content: /*
   * 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 io.airlift.compress.v3.snappy;
  
  import io.airlift.compress.v3.MalformedInputException;
  
  import static io.airlift.compress.v3.snappy.SnappyConstants.LITERAL;
  import static io.airlift.compress.v3.snappy.SnappyConstants.SIZE_OF_INT;
  import static io.airlift.compress.v3.snappy.SnappyConstants.SIZE_OF_LONG;
  import static io.airlift.compress.v3.snappy.UnsafeUtil.UNSAFE;
  
  final class SnappyRawDecompressor
  {
      private static final int[] DEC_32_TABLE = {4, 1, 2, 1, 4, 4, 4, 4};
      private static final int[] DEC_64_TABLE = {0, 0, 0, -1, 0, 1, 2, 3};
  
      private SnappyRawDecompressor() {}
  
      public static int getUncompressedLength(Object compressed, long compressedAddress, long compressedLimit)
      {
          return readUncompressedLength(compressed, compressedAddress, compressedLimit)[0];
      }
  
      public static int decompress(
              final Object inputBase,
              final long inputAddress,
              final long inputLimit,
              final Object outputBase,
              final long outputAddress,
              final long outputLimit)
      {
          // Read the uncompressed length from the front of the input
          long input = inputAddress;
          int[] varInt = readUncompressedLength(inputBase, input, inputLimit);
          int expectedLength = varInt[0];
          input += varInt[1];
  
          SnappyInternalUtils.checkArgument(expectedLength <= (outputLimit - outputAddress),
                  "Uncompressed length %s must be less than %s", expectedLength, (outputLimit - outputAddress));
  
          // Process the entire input
          int uncompressedSize = uncompressAll(
                  inputBase,
                  input,
                  inputLimit,
                  outputBase,
                  outputAddress,
                  outputLimit);
  
          if (!(expectedLength == uncompressedSize)) {
              throw new MalformedInputException(0, String.format("Recorded length is %s bytes but actual length after decompression is %s bytes ",
                      expectedLength,
                      uncompressedSize));
          }
  
          return expectedLength;
      }
  
      private static int uncompressAll(
              final Object inputBase,
              final long inputAddress,
              final long inputLimit,
              final Object outputBase,
              final long outputAddress,
              final long outputLimit)
      {
          final long fastOutputLimit = outputLimit - SIZE_OF_LONG; // maximum offset in output buffer to which it's safe to write long-at-a-time
  
          long output = outputAddress;
          long input = inputAddress;
  
          while (input < inputLimit) {
              int opCode = UNSAFE.getByte(inputBase, input++) & 0xFF;
              int entry = opLookupTable[opCode] & 0xFFFF;
  
              int trailerBytes = entry >>> 11;
              int trailer = 0;
              if (input + SIZE_OF_INT < inputLimit) {
                  trailer = UNSAFE.getInt(inputBase, input) & wordmask[trailerBytes];
              }
              else {
                  if (input + trailerBytes > inputLimit) {
                      throw new MalformedInputException(input - inputAddress);
                  }
                  switch (trailerBytes) {
                      case 4:
                          trailer = (UNSAFE.getByte(inputBase, input + 3) & 0xff) << 24;
                      case 3:
                          trailer |= (UNSAFE.getByte(inputBase, input + 2) & 0xff) << 16;
                      case 2:
                          trailer |= (UNSAFE.getByte(inputBase, input + 1) & 0xff) << 8;
                      case 1:
                          trailer |= (UNSAFE.getByte(inputBase, input) & 0xff);
                  }
              }
              if (trailer < 0) {
                  throw new MalformedInputException(input - inputAddress);
              }
              input += trailerBytes;
  
              int length = entry & 0xff;
              if (length == 0) {
                  continue;
              }
  
              if ((opCode & 0x3) == LITERAL) {
                  int literalLength = length + trailer;
                  if (literalLength < 0) {
                      throw new MalformedInputException(input - inputAddress);
                  }
  
                  // copy literal
                  long literalOutputLimit = output + literalLength;
                  if (literalOutputLimit > fastOutputLimit || input + literalLength > inputLimit - SIZE_OF_LONG) {
                      if (literalOutputLimit > outputLimit || input + literalLength > inputLimit) {
                          throw new MalformedInputException(input - inputAddress);
                      }
  
                      // slow, precise copy
                      UNSAFE.copyMemory(inputBase, input, outputBase, output, literalLength);
                      input += literalLength;
                      output += literalLength;
                  }
                  else {
                      // fast copy. We may over-copy but there's enough room in input and output to not overrun them
                      do {
                          UNSAFE.putLong(outputBase, output, UNSAFE.getLong(inputBase, input));
                          input += SIZE_OF_LONG;
                          output += SIZE_OF_LONG;
                      }
                      while (output < literalOutputLimit);
                      input -= (output - literalOutputLimit); // adjust index if we over-copied
                      output = literalOutputLimit;
                  }
              }
              else {
                  // matchOffset/256 is encoded in bits 8..10.  By just fetching
                  // those bits, we get matchOffset (since the bit-field starts at
                  // bit 8).
                  int matchOffset = entry & 0x700;
                  matchOffset += trailer;
                  if (matchOffset < 0) {
                      throw new MalformedInputException(input - inputAddress);
                  }
  
