/*
    * Copyright 2017 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.http2;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.microbench.util.AbstractMicrobenchmark;
  import org.openjdk.jmh.annotations.Benchmark;
  import org.openjdk.jmh.annotations.BenchmarkMode;
  import org.openjdk.jmh.annotations.Fork;
  import org.openjdk.jmh.annotations.Measurement;
  import org.openjdk.jmh.annotations.Mode;
  import org.openjdk.jmh.annotations.OutputTimeUnit;
  import org.openjdk.jmh.annotations.Scope;
  import org.openjdk.jmh.annotations.Setup;
  import org.openjdk.jmh.annotations.State;
  import org.openjdk.jmh.annotations.Threads;
  import org.openjdk.jmh.annotations.Warmup;
  
  import java.util.concurrent.TimeUnit;
  
  @Threads(1)
  @State(Scope.Benchmark)
  @Fork(1)
  @Warmup(iterations = 5)
  @Measurement(iterations = 10)
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  public class HpackDecoderULE128Benchmark extends AbstractMicrobenchmark {
      private static final Http2Exception DECODE_ULE_128_TO_LONG_DECOMPRESSION_EXCEPTION =
              new Http2Exception(Http2Error.COMPRESSION_ERROR);
      private static final Http2Exception DECODE_ULE_128_TO_INT_DECOMPRESSION_EXCEPTION =
              new Http2Exception(Http2Error.COMPRESSION_ERROR);
      private static final Http2Exception DECODE_ULE_128_DECOMPRESSION_EXCEPTION =
              new Http2Exception(Http2Error.COMPRESSION_ERROR);
  
      private ByteBuf longMaxBuf;
      private ByteBuf intMaxBuf;
  
      @Setup
      public void setup() {
          byte[] longMax = {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF,
                            (byte) 0xFF, (byte) 0x7F};
          longMaxBuf = Unpooled.wrappedBuffer(longMax);
          byte[] intMax = {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0x07};
          intMaxBuf = Unpooled.wrappedBuffer(intMax);
      }
  
      @Benchmark
      @BenchmarkMode(Mode.AverageTime)
      public long decodeMaxLong() throws Http2Exception {
          long v = decodeULE128(longMaxBuf, 0L);
          longMaxBuf.readerIndex(0);
          return v;
      }
  
      @Benchmark
      @BenchmarkMode(Mode.AverageTime)
      public long decodeMaxIntWithLong() throws Http2Exception {
          long v = decodeULE128(intMaxBuf, 0L);
          intMaxBuf.readerIndex(0);
          return v;
      }
  
      @Benchmark
      @BenchmarkMode(Mode.AverageTime)
      public int decodeMaxInt() throws Http2Exception {
          int v = decodeULE128(intMaxBuf, 0);
          intMaxBuf.readerIndex(0);
          return v;
      }
  
      @Benchmark
      @BenchmarkMode(Mode.AverageTime)
      public int decodeMaxIntUsingLong() throws Http2Exception {
          int v = decodeULE128UsingLong(intMaxBuf, 0);
          intMaxBuf.readerIndex(0);
          return v;
      }
  
      static int decodeULE128UsingLong(ByteBuf in, int result) throws Http2Exception {
          final int readerIndex = in.readerIndex();
          final long v = decodeULE128(in, (long) result);
          if (v > Integer.MAX_VALUE) {
              in.readerIndex(readerIndex);
              throw DECODE_ULE_128_TO_INT_DECOMPRESSION_EXCEPTION;
          }
         return (int) v;
     }
 
     static long decodeULE128(ByteBuf in, long result) throws Http2Exception {
         assert result <= 0x7f && result >= 0;
         final boolean resultStartedAtZero = result == 0;
         final int writerIndex = in.writerIndex();
         for (int readerIndex = in.readerIndex(), shift = 0; readerIndex < writerIndex; ++readerIndex, shift += 7) {
             byte b = in.getByte(readerIndex);
             if (shift == 56 && ((b & 0x80) != 0 || b == 0x7F && !resultStartedAtZero)) {
                 // the maximum value that can be represented by a signed 64 bit number is:
                 // [0x01L, 0x7fL] + 0x7fL + (0x7fL << 7) + (0x7fL << 14) + (0x7fL << 21) + (0x7fL << 28) + (0x7fL << 35)
                 // + (0x7fL << 42) + (0x7fL << 49) + (0x7eL << 56)
                 // OR
                 // 0x0L + 0x7fL + (0x7fL << 7) + (0x7fL << 14) + (0x7fL << 21) + (0x7fL << 28) + (0x7fL << 35) +
                 // (0x7fL << 42) + (0x7fL << 49) + (0x7fL << 56)
                 // this means any more shifts will result longMaxBuf overflow so we should break out and throw an error.
                 throw DECODE_ULE_128_TO_LONG_DECOMPRESSION_EXCEPTION;
             }
 
             if ((b & 0x80) == 0) {
                 in.readerIndex(readerIndex + 1);
                 return result + ((b & 0x7FL) << shift);
             }
             result += (b & 0x7FL) << shift;
         }
 
         throw DECODE_ULE_128_DECOMPRESSION_EXCEPTION;
     }
 
     static int decodeULE128(ByteBuf in, int result) throws Http2Exception {
         assert result <= 0x7f && result >= 0;
         final boolean resultStartedAtZero = result == 0;
         final int writerIndex = in.writerIndex();
         for (int readerIndex = in.readerIndex(), shift = 0; readerIndex < writerIndex; ++readerIndex, shift += 7) {
             byte b = in.getByte(readerIndex);
             if (shift == 28 && ((b & 0x80) != 0 || !resultStartedAtZero && b > 6 || resultStartedAtZero && b > 7)) {
                 // the maximum value that can be represented by a signed 32 bit number is:
                 // [0x1,0x7f] + 0x7f + (0x7f << 7) + (0x7f << 14) + (0x7f << 21) + (0x6 << 28)
                 // OR
                 // 0x0 + 0x7f + (0x7f << 7) + (0x7f << 14) + (0x7f << 21) + (0x7 << 28)
                 // this means any more shifts will result longMaxBuf overflow so we should break out and throw an error.
                 throw DECODE_ULE_128_TO_INT_DECOMPRESSION_EXCEPTION;
             }
 
             if ((b & 0x80) == 0) {
                 in.readerIndex(readerIndex + 1);
                 return result + ((b & 0x7F) << shift);
             }
             result += (b & 0x7F) << shift;
         }
 
         throw DECODE_ULE_128_DECOMPRESSION_EXCEPTION;
     }
 }