/*
    * Copyright 2014 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.AsciiString;
  import io.netty.util.CharsetUtil;
  
  import static io.netty.handler.codec.http.HttpConstants.*;
  import static io.netty.handler.codec.http.HttpObjectEncoder.CRLF_SHORT;
  
  final class HttpHeadersEncoder {
      private static final int COLON_AND_SPACE_SHORT = (COLON << 8) | SP;
  
      private HttpHeadersEncoder() {
      }
  
      static void encoderHeader(CharSequence name, CharSequence value, ByteBuf buf) {
          final int nameLen = name.length();
          final int valueLen = value.length();
          final int entryLen = nameLen + valueLen + 4;
          buf.ensureWritable(entryLen);
          int offset = buf.writerIndex();
          writeAscii(buf, offset, name);
          offset += nameLen;
          ByteBufUtil.setShortBE(buf, offset, COLON_AND_SPACE_SHORT);
          offset += 2;
          writeAscii(buf, offset, value);
          offset += valueLen;
          ByteBufUtil.setShortBE(buf, offset, CRLF_SHORT);
          offset += 2;
          buf.writerIndex(offset);
      }
  
      private static void writeAscii(ByteBuf buf, int offset, CharSequence value) {
          if (value instanceof AsciiString) {
              ByteBufUtil.copy((AsciiString) value, 0, buf, offset, value.length());
          } else {
              buf.setCharSequence(offset, value, CharsetUtil.US_ASCII);
          }
      }
  }