries instance for loading JNI native libraries
via for System::loadLibrary use.
1. Support of auto-unloading.  The loaded native libraries are unloaded
   when the class loader is reclaimed.
2. Support of linking of native method.  See JNI spec.
3. Restriction on a native library that can only be loaded by one class loader.
   Each class loader manages its own set of native libraries.
   The same JNI native library cannot be loaded into more than one class loader.
This static factory method is intended only for System::loadLibrary use.
See Also:

     *     JNI Specification: Library and Version Management/**
     * Creates a NativeLibraries instance for loading JNI native libraries
     * via for System::loadLibrary use.
     *
     * 1. Support of auto-unloading.  The loaded native libraries are unloaded
     *    when the class loader is reclaimed.
     * 2. Support of linking of native method.  See JNI spec.
     * 3. Restriction on a native library that can only be loaded by one class loader.
     *    Each class loader manages its own set of native libraries.
     *    The same JNI native library cannot be loaded into more than one class loader.
     *
     * This static factory method is intended only for System::loadLibrary use.
     *
     * @see <a href="${docroot}/specs/jni/invocation.html##library-and-version-management">
     *     JNI Specification: Library and Version Management</a>
     */
    public static NativeLibraries jniNativeLibraries(ClassLoader loader) {
        return new NativeLibraries(loader);
    }

    
Creates a raw NativeLibraries instance that has the following properties:
1. Native libraries loaded in this raw NativeLibraries instance are
   not JNI native libraries.  Hence JNI_OnLoad and JNI_OnUnload will
   be ignored.  No support for linking of native method.
2. Native libraries not auto-unloaded.  They may be explicitly unloaded
   via NativeLibraries::unload.
3. No relationship with class loaders.
This static factory method is restricted for JDK trusted class use.
/**
     * Creates a raw NativeLibraries instance that has the following properties:
     * 1. Native libraries loaded in this raw NativeLibraries instance are
     *    not JNI native libraries.  Hence JNI_OnLoad and JNI_OnUnload will
     *    be ignored.  No support for linking of native method.
     * 2. Native libraries not auto-unloaded.  They may be explicitly unloaded
     *    via NativeLibraries::unload.
     * 3. No relationship with class loaders.
     *
     * This static factory method is restricted for JDK trusted class use.
     */
    public static NativeLibraries rawNativeLibraries(Class<?> trustedCaller,
                                                     boolean searchJavaLibraryPath) {
        return new NativeLibraries(trustedCaller, searchJavaLibraryPath);
    }

    private NativeLibraries(ClassLoader loader) {
        // for null loader, default the caller to this class and
        // do not search java.library.path
        this.loader = loader;
        this.caller = loader != null ? null : NativeLibraries.class;
        this.searchJavaLibraryPath = loader != null ? true : false;
        this.isJNI = true;
    }

    /*
     * Constructs a NativeLibraries instance of no relationship with class loaders
     * and disabled auto unloading.
     */
    private NativeLibraries(Class<?> caller, boolean searchJavaLibraryPath) {
        Objects.requireNonNull(caller);
        if (!VM.isSystemDomainLoader(caller.getClassLoader())) {
            throw new IllegalArgumentException("must be JDK trusted class");
        }
        this.loader = caller.getClassLoader();
        this.caller = caller;
        this.searchJavaLibraryPath = searchJavaLibraryPath;
        this.isJNI = false;
    }

    /*
     * Find the address of the given symbol name from the native libraries
     * loaded in this NativeLibraries instance.
     */
    public long find(String name) {
        if (libraries.isEmpty())
            return 0;

        // the native libraries map may be updated in another thread
        // when a native library is being loaded.  No symbol will be
        // searched from it yet.
        for (NativeLibrary lib : libraries.values()) {
            long entry = lib.find(name);
            if (entry != 0) return entry;
        }
        return 0;
    }

