2003/06/28 06:54:18

[org.ibex.core.git] / src / gnu / regexp / CharIndexed.java

diff --git a/src/gnu/regexp/CharIndexed.java b/src/gnu/regexp/CharIndexed.java
new file mode 100644 (file)
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+++ b/src/gnu/regexp/CharIndexed.java
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+/*
+ *  gnu/regexp/CharIndexed.java
+ *  Copyright (C) 1998-2001 Wes Biggs
+ *
+ *  This library is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU Lesser General Public License as published
+ *  by the Free Software Foundation; either version 2.1 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This library 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 Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+package gnu.regexp;
+
+/**
+ * Defines the interface used internally so that different types of source
+ * text can be accessed in the same way.  Built-in concrete classes provide
+ * support for String, StringBuffer, InputStream and char[] types.
+ * A class that is CharIndexed supports the notion of a cursor within a
+ * block of text.  The cursor must be able to be advanced via the move()
+ * method.  The charAt() method returns the character at the cursor position
+ * plus a given offset.
+ *
+ * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
+ */
+public interface CharIndexed {
+    /**
+     * Defines a constant (0xFFFF was somewhat arbitrarily chosen)
+     * that can be returned by the charAt() function indicating that
+     * the specified index is out of range.
+     */
+    char OUT_OF_BOUNDS = '\uFFFF';
+
+    /**
+     * Returns the character at the given offset past the current cursor
+     * position in the input.  The index of the current position is zero.
+     * It is possible for this method to be called with a negative index.
+     * This happens when using the '^' operator in multiline matching mode
+     * or the '\b' or '\<' word boundary operators.  In any case, the lower
+     * bound is currently fixed at -2 (for '^' with a two-character newline).
+     *
+     * @param index the offset position in the character field to examine
+     * @return the character at the specified index, or the OUT_OF_BOUNDS
+     *   character defined by this interface.
+     */
+    char charAt(int index);
+
+    /**
+     * Shifts the input buffer by a given number of positions.  Returns
+     * true if the new cursor position is valid.
+     */
+    boolean move(int index);
+
+    /**
+     * Returns true if the most recent move() operation placed the cursor
+     * position at a valid position in the input.
+     */
+    boolean isValid();
+}