//
//  ========================================================================
//  Copyright (c) 1995-2019 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.http;

import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.EnumSet;
import java.util.List;
import java.util.Locale;

import org.eclipse.jetty.http.HttpCompliance.Violation;
import org.eclipse.jetty.http.HttpTokens.EndOfContent;
import org.eclipse.jetty.util.ArrayTernaryTrie;
import org.eclipse.jetty.util.ArrayTrie;
import org.eclipse.jetty.util.BufferUtil;
import org.eclipse.jetty.util.StringUtil;
import org.eclipse.jetty.util.Trie;
import org.eclipse.jetty.util.Utf8StringBuilder;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

import static org.eclipse.jetty.http.HttpCompliance.Violation.CASE_SENSITIVE_FIELD_NAME;
import static org.eclipse.jetty.http.HttpCompliance.Violation.MULTIPLE_CONTENT_LENGTHS;
import static org.eclipse.jetty.http.HttpCompliance.Violation.NO_COLON_AFTER_FIELD_NAME;
import static org.eclipse.jetty.http.HttpCompliance.Violation.TRANSFER_ENCODING_WITH_CONTENT_LENGTH;
import static org.eclipse.jetty.http.HttpCompliance.Violation.WHITESPACE_AFTER_FIELD_NAME;

A Parser for 1.0 and 1.1 as defined by RFC7230
 This parser parses HTTP client and server messages from buffers passed in the parseNext(ByteBuffer) method. The parsed elements of the HTTP message are passed as event calls to the HttpHandler instance the parser is constructed with. If the passed handler is a RequestHandler then server side parsing is performed and if it is a ResponseHandler, then client side parsing is done. 
 The contract of the HttpHandler API is that if a call returns true then the call to parseNext(ByteBuffer) will return as soon as possible also with a true response. Typically this indicates that the parsing has reached a stage where the caller should process the events accumulated by the handler. It is the preferred calling style that handling such as calling a servlet to process a request, should be done after a true return from parseNext(ByteBuffer) rather than from within the scope of a call like HttpHandler.messageComplete() 
 For performance, the parse is heavily dependent on the Trie.getBest(ByteBuffer, int, int) method to look ahead in a single pass for both the structure ( : and CRLF ) and semantic (which header and value) of a header. Specifically the static HttpHeader.CACHE is used to lookup common combinations of headers and values (eg. "Connection: close"), or just header names (eg. "Connection:" ). For headers who's value is not known statically (eg. Host, COOKIE) then a per parser dynamic Trie of HttpFields from previous parsed messages is used to help the parsing of subsequent messages. 

The parser can work in varying compliance modes:

RFC7230
(default) Compliance with RFC7230
RFC2616
Wrapped headers and HTTP/0.9 supported
LEGACY
Adherence to Servlet Specification requirement for
exact case of header names, bypassing the header caches, which are case insensitive,
otherwise equivalent to RFC2616

See Also:
RFC 7230/**
 * A Parser for 1.0 and 1.1 as defined by RFC7230
 * <p>
 * This parser parses HTTP client and server messages from buffers
 * passed in the {@link #parseNext(ByteBuffer)} method.  The parsed
 * elements of the HTTP message are passed as event calls to the
 * {@link HttpHandler} instance the parser is constructed with.
 * If the passed handler is a {@link RequestHandler} then server side
 * parsing is performed and if it is a {@link ResponseHandler}, then
 * client side parsing is done.
 * </p>
 * <p>
 * The contract of the {@link HttpHandler} API is that if a call returns
 * true then the call to {@link #parseNext(ByteBuffer)} will return as
 * soon as possible also with a true response.  Typically this indicates
 * that the parsing has reached a stage where the caller should process
 * the events accumulated by the handler.    It is the preferred calling
 * style that handling such as calling a servlet to process a request,
 * should be done after a true return from {@link #parseNext(ByteBuffer)}
 * rather than from within the scope of a call like
 * {@link RequestHandler#messageComplete()}
 * </p>
 * <p>
 * For performance, the parse is heavily dependent on the
 * {@link Trie#getBest(ByteBuffer, int, int)} method to look ahead in a
 * single pass for both the structure ( : and CRLF ) and semantic (which
 * header and value) of a header.  Specifically the static {@link HttpHeader#CACHE}
 * is used to lookup common combinations of headers and values
 * (eg. "Connection: close"), or just header names (eg. "Connection:" ).
 * For headers who's value is not known statically (eg. Host, COOKIE) then a
 * per parser dynamic Trie of {@link HttpFields} from previous parsed messages
 * is used to help the parsing of subsequent messages.
 * </p>
 * <p>
 * The parser can work in varying compliance modes:
 * <dl>
 * <dt>RFC7230</dt><dd>(default) Compliance with RFC7230</dd>
 * <dt>RFC2616</dt><dd>Wrapped headers and HTTP/0.9 supported</dd>
 * <dt>LEGACY</dt><dd>Adherence to Servlet Specification requirement for
 * exact case of header names, bypassing the header caches, which are case insensitive,
 * otherwise equivalent to RFC2616</dd>
 * </dl>
 *
 * @see <a href="http://tools.ietf.org/html/rfc7230">RFC 7230</a>
 */
public class HttpParser
{
    public static final Logger LOG = Log.getLogger(HttpParser.class);
    public static final int INITIAL_URI_LENGTH = 256;
    private static final int MAX_CHUNK_LENGTH = Integer.MAX_VALUE / 16 - 16;

    
Cache of common HttpFields including: 

Common static combinations such as:

Connection: close
Accept-Encoding: gzip
Content-Length: 0

Combinations of Content-Type header for common mime types by common charsets
Most common headers with null values so that a lookup will at least
determine the header name even if the name:value combination is not cached

/**
     * Cache of common {@link HttpField}s including: <UL>
     * <LI>Common static combinations such as:<UL>
     * <li>Connection: close
     * <li>Accept-Encoding: gzip
     * <li>Content-Length: 0
     * </ul>
     * <li>Combinations of Content-Type header for common mime types by common charsets
     * <li>Most common headers with null values so that a lookup will at least
     * determine the header name even if the name:value combination is not cached
     * </ul>
     */
    public static final Trie<HttpField> CACHE = new ArrayTrie<>(2048);

    // States
    public enum FieldState
    {
        FIELD,
        IN_NAME,
        VALUE,
        IN_VALUE,
        WS_AFTER_NAME,
    }

