text: /**
   * 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.
   **/
  
  #include "compression/CompressionDictionaryLite.hpp"
  
  #include <cstddef>
  #include <cstdint>
  
  #include "types/Type.hpp"
  
  #include "glog/logging.h"
  
  using std::size_t;
  using std::uint32_t;
  
  namespace quickstep {
  
  CompressionDictionaryLite::CompressionDictionaryLite(
      const Type &type,
      const void *dictionary_memory,
      const std::size_t dictionary_memory_size)
      : type_(type),
        type_is_variable_length_(type_.isVariableLength()),
        dictionary_memory_(dictionary_memory),
        dictionary_memory_size_(dictionary_memory_size),
        number_of_codes_including_null_(*static_cast<const uint32_t*>(dictionary_memory_)),
        type_fixed_byte_length_(type_.maximumByteLength()) {
    uint32_t non_null_codes = number_of_codes_including_null_;
    if (*(static_cast<const uint32_t*>(dictionary_memory_) + 1)
        == number_of_codes_including_null_) {
      ++number_of_codes_including_null_;
    }
  
    for (code_length_bits_ = 32; code_length_bits_ > 0; --code_length_bits_) {
      if ((number_of_codes_including_null_ - 1) >> (code_length_bits_ - 1)) {
        break;
      }
    }
  
    if (type_is_variable_length_) {
      if (dictionary_memory_size_ <
          2 * sizeof(uint32_t) + non_null_codes * (sizeof(uint32_t) + type_.minimumByteLength())) {
        LOG(FATAL) << "Attempted to create a CompressionDictionary with "
                   << dictionary_memory_size_ << " bytes of memory, which is insufficient for "
                   << non_null_codes << " entries of type " << type_.getName() << ".";
      }
  
      variable_length_data_region_ = static_cast<const char*>(dictionary_memory_)
                                     + (non_null_codes + 2) * sizeof(uint32_t);
  
      DCHECK(paranoidOffsetsCheck());
    } else {
      if (non_null_codes * type_fixed_byte_length_ + 2 * sizeof(uint32_t)
          < dictionary_memory_size_) {
        LOG(FATAL) << "Attempted to create a CompressionDictionary with "
                   << dictionary_memory_size_ << " bytes of memory, which is insufficient for "
                   << non_null_codes << " entries of type " << type_.getName() << ".";
      }
    }
  
    // NOTE(chasseur): If dictionary_memory_size_ is larger than the required
    // amount of memory, it's not strictly an error, but there will be wasted
    // space.
  }
  
  CompressionDictionaryLite::~CompressionDictionaryLite() {
  }
  
  bool CompressionDictionaryLite::paranoidOffsetsCheck() const {
    uint32_t num_codes = *static_cast<const uint32_t*>(dictionary_memory_);
    size_t variable_length_offset = (num_codes + 2) * sizeof(uint32_t);
    const uint32_t *offsets_array = static_cast<const uint32_t*>(dictionary_memory_) + 2;
  
    size_t last_offset = variable_length_offset - 1;
    for (uint32_t code = 0; code < num_codes; ++code) {
      size_t value_offset = variable_length_offset + offsets_array[code];
      if ((value_offset >= dictionary_memory_size_)
          || (value_offset <= last_offset)) {
        return false;
      }
      last_offset = value_offset;
    }
  
    return true;
  }
  
  }  // namespace quickstep
  