/*
    * 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.io.encoding;
  
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValue.KVComparator;
  import org.apache.hadoop.hbase.KeyValueUtil;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.util.ByteBufferUtils;
  import org.apache.hadoop.hbase.util.Bytes;
  
  /**
   * Encoder similar to {@link DiffKeyDeltaEncoder} but supposedly faster.
   *
   * Compress using:
   * - store size of common prefix
   * - save column family once in the first KeyValue
   * - use integer compression for key, value and prefix (7-bit encoding)
   * - use bits to avoid duplication key length, value length
   *   and type if it same as previous
   * - store in 3 bits length of prefix timestamp
   *    with previous KeyValue's timestamp
   * - one bit which allow to omit value if it is the same
   *
   * Format:
   * - 1 byte:    flag
   * - 1-5 bytes: key length (only if FLAG_SAME_KEY_LENGTH is not set in flag)
   * - 1-5 bytes: value length (only if FLAG_SAME_VALUE_LENGTH is not set in flag)
   * - 1-5 bytes: prefix length
   * - ... bytes: rest of the row (if prefix length is small enough)
   * - ... bytes: qualifier (or suffix depending on prefix length)
   * - 1-8 bytes: timestamp suffix
   * - 1 byte:    type (only if FLAG_SAME_TYPE is not set in the flag)
   * - ... bytes: value (only if FLAG_SAME_VALUE is not set in the flag)
   *
   */
  @InterfaceAudience.Private
  public class FastDiffDeltaEncoder extends BufferedDataBlockEncoder {
    final int MASK_TIMESTAMP_LENGTH = (1 << 0) | (1 << 1) | (1 << 2);
    final int SHIFT_TIMESTAMP_LENGTH = 0;
    final int FLAG_SAME_KEY_LENGTH = 1 << 3;
    final int FLAG_SAME_VALUE_LENGTH = 1 << 4;
    final int FLAG_SAME_TYPE = 1 << 5;
    final int FLAG_SAME_VALUE = 1 << 6;
  
    private static class FastDiffCompressionState extends CompressionState {
      byte[] timestamp = new byte[KeyValue.TIMESTAMP_SIZE];
      int prevTimestampOffset;
  
      @Override
      protected void readTimestamp(ByteBuffer in) {
        in.get(timestamp);
      }
  
      @Override
      void copyFrom(CompressionState state) {
        super.copyFrom(state);
        FastDiffCompressionState state2 = (FastDiffCompressionState) state;
        System.arraycopy(state2.timestamp, 0, timestamp, 0,
            KeyValue.TIMESTAMP_SIZE);
        prevTimestampOffset = state2.prevTimestampOffset;
      }
  
      /**
       * Copies the first key/value from the given stream, and initializes
       * decompression state based on it. Assumes that we have already read key
       * and value lengths. Does not set {@link #qualifierLength} (not used by
       * decompression) or {@link #prevOffset} (set by the calle afterwards).
       */
      private void decompressFirstKV(ByteBuffer out, DataInputStream in)
          throws IOException {
        int kvPos = out.position();
        out.putInt(keyLength);
        out.putInt(valueLength);
        prevTimestampOffset = out.position() + keyLength -
            KeyValue.TIMESTAMP_TYPE_SIZE;
        ByteBufferUtils.copyFromStreamToBuffer(out, in, keyLength + valueLength);
        rowLength = out.getShort(kvPos + KeyValue.ROW_OFFSET);
       familyLength = out.get(kvPos + KeyValue.ROW_OFFSET +
           KeyValue.ROW_LENGTH_SIZE + rowLength);
       type = out.get(prevTimestampOffset + KeyValue.TIMESTAMP_SIZE);
     }
 
   }
 
   private int findCommonTimestampPrefix(byte[] curTsBuf, byte[] prevTsBuf) {
     int commonPrefix = 0;
     while (commonPrefix < (KeyValue.TIMESTAMP_SIZE - 1)
         && curTsBuf[commonPrefix] == prevTsBuf[commonPrefix]) {
       commonPrefix++;
     }
     return commonPrefix; // has to be at most 7 bytes
   }
 
   private void uncompressSingleKeyValue(DataInputStream source,
       ByteBuffer out, FastDiffCompressionState state)
           throws IOException, EncoderBufferTooSmallException {
     byte flag = source.readByte();
     int prevKeyLength = state.keyLength;
 