    // States
    public enum State
    {
        START,
        METHOD,
        RESPONSE_VERSION,
        SPACE1,
        STATUS,
        URI,
        SPACE2,
        REQUEST_VERSION,
        REASON,
        PROXY,
        HEADER,
        CONTENT,
        EOF_CONTENT,
        CHUNKED_CONTENT,
        CHUNK_SIZE,
        CHUNK_PARAMS,
        CHUNK,
        TRAILER,
        END,
        CLOSE,  // The associated stream/endpoint should be closed
        CLOSED  // The associated stream/endpoint is at EOF
    }

    private static final EnumSet<State> __idleStates = EnumSet.of(State.START, State.END, State.CLOSE, State.CLOSED);
    private static final EnumSet<State> __completeStates = EnumSet.of(State.END, State.CLOSE, State.CLOSED);

    private final boolean debugEnabled = LOG.isDebugEnabled(); // Cache debug to help branch prediction
    private final HttpHandler _handler;
    private final RequestHandler _requestHandler;
    private final ResponseHandler _responseHandler;
    private final ComplianceViolation.Listener _complianceListener;
    private final int _maxHeaderBytes;
    private final HttpCompliance _complianceMode;
    private HttpField _field;
    private HttpHeader _header;
    private String _headerString;
    private String _valueString;
    private int _responseStatus;
    private int _headerBytes;
    private boolean _host;
    private boolean _headerComplete;

    private volatile State _state = State.START;
    private volatile FieldState _fieldState = FieldState.FIELD;
    private volatile boolean _eof;
    private HttpMethod _method;
    private String _methodString;
    private HttpVersion _version;
    private Utf8StringBuilder _uri = new Utf8StringBuilder(INITIAL_URI_LENGTH); // Tune?
    private EndOfContent _endOfContent;
    private boolean _hasContentLength;
    private long _contentLength = -1;
    private long _contentPosition;
    private int _chunkLength;
    private int _chunkPosition;
    private boolean _headResponse;
    private boolean _cr;
    private ByteBuffer _contentChunk;
    private Trie<HttpField> _fieldCache;

    private int _length;
    private final StringBuilder _string = new StringBuilder();

    static
    {
        CACHE.put(new HttpField(HttpHeader.CONNECTION, HttpHeaderValue.CLOSE));
        CACHE.put(new HttpField(HttpHeader.CONNECTION, HttpHeaderValue.KEEP_ALIVE));
        CACHE.put(new HttpField(HttpHeader.CONNECTION, HttpHeaderValue.UPGRADE));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_ENCODING, "gzip"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_ENCODING, "gzip, deflate"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_ENCODING, "gzip, deflate, br"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_ENCODING, "gzip,deflate,sdch"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_LANGUAGE, "en-US,en;q=0.5"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_LANGUAGE, "en-GB,en-US;q=0.8,en;q=0.6"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_LANGUAGE, "en-AU,en;q=0.9,it-IT;q=0.8,it;q=0.7,en-GB;q=0.6,en-US;q=0.5"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_CHARSET, "ISO-8859-1,utf-8;q=0.7,*;q=0.3"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT, "*/*"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT, "image/png,image/*;q=0.8,*/*;q=0.5"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT, "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT, "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8"));
        CACHE.put(new HttpField(HttpHeader.ACCEPT_RANGES, HttpHeaderValue.BYTES));
        CACHE.put(new HttpField(HttpHeader.PRAGMA, "no-cache"));
        CACHE.put(new HttpField(HttpHeader.CACHE_CONTROL, "private, no-cache, no-cache=Set-Cookie, proxy-revalidate"));
        CACHE.put(new HttpField(HttpHeader.CACHE_CONTROL, "no-cache"));
        CACHE.put(new HttpField(HttpHeader.CACHE_CONTROL, "max-age=0"));
        CACHE.put(new HttpField(HttpHeader.CONTENT_LENGTH, "0"));
        CACHE.put(new HttpField(HttpHeader.CONTENT_ENCODING, "gzip"));
        CACHE.put(new HttpField(HttpHeader.CONTENT_ENCODING, "deflate"));
        CACHE.put(new HttpField(HttpHeader.TRANSFER_ENCODING, "chunked"));
        CACHE.put(new HttpField(HttpHeader.EXPIRES, "Fri, 01 Jan 1990 00:00:00 GMT"));

        // Add common Content types as fields
        for (String type : new String[]{
            "text/plain", "text/html", "text/xml", "text/json", "application/json", "application/x-www-form-urlencoded"
        })
        {
            HttpField field = new PreEncodedHttpField(HttpHeader.CONTENT_TYPE, type);
            CACHE.put(field);

            for (String charset : new String[]{"utf-8", "iso-8859-1"})
            {
                CACHE.put(new PreEncodedHttpField(HttpHeader.CONTENT_TYPE, type + ";charset=" + charset));
                CACHE.put(new PreEncodedHttpField(HttpHeader.CONTENT_TYPE, type + "; charset=" + charset));
                CACHE.put(new PreEncodedHttpField(HttpHeader.CONTENT_TYPE, type + ";charset=" + charset.toUpperCase(Locale.ENGLISH)));
                CACHE.put(new PreEncodedHttpField(HttpHeader.CONTENT_TYPE, type + "; charset=" + charset.toUpperCase(Locale.ENGLISH)));
            }
        }

        // Add headers with null values so HttpParser can avoid looking up name again for unknown values
        for (HttpHeader h : HttpHeader.values())
        {
            if (!CACHE.put(new HttpField(h, (String)null)))
                throw new IllegalStateException("CACHE FULL");
        }
    }

    private static HttpCompliance compliance()
    {
        return HttpCompliance.RFC7230;
    }

    public HttpParser(RequestHandler handler)
    {
        this(handler, -1, compliance());
    }

    public HttpParser(ResponseHandler handler)
    {
        this(handler, -1, compliance());
    }

    public HttpParser(RequestHandler handler, int maxHeaderBytes)
    {
        this(handler, maxHeaderBytes, compliance());
    }

    public HttpParser(ResponseHandler handler, int maxHeaderBytes)
    {
        this(handler, maxHeaderBytes, compliance());
    }

    public HttpParser(RequestHandler handler, HttpCompliance compliance)
    {
        this(handler, -1, compliance);
    }

    public HttpParser(RequestHandler handler, int maxHeaderBytes, HttpCompliance compliance)
    {
        this(handler, null, maxHeaderBytes, compliance == null ? compliance() : compliance);
    }

    public HttpParser(ResponseHandler handler, int maxHeaderBytes, HttpCompliance compliance)
    {
        this(null, handler, maxHeaderBytes, compliance == null ? compliance() : compliance);
    }

    private HttpParser(RequestHandler requestHandler, ResponseHandler responseHandler, int maxHeaderBytes, HttpCompliance compliance)
    {
        _handler = requestHandler != null ? requestHandler : responseHandler;
        _requestHandler = requestHandler;
        _responseHandler = responseHandler;
        _maxHeaderBytes = maxHeaderBytes;
        _complianceMode = compliance;
        _complianceListener = (ComplianceViolation.Listener)(_handler instanceof ComplianceViolation.Listener ? _handler : null);
    }

