jdk/src/windows/classes/java/util/prefs/WindowsPreferences.java
changeset 2 90ce3da70b43
child 3861 a98a057ec335
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/windows/classes/java/util/prefs/WindowsPreferences.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1111 @@
+/*
+ * Copyright 2000-2002 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.util.prefs;
+
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.StringTokenizer;
+import java.io.ByteArrayOutputStream;
+import java.util.logging.Logger;
+
+/**
+ * Windows registry based implementation of  <tt>Preferences</tt>.
+ * <tt>Preferences</tt>' <tt>systemRoot</tt> and <tt>userRoot</tt> are stored in
+ * <tt>HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Prefs</tt> and
+ * <tt>HKEY_CURRENT_USER\Software\JavaSoft\Prefs</tt> correspondingly.
+ *
+ * @author  Konstantin Kladko
+ * @see Preferences
+ * @see PreferencesFactory
+ * @since 1.4
+ */
+
+class WindowsPreferences extends AbstractPreferences{
+
+    /**
+     * Logger for error messages
+     */
+    private static Logger logger;
+
+    /**
+     * Windows registry path to <tt>Preferences</tt>'s root nodes.
+     */
+    private static final byte[] WINDOWS_ROOT_PATH
+                               = stringToByteArray("Software\\JavaSoft\\Prefs");
+
+    /**
+     * Windows handles to <tt>HKEY_CURRENT_USER</tt> and
+     * <tt>HKEY_LOCAL_MACHINE</tt> hives.
+     */
+    private static final int HKEY_CURRENT_USER = 0x80000001;
+    private static final int HKEY_LOCAL_MACHINE = 0x80000002;
+
+    /**
+     * Mount point for <tt>Preferences</tt>'  user root.
+     */
+    private static final int USER_ROOT_NATIVE_HANDLE = HKEY_CURRENT_USER;
+
+    /**
+     * Mount point for <tt>Preferences</tt>'  system root.
+     */
+    private static final int SYSTEM_ROOT_NATIVE_HANDLE = HKEY_LOCAL_MACHINE;
+
+    /**
+     * Maximum byte-encoded path length for Windows native functions,
+     * ending <tt>null</tt> character not included.
+     */
+    private static final int MAX_WINDOWS_PATH_LENGTH = 256;
+
+    /**
+     * User root node.
+     */
+    static final Preferences userRoot =
+         new WindowsPreferences(USER_ROOT_NATIVE_HANDLE, WINDOWS_ROOT_PATH);
+
+    /**
+     * System root node.
+     */
+    static final Preferences systemRoot =
+        new WindowsPreferences(SYSTEM_ROOT_NATIVE_HANDLE, WINDOWS_ROOT_PATH);
+
+    /*  Windows error codes. */
+    private static final int ERROR_SUCCESS = 0;
+    private static final int ERROR_FILE_NOT_FOUND = 2;
+    private static final int ERROR_ACCESS_DENIED = 5;
+
+    /* Constants used to interpret returns of native functions    */
+    private static final int NATIVE_HANDLE = 0;
+    private static final int ERROR_CODE = 1;
+    private static final int SUBKEYS_NUMBER = 0;
+    private static final int VALUES_NUMBER = 2;
+    private static final int MAX_KEY_LENGTH = 3;
+    private static final int MAX_VALUE_NAME_LENGTH = 4;
+    private static final int DISPOSITION = 2;
+    private static final int REG_CREATED_NEW_KEY = 1;
+    private static final int REG_OPENED_EXISTING_KEY = 2;
+    private static final int NULL_NATIVE_HANDLE = 0;
+
+    /* Windows security masks */
+    private static final int DELETE = 0x10000;
+    private static final int KEY_QUERY_VALUE = 1;
+    private static final int KEY_SET_VALUE = 2;
+    private static final int KEY_CREATE_SUB_KEY = 4;
+    private static final int KEY_ENUMERATE_SUB_KEYS = 8;
+    private static final int KEY_READ = 0x20019;
+    private static final int KEY_WRITE = 0x20006;
+    private static final int KEY_ALL_ACCESS = 0xf003f;
+
+    /**
+     * Initial time between registry access attempts, in ms. The time is doubled
+     * after each failing attempt (except the first).
+     */
+    private static int INIT_SLEEP_TIME = 50;
+
+    /**
+     * Maximum number of registry access attempts.
+     */
+    private static int MAX_ATTEMPTS = 5;
+
+    /**
+     * BackingStore availability flag.
+     */
+    private boolean isBackingStoreAvailable = true;
+
+    /**
+     * Java wrapper for Windows registry API RegOpenKey()
+     */
+    private static native int[] WindowsRegOpenKey(int hKey, byte[] subKey,
+                                                         int securityMask);
+    /**
+     * Retries RegOpenKey() MAX_ATTEMPTS times before giving up.