     if ((flag & FLAG_SAME_KEY_LENGTH) == 0) {
       state.keyLength = ByteBufferUtils.readCompressedInt(source);
     }
     if ((flag & FLAG_SAME_VALUE_LENGTH) == 0) {
       state.valueLength = ByteBufferUtils.readCompressedInt(source);
     }
     int commonLength = ByteBufferUtils.readCompressedInt(source);
 
     ensureSpace(out, state.keyLength + state.valueLength + KeyValue.ROW_OFFSET);
 
     int kvPos = out.position();
 
     if (!state.isFirst()) {
       // copy the prefix
       int common;
       int prevOffset;
 
       if ((flag & FLAG_SAME_VALUE_LENGTH) == 0) {
         out.putInt(state.keyLength);
         out.putInt(state.valueLength);
         prevOffset = state.prevOffset + KeyValue.ROW_OFFSET;
         common = commonLength;
       } else {
         if ((flag & FLAG_SAME_KEY_LENGTH) != 0) {
           prevOffset = state.prevOffset;
           common = commonLength + KeyValue.ROW_OFFSET;
         } else {
           out.putInt(state.keyLength);
           prevOffset = state.prevOffset + KeyValue.KEY_LENGTH_SIZE;
           common = commonLength + KeyValue.KEY_LENGTH_SIZE;
         }
       }
 
       ByteBufferUtils.copyFromBufferToBuffer(out, out, prevOffset, common);
 
       // copy the rest of the key from the buffer
       int keyRestLength;
       if (commonLength < state.rowLength + KeyValue.ROW_LENGTH_SIZE) {
         // omit the family part of the key, it is always the same
         int rowWithSizeLength;
         int rowRestLength;
 
         // check length of row
         if (commonLength < KeyValue.ROW_LENGTH_SIZE) {
           // not yet copied, do it now
           ByteBufferUtils.copyFromStreamToBuffer(out, source,
               KeyValue.ROW_LENGTH_SIZE - commonLength);
 
           rowWithSizeLength = out.getShort(out.position() -
               KeyValue.ROW_LENGTH_SIZE) + KeyValue.ROW_LENGTH_SIZE;
           rowRestLength = rowWithSizeLength - KeyValue.ROW_LENGTH_SIZE;
         } else {
           // already in kvBuffer, just read it
           rowWithSizeLength = out.getShort(kvPos + KeyValue.ROW_OFFSET) +
               KeyValue.ROW_LENGTH_SIZE;
           rowRestLength = rowWithSizeLength - commonLength;
         }
 
         // copy the rest of row
         ByteBufferUtils.copyFromStreamToBuffer(out, source, rowRestLength);
 
         // copy the column family
         ByteBufferUtils.copyFromBufferToBuffer(out, out,
             state.prevOffset + KeyValue.ROW_OFFSET + KeyValue.ROW_LENGTH_SIZE
                 + state.rowLength, state.familyLength
                 + KeyValue.FAMILY_LENGTH_SIZE);
         state.rowLength = (short) (rowWithSizeLength -
             KeyValue.ROW_LENGTH_SIZE);
 
         keyRestLength = state.keyLength - rowWithSizeLength -
             state.familyLength -
             (KeyValue.FAMILY_LENGTH_SIZE + KeyValue.TIMESTAMP_TYPE_SIZE);
       } else {
         // prevRowWithSizeLength is the same as on previous row
         keyRestLength = state.keyLength - commonLength -
             KeyValue.TIMESTAMP_TYPE_SIZE;
       }
       // copy the rest of the key, after column family == column qualifier
       ByteBufferUtils.copyFromStreamToBuffer(out, source, keyRestLength);
 
       // copy timestamp
       int prefixTimestamp =
           (flag & MASK_TIMESTAMP_LENGTH) >>> SHIFT_TIMESTAMP_LENGTH;
       ByteBufferUtils.copyFromBufferToBuffer(out, out,
           state.prevTimestampOffset, prefixTimestamp);
       state.prevTimestampOffset = out.position() - prefixTimestamp;
       ByteBufferUtils.copyFromStreamToBuffer(out, source,
           KeyValue.TIMESTAMP_SIZE - prefixTimestamp);
 