    /*
     * Load a native library from the given file.  Returns null if file does not exist.
     *
     * @param fromClass the caller class calling System::loadLibrary
     * @param file the path of the native library
     * @throws UnsatisfiedLinkError if any error in loading the native library
     */
    public NativeLibrary loadLibrary(Class<?> fromClass, File file) {
        // Check to see if we're attempting to access a static library
        String name = findBuiltinLib(file.getName());
        boolean isBuiltin = (name != null);
        if (!isBuiltin) {
            name = AccessController.doPrivileged(new PrivilegedAction<>() {
                public String run() {
                    try {
                        return file.exists() ? file.getCanonicalPath() : null;
                    } catch (IOException e) {
                        return null;
                    }
                }
            });
            if (name == null) {
                return null;
            }
        }
        return loadLibrary(fromClass, name, isBuiltin);
    }

    
Returns a NativeLibrary of the given name.
Params:
fromClass – the caller class calling System::loadLibrary
name –      library name
isBuiltin – built-in library
Throws:
UnsatisfiedLinkError – if the native library has already been loaded
     and registered in another NativeLibraries/**
     * Returns a NativeLibrary of the given name.
     *
     * @param fromClass the caller class calling System::loadLibrary
     * @param name      library name
     * @param isBuiltin built-in library
     * @throws UnsatisfiedLinkError if the native library has already been loaded
     *      and registered in another NativeLibraries
     */
    private NativeLibrary loadLibrary(Class<?> fromClass, String name, boolean isBuiltin) {
        ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
        if (this.loader != loader) {
            throw new InternalError(fromClass.getName() + " not allowed to load library");
        }

        synchronized (loadedLibraryNames) {
            // find if this library has already been loaded and registered in this NativeLibraries
            NativeLibrary cached = libraries.get(name);
            if (cached != null) {
                return cached;
            }

            // cannot be loaded by other class loaders
            if (loadedLibraryNames.contains(name)) {
                throw new UnsatisfiedLinkError("Native Library " + name +
                        " already loaded in another classloader");
            }

            /*
             * When a library is being loaded, JNI_OnLoad function can cause
             * another loadLibrary invocation that should succeed.
             *
             * We use a static stack to hold the list of libraries we are
             * loading because this can happen only when called by the
             * same thread because this block is synchronous.
             *
             * If there is a pending load operation for the library, we
             * immediately return success; otherwise, we raise
             * UnsatisfiedLinkError.
             */
            for (NativeLibraryImpl lib : nativeLibraryContext) {
                if (name.equals(lib.name())) {
                    if (loader == lib.fromClass.getClassLoader()) {
                        return lib;
                    } else {
                        throw new UnsatisfiedLinkError("Native Library " +
                                name + " is being loaded in another classloader");
                    }
                }
            }

            NativeLibraryImpl lib = new NativeLibraryImpl(fromClass, name, isBuiltin, isJNI);
            // load the native library
            nativeLibraryContext.push(lib);
            try {
                if (!lib.open()) {
                    return null;    // fail to open the native library
                }
                // auto unloading is only supported for JNI native libraries
                // loaded by custom class loaders that can be unloaded.
                // built-in class loaders are never unloaded.
                boolean autoUnload = isJNI && !VM.isSystemDomainLoader(loader)
                        && loader != ClassLoaders.appClassLoader();
                if (autoUnload) {
                    // register the loaded native library for auto unloading
                    // when the class loader is reclaimed, all native libraries
                    // loaded that class loader will be unloaded.
                    // The entries in the libraries map are not removed since
                    // the entire map will be reclaimed altogether.
                    CleanerFactory.cleaner().register(loader, lib.unloader());
                }
            } finally {
                nativeLibraryContext.pop();
            }
            // register the loaded native library
            loadedLibraryNames.add(name);
            libraries.put(name, lib);
            return lib;
        }
    }