+     */
+    private static int[] WindowsRegOpenKey1(int hKey, byte[] subKey,
+                                                      int securityMask) {
+        int[] result = WindowsRegOpenKey(hKey, subKey, securityMask);
+        if (result[ERROR_CODE] == ERROR_SUCCESS) {
+            return result;
+        } else if (result[ERROR_CODE] == ERROR_FILE_NOT_FOUND) {
+            logger().warning("Trying to recreate Windows registry node " +
+            byteArrayToString(subKey) + " at root 0x" +
+            Integer.toHexString(hKey) + ".");
+            // Try recreation
+            int handle = WindowsRegCreateKeyEx(hKey, subKey)[NATIVE_HANDLE];
+            WindowsRegCloseKey(handle);
+            return WindowsRegOpenKey(hKey, subKey, securityMask);
+        } else if (result[ERROR_CODE] != ERROR_ACCESS_DENIED) {
+            long sleepTime = INIT_SLEEP_TIME;
+            for (int i = 0; i < MAX_ATTEMPTS; i++) {
+            try {
+                Thread.sleep(sleepTime);
+            } catch(InterruptedException e) {
+                return result;
+            }
+            sleepTime *= 2;
+            result = WindowsRegOpenKey(hKey, subKey, securityMask);
+            if (result[ERROR_CODE] == ERROR_SUCCESS) {
+                return result;
+            }
+            }
+        }
+        return result;
+    }
+
+     /**
+     * Java wrapper for Windows registry API RegCloseKey()
+     */
+    private static native int WindowsRegCloseKey(int hKey);
+
+    /**
+     * Java wrapper for Windows registry API RegCreateKeyEx()
+     */
+    private static native int[] WindowsRegCreateKeyEx(int hKey, byte[] subKey);
+
+    /**
+     * Retries RegCreateKeyEx() MAX_ATTEMPTS times before giving up.
+     */
+    private static int[] WindowsRegCreateKeyEx1(int hKey, byte[] subKey) {
+        int[] result = WindowsRegCreateKeyEx(hKey, subKey);
+        if (result[ERROR_CODE] == ERROR_SUCCESS) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegCreateKeyEx(hKey, subKey);
+                if (result[ERROR_CODE] == ERROR_SUCCESS) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+    /**
+     * Java wrapper for Windows registry API RegDeleteKey()
+     */
+    private static native int WindowsRegDeleteKey(int hKey, byte[] subKey);
+
+    /**
+     * Java wrapper for Windows registry API RegFlushKey()
+     */
+    private static native int WindowsRegFlushKey(int hKey);
+
+    /**
+     * Retries RegFlushKey() MAX_ATTEMPTS times before giving up.
+     */
+    private static int WindowsRegFlushKey1(int hKey) {
+        int result = WindowsRegFlushKey(hKey);
+        if (result == ERROR_SUCCESS) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegFlushKey(hKey);
+                if (result == ERROR_SUCCESS) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Java wrapper for Windows registry API RegQueryValueEx()
+     */
+    private static native byte[] WindowsRegQueryValueEx(int hKey,
+                                                              byte[] valueName);
+    /**
+     * Java wrapper for Windows registry API RegSetValueEx()
+     */
+    private static native int WindowsRegSetValueEx(int hKey, byte[] valueName,
+                                                         byte[] value);
+    /**
+     * Retries RegSetValueEx() MAX_ATTEMPTS times before giving up.
+     */
+    private static int WindowsRegSetValueEx1(int hKey, byte[] valueName,
+                                                         byte[] value) {
+        int result = WindowsRegSetValueEx(hKey, valueName, value);
+        if (result == ERROR_SUCCESS) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegSetValueEx(hKey, valueName, value);
+                if (result == ERROR_SUCCESS) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Java wrapper for Windows registry API RegDeleteValue()
+     */
+    private static native int WindowsRegDeleteValue(int hKey, byte[] valueName);
+
+    /**
+     * Java wrapper for Windows registry API RegQueryInfoKey()
+     */
+    private static native int[] WindowsRegQueryInfoKey(int hKey);
+
+    /**
+     * Retries RegQueryInfoKey() MAX_ATTEMPTS times before giving up.
+     */
+    private static int[] WindowsRegQueryInfoKey1(int hKey) {
+        int[] result = WindowsRegQueryInfoKey(hKey);
+        if (result[ERROR_CODE] == ERROR_SUCCESS) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegQueryInfoKey(hKey);
+                if (result[ERROR_CODE] == ERROR_SUCCESS) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Java wrapper for Windows registry API RegEnumKeyEx()
+     */
+    private static native byte[] WindowsRegEnumKeyEx(int hKey, int subKeyIndex,
+                                      int maxKeyLength);
+
+    /**
+     * Retries RegEnumKeyEx() MAX_ATTEMPTS times before giving up.