    public HttpHandler getHandler()
    {
        return _handler;
    }

    protected void checkViolation(Violation violation) throws BadMessageException
    {
        if (violation.isAllowedBy(_complianceMode))
            reportComplianceViolation(violation, violation.getDescription());
        else
            throw new BadMessageException(HttpStatus.BAD_REQUEST_400, violation.getDescription());
    }

    protected void reportComplianceViolation(Violation violation)
    {
        reportComplianceViolation(violation, violation.getDescription());
    }

    protected void reportComplianceViolation(Violation violation, String reason)
    {
        if (_complianceListener != null)
            _complianceListener.onComplianceViolation(_complianceMode, violation, reason);
    }

    protected String caseInsensitiveHeader(String orig, String normative)
    {
        if (CASE_SENSITIVE_FIELD_NAME.isAllowedBy(_complianceMode))
            return normative;
        if (!orig.equals(normative))
            reportComplianceViolation(CASE_SENSITIVE_FIELD_NAME, orig);
        return orig;
    }

    public long getContentLength()
    {
        return _contentLength;
    }

    public long getContentRead()
    {
        return _contentPosition;
    }

    
Set if a HEAD response is expected
Params:
head – true if head response is expected/**
     * Set if a HEAD response is expected
     *
     * @param head true if head response is expected
     */
    public void setHeadResponse(boolean head)
    {
        _headResponse = head;
    }

    protected void setResponseStatus(int status)
    {
        _responseStatus = status;
    }

    public State getState()
    {
        return _state;
    }

    public boolean inContentState()
    {
        return _state.ordinal() >= State.CONTENT.ordinal() && _state.ordinal() < State.END.ordinal();
    }

    public boolean inHeaderState()
    {
        return _state.ordinal() < State.CONTENT.ordinal();
    }

    public boolean isChunking()
    {
        return _endOfContent == EndOfContent.CHUNKED_CONTENT;
    }

    public boolean isStart()
    {
        return isState(State.START);
    }

    public boolean isClose()
    {
        return isState(State.CLOSE);
    }

    public boolean isClosed()
    {
        return isState(State.CLOSED);
    }

    public boolean isIdle()
    {
        return __idleStates.contains(_state);
    }

    public boolean isComplete()
    {
        return __completeStates.contains(_state);
    }

    public boolean isState(State state)
    {
        return _state == state;
    }

    private HttpTokens.Token next(ByteBuffer buffer)
    {
        byte ch = buffer.get();

        HttpTokens.Token t = HttpTokens.TOKENS[0xff & ch];

        switch (t.getType())
        {
            case CNTL:
                throw new IllegalCharacterException(_state, t, buffer);

            case LF:
                _cr = false;
                break;

            case CR:
                if (_cr)
                    throw new BadMessageException("Bad EOL");

                _cr = true;
                if (buffer.hasRemaining())
                {
                    // Don't count the CRs and LFs of the chunked encoding.
                    if (_maxHeaderBytes > 0 && (_state == State.HEADER || _state == State.TRAILER))
                        _headerBytes++;
                    return next(buffer);
                }

                return null;

            case ALPHA:
            case DIGIT:
            case TCHAR:
            case VCHAR:
            case HTAB:
            case SPACE:
            case OTEXT:
            case COLON:
                if (_cr)
                    throw new BadMessageException("Bad EOL");
                break;

            default:
                break;
        }

        return t;
    }

    /* Quick lookahead for the start state looking for a request method or a HTTP version,
     * otherwise skip white space until something else to parse.
     */
    private boolean quickStart(ByteBuffer buffer)
    {
        if (_requestHandler != null)
        {
            _method = HttpMethod.lookAheadGet(buffer);
            if (_method != null)
            {
                _methodString = _method.asString();
                buffer.position(buffer.position() + _methodString.length() + 1);

                setState(State.SPACE1);
                return false;
            }
        }
        else if (_responseHandler != null)
        {
            _version = HttpVersion.lookAheadGet(buffer);
            if (_version != null)
            {
                buffer.position(buffer.position() + _version.asString().length() + 1);
                setState(State.SPACE1);
                return false;
            }
        }

        // Quick start look
        while (_state == State.START && buffer.hasRemaining())
        {
            HttpTokens.Token t = next(buffer);
            if (t == null)
                break;

            switch (t.getType())
            {
                case ALPHA:
                case DIGIT:
                case TCHAR:
                case VCHAR:
                {
                    _string.setLength(0);
                    _string.append(t.getChar());
                    setState(_requestHandler != null ? State.METHOD : State.RESPONSE_VERSION);
                    return false;
                }
                case OTEXT:
                case SPACE:
                case HTAB:
                    throw new IllegalCharacterException(_state, t, buffer);

                default:
                    break;
            }

            // count this white space as a header byte to avoid DOS
            if (_maxHeaderBytes > 0 && ++_headerBytes > _maxHeaderBytes)
            {
                LOG.warn("padding is too large >" + _maxHeaderBytes);
                throw new BadMessageException(HttpStatus.BAD_REQUEST_400);
            }
        }
        return false;
    }

    private void setString(String s)
    {
        _string.setLength(0);
        _string.append(s);
        _length = s.length();
    }

    private String takeString()
    {
        _string.setLength(_length);
        String s = _string.toString();
        _string.setLength(0);
        _length = -1;
        return s;
    }

    private boolean handleHeaderContentMessage()
    {
        boolean handleHeader = _handler.headerComplete();
        _headerComplete = true;
        boolean handleContent = _handler.contentComplete();
        boolean handleMessage = _handler.messageComplete();
        return handleHeader || handleContent || handleMessage;
    }

    private boolean handleContentMessage()
    {
        boolean handleContent = _handler.contentComplete();
        boolean handleMessage = _handler.messageComplete();
        return handleContent || handleMessage;
    }

    /* Parse a request or response line
     */
    private boolean parseLine(ByteBuffer buffer)
    {
        boolean handle = false;

        // Process headers
        while (_state.ordinal() < State.HEADER.ordinal() && buffer.hasRemaining() && !handle)
        {
            // process each character
            HttpTokens.Token t = next(buffer);
            if (t == null)
                break;

            if (_maxHeaderBytes > 0 && ++_headerBytes > _maxHeaderBytes)
            {
                if (_state == State.URI)
                {
                    LOG.warn("URI is too large >" + _maxHeaderBytes);
                    throw new BadMessageException(HttpStatus.URI_TOO_LONG_414);
                }
                else
                {
                    if (_requestHandler != null)
                        LOG.warn("request is too large >" + _maxHeaderBytes);
                    else
                        LOG.warn("response is too large >" + _maxHeaderBytes);
                    throw new BadMessageException(HttpStatus.REQUEST_HEADER_FIELDS_TOO_LARGE_431);
                }
            }

            switch (_state)
            {
                case METHOD:
                    switch (t.getType())
                    {
                        case SPACE:
                            _length = _string.length();
                            _methodString = takeString();

