Filter Reader that strips out those lines that begin with a comment tag.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271524 13f79535-47bb-0310-9956-ffa450edef68

proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters/StripLineComments.java

@@ -0,0 +1,136 @@
+package org.apache.tools.ant.filters;
+
+import java.io.FilterReader;
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Vector;
+
+import org.apache.tools.ant.types.Parameter;
+import org.apache.tools.ant.types.Parameterizable;
+
+/**
+ * This is a line comment stripper reader
+ *
+ * Example:
+ * =======
+ *
+ * <filterreader classname="org.apache.tools.ant.filters.StripLineComments">
+ *    <param name="comment" value="#"/>
+ *    <param name="comment" value="--"/>
+ *    <param name="comment" value="REM "/>
+ *    <param name="comment" value="rem "/>
+ *    <param name="comment" value="//"/>
+ * </filterreader>
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class StripLineComments
+    extends FilterReader
+    implements Parameterizable
+{
+    private static final String COMMENTS_KEY = "comment";
+
+    private Parameter[] parameters;
+
+    private boolean initialized = false;
+
+    private final Vector comments = new Vector();
+
+    private int commentsSize = 0;
+
+    private String line = null;
+
+    /**
+     * Create a new filtered reader.
+     *
+     * @param in  a Reader object providing the underlying stream.
+     */
+    public StripLineComments(final Reader in) {
+        super(in);
+    }
+
+    public final int read() throws IOException {
+        if (!initialized) {
+            initialize();
+            initialized = true;
+        }
+
+        int ch = -1;
+
+        if (line != null) {
+            ch = line.charAt(0);
+            if (line.length() == 1) {
+                line = null;
+            } else {
+                line = line.substring(1);
+            }
+        } else {
+            ch = in.read();
+            while (ch != -1) {
+                if (line == null) {
+                    line = "";
+                }
+                line = line + (char) ch;
+                if (ch == '\n') {
+                    break;
+                }
+                ch = in.read();
+            }
+
+            if (line != null) {
+                for (int i = 0; i < commentsSize; i++) {
+                    String comment = (String) comments.elementAt(i);
+                    if (line.startsWith(comment)) {
+                        line = null;
+                        break;
+                    }
+                }
+                return read();
+            }
+        }
+
+        return ch;
+    }
+
+    public final int read(final char cbuf[], final int off,
+                          final int len) throws IOException {
+        for (int i = 0; i < len; i++) {
+            final int ch = read();
+            if (ch == -1) {
+                if (i == 0) {
+                    return -1;
+                } else {
+                    return i;
+                }
+            }
+            cbuf[off + i] = (char) ch;
+        }
+        return len;
+    }
+
+    public final long skip(final long n) throws IOException {
+        for (long i = 0; i < n; i++) {
+            if (in.read() == -1) return i;
+        }
+        return n;
+    }
+
+    /**
+     * Set Parameters
+     */
+    public final void setParameters(final Parameter[] parameters) {
+        this.parameters = parameters;
+        initialized = false;
+    }
+
+    private final void initialize() {
+        if (parameters != null) {
+            for (int i = 0; i < parameters.length; i++) {
+                if (COMMENTS_KEY.equals(parameters[i].getName())) {
+                    comments.addElement(parameters[i].getValue());
+                }
+            }
+            commentsSize = comments.size();
+        }
+    }
+}