+     */
+    private static byte[] WindowsRegEnumKeyEx1(int hKey, int subKeyIndex,
+                                      int maxKeyLength) {
+        byte[] result = WindowsRegEnumKeyEx(hKey, subKeyIndex, maxKeyLength);
+        if (result != null) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegEnumKeyEx(hKey, subKeyIndex, maxKeyLength);
+                if (result != null) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Java wrapper for Windows registry API RegEnumValue()
+     */
+    private static native byte[] WindowsRegEnumValue(int hKey, int valueIndex,
+                                      int maxValueNameLength);
+    /**
+     * Retries RegEnumValueEx() MAX_ATTEMPTS times before giving up.
+     */
+    private static byte[] WindowsRegEnumValue1(int hKey, int valueIndex,
+                                      int maxValueNameLength) {
+        byte[] result = WindowsRegEnumValue(hKey, valueIndex,
+                                                            maxValueNameLength);
+        if (result != null) {
+                return result;
+            } else {
+                long sleepTime = INIT_SLEEP_TIME;
+                for (int i = 0; i < MAX_ATTEMPTS; i++) {
+                try {
+                    Thread.sleep(sleepTime);
+                } catch(InterruptedException e) {
+                    return result;
+                }
+                sleepTime *= 2;
+                result = WindowsRegEnumValue(hKey, valueIndex,
+                                                            maxValueNameLength);
+                if (result != null) {
+                return result;
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Constructs a <tt>WindowsPreferences</tt> node, creating underlying
+     * Windows registry node and all its Windows parents, if they are not yet
+     * created.
+     * Logs a warning message, if Windows Registry is unavailable.
+     */
+    private WindowsPreferences(WindowsPreferences parent, String name) {
+        super(parent, name);
+        int parentNativeHandle = parent.openKey(KEY_CREATE_SUB_KEY, KEY_READ);
+        if (parentNativeHandle == NULL_NATIVE_HANDLE) {
+            // if here, openKey failed and logged
+            isBackingStoreAvailable = false;
+            return;
+        }
+        int[] result =
+               WindowsRegCreateKeyEx1(parentNativeHandle, toWindowsName(name));
+        if (result[ERROR_CODE] != ERROR_SUCCESS) {
+            logger().warning("Could not create windows registry "
+            + "node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegCreateKeyEx(...) returned error code " +
+            result[ERROR_CODE] + ".");
+            isBackingStoreAvailable = false;
+            return;
+        }
+        newNode = (result[DISPOSITION] == REG_CREATED_NEW_KEY);
+        closeKey(parentNativeHandle);
+        closeKey(result[NATIVE_HANDLE]);
+    }
+
+    /**
+     * Constructs a root node creating the underlying
+     * Windows registry node and all of its parents, if they have not yet been
+     * created.
+     * Logs a warning message, if Windows Registry is unavailable.
+     * @param rootNativeHandle Native handle to one of Windows top level keys.
+     * @param rootDirectory Path to root directory, as a byte-encoded string.
+     */
+    private  WindowsPreferences(int rootNativeHandle, byte[] rootDirectory) {
+        super(null,"");
+        int[] result =
+                WindowsRegCreateKeyEx1(rootNativeHandle, rootDirectory);
+        if (result[ERROR_CODE] != ERROR_SUCCESS) {
+            logger().warning("Could not open/create prefs root node " +
+            byteArrayToString(windowsAbsolutePath()) + " at root 0x" +
+            Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegCreateKeyEx(...) returned error code " +
+            result[ERROR_CODE] + ".");
+            isBackingStoreAvailable = false;
+            return;
+        }
+        // Check if a new node
+        newNode = (result[DISPOSITION] == REG_CREATED_NEW_KEY);
+        closeKey(result[NATIVE_HANDLE]);
+    }
+
+    /**
+     * Returns Windows absolute path of the current node as a byte array.
+     * Java "/" separator is transformed into Windows "\".
+     * @see Preferences#absolutePath()
+     */
+    private byte[] windowsAbsolutePath() {
+        ByteArrayOutputStream bstream = new ByteArrayOutputStream();
+        bstream.write(WINDOWS_ROOT_PATH, 0, WINDOWS_ROOT_PATH.length-1);
+        StringTokenizer tokenizer = new StringTokenizer(absolutePath(),"/");
+        while (tokenizer.hasMoreTokens()) {
+            bstream.write((byte)'\\');
+            String nextName = tokenizer.nextToken();
+            byte[] windowsNextName = toWindowsName(nextName);
+            bstream.write(windowsNextName, 0, windowsNextName.length-1);
+        }
+        bstream.write(0);
+        return bstream.toByteArray();
+    }
+
+    /**
+     * Opens current node's underlying Windows registry key using a
+     * given security mask.
+     * @param securityMask Windows security mask.
+     * @return Windows registry key's handle.
+     * @see #openKey(byte[], int)
+     * @see #openKey(int, byte[], int)
+     * @see #closeKey(int)
+     */
+    private int openKey(int securityMask) {
+        return openKey(securityMask, securityMask);
+    }
+
+    /**
+     * Opens current node's underlying Windows registry key using a
+     * given security mask.