    
Loads a native library from the system library path and java library path.
Params:
name – library name
Throws:
UnsatisfiedLinkError – if the native library has already been loaded
     and registered in another NativeLibraries/**
     * Loads a native library from the system library path and java library path.
     *
     * @param name library name
     *
     * @throws UnsatisfiedLinkError if the native library has already been loaded
     *      and registered in another NativeLibraries
     */
    public NativeLibrary loadLibrary(String name) {
        assert name.indexOf(File.separatorChar) < 0;
        assert caller != null;

        return loadLibrary(caller, name);
    }

    
Loads a native library from the system library path and java library path.
Params:
name – library name
fromClass – the caller class calling System::loadLibrary
Throws:
UnsatisfiedLinkError – if the native library has already been loaded
     and registered in another NativeLibraries/**
     * Loads a native library from the system library path and java library path.
     *
     * @param name library name
     * @param fromClass the caller class calling System::loadLibrary
     *
     * @throws UnsatisfiedLinkError if the native library has already been loaded
     *      and registered in another NativeLibraries
     */
    public NativeLibrary loadLibrary(Class<?> fromClass, String name) {
        assert name.indexOf(File.separatorChar) < 0;

        NativeLibrary lib = findFromPaths(LibraryPaths.SYS_PATHS, fromClass, name);
        if (lib == null && searchJavaLibraryPath) {
            lib = findFromPaths(LibraryPaths.USER_PATHS, fromClass, name);
        }
        return lib;
    }

    
Unloads the given native library
Params:
lib – native library/**
     * Unloads the given native library
     *
     * @param lib native library
     */
    public void unload(NativeLibrary lib) {
        if (isJNI) {
            throw new UnsupportedOperationException("explicit unloading cannot be used with auto unloading");
        }
        Objects.requireNonNull(lib);
        synchronized (loadedLibraryNames) {
            NativeLibraryImpl nl = libraries.remove(lib.name());
            if (nl != lib) {
                throw new IllegalArgumentException(lib.name() + " not loaded by this NativeLibraries instance");
            }
            // unload the native library and also remove from the global name registry
            nl.unloader().run();
        }
    }

    private NativeLibrary findFromPaths(String[] paths, Class<?> fromClass, String name) {
        for (String path : paths) {
            File libfile = new File(path, System.mapLibraryName(name));
            NativeLibrary nl = loadLibrary(fromClass, libfile);
            if (nl != null) {
                return nl;
            }
            libfile = ClassLoaderHelper.mapAlternativeName(libfile);
            if (libfile != null) {
                nl = loadLibrary(fromClass, libfile);
                if (nl != null) {
                    return nl;
                }
            }
        }
        return null;
    }

    
NativeLibraryImpl denotes a loaded native library instance. Each NativeLibraries contains a map of loaded native libraries in the private field libraries. Every native library requires a particular version of JNI. This is denoted by the private jniVersion field. This field is set by the VM when it loads the library, and used by the VM to pass the correct version of JNI to the native methods. /**
     * NativeLibraryImpl denotes a loaded native library instance.
     * Each NativeLibraries contains a map of loaded native libraries in the
     * private field {@code libraries}.
     *
     * Every native library requires a particular version of JNI. This is
     * denoted by the private {@code jniVersion} field.  This field is set by
     * the VM when it loads the library, and used by the VM to pass the correct
     * version of JNI to the native methods.
     */
    static class NativeLibraryImpl implements NativeLibrary {
        // the class from which the library is loaded, also indicates
        // the loader this native library belongs.
        final Class<?> fromClass;
        // the canonicalized name of the native library.
        // or static library name
        final String name;
        // Indicates if the native library is linked into the VM
        final boolean isBuiltin;
        // Indicate if this is JNI native library
        final boolean isJNI;

        // opaque handle to native library, used in native code.
        long handle;
        // the version of JNI environment the native library requires.
        int jniVersion;