       // copy the type and value
       if ((flag & FLAG_SAME_TYPE) != 0) {
         out.put(state.type);
         if ((flag & FLAG_SAME_VALUE) != 0) {
           ByteBufferUtils.copyFromBufferToBuffer(out, out, state.prevOffset +
               KeyValue.ROW_OFFSET + prevKeyLength, state.valueLength);
         } else {
           ByteBufferUtils.copyFromStreamToBuffer(out, source,
               state.valueLength);
         }
       } else {
         if ((flag & FLAG_SAME_VALUE) != 0) {
           ByteBufferUtils.copyFromStreamToBuffer(out, source,
               KeyValue.TYPE_SIZE);
           ByteBufferUtils.copyFromBufferToBuffer(out, out, state.prevOffset +
               KeyValue.ROW_OFFSET + prevKeyLength, state.valueLength);
         } else {
           ByteBufferUtils.copyFromStreamToBuffer(out, source,
               state.valueLength + KeyValue.TYPE_SIZE);
         }
         state.type = out.get(state.prevTimestampOffset +
             KeyValue.TIMESTAMP_SIZE);
       }
     } else { // this is the first element
       state.decompressFirstKV(out, source);
     }
 
     state.prevOffset = kvPos;
   }
 
   @Override
   public int internalEncode(Cell cell, HFileBlockDefaultEncodingContext encodingContext,
       DataOutputStream out) throws IOException {
     EncodingState state = encodingContext.getEncodingState();
     int size = compressSingleKeyValue(out, cell, state.prevCell);
     size += afterEncodingKeyValue(cell, out, encodingContext);
     state.prevCell = cell;
     return size;
   }
 
   private int compressSingleKeyValue(DataOutputStream out, Cell cell, Cell prevCell)
       throws IOException {
     int flag = 0; // Do not use more bits than will fit into a byte
     int kLength = KeyValueUtil.keyLength(cell);
     int vLength = cell.getValueLength();
 
     if (prevCell == null) {
       // copy the key, there is no common prefix with none
       out.write(flag);
       ByteBufferUtils.putCompressedInt(out, kLength);
       ByteBufferUtils.putCompressedInt(out, vLength);
       ByteBufferUtils.putCompressedInt(out, 0);
       CellUtil.writeFlatKey(cell, out);
       // Write the value part
       out.write(cell.getValueArray(), cell.getValueOffset(), cell.getValueLength());
     } else {
       int preKeyLength = KeyValueUtil.keyLength(prevCell);
       int preValLength = prevCell.getValueLength();
       // find a common prefix and skip it
       int commonPrefix = CellUtil.findCommonPrefixInFlatKey(cell, prevCell, true, false);
 
       if (kLength == preKeyLength) {
         flag |= FLAG_SAME_KEY_LENGTH;
       }
       if (vLength == prevCell.getValueLength()) {
         flag |= FLAG_SAME_VALUE_LENGTH;
       }
       if (cell.getTypeByte() == prevCell.getTypeByte()) {
         flag |= FLAG_SAME_TYPE;
       }
 
       byte[] curTsBuf = Bytes.toBytes(cell.getTimestamp());
       int commonTimestampPrefix = findCommonTimestampPrefix(curTsBuf,
           Bytes.toBytes(prevCell.getTimestamp()));
 
       flag |= commonTimestampPrefix << SHIFT_TIMESTAMP_LENGTH;
 
       // Check if current and previous values are the same. Compare value
       // length first as an optimization.
       if (vLength == preValLength
           && Bytes.equals(cell.getValueArray(), cell.getValueOffset(), vLength,
               prevCell.getValueArray(), prevCell.getValueOffset(), preValLength)) {
         flag |= FLAG_SAME_VALUE;
       }
 
       out.write(flag);
       if ((flag & FLAG_SAME_KEY_LENGTH) == 0) {
         ByteBufferUtils.putCompressedInt(out, kLength);
       }
       if ((flag & FLAG_SAME_VALUE_LENGTH) == 0) {
         ByteBufferUtils.putCompressedInt(out, vLength);
       }
       ByteBufferUtils.putCompressedInt(out, commonPrefix);
       short rLen = cell.getRowLength();
       if (commonPrefix < rLen + KeyValue.ROW_LENGTH_SIZE) {
         // Previous and current rows are different. Copy the differing part of
         // the row, skip the column family, and copy the qualifier.
         CellUtil.writeRowKeyExcludingCommon(cell, rLen, commonPrefix, out);
         out.write(cell.getQualifierArray(), cell.getQualifierOffset(), cell.getQualifierLength());
       } else {
         // The common part includes the whole row. As the column family is the
         // same across the whole file, it will automatically be included in the
         // common prefix, so we need not special-case it here.
         // What we write here is the non common part of the qualifier
         int commonQualPrefix = commonPrefix - (rLen + KeyValue.ROW_LENGTH_SIZE)
             - (cell.getFamilyLength() + KeyValue.FAMILY_LENGTH_SIZE);
         out.write(cell.getQualifierArray(), cell.getQualifierOffset() + commonQualPrefix,
             cell.getQualifierLength() - commonQualPrefix);
       }
       // Write non common ts part
       out.write(curTsBuf, commonTimestampPrefix, KeyValue.TIMESTAMP_SIZE - commonTimestampPrefix);
 
