[CSV-131] Save positions of records to enable random access. First commit for this new feature. Let the ExtendedBufferedReader track how many characters it has read so far.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/csv/trunk@1625455 13f79535-47bb-0310-9956-ffa450edef68

Author: garydgregory

src/main/java/org/apache/commons/csv/ExtendedBufferedReader.java

@@ -30,7 +30,8 @@
  * A special buffered reader which supports sophisticated read access.
  * <p>
  * In particular the reader supports a look-ahead option, which allows you to see the next char returned by
- * {@link #read()}.
+ * {@link #read()}. This reader also tracks how many characters have been read with {@link #getPosition()}.
+ * </p>
  *
  * @version $Id$
  */
@@ -42,6 +43,9 @@ final class ExtendedBufferedReader extends BufferedReader {
     /** The count of EOLs (CR/LF/CRLF) seen so far */
     private long eolCounter = 0;
 
+    /** The position, which is number of characters read so far */
+    private long position = 0;
+
     private boolean closed;
 
     /**
@@ -58,6 +62,7 @@ public int read() throws IOException {
             eolCounter++;
         }
         lastChar = current;
+        this.position++;
         return lastChar;
     }
 
@@ -100,6 +105,7 @@ public int read(final char[] buf, final int offset, final int length) throws IOE
             lastChar = END_OF_STREAM;
         }
 
+        position += len;
         return len;
     }
 
@@ -157,6 +163,15 @@ long getCurrentLineNumber() {
         return eolCounter + 1; // Allow for counter being incremented only at EOL
     }
 
+    /**
+     * Gets the character position in the reader.
+     * 
+     * @return the current position in the reader (counting characters, not bytes since this is a Reader)
+     */
+    long getPosition() {
+        return this.position;
+    }
+
     public boolean isClosed() {
         return closed;
     }