Initial revision

From-SVN: r102074

libjava/classpath/java/io/StringReader.java

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+/* StringReader.java -- permits a String to be read as a character input stream
+   Copyright (C) 1998, 1999, 2000, 2003  Free Software Foundation
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath 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
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.io;
+
+/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
+ * "The Java Language Specification", ISBN 0-201-63451-1
+ * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
+ * Status:  Believed complete and correct
+ */
+
+/**
+ * This class permits a <code>String</code> to be read as a character 
+ * input stream.
+ * <p>
+ * The mark/reset functionality in this class behaves differently than
+ * normal.  If no mark has been set, then calling the <code>reset()</code>
+ * method rewinds the read pointer to the beginning of the <code>String</code>.
+ *
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ * @author Warren Levy (warrenl@cygnus.com)
+ * @date October 19, 1998.  
+ */
+public class StringReader extends Reader
+{
+  /* A String provided by the creator of the stream. */
+  private String buf;
+
+  /* Position of the next char in buf to be read. */
+  private int pos;
+
+  /* The currently marked position in the stream. */
+  private int markedPos;
+
+  /* The index in buf one greater than the last valid character. */
+  private int count;
+
+  /**
+   * Create a new <code>StringReader</code> that will read chars from the 
+   * passed in <code>String</code>.  This stream will read from the beginning 
+   * to the end of the <code>String</code>.
+   *
+   * @param buffer The <code>String</code> this stream will read from.
+   */
+  public StringReader(String buffer)
+  {
+    super();
+    buf = buffer;
+
+    count = buffer.length();
+    markedPos = pos = 0;
+  }
+
+  public void close()
+  {
+    synchronized (lock)
+    {
+      buf = null;
+    }
+  }
+
+  public void mark(int readAheadLimit) throws IOException
+  {
+    synchronized (lock)
+    {
+      if (buf == null)
+        throw new IOException("Stream closed");
+
+      // readAheadLimit is ignored per Java Class Lib. book, p. 1692.
+      markedPos = pos;
+    }
+  }
+
+  public boolean markSupported()
+  {
+    return true;
+  }
+
+  public int read() throws IOException
+  {
+    synchronized (lock)
+    {
+      if (buf == null)
+        throw new IOException("Stream closed");
+
+      if (pos < count)
+        return ((int) buf.charAt(pos++)) & 0xFFFF;
+      return -1;
+    }
+  }
+
+  public int read(char[] b, int off, int len) throws IOException
+  {
+    synchronized (lock)
+    {
+      if (buf == null)
+        throw new IOException("Stream closed");
+
+      /* Don't need to check pos value, arraycopy will check it. */
+      if (off < 0 || len < 0 || off + len > b.length)
+        throw new ArrayIndexOutOfBoundsException();
+
+      if (pos >= count)
+        return -1;
+
+      int lastChar = Math.min(count, pos + len);
+      buf.getChars(pos, lastChar, b, off);
+      int numChars = lastChar - pos;
+      pos = lastChar;
+      return numChars;
+    }
+  }
+
+  /**
+   * This method determines if the stream is ready to be read.  This class
+   * is always ready to read and so always returns <code>true</code>, unless
+   * close() has previously been called in which case an IOException is
+   * thrown.
+   *
+   * @return <code>true</code> to indicate that this object is ready to be read.
+   * @exception IOException If the stream is closed.
+   */
+  public boolean ready() throws IOException
+  {
+    if (buf == null)
+      throw new IOException("Stream closed");
+
+    return true;
+  }
+
+  /**
+   * Sets the read position in the stream to the previously
+   * marked position or to 0 (i.e., the beginning of the stream) if the mark
+   * has not already been set.
+   */
+  public void reset() throws IOException
+  {
+    synchronized (lock)
+    {
+      if (buf == null)
+        throw new IOException("Stream closed");
+
+      pos = markedPos;
+    }
+  }
+
+  /**
+    * This method attempts to skip the requested number of chars in the
+    * input stream.  It does this by advancing the <code>pos</code> value by 
+    * the specified number of chars.  It this would exceed the length of the
+    * buffer, then only enough chars are skipped to position the stream at
+    * the end of the buffer.  The actual number of chars skipped is returned.
+    *
+    * @param n The requested number of chars to skip
+    *
+    * @return The actual number of chars skipped.
+    */
+  public long skip(long n) throws IOException
+  {
+    synchronized (lock)
+    {
+      if (buf == null)
+        throw new IOException("Stream closed");
+
+      // Even though the var numChars is a long, in reality it can never
+      // be larger than an int since the result of subtracting 2 positive
+      // ints will always fit in an int.  Since we have to return a long
+      // anyway, numChars might as well just be a long.
+      long numChars = Math.min((long) (count - pos), n < 0 ? 0L : n);
+      pos += numChars;
+      return numChars;
+    }
+  }
+}
+