+     * @param mask1 Preferred Windows security mask.
+     * @param mask2 Alternate Windows security mask.
+     * @return Windows registry key's handle.
+     * @see #openKey(byte[], int)
+     * @see #openKey(int, byte[], int)
+     * @see #closeKey(int)
+     */
+    private int openKey(int mask1, int mask2) {
+        return openKey(windowsAbsolutePath(), mask1,  mask2);
+    }
+
+     /**
+     * Opens Windows registry key at a given absolute path using a given
+     * security mask.
+     * @param windowsAbsolutePath Windows absolute path of the
+     *        key as a byte-encoded string.
+     * @param mask1 Preferred Windows security mask.
+     * @param mask2 Alternate Windows security mask.
+     * @return Windows registry key's handle.
+     * @see #openKey(int)
+     * @see #openKey(int, byte[],int)
+     * @see #closeKey(int)
+     */
+    private int openKey(byte[] windowsAbsolutePath, int mask1, int mask2) {
+        /*  Check if key's path is short enough be opened at once
+            otherwise use a path-splitting procedure */
+        if (windowsAbsolutePath.length <= MAX_WINDOWS_PATH_LENGTH + 1) {
+             int[] result = WindowsRegOpenKey1(rootNativeHandle(),
+                                               windowsAbsolutePath, mask1);
+             if (result[ERROR_CODE] == ERROR_ACCESS_DENIED && mask2 != mask1)
+                 result = WindowsRegOpenKey1(rootNativeHandle(),
+                                             windowsAbsolutePath, mask2);
+
+             if (result[ERROR_CODE] != ERROR_SUCCESS) {
+                logger().warning("Could not open windows "
+                + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+                " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+                ". Windows RegOpenKey(...) returned error code " +
+                result[ERROR_CODE] + ".");
+                result[NATIVE_HANDLE] = NULL_NATIVE_HANDLE;
+                if (result[ERROR_CODE] == ERROR_ACCESS_DENIED) {
+                    throw new SecurityException("Could not open windows "
+                + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+                " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+                ": Access denied");
+                }
+             }
+             return result[NATIVE_HANDLE];
+        } else {
+            return openKey(rootNativeHandle(), windowsAbsolutePath, mask1, mask2);
+        }
+    }
+
+     /**
+     * Opens Windows registry key at a given relative path
+     * with respect to a given Windows registry key.
+     * @param windowsAbsolutePath Windows relative path of the
+     *        key as a byte-encoded string.
+     * @param nativeHandle handle to the base Windows key.
+     * @param mask1 Preferred Windows security mask.
+     * @param mask2 Alternate Windows security mask.
+     * @return Windows registry key's handle.
+     * @see #openKey(int)
+     * @see #openKey(byte[],int)
+     * @see #closeKey(int)
+     */
+    private int openKey(int nativeHandle, byte[] windowsRelativePath,
+                        int mask1, int mask2) {
+    /* If the path is short enough open at once. Otherwise split the path */
+        if (windowsRelativePath.length <= MAX_WINDOWS_PATH_LENGTH + 1 ) {
+             int[] result = WindowsRegOpenKey1(nativeHandle,
+                                               windowsRelativePath, mask1);
+             if (result[ERROR_CODE] == ERROR_ACCESS_DENIED && mask2 != mask1)
+                 result = WindowsRegOpenKey1(nativeHandle,
+                                             windowsRelativePath, mask2);
+
+             if (result[ERROR_CODE] != ERROR_SUCCESS) {
+                logger().warning("Could not open windows "
+                + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+                " at root 0x" + Integer.toHexString(nativeHandle) +
+                ". Windows RegOpenKey(...) returned error code " +
+                result[ERROR_CODE] + ".");
+                result[NATIVE_HANDLE] = NULL_NATIVE_HANDLE;
+             }
+             return result[NATIVE_HANDLE];
+        } else {
+            int separatorPosition = -1;
+            // Be greedy - open the longest possible path
+            for (int i = MAX_WINDOWS_PATH_LENGTH; i > 0; i--) {
+                if (windowsRelativePath[i] == ((byte)'\\')) {
+                    separatorPosition = i;
+                    break;
+                }
+            }
+            // Split the path and do the recursion
+            byte[] nextRelativeRoot = new byte[separatorPosition+1];
+            System.arraycopy(windowsRelativePath, 0, nextRelativeRoot,0,
+                                                      separatorPosition);
+            nextRelativeRoot[separatorPosition] = 0;
+            byte[] nextRelativePath = new byte[windowsRelativePath.length -
+                                      separatorPosition - 1];
+            System.arraycopy(windowsRelativePath, separatorPosition+1,
+                             nextRelativePath, 0, nextRelativePath.length);
+            int nextNativeHandle = openKey(nativeHandle, nextRelativeRoot,
+                                           mask1, mask2);
+            if (nextNativeHandle == NULL_NATIVE_HANDLE) {
+                return NULL_NATIVE_HANDLE;
+            }
+            int result = openKey(nextNativeHandle, nextRelativePath,
+                                 mask1,mask2);
+            closeKey(nextNativeHandle);
+            return result;
+        }
+    }
+
+     /**
+     * Closes Windows registry key.