                            if (Violation.CASE_INSENSITIVE_METHOD.isAllowedBy(_complianceMode))
                            {
                                HttpMethod method = HttpMethod.INSENSITIVE_CACHE.get(_methodString);
                                if (method != null)
                                {
                                    if (!method.asString().equals(_methodString))
                                        reportComplianceViolation(Violation.CASE_INSENSITIVE_METHOD, _methodString);
                                    _methodString = method.asString();
                                }
                            }
                            else
                            {
                                HttpMethod method = HttpMethod.CACHE.get(_methodString);
                                if (method != null)
                                    _methodString = method.asString();
                            }

                            setState(State.SPACE1);
                            break;

                        case LF:
                            throw new BadMessageException("No URI");

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                            _string.append(t.getChar());
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case RESPONSE_VERSION:
                    switch (t.getType())
                    {
                        case SPACE:
                            _length = _string.length();
                            String version = takeString();
                            _version = HttpVersion.CACHE.get(version);
                            checkVersion();
                            setState(State.SPACE1);
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                            _string.append(t.getChar());
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case SPACE1:
                    switch (t.getType())
                    {
                        case SPACE:
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                            if (_responseHandler != null)
                            {
                                if (t.getType() != HttpTokens.Type.DIGIT)
                                    throw new IllegalCharacterException(_state, t, buffer);
                                setState(State.STATUS);
                                setResponseStatus(t.getByte() - '0');
                            }
                            else
                            {
                                _uri.reset();
                                setState(State.URI);
                                // quick scan for space or EoBuffer
                                if (buffer.hasArray())
                                {
                                    byte[] array = buffer.array();
                                    int p = buffer.arrayOffset() + buffer.position();
                                    int l = buffer.arrayOffset() + buffer.limit();
                                    int i = p;
                                    while (i < l && array[i] > HttpTokens.SPACE)
                                    {
                                        i++;
                                    }

                                    int len = i - p;
                                    _headerBytes += len;

                                    if (_maxHeaderBytes > 0 && ++_headerBytes > _maxHeaderBytes)
                                    {
                                        LOG.warn("URI is too large >" + _maxHeaderBytes);
                                        throw new BadMessageException(HttpStatus.URI_TOO_LONG_414);
                                    }
                                    _uri.append(array, p - 1, len + 1);
                                    buffer.position(i - buffer.arrayOffset());
                                }
                                else
                                    _uri.append(t.getByte());
                            }
                            break;

                        default:
                            throw new BadMessageException(HttpStatus.BAD_REQUEST_400, _requestHandler != null ? "No URI" : "No Status");
                    }
                    break;

                case STATUS:
                    switch (t.getType())
                    {
                        case SPACE:
                            setState(State.SPACE2);
                            break;

                        case DIGIT:
                            _responseStatus = _responseStatus * 10 + (t.getByte() - '0');
                            if (_responseStatus >= 1000)
                                throw new BadMessageException("Bad status");
                            break;

                        case LF:
                            setState(State.HEADER);
                            handle |= _responseHandler.startResponse(_version, _responseStatus, null);
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case URI:
                    switch (t.getType())
                    {
                        case SPACE:
                            setState(State.SPACE2);
                            break;

                        case LF:
                            // HTTP/0.9
                            checkViolation(Violation.HTTP_0_9);
                            handle = _requestHandler.startRequest(_methodString, _uri.toString(), HttpVersion.HTTP_0_9);
                            setState(State.END);
                            BufferUtil.clear(buffer);
                            handle |= handleHeaderContentMessage();
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT:
                            _uri.append(t.getByte());
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case SPACE2:
                    switch (t.getType())
                    {
                        case SPACE:
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                            _string.setLength(0);
                            _string.append(t.getChar());
                            if (_responseHandler != null)
                            {
                                _length = 1;
                                setState(State.REASON);
                            }
                            else
                            {
                                setState(State.REQUEST_VERSION);

                                // try quick look ahead for HTTP Version
                                HttpVersion version;
                                if (buffer.position() > 0 && buffer.hasArray())
                                    version = HttpVersion.lookAheadGet(buffer.array(), buffer.arrayOffset() + buffer.position() - 1, buffer.arrayOffset() + buffer.limit());
                                else
                                    version = HttpVersion.CACHE.getBest(buffer, 0, buffer.remaining());

                                if (version != null)
                                {
                                    int pos = buffer.position() + version.asString().length() - 1;
                                    if (pos < buffer.limit())
                                    {
                                        byte n = buffer.get(pos);
                                        if (n == HttpTokens.CARRIAGE_RETURN)
                                        {
                                            _cr = true;
                                            _version = version;
                                            checkVersion();
                                            _string.setLength(0);
                                            buffer.position(pos + 1);
                                        }
                                        else if (n == HttpTokens.LINE_FEED)
                                        {
                                            _version = version;
                                            checkVersion();
                                            _string.setLength(0);
                                            buffer.position(pos);
                                        }
                                    }
                                }
                            }
                            break;

                        case LF:
                            if (_responseHandler != null)
                            {
                                setState(State.HEADER);
                                handle |= _responseHandler.startResponse(_version, _responseStatus, null);
                            }
                            else
                            {
                                // HTTP/0.9
                                checkViolation(Violation.HTTP_0_9);
                                handle = _requestHandler.startRequest(_methodString, _uri.toString(), HttpVersion.HTTP_0_9);
                                setState(State.END);
                                BufferUtil.clear(buffer);
                                handle |= handleHeaderContentMessage();
                            }
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case REQUEST_VERSION:
                    switch (t.getType())
                    {
                        case LF:
                            if (_version == null)
                            {
                                _length = _string.length();
                                _version = HttpVersion.CACHE.get(takeString());
                            }
                            checkVersion();

                            // Should we try to cache header fields?
                            if (_fieldCache == null && _version.getVersion() >= HttpVersion.HTTP_1_1.getVersion() && _handler.getHeaderCacheSize() > 0)
                            {
                                int headerCache = _handler.getHeaderCacheSize();
                                _fieldCache = new ArrayTernaryTrie<>(headerCache);
                            }

                            setState(State.HEADER);

                            handle |= _requestHandler.startRequest(_methodString, _uri.toString(), _version);
                            continue;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                            _string.append(t.getChar());
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case REASON:
                    switch (t.getType())
                    {
                        case LF:
                            String reason = takeString();
                            setState(State.HEADER);
                            handle |= _responseHandler.startResponse(_version, _responseStatus, reason);
                            continue;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT: // TODO should this be UTF8
                            _string.append(t.getChar());
                            _length = _string.length();
                            break;

