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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package io.netty.handler.codec.http;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufUtil;
  import io.netty.util.CharsetUtil;
  
  import static io.netty.handler.codec.http.HttpConstants.SP;
  
  /**
   * Encodes an {@link HttpRequest} or an {@link HttpContent} into
   * a {@link ByteBuf}.
   */
  public class HttpRequestEncoder extends HttpObjectEncoder<HttpRequest> {
      private static final char SLASH = '/';
      private static final char QUESTION_MARK = '?';
      private static final int SLASH_AND_SPACE_SHORT = (SLASH << 8) | SP;
      private static final int SPACE_SLASH_AND_SPACE_MEDIUM = (SP << 16) | SLASH_AND_SPACE_SHORT;
  
      @Override
      public boolean acceptOutboundMessage(Object msg) throws Exception {
          return super.acceptOutboundMessage(msg) && !(msg instanceof HttpResponse);
      }
  
      @Override
      protected void encodeInitialLine(ByteBuf buf, HttpRequest request) throws Exception {
          ByteBufUtil.copy(request.method().asciiName(), buf);
  
          String uri = request.uri();
  
          if (uri.isEmpty()) {
              // Add " / " as absolute path if uri is not present.
              // See https://tools.ietf.org/html/rfc2616#section-5.1.2
              ByteBufUtil.writeMediumBE(buf, SPACE_SLASH_AND_SPACE_MEDIUM);
          } else {
              CharSequence uriCharSequence = uri;
              boolean needSlash = false;
              int start = uri.indexOf("://");
              if (start != -1 && uri.charAt(0) != SLASH) {
                  start += 3;
                  // Correctly handle query params.
                  // See https://github.com/netty/netty/issues/2732
                  int index = uri.indexOf(QUESTION_MARK, start);
                  if (index == -1) {
                      if (uri.lastIndexOf(SLASH) < start) {
                          needSlash = true;
                      }
                  } else {
                      if (uri.lastIndexOf(SLASH, index) < start) {
                          uriCharSequence = new StringBuilder(uri).insert(index, SLASH);
                      }
                  }
              }
              buf.writeByte(SP).writeCharSequence(uriCharSequence, CharsetUtil.UTF_8);
              if (needSlash) {
                  // write "/ " after uri
                  ByteBufUtil.writeShortBE(buf, SLASH_AND_SPACE_SHORT);
              } else {
                  buf.writeByte(SP);
              }
          }
  
          request.protocolVersion().encode(buf);
          ByteBufUtil.writeShortBE(buf, CRLF_SHORT);
      }
  }