/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
    *
   *     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 org.apache.hadoop.hbase.util.vint;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  /**
   * Simple Variable Length Integer encoding.  Left bit of 0 means we are on the last byte.  If left
   * bit of the current byte is 1, then there is at least one more byte.
   */
  @InterfaceAudience.Private
  public class UVIntTool {
  
    public static final byte
      BYTE_7_RIGHT_BITS_SET = 127,
      BYTE_LEFT_BIT_SET = -128;
  
    public static final long
      INT_7_RIGHT_BITS_SET = 127,
      INT_8TH_BIT_SET = 128;
  
    public static final byte[]
      MAX_VALUE_BYTES = new byte[] { -1, -1, -1, -1, 7 };
  
    /********************* int -> bytes **************************/
  
    public static int numBytes(int in) {
      if (in == 0) {
        // doesn't work with the formula below
        return 1;
      }
      return (38 - Integer.numberOfLeadingZeros(in)) / 7;// 38 comes from 32+(7-1)
    }
  
    public static byte[] getBytes(int value) {
      int numBytes = numBytes(value);
      byte[] bytes = new byte[numBytes];
      int remainder = value;
      for (int i = 0; i < numBytes - 1; ++i) {
        // set the left bit
        bytes[i] = (byte) ((remainder & INT_7_RIGHT_BITS_SET) | INT_8TH_BIT_SET);
        remainder >>= 7;
      }
      // do not set the left bit
      bytes[numBytes - 1] = (byte) (remainder & INT_7_RIGHT_BITS_SET);
      return bytes;
    }
  
    public static int writeBytes(int value, OutputStream os) throws IOException {
      int numBytes = numBytes(value);
      int remainder = value;
      for (int i = 0; i < numBytes - 1; ++i) {
        // set the left bit
        os.write((byte) ((remainder & INT_7_RIGHT_BITS_SET) | INT_8TH_BIT_SET));
        remainder >>= 7;
      }
      // do not set the left bit
      os.write((byte) (remainder & INT_7_RIGHT_BITS_SET));
      return numBytes;
    }
  
    /******************** bytes -> int **************************/
  
    public static int getInt(byte[] bytes) {
      return getInt(bytes, 0);
    }
  
    public static int getInt(byte[] bytes, int offset) {
      int value = 0;
      for (int i = 0;; ++i) {
        byte b = bytes[offset + i];
        int shifted = BYTE_7_RIGHT_BITS_SET & b;// kill leftmost bit
        shifted <<= 7 * i;
        value |= shifted;
        if (b >= 0) {
          break;
        }
      }
      return value;
   }
 
   public static int getInt(InputStream is) throws IOException {
     int value = 0;
     int i = 0;
     int b;
     do{
       b = is.read();
       int shifted = BYTE_7_RIGHT_BITS_SET & b;// kill leftmost bit
       shifted <<= 7 * i;
       value |= shifted;
       ++i;
     }while(b > Byte.MAX_VALUE);
     return value;
   }
 }