                        case SPACE:
                        case HTAB:
                            _string.append(t.getChar());
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                default:
                    throw new IllegalStateException(_state.toString());
            }
        }

        return handle;
    }

    private void checkVersion()
    {
        if (_version == null)
            throw new BadMessageException(HttpStatus.BAD_REQUEST_400, "Unknown Version");

        if (_version.getVersion() < 10 || _version.getVersion() > 20)
            throw new BadMessageException(HttpStatus.BAD_REQUEST_400, "Bad Version");
    }

    private void parsedHeader()
    {
        // handler last header if any.  Delayed to here just in case there was a continuation line (above)
        if (_headerString != null || _valueString != null)
        {
            // Handle known headers
            if (_header != null)
            {
                boolean addToConnectionTrie = false;
                switch (_header)
                {
                    case CONTENT_LENGTH:
                        if (_hasContentLength)
                        {
                            checkViolation(MULTIPLE_CONTENT_LENGTHS);
                            if (convertContentLength(_valueString) != _contentLength)
                                throw new BadMessageException(HttpStatus.BAD_REQUEST_400, MULTIPLE_CONTENT_LENGTHS.getDescription());
                        }
                        _hasContentLength = true;

                        if (_endOfContent == EndOfContent.CHUNKED_CONTENT)
                            checkViolation(TRANSFER_ENCODING_WITH_CONTENT_LENGTH);

                        if (_endOfContent != EndOfContent.CHUNKED_CONTENT)
                        {
                            _contentLength = convertContentLength(_valueString);
                            if (_contentLength <= 0)
                                _endOfContent = EndOfContent.NO_CONTENT;
                            else
                                _endOfContent = EndOfContent.CONTENT_LENGTH;
                        }
                        break;

                    case TRANSFER_ENCODING:
                        if (_hasContentLength)
                            checkViolation(TRANSFER_ENCODING_WITH_CONTENT_LENGTH);

                        if (HttpHeaderValue.CHUNKED.is(_valueString))
                        {
                            _endOfContent = EndOfContent.CHUNKED_CONTENT;
                            _contentLength = -1;
                        }
                        else
                        {
                            List<String> values = new QuotedCSV(_valueString).getValues();
                            if (!values.isEmpty() && HttpHeaderValue.CHUNKED.is(values.get(values.size() - 1)))
                            {
                                _endOfContent = EndOfContent.CHUNKED_CONTENT;
                                _contentLength = -1;
                            }
                            else if (values.stream().anyMatch(HttpHeaderValue.CHUNKED::is))
                                throw new BadMessageException(HttpStatus.BAD_REQUEST_400, "Bad chunking");
                        }

                        break;

                    case HOST:
                        _host = true;
                        if (!(_field instanceof HostPortHttpField) && _valueString != null && !_valueString.isEmpty())
                        {
                            _field = new HostPortHttpField(_header,
                                CASE_SENSITIVE_FIELD_NAME.isAllowedBy(_complianceMode) ? _headerString : _header.asString(),
                                _valueString);
                            addToConnectionTrie = _fieldCache != null;
                        }
                        break;

                    case CONNECTION:
                        // Don't cache headers if not persistent
                        if (HttpHeaderValue.CLOSE.is(_valueString) || new QuotedCSV(_valueString).getValues().stream().anyMatch(HttpHeaderValue.CLOSE::is))
                            _fieldCache = null;
                        break;

                    case AUTHORIZATION:
                    case ACCEPT:
                    case ACCEPT_CHARSET:
                    case ACCEPT_ENCODING:
                    case ACCEPT_LANGUAGE:
                    case COOKIE:
                    case CACHE_CONTROL:
                    case USER_AGENT:
                        addToConnectionTrie = _fieldCache != null && _field == null;
                        break;

                    default:
                        break;
                }

                if (addToConnectionTrie && !_fieldCache.isFull() && _header != null && _valueString != null)
                {
                    if (_field == null)
                        _field = new HttpField(_header, caseInsensitiveHeader(_headerString, _header.asString()), _valueString);
                    _fieldCache.put(_field);
                }
            }
            _handler.parsedHeader(_field != null ? _field : new HttpField(_header, _headerString, _valueString));
        }

        _headerString = _valueString = null;
        _header = null;
        _field = null;
    }

    private void parsedTrailer()
    {
        // handler last header if any.  Delayed to here just in case there was a continuation line (above)
        if (_headerString != null || _valueString != null)
            _handler.parsedTrailer(_field != null ? _field : new HttpField(_header, _headerString, _valueString));

        _headerString = _valueString = null;
        _header = null;
        _field = null;
    }

    private long convertContentLength(String valueString)
    {
        try
        {
            return Long.parseLong(valueString);
        }
        catch (NumberFormatException e)
        {
            LOG.ignore(e);
            throw new BadMessageException(HttpStatus.BAD_REQUEST_400, "Invalid Content-Length Value", e);
        }
    }

    /*
     * Parse the message headers and return true if the handler has signalled for a return
     */
    protected boolean parseFields(ByteBuffer buffer)
    {
        // Process headers
        while ((_state == State.HEADER || _state == State.TRAILER) && buffer.hasRemaining())
        {
            // process each character
            HttpTokens.Token t = next(buffer);
            if (t == null)
                break;

            if (_maxHeaderBytes > 0 && ++_headerBytes > _maxHeaderBytes)
            {
                boolean header = _state == State.HEADER;
                LOG.warn("{} is too large {}>{}", header ? "Header" : "Trailer", _headerBytes, _maxHeaderBytes);
                throw new BadMessageException(header
                    ? HttpStatus.REQUEST_HEADER_FIELDS_TOO_LARGE_431
                    : HttpStatus.PAYLOAD_TOO_LARGE_413);
            }

            switch (_fieldState)
            {
                case FIELD:
                    switch (t.getType())
                    {
                        case COLON:
                        case SPACE:
                        case HTAB:
                        {
                            checkViolation(Violation.MULTILINE_FIELD_VALUE);

                            // header value without name - continuation?
                            if (StringUtil.isEmpty(_valueString))
                            {
                                _string.setLength(0);
                                _length = 0;
                            }
                            else
                            {
                                setString(_valueString);
                                _string.append(' ');
                                _length++;
                                _valueString = null;
                            }
                            setState(FieldState.VALUE);
                            break;
                        }

                        case LF:
                        {
                            // process previous header
                            if (_state == State.HEADER)
                                parsedHeader();
                            else
                                parsedTrailer();

                            _contentPosition = 0;

                            // End of headers or trailers?
                            if (_state == State.TRAILER)
                            {
                                setState(State.END);
                                return _handler.messageComplete();
                            }

                            // Was there a required host header?
                            if (!_host && _version == HttpVersion.HTTP_1_1 && _requestHandler != null)
                            {
                                throw new BadMessageException(HttpStatus.BAD_REQUEST_400, "No Host");
                            }