                  long matchAddress = output - matchOffset;
                  if (matchAddress < outputAddress || output + length > outputLimit) {
                      throw new MalformedInputException(input - inputAddress);
                  }
                  long matchOutputLimit = output + length;
                  if (matchOutputLimit > outputLimit) {
                      throw new MalformedInputException(input - inputAddress);
                  }
  
                  if (output > fastOutputLimit) {
                      // slow match copy
                      while (output < matchOutputLimit) {
                          UNSAFE.putByte(outputBase, output++, UNSAFE.getByte(outputBase, matchAddress++));
                      }
                  }
                  else {
                      // copy repeated sequence
                      if (matchOffset < SIZE_OF_LONG) {
                          // 8 bytes apart so that we can copy long-at-a-time below
                          int increment32 = DEC_32_TABLE[matchOffset];
                          int decrement64 = DEC_64_TABLE[matchOffset];
  
                          UNSAFE.putByte(outputBase, output, UNSAFE.getByte(outputBase, matchAddress));
                          UNSAFE.putByte(outputBase, output + 1, UNSAFE.getByte(outputBase, matchAddress + 1));
                          UNSAFE.putByte(outputBase, output + 2, UNSAFE.getByte(outputBase, matchAddress + 2));
                          UNSAFE.putByte(outputBase, output + 3, UNSAFE.getByte(outputBase, matchAddress + 3));
                          output += SIZE_OF_INT;
                          matchAddress += increment32;
  
                          UNSAFE.putInt(outputBase, output, UNSAFE.getInt(outputBase, matchAddress));
                          output += SIZE_OF_INT;
                          matchAddress -= decrement64;
                      }
                      else {
                          UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
                          matchAddress += SIZE_OF_LONG;
                          output += SIZE_OF_LONG;
                      }
  
                      if (matchOutputLimit > fastOutputLimit) {
                          while (output < fastOutputLimit) {
                              UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
                              matchAddress += SIZE_OF_LONG;
                              output += SIZE_OF_LONG;
                          }
  
                          while (output < matchOutputLimit) {
                              UNSAFE.putByte(outputBase, output++, UNSAFE.getByte(outputBase, matchAddress++));
                          }
                      }
                      else {
                          while (output < matchOutputLimit) {
                              UNSAFE.putLong(outputBase, output, UNSAFE.getLong(outputBase, matchAddress));
                              matchAddress += SIZE_OF_LONG;
                              output += SIZE_OF_LONG;
                          }
                      }
                  }
                  output = matchOutputLimit; // correction in case we over-copied
              }
          }
  
          return (int) (output - outputAddress);
      }
  
      // Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits
      private static final int[] wordmask = new int[] {
              0, 0xff, 0xffff, 0xffffff, 0xffffffff
      };
  
      // Data stored per entry in lookup table:
      //      Range   Bits-used       Description
      //      ------------------------------------
      //      1..64   0..7            Literal/copy length encoded in opcode byte
      //      0..7    8..10           Copy offset encoded in opcode byte / 256
      //      0..4    11..13          Extra bytes after opcode
      //
      // We use eight bits for the length even though 7 would have sufficed
      // because of efficiency reasons:
      //      (1) Extracting a byte is faster than a bit-field
      //      (2) It properly aligns copy offset so we do not need a <<8
      private static final short[] opLookupTable = new short[] {
              0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
              0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
              0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
              0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
              0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
              0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
              0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
              0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
              0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
              0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
              0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
              0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
              0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
              0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
              0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
              0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
              0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
              0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
              0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
              0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
              0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
              0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
              0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
              0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
              0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
              0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
              0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
              0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
              0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
              0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
              0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
              0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
      };
  
      /**
       * Reads the variable length integer encoded a the specified offset, and
       * returns this length with the number of bytes read.
       */
      static int[] readUncompressedLength(Object compressed, long compressedAddress, long compressedLimit)
      {
          int result;
          int bytesRead = 0;
          {
              int b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
              bytesRead++;
              result = b & 0x7f;
              if ((b & 0x80) != 0) {
                  b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
                  bytesRead++;
                  result |= (b & 0x7f) << 7;
                  if ((b & 0x80) != 0) {
                      b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
                      bytesRead++;
                      result |= (b & 0x7f) << 14;
                      if ((b & 0x80) != 0) {
                          b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
                          bytesRead++;
                          result |= (b & 0x7f) << 21;
                          if ((b & 0x80) != 0) {
                              b = getUnsignedByteSafe(compressed, compressedAddress + bytesRead, compressedLimit);
                              bytesRead++;
                              result |= (b & 0x7f) << 28;
                              if ((b & 0x80) != 0) {
                                  throw new MalformedInputException(compressedAddress + bytesRead, "last byte of compressed length int has high bit set");
                              }
                          }
                      }
                  }
              }
          }
          if (result < 0) {
              throw new MalformedInputException(compressedAddress, "invalid compressed length");
          }
          return new int[] {result, bytesRead};
      }
  
      private static int getUnsignedByteSafe(Object base, long address, long limit)
      {
          if (address >= limit) {
              throw new MalformedInputException(limit - address, "Input is truncated");
          }
          return UNSAFE.getByte(base, address) & 0xFF;
      }
  }
  