text: /*
   * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "DIE.h"
  #include "CompilationUnit.h"
  #include "DwarfInfo.h"
  #include <AK/ByteBuffer.h>
  #include <AK/Stream.h>
  
  namespace Debug::Dwarf {
  
  DIE::DIE(const CompilationUnit& unit, u32 offset)
      : m_compilation_unit(unit)
      , m_offset(offset)
  {
      InputMemoryStream stream(m_compilation_unit.dwarf_info().debug_info_data());
      stream.discard_or_error(m_offset);
      stream.read_LEB128_unsigned(m_abbreviation_code);
      m_data_offset = stream.offset();
  
      if (m_abbreviation_code == 0) {
          // An abbrevation code of 0 ( = null DIE entry) means the end of a chain of sibilings
          m_tag = EntryTag::None;
      } else {
          auto abbreviation_info = m_compilation_unit.abbreviations_map().get(m_abbreviation_code);
          ASSERT(abbreviation_info.has_value());
  
          m_tag = abbreviation_info.value().tag;
          m_has_children = abbreviation_info.value().has_children;
  
          // We iterate the attributes data only to calculate this DIE's size
          for (auto attribute_spec : abbreviation_info.value().attribute_specifications) {
              get_attribute_value(attribute_spec.form, stream);
          }
      }
      m_size = stream.offset() - m_offset;
  }
  
  DIE::AttributeValue DIE::get_attribute_value(AttributeDataForm form,
      InputMemoryStream& debug_info_stream) const
  {
      AttributeValue value;
  
      auto assign_raw_bytes_value = [&](size_t length) {
          value.data.as_raw_bytes.length = length;
          value.data.as_raw_bytes.bytes = reinterpret_cast<const u8*>(m_compilation_unit.dwarf_info().debug_info_data().data()
              + debug_info_stream.offset());
  
          debug_info_stream.discard_or_error(length);
      };
  
      switch (form) {
      case AttributeDataForm::StringPointer: {
          u32 offset;
          debug_info_stream >> offset;
          value.type = AttributeValue::Type::String;
  
          auto strings_data = m_compilation_unit.dwarf_info().debug_strings_data();
          value.data.as_string = reinterpret_cast<const char*>(strings_data.data() + offset);
          break;
      }
      case AttributeDataForm::Data1: {
          u8 data;
          debug_info_stream >> data;
          value.type = AttributeValue::Type::UnsignedNumber;
          value.data.as_u32 = data;
          break;
      }
      case AttributeDataForm::Data2: {
          u16 data;
          debug_info_stream >> data;
          value.type = AttributeValue::Type::UnsignedNumber;
          value.data.as_u32 = data;
          break;
      }
      case AttributeDataForm::Addr: {
          u32 address;
          debug_info_stream >> address;
          value.type = AttributeValue::Type::UnsignedNumber;
          value.data.as_u32 = address;
          break;
      }
      case AttributeDataForm::SecOffset: {
          u32 data;
          debug_info_stream >> data;
          value.type = AttributeValue::Type::SecOffset;
          value.data.as_u32 = data;
          break;
      }
      case AttributeDataForm::Data4: {
          u32 data;
          debug_info_stream >> data;
          value.type = AttributeValue::Type::UnsignedNumber;
          value.data.as_u32 = data;
          break;
      }
      case AttributeDataForm::Ref4: {
          u32 data;
          debug_info_stream >> data;
          value.type = AttributeValue::Type::DieReference;
          value.data.as_u32 = data + m_compilation_unit.offset();
          break;
      }
      case AttributeDataForm::FlagPresent: {
          value.type = AttributeValue::Type::Boolean;
          value.data.as_bool = true;
          break;
      }
      case AttributeDataForm::ExprLoc: {
          size_t length;
          debug_info_stream.read_LEB128_unsigned(length);
          value.type = AttributeValue::Type::DwarfExpression;
          assign_raw_bytes_value(length);
          break;
      }
      case AttributeDataForm::String: {
          String str;
          u32 str_offset = debug_info_stream.offset();
          debug_info_stream >> str;
          value.type = AttributeValue::Type::String;
          value.data.as_string = reinterpret_cast<const char*>(str_offset + m_compilation_unit.dwarf_info().debug_info_data().data());
          break;
      }
      case AttributeDataForm::Block1: {
          value.type = AttributeValue::Type::RawBytes;
          u8 length;
          debug_info_stream >> length;
          assign_raw_bytes_value(length);
          break;
      }
      case AttributeDataForm::Block2: {
          value.type = AttributeValue::Type::RawBytes;
          u16 length;
          debug_info_stream >> length;
          assign_raw_bytes_value(length);
          break;
      }
      case AttributeDataForm::Block4: {
          value.type = AttributeValue::Type::RawBytes;
          u32 length;
          debug_info_stream >> length;
          assign_raw_bytes_value(length);
          break;
      }
      case AttributeDataForm::Block: {
          value.type = AttributeValue::Type::RawBytes;
          size_t length;
          debug_info_stream.read_LEB128_unsigned(length);
          assign_raw_bytes_value(length);
          break;
      }
      default:
          dbg() << "Unimplemented AttributeDataForm: " << (u32)form;
          ASSERT_NOT_REACHED();
      }
      return value;
  }
  
  Optional<DIE::AttributeValue> DIE::get_attribute(const Attribute& attribute) const
  {
      InputMemoryStream stream { m_compilation_unit.dwarf_info().debug_info_data() };
      stream.discard_or_error(m_data_offset);
  
      auto abbreviation_info = m_compilation_unit.abbreviations_map().get(m_abbreviation_code);
      ASSERT(abbreviation_info.has_value());
  
      for (const auto& attribute_spec : abbreviation_info.value().attribute_specifications) {
          auto value = get_attribute_value(attribute_spec.form, stream);
          if (attribute_spec.attribute == attribute) {
              return value;
          }
      }
      return {};
  }
  
  void DIE::for_each_child(Function<void(const DIE& child)> callback) const
  {
      if (!m_has_children)
          return;
  
      NonnullOwnPtr<DIE> current_child = make<DIE>(m_compilation_unit, m_offset + m_size);
      while (true) {
          callback(*current_child);
          if (current_child->is_null())
              break;
          if (!current_child->has_children()) {
              current_child = make<DIE>(m_compilation_unit, current_child->offset() + current_child->size());
              continue;
          }
  
          auto sibling = current_child->get_attribute(Attribute::Sibling);
          u32 sibling_offset = 0;
          if (sibling.has_value()) {
              sibling_offset = sibling.value().data.as_u32;
          }
  
          if (!sibling.has_value()) {
              // NOTE: According to the spec, the compiler does't have to supply the sibling information.
              // When it doesn't, we have to recursively iterate the current child's children to find where they end
              current_child->for_each_child([&](const DIE& sub_child) {
                  sibling_offset = sub_child.offset() + sub_child.size();
              });
          }
          current_child = make<DIE>(m_compilation_unit, sibling_offset);
      }
  }
  
  DIE DIE::get_die_at_offset(u32 offset) const
  {
      ASSERT(offset >= m_compilation_unit.offset() && offset < m_compilation_unit.offset() + m_compilation_unit.size());
      return DIE(m_compilation_unit, offset);
  }
  
  }
  