Reading CRLF terminated lines that contain only US-ASCII characters from an input stream
import java.io.*;
/**
* This class is to support reading CRLF terminated lines that
* contain only US-ASCII characters from an input stream. Provides
* functionality that is similar to the deprecated
* <code>DataInputStream.readLine()</code>. Expected use is to read
* lines as String objects from a RFC822 stream.
*
* It is implemented as a FilterInputStream, so one can just wrap
* this class around any input stream and read bytes from this filter.
*
* @author John Mani
*/
public class LineInputStream extends FilterInputStream {
private char[] lineBuffer = null; // reusable byte buffer
public LineInputStream(InputStream in) {
super(in);
}
/**
* Read a line containing only ASCII characters from the input
* stream. A line is terminated by a CR or NL or CR-NL sequence.
* A common error is a CR-CR-NL sequence, which will also terminate
* a line.
* The line terminator is not returned as part of the returned
* String. Returns null if no data is available. <p>
*
* This class is similar to the deprecated
* <code>DataInputStream.readLine()</code>
*/
public String readLine() throws IOException {
InputStream in = this.in;
char[] buf = lineBuffer;
if (buf == null)
buf = lineBuffer = new char[128];
int c1;
int room = buf.length;
int offset = 0;
while ((c1 = in.read()) != -1) {
if (c1 == '\n') // Got NL, outa here.
break;
else if (c1 == '\r') {
// Got CR, is the next char NL ?
int c2 = in.read();
if (c2 == '\r') // discard extraneous CR
c2 = in.read();
if (c2 != '\n') {
// If not NL, push it back
if (!(in instanceof PushbackInputStream))
in = this.in = new PushbackInputStream(in);
((PushbackInputStream)in).unread(c2);
}
break; // outa here.
}
// Not CR, NL or CR-NL ...
// .. Insert the byte into our byte buffer
if (--room < 0) { // No room, need to grow.
buf = new char[offset + 128];
room = buf.length - offset - 1;
System.arraycopy(lineBuffer, 0, buf, 0, offset);
lineBuffer = buf;
}
buf[offset++] = (char)c1;
}
if ((c1 == -1) && (offset == 0))
return null;
return String.copyValueOf(buf, 0, offset);
}
}
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