       // Write the type if it is not the same as before.
       if ((flag & FLAG_SAME_TYPE) == 0) {
         out.write(cell.getTypeByte());
       }
 
       // Write the value if it is not the same as before.
       if ((flag & FLAG_SAME_VALUE) == 0) {
         out.write(cell.getValueArray(), cell.getValueOffset(), vLength);
       }
     }
     return kLength + vLength + KeyValue.KEYVALUE_INFRASTRUCTURE_SIZE;
   }
 
   @Override
   protected ByteBuffer internalDecodeKeyValues(DataInputStream source, int allocateHeaderLength,
       int skipLastBytes, HFileBlockDefaultDecodingContext decodingCtx) throws IOException {
     int decompressedSize = source.readInt();
     ByteBuffer buffer = ByteBuffer.allocate(decompressedSize +
         allocateHeaderLength);
     buffer.position(allocateHeaderLength);
     FastDiffCompressionState state = new FastDiffCompressionState();
     while (source.available() > skipLastBytes) {
       uncompressSingleKeyValue(source, buffer, state);
       afterDecodingKeyValue(source, buffer, decodingCtx);
     }
 
     if (source.available() != skipLastBytes) {
       throw new IllegalStateException("Read too much bytes.");
     }
 
     return buffer;
   }
 
   @Override
   public ByteBuffer getFirstKeyInBlock(ByteBuffer block) {
     block.mark();
     block.position(Bytes.SIZEOF_INT + Bytes.SIZEOF_BYTE);
     int keyLength = ByteBufferUtils.readCompressedInt(block);
     ByteBufferUtils.readCompressedInt(block); // valueLength
     ByteBufferUtils.readCompressedInt(block); // commonLength
     int pos = block.position();
     block.reset();
     ByteBuffer dup = block.duplicate();
     dup.position(pos);
     dup.limit(pos + keyLength);
     return dup.slice();
   }
 
   @Override
   public String toString() {
     return FastDiffDeltaEncoder.class.getSimpleName();
   }
 
   protected static class FastDiffSeekerState extends SeekerState {
     private byte[] prevTimestampAndType =
         new byte[KeyValue.TIMESTAMP_TYPE_SIZE];
     private int rowLengthWithSize;
     private int familyLengthWithSize;
 
     public FastDiffSeekerState() {
       super();
     }
 
     @Override
     protected void copyFromNext(SeekerState that) {
       super.copyFromNext(that);
       FastDiffSeekerState other = (FastDiffSeekerState) that;
       System.arraycopy(other.prevTimestampAndType, 0,
           prevTimestampAndType, 0,
           KeyValue.TIMESTAMP_TYPE_SIZE);
       rowLengthWithSize = other.rowLengthWithSize;
       familyLengthWithSize = other.familyLengthWithSize;
     }
   }
 
   @Override
   public EncodedSeeker createSeeker(KVComparator comparator,
       final HFileBlockDecodingContext decodingCtx) {
     return new FastDiffSeekerStateBufferedEncodedSeeker(comparator, decodingCtx);
   }
 
   private class FastDiffSeekerStateBufferedEncodedSeeker
       extends BufferedEncodedSeeker<FastDiffSeekerState> {
 
     private FastDiffSeekerStateBufferedEncodedSeeker(KVComparator comparator,
       HFileBlockDecodingContext decodingCtx) {
       super(comparator, decodingCtx);
     }
 
     private void decode(boolean isFirst) {
       byte flag = currentBuffer.get();
       if ((flag & FLAG_SAME_KEY_LENGTH) == 0) {
         if (!isFirst) {
           System.arraycopy(current.keyBuffer,
               current.keyLength - current.prevTimestampAndType.length,
               current.prevTimestampAndType, 0,
               current.prevTimestampAndType.length);
         }
         current.keyLength = ByteBufferUtils.readCompressedInt(currentBuffer);
       }
       if ((flag & FLAG_SAME_VALUE_LENGTH) == 0) {
         current.valueLength =
             ByteBufferUtils.readCompressedInt(currentBuffer);
       }
       current.lastCommonPrefix =
           ByteBufferUtils.readCompressedInt(currentBuffer);
 
       current.ensureSpaceForKey();
 
       if (isFirst) {
         // copy everything
         currentBuffer.get(current.keyBuffer, current.lastCommonPrefix,
             current.keyLength - current.prevTimestampAndType.length);
         current.rowLengthWithSize = Bytes.toShort(current.keyBuffer, 0) +
             Bytes.SIZEOF_SHORT;
         current.familyLengthWithSize =
             current.keyBuffer[current.rowLengthWithSize] + Bytes.SIZEOF_BYTE;
       } else if (current.lastCommonPrefix < Bytes.SIZEOF_SHORT) {
         // length of row is different, copy everything except family
 