                            // is it a response that cannot have a body?
                            if (_responseHandler != null && // response
                                (_responseStatus == 304 || // not-modified response
                                    _responseStatus == 204 || // no-content response
                                    _responseStatus < 200)) // 1xx response
                                _endOfContent = EndOfContent.NO_CONTENT; // ignore any other headers set

                                // else if we don't know framing
                            else if (_endOfContent == EndOfContent.UNKNOWN_CONTENT)
                            {
                                if (_responseStatus == 0 || // request
                                    _responseStatus == 304 || // not-modified response
                                    _responseStatus == 204 || // no-content response
                                    _responseStatus < 200) // 1xx response
                                    _endOfContent = EndOfContent.NO_CONTENT;
                                else
                                    _endOfContent = EndOfContent.EOF_CONTENT;
                            }

                            // How is the message ended?
                            switch (_endOfContent)
                            {
                                case EOF_CONTENT:
                                {
                                    setState(State.EOF_CONTENT);
                                    boolean handle = _handler.headerComplete();
                                    _headerComplete = true;
                                    return handle;
                                }
                                case CHUNKED_CONTENT:
                                {
                                    setState(State.CHUNKED_CONTENT);
                                    boolean handle = _handler.headerComplete();
                                    _headerComplete = true;
                                    return handle;
                                }
                                case NO_CONTENT:
                                {
                                    setState(State.END);
                                    return handleHeaderContentMessage();
                                }
                                default:
                                {
                                    setState(State.CONTENT);
                                    boolean handle = _handler.headerComplete();
                                    _headerComplete = true;
                                    return handle;
                                }
                            }
                        }

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        {
                            // process previous header
                            if (_state == State.HEADER)
                                parsedHeader();
                            else
                                parsedTrailer();

                            // handle new header
                            if (buffer.hasRemaining())
                            {
                                // Try a look ahead for the known header name and value.
                                HttpField cachedField = _fieldCache == null ? null : _fieldCache.getBest(buffer, -1, buffer.remaining());
                                if (cachedField == null)
                                    cachedField = CACHE.getBest(buffer, -1, buffer.remaining());

                                if (cachedField != null)
                                {
                                    String n = cachedField.getName();
                                    String v = cachedField.getValue();

                                    if (CASE_SENSITIVE_FIELD_NAME.isAllowedBy(_complianceMode))
                                    {
                                        // Have to get the fields exactly from the buffer to match case
                                        String en = BufferUtil.toString(buffer, buffer.position() - 1, n.length(), StandardCharsets.US_ASCII);
                                        if (!n.equals(en))
                                        {
                                            reportComplianceViolation(CASE_SENSITIVE_FIELD_NAME, en);
                                            n = en;
                                            cachedField = new HttpField(cachedField.getHeader(), n, v);
                                        }
                                    }

                                    if (v != null && _handler.isHeaderCacheCaseSensitive())
                                    {
                                        String ev = BufferUtil.toString(buffer, buffer.position() + n.length() + 1, v.length(), StandardCharsets.ISO_8859_1);
                                        if (!v.equals(ev))
                                        {
                                            v = ev;
                                            cachedField = new HttpField(cachedField.getHeader(), n, v);
                                        }
                                    }

                                    _header = cachedField.getHeader();
                                    _headerString = n;

                                    if (v == null)
                                    {
                                        // Header only
                                        setState(FieldState.VALUE);
                                        _string.setLength(0);
                                        _length = 0;
                                        buffer.position(buffer.position() + n.length() + 1);
                                        break;
                                    }

                                    // Header and value
                                    int pos = buffer.position() + n.length() + v.length() + 1;
                                    byte peek = buffer.get(pos);
                                    if (peek == HttpTokens.CARRIAGE_RETURN || peek == HttpTokens.LINE_FEED)
                                    {
                                        _field = cachedField;
                                        _valueString = v;
                                        setState(FieldState.IN_VALUE);

                                        if (peek == HttpTokens.CARRIAGE_RETURN)
                                        {
                                            _cr = true;
                                            buffer.position(pos + 1);
                                        }
                                        else
                                            buffer.position(pos);
                                        break;
                                    }
                                    setState(FieldState.IN_VALUE);
                                    setString(v);
                                    buffer.position(pos);
                                    break;
                                }
                            }

                            // New header
                            setState(FieldState.IN_NAME);
                            _string.setLength(0);
                            _string.append(t.getChar());
                            _length = 1;
                            break;
                        }

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case IN_NAME:
                    switch (t.getType())
                    {
                        case SPACE:
                        case HTAB:
                            //Ignore trailing whitespaces ?
                            if (WHITESPACE_AFTER_FIELD_NAME.isAllowedBy(_complianceMode))
                            {
                                _headerString = takeString();
                                reportComplianceViolation(WHITESPACE_AFTER_FIELD_NAME, "Space after " + _headerString);
                                _header = HttpHeader.CACHE.get(_headerString);
                                _length = -1;
                                setState(FieldState.WS_AFTER_NAME);
                                break;
                            }
                            throw new IllegalCharacterException(_state, t, buffer);

                        case COLON:
                            _headerString = takeString();
                            _header = HttpHeader.CACHE.get(_headerString);
                            _length = -1;
                            setState(FieldState.VALUE);
                            break;

                        case LF:
                            _headerString = takeString();
                            _header = HttpHeader.CACHE.get(_headerString);
                            _string.setLength(0);
                            _valueString = "";
                            _length = -1;

                            if (NO_COLON_AFTER_FIELD_NAME.isAllowedBy(_complianceMode))
                            {
                                reportComplianceViolation(NO_COLON_AFTER_FIELD_NAME, "Field " + _headerString);
                                setState(FieldState.FIELD);
                                break;
                            }
                            throw new IllegalCharacterException(_state, t, buffer);

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                            _string.append(t.getChar());
                            _length = _string.length();
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case WS_AFTER_NAME:

                    switch (t.getType())
                    {
                        case SPACE:
                        case HTAB:
                            break;

                        case COLON:
                            setState(FieldState.VALUE);
                            break;

                        case LF:
                            if (NO_COLON_AFTER_FIELD_NAME.isAllowedBy(_complianceMode))
                            {
                                reportComplianceViolation(NO_COLON_AFTER_FIELD_NAME, "Field " + _headerString);
                                setState(FieldState.FIELD);
                                break;
                            }
                            throw new IllegalCharacterException(_state, t, buffer);

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case VALUE:
                    switch (t.getType())
                    {
                        case LF:
                            _string.setLength(0);
                            _valueString = "";
                            _length = -1;

                            setState(FieldState.FIELD);
                            break;

