windowspreferences.java

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            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;
    }
}