+     * Logs a warning if Windows registry is unavailable.
+     * @param key's Windows registry handle.
+     * @see #openKey(int)
+     * @see #openKey(byte[],int)
+     * @see #openKey(int, byte[],int)
+    */
+    private void closeKey(int nativeHandle) {
+        int result = WindowsRegCloseKey(nativeHandle);
+        if (result != ERROR_SUCCESS) {
+            logger().warning("Could not close windows "
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegCloseKey(...) returned error code " + result + ".");
+        }
+    }
+
+     /**
+     * Implements <tt>AbstractPreferences</tt> <tt>putSpi()</tt> method.
+     * Puts name-value pair into the underlying Windows registry node.
+     * Logs a warning, if Windows registry is unavailable.
+     * @see #getSpi(String)
+     */
+    protected void putSpi(String javaName, String value) {
+    int nativeHandle = openKey(KEY_SET_VALUE);
+    if (nativeHandle == NULL_NATIVE_HANDLE) {
+        isBackingStoreAvailable = false;
+        return;
+    }
+    int result =  WindowsRegSetValueEx1(nativeHandle,
+                          toWindowsName(javaName), toWindowsValueString(value));
+    if (result != ERROR_SUCCESS) {
+        logger().warning("Could not assign value to key " +
+        byteArrayToString(toWindowsName(javaName))+ " at Windows registry node "
+       + byteArrayToString(windowsAbsolutePath()) + " at root 0x"
+       + Integer.toHexString(rootNativeHandle()) +
+       ". Windows RegSetValueEx(...) returned error code " + result + ".");
+        isBackingStoreAvailable = false;
+        }
+    closeKey(nativeHandle);
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>getSpi()</tt> method.
+     * Gets a string value from the underlying Windows registry node.
+     * Logs a warning, if Windows registry is unavailable.
+     * @see #putSpi(String, String)
+     */
+    protected String getSpi(String javaName) {
+    int nativeHandle = openKey(KEY_QUERY_VALUE);
+    if (nativeHandle == NULL_NATIVE_HANDLE) {
+        return null;
+    }
+    Object resultObject =  WindowsRegQueryValueEx(nativeHandle,
+                                                  toWindowsName(javaName));
+    if (resultObject == null) {
+        closeKey(nativeHandle);
+        return null;
+    }
+    closeKey(nativeHandle);
+    return toJavaValueString((byte[]) resultObject);
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>removeSpi()</tt> method.
+     * Deletes a string name-value pair from the underlying Windows registry
+     * node, if this value still exists.
+     * Logs a warning, if Windows registry is unavailable or key has already
+     * been deleted.
+     */
+    protected void removeSpi(String key) {
+        int nativeHandle = openKey(KEY_SET_VALUE);
+        if (nativeHandle == NULL_NATIVE_HANDLE) {
+        return;
+        }
+        int result =
+            WindowsRegDeleteValue(nativeHandle, toWindowsName(key));
+        if (result != ERROR_SUCCESS && result != ERROR_FILE_NOT_FOUND) {
+            logger().warning("Could not delete windows registry "
+            + "value " + byteArrayToString(windowsAbsolutePath())+ "\\" +
+            toWindowsName(key) + " at root 0x" +
+            Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegDeleteValue(...) returned error code " +
+            result + ".");
+            isBackingStoreAvailable = false;
+        }
+        closeKey(nativeHandle);
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>keysSpi()</tt> method.
+     * Gets value names from the underlying Windows registry node.
+     * Throws a BackingStoreException and logs a warning, if
+     * Windows registry is unavailable.
+     */
+    protected String[] keysSpi() throws BackingStoreException{
+        // Find out the number of values
+        int nativeHandle = openKey(KEY_QUERY_VALUE);
+        if (nativeHandle == NULL_NATIVE_HANDLE) {
+            throw new BackingStoreException("Could not open windows"
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) + ".");
+        }
+        int[] result =  WindowsRegQueryInfoKey1(nativeHandle);
+        if (result[ERROR_CODE] != ERROR_SUCCESS) {
+            String info = "Could not query windows"
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegQueryInfoKeyEx(...) returned error code " +
+            result[ERROR_CODE] + ".";
+            logger().warning(info);
+            throw new BackingStoreException(info);
+        }
+        int maxValueNameLength = result[MAX_VALUE_NAME_LENGTH];
+        int valuesNumber = result[VALUES_NUMBER];
+        if (valuesNumber == 0) {
+            closeKey(nativeHandle);
+            return new String[0];
+       }
+       // Get the values
+       String[] valueNames = new String[valuesNumber];
+       for (int i = 0; i < valuesNumber; i++) {
+            byte[] windowsName = WindowsRegEnumValue1(nativeHandle, i,
+                                                        maxValueNameLength+1);
+            if (windowsName == null) {
+                String info =
+                "Could not enumerate value #" + i + "  of windows node " +
+                byteArrayToString(windowsAbsolutePath()) + " at root 0x" +
+                Integer.toHexString(rootNativeHandle()) + ".";
+                logger().warning(info);
+                throw new BackingStoreException(info);
+            }
+            valueNames[i] = toJavaName(windowsName);
+        }
+        closeKey(nativeHandle);
+        return valueNames;
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>childrenNamesSpi()</tt> method.
