String to be read as a character
* input stream.
*
* The mark/reset functionality in this class behaves differently than
* normal. If no mark has been set, then calling the reset()
* method rewinds the read pointer to the beginning of the String.
*
* @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 StringReader that will read chars from the
* passed in String. This stream will read from the beginning
* to the end of the String.
*
* @param buffer The String 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 true, unless
* close() has previously been called in which case an IOException is
* thrown.
*
* @return true 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 pos 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;
}
}
}