content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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
   *
   *      http://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 com.alibaba.csp.sentinel.eagleeye;
  
  import java.text.SimpleDateFormat;
  import java.util.Date;
  import java.util.TimeZone;
  
  class FastDateFormat {
  
      private final SimpleDateFormat fmt = createSimpleDateFormat();
  
      private char[] buffer = new char[23];
  
      private long lastSecond = -1;
      private long lastMillis = -1;
  
      public String format(long timestamp) {
          formatToBuffer(timestamp);
          return new String(buffer, 0, 23);
      }
  
      public String format(Date date) {
          return format(date.getTime());
      }
  
      public void formatAndAppendTo(long timestamp, StringBuilder appender) {
          formatToBuffer(timestamp);
          appender.append(buffer, 0, 23);
      }
  
      private void formatToBuffer(long timestamp) {
          if (timestamp == lastMillis) {
              return;
          }
          long diff = timestamp - lastSecond;
          if (diff >= 0 && diff < 1000) {
              int ms = (int)(timestamp % 1000);
              buffer[22] = (char)(ms % 10 + '0');
              ms /= 10;
              buffer[21] = (char)(ms % 10 + '0');
              buffer[20] = (char)(ms / 10 + '0');
              lastMillis = timestamp;
          } else {
              String result = fmt.format(new Date(timestamp));
              result.getChars(0, result.length(), buffer, 0);
              lastSecond = timestamp / 1000 * 1000;
              lastMillis = timestamp;
          }
      }
  
      String formatWithoutMs(long timestamp) {
          long diff = timestamp - lastSecond;
          if (diff < 0 || diff >= 1000) {
              String result = fmt.format(new Date(timestamp));
              result.getChars(0, result.length(), buffer, 0);
              lastSecond = timestamp / 1000 * 1000;
              lastMillis = timestamp;
          }
          return new String(buffer, 0, 19);
      }
  
      private SimpleDateFormat createSimpleDateFormat() {
          SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
          fmt.setTimeZone(TimeZone.getDefault());
          return fmt;
      }
  }
  