+     * Calls Windows registry to retrive children of this node.
+     * Throws a BackingStoreException and logs a warning message,
+     * if Windows registry is not available.
+     */
+    protected String[] childrenNamesSpi() throws BackingStoreException {
+        // Open key
+        int nativeHandle = openKey(KEY_ENUMERATE_SUB_KEYS| KEY_QUERY_VALUE);
+        if (nativeHandle == NULL_NATIVE_HANDLE) {
+            throw new BackingStoreException("Could not open windows"
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) + ".");
+        }
+        // Get number of children
+        int[] result =  WindowsRegQueryInfoKey1(nativeHandle);
+        if (result[ERROR_CODE] != ERROR_SUCCESS) {
+            String info = "Could not query windows"
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegQueryInfoKeyEx(...) returned error code " +
+            result[ERROR_CODE] + ".";
+            logger().warning(info);
+            throw new BackingStoreException(info);
+        }
+        int maxKeyLength = result[MAX_KEY_LENGTH];
+        int subKeysNumber = result[SUBKEYS_NUMBER];
+        if (subKeysNumber == 0) {
+            closeKey(nativeHandle);
+            return new String[0];
+        }
+        String[] subkeys = new String[subKeysNumber];
+        String[] children = new String[subKeysNumber];
+        // Get children
+        for (int i = 0; i < subKeysNumber; i++) {
+            byte[] windowsName = WindowsRegEnumKeyEx1(nativeHandle, i,
+                                                                maxKeyLength+1);
+            if (windowsName == null) {
+                String info =
+                "Could not enumerate key #" + i + "  of windows node " +
+                byteArrayToString(windowsAbsolutePath()) + " at root 0x" +
+                Integer.toHexString(rootNativeHandle()) + ". ";
+                logger().warning(info);
+                throw new BackingStoreException(info);
+            }
+            String javaName = toJavaName(windowsName);
+            children[i] = javaName;
+        }
+        closeKey(nativeHandle);
+        return children;
+    }
+
+    /**
+     * Implements <tt>Preferences</tt> <tt>flush()</tt> method.
+     * Flushes Windows registry changes to disk.
+     * Throws a BackingStoreException and logs a warning message if Windows
+     * registry is not available.
+     */
+    public void flush() throws BackingStoreException{
+
+        if (isRemoved()) {
+            parent.flush();
+            return;
+        }
+        if (!isBackingStoreAvailable) {
+            throw new BackingStoreException(
+                                       "flush(): Backing store not available.");
+        }
+        int nativeHandle = openKey(KEY_READ);
+        if (nativeHandle == NULL_NATIVE_HANDLE) {
+            throw new BackingStoreException("Could not open windows"
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) + ".");
+        }
+        int result = WindowsRegFlushKey1(nativeHandle);
+        if (result != ERROR_SUCCESS) {
+            String info = "Could not flush windows "
+            + "registry node " + byteArrayToString(windowsAbsolutePath())
+            + " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegFlushKey(...) returned error code " + result + ".";
+            logger().warning(info);
+            throw new BackingStoreException(info);
+        }
+        closeKey(nativeHandle);
+    }
+
+
+    /**
+     * Implements <tt>Preferences</tt> <tt>sync()</tt> method.
+     * Flushes Windows registry changes to disk. Equivalent to flush().
+     * @see flush()
+     */
+    public void sync() throws BackingStoreException{
+        if (isRemoved())
+            throw new IllegalStateException("Node has been removed");
+        flush();
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>childSpi()</tt> method.
+     * Constructs a child node with a
+     * given name and creates its underlying Windows registry node,
+     * if it does not exist.
+     * Logs a warning message, if Windows Registry is unavailable.
+     */
+    protected AbstractPreferences childSpi(String name) {
+            return new WindowsPreferences(this, name);
+    }
+
+    /**
+     * Implements <tt>AbstractPreferences</tt> <tt>removeNodeSpi()</tt> method.
+     * Deletes underlying Windows registry node.
+     * Throws a BackingStoreException and logs a warning, if Windows registry
+     * is not available.
