DataInputStream.readLine(). 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
+ */
+
+final class LineInputStream extends FilterInputStream {
+
+ private char[] lineBuffer = null; // reusable byte buffer
+ private static int MAX_INCR = 1024*1024; // 1MB
+
+ 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.
+ *
+ * This class is similar to the deprecated
+ * DataInputStream.readLine()
+ */
+ 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') {
+ break;
+ } else if (c1 == '\r') {
+ // Got CR, is the next char NL ?
+ boolean twoCRs = false;
+ if (in.markSupported()) {
+ in.mark(2);
+ }
+ int c2 = in.read();
+ if (c2 == '\r') { // discard extraneous CR
+ twoCRs = true;
+ c2 = in.read();
+ }
+ if (c2 != '\n') {
+ /*
+ * If the stream supports it (which we hope will always
+ * be the case), reset to after the first CR. Otherwise,
+ * we wrap a PushbackInputStream around the stream so we
+ * can unread the characters we don't need. The only
+ * problem with that is that the caller might stop
+ * reading from this LineInputStream, throw it away,
+ * and then start reading from the underlying stream.
+ * If that happens, the pushed back characters will be
+ * lost forever.
+ */
+ if (in.markSupported()) {
+ in.reset();
+ } else {
+ if (!(in instanceof PushbackInputStream)) {
+ in /*= this.in*/ = new PushbackInputStream(in, 2);
+ }
+ if (c2 != -1) {
+ ((PushbackInputStream)in).unread(c2);
+ }
+ if (twoCRs) {
+ ((PushbackInputStream)in).unread('\r');
+ }
+ }
+ }
+ break; // outa here.
+ }
+
+ // Not CR, NL or CR-NL ...
+ // .. Insert the byte into our byte buffer
+ if (--room < 0) { // No room, need to grow.
+ if (buf.length < MAX_INCR) {
+ buf = new char[buf.length * 2];
+ } else {
+ buf = new char[buf.length + MAX_INCR];
+ }
+ 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);
+ }
+}