content: /*
   * Copyright 1999-2012 Alibaba Group.
   *  
   * 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.cobar.mysql;
  
  /**
   * @author xianmao.hexm
   */
  public class ByteUtil {
  
      public static int readUB2(byte[] data, int offset) {
          int i = data[offset] & 0xff;
          i |= (data[++offset] & 0xff) << 8;
          return i;
      }
  
      public static int readUB3(byte[] data, int offset) {
          int i = data[offset] & 0xff;
          i |= (data[++offset] & 0xff) << 8;
          i |= (data[++offset] & 0xff) << 16;
          return i;
      }
  
      public static long readUB4(byte[] data, int offset) {
          long l = data[offset] & 0xff;
          l |= (data[++offset] & 0xff) << 8;
          l |= (data[++offset] & 0xff) << 16;
          l |= (data[++offset] & 0xff) << 24;
          return l;
      }
  
      public static long readLong(byte[] data, int offset) {
          long l = (long) (data[offset] & 0xff);
          l |= (long) (data[++offset] & 0xff) << 8;
          l |= (long) (data[++offset] & 0xff) << 16;
          l |= (long) (data[++offset] & 0xff) << 24;
          l |= (long) (data[++offset] & 0xff) << 32;
          l |= (long) (data[++offset] & 0xff) << 40;
          l |= (long) (data[++offset] & 0xff) << 48;
          l |= (long) (data[++offset] & 0xff) << 56;
          return l;
      }
  
      public static long readLength(byte[] data, int offset) {
          int length = data[offset++] & 0xff;
          switch (length) {
          case 251:
              return MySQLMessage.NULL_LENGTH;
          case 252:
              return readUB2(data, offset);
          case 253:
              return readUB3(data, offset);
          case 254:
              return readLong(data, offset);
          default:
              return length;
          }
      }
  
      public static int lengthToZero(byte[] data, int offset) {
          int start = offset;
          for (int i = start; i < data.length; i++) {
              if (data[i] == 0) {
                  return (i - start);
              }
          }
          int remaining = data.length - start;
          return remaining > 0 ? remaining : 0;
      }
  
      public static int decodeLength(byte[] src) {
          int length = src.length;
          if (length < 251) {
              return 1 + length;
          } else if (length < 0x10000L) {
              return 3 + length;
          } else if (length < 0x1000000L) {
              return 4 + length;
          } else {
              return 9 + length;
          }
      }
  
      public static int decodeLength(long length) {
          if (length < 251) {
              return 1;
          } else if (length < 0x10000L) {
              return 3;
          } else if (length < 0x1000000L) {
              return 4;
          } else {
              return 9;
          }
      }
  
  }
  