+     */
+    public void removeNodeSpi() throws BackingStoreException {
+        int parentNativeHandle =
+                         ((WindowsPreferences)parent()).openKey(DELETE);
+        if (parentNativeHandle == NULL_NATIVE_HANDLE) {
+            throw new BackingStoreException("Could not open parent windows"
+            + "registry node of " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) + ".");
+        }
+        int result =
+                WindowsRegDeleteKey(parentNativeHandle, toWindowsName(name()));
+        if (result != ERROR_SUCCESS) {
+            String info = "Could not delete windows "
+            + "registry node " + byteArrayToString(windowsAbsolutePath()) +
+            " at root 0x" + Integer.toHexString(rootNativeHandle()) +
+            ". Windows RegDeleteKeyEx(...) returned error code " +
+            result + ".";
+            logger().warning(info);
+            throw new BackingStoreException(info);
+        }
+        closeKey(parentNativeHandle);
+    }
+
+    /**
+     * Converts value's or node's name from its byte array representation to
+     * java string. Two encodings, simple and altBase64 are used. See
+     * {@link #toWindowsName(String) toWindowsName()} for a detailed
+     * description of encoding conventions.
+     * @param windowsNameArray Null-terminated byte array.
+     */
+    private static String toJavaName(byte[] windowsNameArray) {
+        String windowsName = byteArrayToString(windowsNameArray);
+        // check if Alt64
+        if ((windowsName.length()>1) &&
+                                   (windowsName.substring(0,2).equals("/!"))) {
+            return toJavaAlt64Name(windowsName);
+        }
+        StringBuffer javaName = new StringBuffer();
+        char ch;
+        // Decode from simple encoding
+        for (int i = 0; i < windowsName.length(); i++){
+            if ((ch = windowsName.charAt(i)) == '/') {
+                char next = ' ';
+                if ((windowsName.length() > i + 1) &&
+                   ((next = windowsName.charAt(i+1)) >= 'A') && (next <= 'Z')) {
+                ch = next;
+                i++;
+                } else  if ((windowsName.length() > i + 1) && (next == '/')) {
+                ch = '\\';
+                i++;
+                }
+            } else if (ch == '\\') {
+                ch = '/';
+            }
+            javaName.append(ch);
+        }
+        return javaName.toString();
+    }
+
+    /**
+     * Converts value's or node's name from its Windows representation to java
+     * string, using altBase64 encoding. See
+     * {@link #toWindowsName(String) toWindowsName()} for a detailed
+     * description of encoding conventions.
+     */
+
+    private static String toJavaAlt64Name(String windowsName) {
+        byte[] byteBuffer =
+                          Base64.altBase64ToByteArray(windowsName.substring(2));
+        StringBuffer result = new StringBuffer();
+        for (int i = 0; i < byteBuffer.length; i++) {
+            int firstbyte = (byteBuffer[i++] & 0xff);
+            int secondbyte =  (byteBuffer[i] & 0xff);
+            result.append((char)((firstbyte << 8) + secondbyte));
+        }
+        return result.toString();
+    }
+
+    /**
+     * Converts value's or node's name to its Windows representation
+     * as a byte-encoded string.
+     * Two encodings, simple and altBase64 are used.
+     * <p>
+     * <i>Simple</i> encoding is used, if java string does not contain
+     * any characters less, than 0x0020, or greater, than 0x007f.
+     * Simple encoding adds "/" character to capital letters, i.e.
+     * "A" is encoded as "/A". Character '\' is encoded as '//',
+     * '/' is encoded as '\'.
+     * The constructed string is converted to byte array by truncating the
+     * highest byte and adding the terminating <tt>null</tt> character.
+     * <p>
+     * <i>altBase64</i>  encoding is used, if java string does contain at least
+     * one character less, than 0x0020, or greater, than 0x007f.
+     * This encoding is marked by setting first two bytes of the
+     * Windows string to '/!'. The java name is then encoded using
+     * byteArrayToAltBase64() method from
+     * Base64 class.
+     */
+    private static byte[] toWindowsName(String javaName) {
+        StringBuffer windowsName = new StringBuffer();
+        for (int i = 0; i < javaName.length(); i++) {
+            char ch =javaName.charAt(i);
+            if ((ch < 0x0020)||(ch > 0x007f)) {
+                // If a non-trivial character encountered, use altBase64
+                return toWindowsAlt64Name(javaName);
+            }
+            if (ch == '\\') {
+                windowsName.append("//");
+            } else if (ch == '/') {
+                windowsName.append('\\');
+            } else if ((ch >= 'A') && (ch <='Z')) {
+                windowsName.append("/" + ch);
+            } else {
+                windowsName.append(ch);
+            }
+        }
+        return stringToByteArray(windowsName.toString());
+    }
+
+    /**
+     * Converts value's or node's name to its Windows representation
+     * as a byte-encoded string, using altBase64 encoding. See
+     * {@link #toWindowsName(String) toWindowsName()} for a detailed
+     * description of encoding conventions.
