GUAC-868: Implement FilteredGuacamoleWriter and test.

guacamole-common/src/main/java/org/glyptodon/guacamole/protocol/FilteredGuacamoleWriter.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2014 Glyptodon LLC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package org.glyptodon.guacamole.protocol;
+
+import org.glyptodon.guacamole.GuacamoleException;
+import org.glyptodon.guacamole.GuacamoleServerException;
+import org.glyptodon.guacamole.io.GuacamoleWriter;
+
+/**
+ * GuacamoleWriter which applies a given GuacamoleFilter to observe or alter
+ * all written instructions. Instructions may also be dropped or denied by
+ * the filter.
+ *
+ * @author Michael Jumper
+ */
+public class FilteredGuacamoleWriter implements GuacamoleWriter {
+
+    /**
+     * The wrapped GuacamoleWriter.
+     */
+    private final GuacamoleWriter writer;
+
+    /**
+     * The filter to apply when writing instructions.
+     */
+    private final GuacamoleFilter filter;
+
+    /**
+     * Parser for reading instructions prior to writing, such that they can be
+     * passed on to the filter.
+     */
+    private final GuacamoleParser parser = new GuacamoleParser();
+    
+    /**
+     * Wraps the given GuacamoleWriter, applying the given filter to all written 
+     * instructions. Future writes will only write instructions which pass
+     * the filter.
+     *
+     * @param writer The GuacamoleWriter to wrap.
+     * @param filter The filter which dictates which instructions are written,
+     *               and how.
+     */
+    public FilteredGuacamoleWriter(GuacamoleWriter writer, GuacamoleFilter filter) {
+        this.writer = writer;
+        this.filter = filter;
+    }
+ 
+    @Override
+    public void write(char[] chunk, int offset, int length) throws GuacamoleException {
+
+        // Write all data in chunk
+        while (length > 0) {
+
+            // Pass as much data through the parser as possible
+            int parsed;
+            while ((parsed = parser.append(chunk, offset, length)) != 0) {
+                offset += parsed;
+                length -= parsed;
+            }
+
+            // If no instruction is available, it must be incomplete
+            if (!parser.hasNext())
+                throw new GuacamoleServerException("Filtered write() contained an incomplete instruction.");
+
+            // Write single instruction through filter
+            writeInstruction(parser.next());
+
+        }
+        
+    }
+
+    @Override
+    public void write(char[] chunk) throws GuacamoleException {
+        write(chunk, 0, chunk.length);
+    }
+
+    @Override
+    public void writeInstruction(GuacamoleInstruction instruction) throws GuacamoleException {
+
+        // Write instruction only if not dropped
+        GuacamoleInstruction filteredInstruction = filter.filter(instruction);
+        if (filteredInstruction != null)
+            writer.writeInstruction(filteredInstruction);
+
+    }
+
+}