         // copy the row size
         int oldRowLengthWithSize = current.rowLengthWithSize;
         currentBuffer.get(current.keyBuffer, current.lastCommonPrefix,
             Bytes.SIZEOF_SHORT - current.lastCommonPrefix);
         current.rowLengthWithSize = Bytes.toShort(current.keyBuffer, 0) +
             Bytes.SIZEOF_SHORT;
 
         // move the column family
         System.arraycopy(current.keyBuffer, oldRowLengthWithSize,
             current.keyBuffer, current.rowLengthWithSize,
             current.familyLengthWithSize);
 
         // copy the rest of row
         currentBuffer.get(current.keyBuffer, Bytes.SIZEOF_SHORT,
             current.rowLengthWithSize - Bytes.SIZEOF_SHORT);
 
         // copy the qualifier
         currentBuffer.get(current.keyBuffer, current.rowLengthWithSize
             + current.familyLengthWithSize, current.keyLength
             - current.rowLengthWithSize - current.familyLengthWithSize
             - current.prevTimestampAndType.length);
       } else if (current.lastCommonPrefix < current.rowLengthWithSize) {
         // We have to copy part of row and qualifier, but the column family
         // is in the right place.
 
         // before column family (rest of row)
         currentBuffer.get(current.keyBuffer, current.lastCommonPrefix,
             current.rowLengthWithSize - current.lastCommonPrefix);
 
         // after column family (qualifier)
         currentBuffer.get(current.keyBuffer, current.rowLengthWithSize
             + current.familyLengthWithSize, current.keyLength
             - current.rowLengthWithSize - current.familyLengthWithSize
             - current.prevTimestampAndType.length);
       } else {
         // copy just the ending
         currentBuffer.get(current.keyBuffer, current.lastCommonPrefix,
             current.keyLength - current.prevTimestampAndType.length
                 - current.lastCommonPrefix);
       }
 
       // timestamp
       int pos = current.keyLength - current.prevTimestampAndType.length;
       int commonTimestampPrefix = (flag & MASK_TIMESTAMP_LENGTH) >>>
         SHIFT_TIMESTAMP_LENGTH;
       if ((flag & FLAG_SAME_KEY_LENGTH) == 0) {
         System.arraycopy(current.prevTimestampAndType, 0, current.keyBuffer,
             pos, commonTimestampPrefix);
       }
       pos += commonTimestampPrefix;
       currentBuffer.get(current.keyBuffer, pos,
           Bytes.SIZEOF_LONG - commonTimestampPrefix);
       pos += Bytes.SIZEOF_LONG - commonTimestampPrefix;
 
       // type
       if ((flag & FLAG_SAME_TYPE) == 0) {
         currentBuffer.get(current.keyBuffer, pos, Bytes.SIZEOF_BYTE);
       } else if ((flag & FLAG_SAME_KEY_LENGTH) == 0) {
         current.keyBuffer[pos] =
             current.prevTimestampAndType[Bytes.SIZEOF_LONG];
       }
 
       // handle value
       if ((flag & FLAG_SAME_VALUE) == 0) {
         current.valueOffset = currentBuffer.position();
         ByteBufferUtils.skip(currentBuffer, current.valueLength);
       }
 
       if (includesTags()) {
         decodeTags();
       }
       if (includesMvcc()) {
         current.memstoreTS = ByteBufferUtils.readVLong(currentBuffer);
       } else {
         current.memstoreTS = 0;
       }
       current.nextKvOffset = currentBuffer.position();
     }
 
     @Override
     protected void decodeFirst() {
       ByteBufferUtils.skip(currentBuffer, Bytes.SIZEOF_INT);
       decode(true);
     }
 
     @Override
     protected void decodeNext() {
       decode(false);
     }
 
     @Override
     protected FastDiffSeekerState createSeekerState() {
       return new FastDiffSeekerState();
     }
   }
 }