+     */
+    private static byte[] toWindowsAlt64Name(String javaName) {
+        byte[] javaNameArray = new byte[2*javaName.length()];
+        // Convert to byte pairs
+        int counter = 0;
+        for (int i = 0; i < javaName.length();i++) {
+                int ch = javaName.charAt(i);
+                javaNameArray[counter++] = (byte)(ch >>> 8);
+                javaNameArray[counter++] = (byte)ch;
+        }
+
+        return stringToByteArray(
+                           "/!" + Base64.byteArrayToAltBase64(javaNameArray));
+    }
+
+    /**
+     * Converts value string from its Windows representation
+     * to java string.  See
+     * {@link #toWindowsValueString(String) toWindowsValueString()} for the
+     * description of the encoding algorithm.
+     */
+     private static String toJavaValueString(byte[] windowsNameArray) {
+        // Use modified native2ascii algorithm
+        String windowsName = byteArrayToString(windowsNameArray);
+        StringBuffer javaName = new StringBuffer();
+        char ch;
+        for (int i = 0; i < windowsName.length(); i++){
+            if ((ch = windowsName.charAt(i)) == '/') {
+                char next = ' ';
+
+                if (windowsName.length() > i + 1 &&
+                                    (next = windowsName.charAt(i + 1)) == 'u') {
+                    if (windowsName.length() < i + 6){
+                        break;
+                    } else {
+                        ch = (char)Integer.parseInt
+                                      (windowsName.substring(i + 2, i + 6), 16);
+                        i += 5;
+                    }
+                } else
+                if ((windowsName.length() > i + 1) &&
+                          ((windowsName.charAt(i+1)) >= 'A') && (next <= 'Z')) {
+                ch = next;
+                i++;
+                } else  if ((windowsName.length() > i + 1) &&
+                                               (next == '/')) {
+                ch = '\\';
+                i++;
+                }
+            } else if (ch == '\\') {
+                ch = '/';
+            }
+            javaName.append(ch);
+        }
+        return javaName.toString();
+    }
+
+    /**
+     * Converts value string to it Windows representation.
+     * as a byte-encoded string.
+     * Encoding algorithm adds "/" character to capital letters, i.e.
+     * "A" is encoded as "/A". Character '\' is encoded as '//',
+     * '/' is encoded as  '\'.
+     * Then encoding scheme similar to jdk's native2ascii converter is used
+     * to convert java string to a byte array of ASCII characters.
+     */
+    private static byte[] toWindowsValueString(String javaName) {
+        StringBuffer windowsName = new StringBuffer();
+        for (int i = 0; i < javaName.length(); i++) {
+            char ch =javaName.charAt(i);
+            if ((ch < 0x0020)||(ch > 0x007f)){
+                // write \udddd
+                windowsName.append("/u");
+                String hex = Integer.toHexString(javaName.charAt(i));
+                StringBuffer hex4 = new StringBuffer(hex);
+                hex4.reverse();
+                int len = 4 - hex4.length();
+                for (int j = 0; j < len; j++){
+                    hex4.append('0');
+                }
+                for (int j = 0; j < 4; j++){
+                    windowsName.append(hex4.charAt(3 - j));
+                }
+            } else if (ch == '\\') {
+                windowsName.append("//");
+            } else if (ch == '/') {
+                windowsName.append('\\');
+            } else if ((ch >= 'A') && (ch <='Z')) {
+                windowsName.append("/" + ch);
+            } else {
+                windowsName.append(ch);
+            }
+        }
+        return stringToByteArray(windowsName.toString());
+    }
+
+    /**
+     * Returns native handle for the top Windows node for this node.
+     */
+    private int rootNativeHandle() {
+        return (isUserNode()? USER_ROOT_NATIVE_HANDLE :
+                              SYSTEM_ROOT_NATIVE_HANDLE);
+    }
+
+    /**
+     * Returns this java string as a null-terminated byte array
+     */
+    private static byte[] stringToByteArray(String str) {
+        byte[] result = new byte[str.length()+1];
+        for (int i = 0; i < str.length(); i++) {
+            result[i] = (byte) str.charAt(i);
+        }
+        result[str.length()] = 0;
+        return result;
+    }
+
+    /**
+     * Converts a null-terminated byte array to java string
+     */
+    private static String byteArrayToString(byte[] array) {
+        StringBuffer result = new StringBuffer();
+        for (int i = 0; i < array.length - 1; i++) {
+            result.append((char)array[i]);
+        }
+        return result.toString();
+    }
+
+   /**
+    * Empty, never used implementation  of AbstractPreferences.flushSpi().
+    */
+    protected void flushSpi() throws BackingStoreException {
+        // assert false;
+    }
+
+   /**
+    * Empty, never used implementation  of AbstractPreferences.flushSpi().
+    */
+    protected void syncSpi() throws BackingStoreException {
+        // assert false;
+    }
+
+    private static synchronized Logger logger() {
+        if (logger == null) {
+            logger = Logger.getLogger("java.util.prefs");
+        }
+        return logger;
+    }
+}