                        case SPACE:
                        case HTAB:
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT: // TODO review? should this be a utf8 string?
                            _string.append(t.getChar());
                            _length = _string.length();
                            setState(FieldState.IN_VALUE);
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                case IN_VALUE:
                    switch (t.getType())
                    {
                        case LF:
                            if (_length > 0)
                            {
                                _valueString = takeString();
                                _length = -1;
                            }
                            setState(FieldState.FIELD);
                            break;

                        case SPACE:
                        case HTAB:
                            _string.append(t.getChar());
                            break;

                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT: // TODO review? should this be a utf8 string?
                            _string.append(t.getChar());
                            _length = _string.length();
                            break;

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;

                default:
                    throw new IllegalStateException(_state.toString());
            }
        }

        return false;
    }

    
Parse until next Event.
Params:
buffer – the buffer to parse
Returns:
True if an RequestHandler method was called and it returned true;/**
     * Parse until next Event.
     *
     * @param buffer the buffer to parse
     * @return True if an {@link RequestHandler} method was called and it returned true;
     */
    public boolean parseNext(ByteBuffer buffer)
    {
        if (debugEnabled)
            LOG.debug("parseNext s={} {}", _state, BufferUtil.toDetailString(buffer));
        try
        {
            // Start a request/response
            if (_state == State.START)
            {
                _version = null;
                _method = null;
                _methodString = null;
                _endOfContent = EndOfContent.UNKNOWN_CONTENT;
                _header = null;
                if (quickStart(buffer))
                    return true;
            }

            // Request/response line
            if (_state.ordinal() >= State.START.ordinal() && _state.ordinal() < State.HEADER.ordinal())
            {
                if (parseLine(buffer))
                    return true;
            }

            // parse headers
            if (_state == State.HEADER)
            {
                if (parseFields(buffer))
                    return true;
            }

            // parse content
            if (_state.ordinal() >= State.CONTENT.ordinal() && _state.ordinal() < State.TRAILER.ordinal())
            {
                // Handle HEAD response
                if (_responseStatus > 0 && _headResponse)
                {
                    setState(State.END);
                    return handleContentMessage();
                }
                else
                {
                    if (parseContent(buffer))
                        return true;
                }
            }

            // parse headers
            if (_state == State.TRAILER)
            {
                if (parseFields(buffer))
                    return true;
            }

            // handle end states
            if (_state == State.END)
            {
                // eat white space
                while (buffer.remaining() > 0 && buffer.get(buffer.position()) <= HttpTokens.SPACE)
                {
                    buffer.get();
                }
            }
            else if (isClose() || isClosed())
            {
                BufferUtil.clear(buffer);
            }

            // Handle EOF
            if (_eof && !buffer.hasRemaining())
            {
                switch (_state)
                {
                    case CLOSED:
                        break;

                    case START:
                        setState(State.CLOSED);
                        _handler.earlyEOF();
                        break;

                    case END:
                    case CLOSE:
                        setState(State.CLOSED);
                        break;

                    case EOF_CONTENT:
                    case TRAILER:
                        if (_fieldState == FieldState.FIELD)
                        {
                            // Be forgiving of missing last CRLF
                            setState(State.CLOSED);
                            return handleContentMessage();
                        }
                        setState(State.CLOSED);
                        _handler.earlyEOF();
                        break;

                    case CONTENT:
                    case CHUNKED_CONTENT:
                    case CHUNK_SIZE:
                    case CHUNK_PARAMS:
                    case CHUNK:
                        setState(State.CLOSED);
                        _handler.earlyEOF();
                        break;

                    default:
                        if (debugEnabled)
                            LOG.debug("{} EOF in {}", this, _state);
                        setState(State.CLOSED);
                        _handler.badMessage(new BadMessageException(HttpStatus.BAD_REQUEST_400));
                        break;
                }
            }
        }
        catch (BadMessageException x)
        {
            BufferUtil.clear(buffer);
            badMessage(x);
        }
        catch (Throwable x)
        {
            BufferUtil.clear(buffer);
            badMessage(new BadMessageException(HttpStatus.BAD_REQUEST_400, _requestHandler != null ? "Bad Request" : "Bad Response", x));
        }
        return false;
    }

    protected void badMessage(BadMessageException x)
    {
        if (debugEnabled)
            LOG.debug("Parse exception: " + this + " for " + _handler, x);
        setState(State.CLOSE);
        if (_headerComplete)
            _handler.earlyEOF();
        else
            _handler.badMessage(x);
    }

    protected boolean parseContent(ByteBuffer buffer)
    {
        int remaining = buffer.remaining();
        if (remaining == 0 && _state == State.CONTENT)
        {
            long content = _contentLength - _contentPosition;
            if (content == 0)
            {
                setState(State.END);
                return handleContentMessage();
            }
        }

        // Handle _content
        byte ch;
        while (_state.ordinal() < State.TRAILER.ordinal() && remaining > 0)
        {
            switch (_state)
            {
                case EOF_CONTENT:
                    _contentChunk = buffer.asReadOnlyBuffer();
                    _contentPosition += remaining;
                    buffer.position(buffer.position() + remaining);
                    if (_handler.content(_contentChunk))
                        return true;
                    break;

                case CONTENT:
                {
                    long content = _contentLength - _contentPosition;
                    if (content == 0)
                    {
                        setState(State.END);
                        return handleContentMessage();
                    }
                    else
                    {
                        _contentChunk = buffer.asReadOnlyBuffer();

                        // limit content by expected size
                        if (remaining > content)
                        {
                            // We can cast remaining to an int as we know that it is smaller than
                            // or equal to length which is already an int.
                            _contentChunk.limit(_contentChunk.position() + (int)content);
                        }

                        _contentPosition += _contentChunk.remaining();
                        buffer.position(buffer.position() + _contentChunk.remaining());

                        if (_handler.content(_contentChunk))
                            return true;

                        if (_contentPosition == _contentLength)
                        {
                            setState(State.END);
                            return handleContentMessage();
                        }
                    }
                    break;
                }

                case CHUNKED_CONTENT:
                {
                    HttpTokens.Token t = next(buffer);
                    if (t == null)
                        break;
                    switch (t.getType())
                    {
                        case LF:
                            break;

                        case DIGIT:
                            _chunkLength = t.getHexDigit();
                            _chunkPosition = 0;
                            setState(State.CHUNK_SIZE);
                            break;

                        case ALPHA:
                            if (t.isHexDigit())
                            {
                                _chunkLength = t.getHexDigit();
                                _chunkPosition = 0;
                                setState(State.CHUNK_SIZE);
                                break;
                            }
                            throw new IllegalCharacterException(_state, t, buffer);

                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                }

                case CHUNK_SIZE:
                {
                    HttpTokens.Token t = next(buffer);
                    if (t == null)
                        break;

                    switch (t.getType())
                    {
                        case LF:
                            if (_chunkLength == 0)
                            {
                                setState(State.TRAILER);
                                if (_handler.contentComplete())
                                    return true;
                            }
                            else
                                setState(State.CHUNK);
                            break;

