Java SCGI connector

SCGI.java

/*
   Copyright (c) 2008 ArtemGr

   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.util.HashMap;

/**
 * SCGI connector.<br>
 * Version: 1.0<br>
 * Home page: http://gist.github.com/38425
 * See also: http://en.wikipedia.org/wiki/SCGI
 */
public class SCGI {
  public static class SCGIException extends IOException {
    private static final long serialVersionUID = 1L;

    public SCGIException(String message) {
      super(message);
    }
  }

  /** Used to decode the headers. */
  public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");

  /**
   * Read the <a href="http://python.ca/scgi/protocol.txt">SCGI</a> request headers.<br>
   * After the headers had been loaded,
   * you can read the body of the request manually from the same {@code input} stream:<pre>
   *   // Load the SCGI headers.
   *   Socket clientSocket = socket.accept();
   *   BufferedInputStream bis = new BufferedInputStream(clientSocket.getInputStream(), 4096);
   *   HashMap<String, String> env = SCGI.parse(bis);
   *   // Read the body of the request.
   *   bis.read(new byte[Integer.parseInt(env.get("CONTENT_LENGTH"))]);
   * </pre>
   * @param input an efficient (buffered) input stream.
   * @return strings passed via the SCGI request.
   */
  public static HashMap parse(InputStream input) throws IOException {
    StringBuilder lengthString = new StringBuilder(12);
    String headers = "";
    for (;;) {
      char ch = (char) input.read();
      if (ch >= '0' && ch <= '9') {
        lengthString.append(ch);
      } else if (ch == ':') {
        int length = Integer.parseInt(lengthString.toString());
        byte[] headersBuf = new byte[length];
        int read = input.read(headersBuf);
        if (read != headersBuf.length)
          throw new SCGIException("Couldn't read all the headers (" + length + ").");
        headers = ISO_8859_1.decode(ByteBuffer.wrap(headersBuf)).toString();
        if (input.read() != ',') throw new SCGIException("Wrong SCGI header length: " + lengthString);
        break;
      } else {
        lengthString.append(ch);
        throw new SCGIException("Wrong SCGI header length: " + lengthString);
      }
    }
    HashMap env = new HashMap();
    while (headers.length() != 0) {
      int sep1 = headers.indexOf(0);
      int sep2 = headers.indexOf(0, sep1 + 1);
      env.put(headers.substring(0, sep1), headers.substring(sep1 + 1, sep2));
      headers = headers.substring(sep2 + 1);
    }
    return env;
  }
}