        NativeLibraryImpl(Class<?> fromClass, String name, boolean isBuiltin, boolean isJNI) {
            assert !isBuiltin || isJNI : "a builtin native library must be JNI library";

            this.fromClass = fromClass;
            this.name = name;
            this.isBuiltin = isBuiltin;
            this.isJNI = isJNI;
        }

        @Override
        public String name() {
            return name;
        }

        @Override
        public long find(String name) {
            return findEntry0(this, name);
        }

        Runnable unloader() {
            return new Unloader(name, handle, isBuiltin, isJNI);
        }

        /*
         * Loads the named native library
         */
        boolean open() {
            if (handle != 0) {
                throw new InternalError("Native library " + name + " has been loaded");
            }

            return load(this, name, isBuiltin, isJNI);
        }
    }

    public static final NativeLibrary defaultLibrary = new NativeLibraryImpl(Object.class, "<default>", true, true) {

        @Override
        boolean open() {
            throw new UnsupportedOperationException("Cannot load default library");
        }

        @Override
        public long find(String name) {
            return NativeLibraries.findEntryInProcess(name);
        }

    };

    /*
     * The run() method will be invoked when this class loader becomes
     * phantom reachable to unload the native library.
     */
    static class Unloader implements Runnable {
        // This represents the context when a native library is unloaded
        // and getFromClass() will return null,
        static final NativeLibraryImpl UNLOADER =
                new NativeLibraryImpl(null, "dummy", false, false);

        final String name;
        final long handle;
        final boolean isBuiltin;
        final boolean isJNI;

        Unloader(String name, long handle, boolean isBuiltin, boolean isJNI) {
            assert !isBuiltin || isJNI : "a builtin native library must be JNI library";
            if (handle == 0) {
                throw new IllegalArgumentException(
                        "Invalid handle for native library " + name);
            }

            this.name = name;
            this.handle = handle;
            this.isBuiltin = isBuiltin;
            this.isJNI = isJNI;
        }

        @Override
        public void run() {
            synchronized (loadedLibraryNames) {
                /* remove the native library name */
                if (!loadedLibraryNames.remove(name)) {
                    throw new IllegalStateException(name + " has already been unloaded");
                }
                nativeLibraryContext.push(UNLOADER);
                try {
                    unload(name, isBuiltin, isJNI, handle);
                } finally {
                    nativeLibraryContext.pop();
                }
            }
        }
    }

    /*
     * Holds system and user library paths derived from the
     * {@code java.library.path} and {@code sun.boot.library.path} system
     * properties. The system properties are eagerly read at bootstrap, then
     * lazily parsed on first use to avoid initialization ordering issues.
     */
    static class LibraryPaths {
        // The paths searched for libraries
        static final String[] SYS_PATHS = ClassLoaderHelper.parsePath(StaticProperty.sunBootLibraryPath());
        static final String[] USER_PATHS = ClassLoaderHelper.parsePath(StaticProperty.javaLibraryPath());
    }

    // All native libraries we've loaded.
    // This also serves as the lock to obtain nativeLibraries
    // and write to nativeLibraryContext.
    private static final Set<String> loadedLibraryNames = new HashSet<>();

    // native libraries being loaded
    private static Deque<NativeLibraryImpl> nativeLibraryContext = new ArrayDeque<>(8);

    // Invoked in the VM to determine the context class in JNI_OnLoad
    // and JNI_OnUnload
    private static Class<?> getFromClass() {
        if (nativeLibraryContext.isEmpty()) { // only default library
            return Object.class;
        }
        return nativeLibraryContext.peek().fromClass;
    }

    // JNI FindClass expects the caller class if invoked from JNI_OnLoad
    // and JNI_OnUnload is NativeLibrary class
    private static native boolean load(NativeLibraryImpl impl, String name, boolean isBuiltin, boolean isJNI);
    private static native void unload(String name, boolean isBuiltin, boolean isJNI, long handle);
    private static native String findBuiltinLib(String name);
    private static native long findEntry0(NativeLibraryImpl lib, String name);
    private static native long findEntryInProcess(String name);
}