                        case SPACE:
                            setState(State.CHUNK_PARAMS);
                            break;

                        default:
                            if (t.isHexDigit())
                            {
                                if (_chunkLength > MAX_CHUNK_LENGTH)
                                    throw new BadMessageException(HttpStatus.PAYLOAD_TOO_LARGE_413);
                                _chunkLength = _chunkLength * 16 + t.getHexDigit();
                            }
                            else
                            {
                                setState(State.CHUNK_PARAMS);
                            }
                    }
                    break;
                }

                case CHUNK_PARAMS:
                {
                    HttpTokens.Token t = next(buffer);
                    if (t == null)
                        break;

                    switch (t.getType())
                    {
                        case LF:
                            if (_chunkLength == 0)
                            {
                                setState(State.TRAILER);
                                if (_handler.contentComplete())
                                    return true;
                            }
                            else
                                setState(State.CHUNK);
                            break;
                        default:
                            break; // TODO review
                    }
                    break;
                }

                case CHUNK:
                {
                    int chunk = _chunkLength - _chunkPosition;
                    if (chunk == 0)
                    {
                        setState(State.CHUNKED_CONTENT);
                    }
                    else
                    {
                        _contentChunk = buffer.asReadOnlyBuffer();

                        if (remaining > chunk)
                            _contentChunk.limit(_contentChunk.position() + chunk);
                        chunk = _contentChunk.remaining();

                        _contentPosition += chunk;
                        _chunkPosition += chunk;
                        buffer.position(buffer.position() + chunk);
                        if (_handler.content(_contentChunk))
                            return true;
                    }
                    break;
                }

                case CLOSED:
                {
                    BufferUtil.clear(buffer);
                    return false;
                }

                default:
                    break;
            }

            remaining = buffer.remaining();
        }
        return false;
    }

    public boolean isAtEOF()
    {
        return _eof;
    }

    
Signal that the associated data source is at EOF
/**
     * Signal that the associated data source is at EOF
     */
    public void atEOF()
    {
        if (debugEnabled)
            LOG.debug("atEOF {}", this);
        _eof = true;
    }

    
Request that the associated data source be closed
/**
     * Request that the associated data source be closed
     */
    public void close()
    {
        if (debugEnabled)
            LOG.debug("close {}", this);
        setState(State.CLOSE);
    }

    public void reset()
    {
        if (debugEnabled)
            LOG.debug("reset {}", this);

        // reset state
        if (_state == State.CLOSE || _state == State.CLOSED)
            return;

        setState(State.START);
        _endOfContent = EndOfContent.UNKNOWN_CONTENT;
        _contentLength = -1;
        _hasContentLength = false;
        _contentPosition = 0;
        _responseStatus = 0;
        _contentChunk = null;
        _headerBytes = 0;
        _host = false;
        _headerComplete = false;
    }

    protected void setState(State state)
    {
        if (debugEnabled)
            LOG.debug("{} --> {}", _state, state);
        _state = state;
    }

    protected void setState(FieldState state)
    {
        if (debugEnabled)
            LOG.debug("{}:{} --> {}", _state, _field != null ? _field : _headerString != null ? _headerString : _string, state);
        _fieldState = state;
    }

    public Trie<HttpField> getFieldCache()
    {
        return _fieldCache;
    }

    @Override
    public String toString()
    {
        return String.format("%s{s=%s,%d of %d}",
            getClass().getSimpleName(),
            _state,
            _contentPosition,
            _contentLength);
    }

    /* Event Handler interface
     * These methods return true if the caller should process the events
     * so far received (eg return from parseNext and call HttpChannel.handle).
     * If multiple callbacks are called in sequence (eg
     * headerComplete then messageComplete) from the same point in the parsing
     * then it is sufficient for the caller to process the events only once.
     */
    public interface HttpHandler
    {
        boolean content(ByteBuffer item);

        boolean headerComplete();

        boolean contentComplete();

        boolean messageComplete();

        
This is the method called by parser when a HTTP Header name and value is found
Params:
field – The field parsed/**
         * This is the method called by parser when a HTTP Header name and value is found
         *
         * @param field The field parsed
         */
        void parsedHeader(HttpField field);

        
This is the method called by parser when a HTTP Trailer name and value is found
Params:
field – The field parsed/**
         * This is the method called by parser when a HTTP Trailer name and value is found
         *
         * @param field The field parsed
         */
        default void parsedTrailer(HttpField field)
        {
        }

        
Called to signal that an EOF was received unexpectedly
during the parsing of a HTTP message
/**
         * Called to signal that an EOF was received unexpectedly
         * during the parsing of a HTTP message
         */
        void earlyEOF();

        
Called to signal that a bad HTTP message has been received.
Params:
failure – the failure with the bad message information/**
         * Called to signal that a bad HTTP message has been received.
         *
         * @param failure the failure with the bad message information
         */
        default void badMessage(BadMessageException failure)
        {
        }

        
Returns:
the size in bytes of the per parser header cache/**
         * @return the size in bytes of the per parser header cache
         */
        int getHeaderCacheSize();

        boolean isHeaderCacheCaseSensitive();
    }

    public interface RequestHandler extends HttpHandler
    {
        
This is the method called by parser when the HTTP request line is parsed
Params:
method – The method
uri – The raw bytes of the URI.  These are copied into a ByteBuffer that will not be changed until this parser is reset and reused.
version – the http version in use
Returns:
true if handling parsing should return./**
         * This is the method called by parser when the HTTP request line is parsed
         *
         * @param method The method
         * @param uri The raw bytes of the URI.  These are copied into a ByteBuffer that will not be changed until this parser is reset and reused.
         * @param version the http version in use
         * @return true if handling parsing should return.
         */
        boolean startRequest(String method, String uri, HttpVersion version);
    }

    public interface ResponseHandler extends HttpHandler
    {
        
This is the method called by parser when the HTTP request line is parsed
Params:
version – the http version in use
status – the response status
reason – the response reason phrase
Returns:
true if handling parsing should return/**
         * This is the method called by parser when the HTTP request line is parsed
         *
         * @param version the http version in use
         * @param status the response status
         * @param reason the response reason phrase
         * @return true if handling parsing should return
         */
        boolean startResponse(HttpVersion version, int status, String reason);
    }

    @SuppressWarnings("serial")
    private static class IllegalCharacterException extends BadMessageException
    {
        private IllegalCharacterException(State state, HttpTokens.Token token, ByteBuffer buffer)
        {
            super(400, String.format("Illegal character %s", token));
            if (LOG.isDebugEnabled())
                LOG.debug(String.format("Illegal character %s in state=%s for buffer %s", token, state, BufferUtil.toDetailString(buffer)));
        }
    }
}