idmap2/libidmap2/XmlParser.cpp

/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * 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.
 */

#include "idmap2/XmlParser.h"

#include <memory>
#include <string>
#include <utility>

namespace android::idmap2 {

template <typename T>
ResXMLParser::ResXMLPosition get_tree_position(const T& tree) {
  ResXMLParser::ResXMLPosition pos{};
  tree.getPosition(&pos);
  return pos;
}

XmlParser::Node::Node(const ResXMLTree& tree) : Node(tree, get_tree_position(tree)) {
}
XmlParser::Node::Node(const ResXMLTree& tree, const ResXMLParser::ResXMLPosition& pos)
    : parser_(tree) {
  set_position(pos);
}

bool XmlParser::Node::operator==(const XmlParser::Node& rhs) const {
  ResXMLParser::ResXMLPosition pos = get_position();
  ResXMLParser::ResXMLPosition rhs_pos = rhs.get_position();
  return pos.curExt == rhs_pos.curExt && pos.curNode == rhs_pos.curNode &&
         pos.eventCode == rhs_pos.eventCode;
}

bool XmlParser::Node::operator!=(const XmlParser::Node& rhs) const {
  return !(*this == rhs);
}

ResXMLParser::ResXMLPosition XmlParser::Node::get_position() const {
  return get_tree_position(parser_);
}

void XmlParser::Node::set_position(const ResXMLParser::ResXMLPosition& pos) {
  parser_.setPosition(pos);
}

bool XmlParser::Node::Seek(bool inner_child) {
  if (parser_.getEventType() == XmlParser::Event::END_TAG) {
    return false;
  }

  ssize_t depth = 0;
  XmlParser::Event code;
  while ((code = parser_.next()) != XmlParser::Event::BAD_DOCUMENT &&
         code != XmlParser::Event::END_DOCUMENT) {
    if (code == XmlParser::Event::START_TAG) {
      if (++depth == (inner_child ? 1 : 0)) {
        return true;
      }
    } else if (code == XmlParser::Event::END_TAG) {
      if (--depth == (inner_child ? -1 : -2)) {
        return false;
      }
    }
  }

  return false;
}

XmlParser::Event XmlParser::Node::event() const {
  return parser_.getEventType();
}

std::string XmlParser::Node::name() const {
  size_t len;
  const String16 key16(parser_.getElementName(&len));
  return String8(key16).c_str();
}

template <typename Func>
Result<Res_value> FindAttribute(const ResXMLParser& parser, const std::string& label,
                                Func&& predicate) {
  for (size_t i = 0; i < parser.getAttributeCount(); i++) {
    if (!predicate(i)) {
      continue;
    }
    Res_value res_value{};
    if (parser.getAttributeValue(i, &res_value) == BAD_TYPE) {
      return Error(R"(Bad value for attribute "%s")", label.c_str());
    }
    return res_value;
  }
  return Error(R"(Failed to find attribute "%s")", label.c_str());
}

Result<std::string> GetStringValue(const ResXMLParser& parser, const Res_value& value,
                                   const std::string& label) {
  switch (value.dataType) {
    case Res_value::TYPE_STRING: {
      if (auto str = parser.getStrings().string8ObjectAt(value.data); str.ok()) {
        return std::string(str->c_str());
      }
      break;
    }
    case Res_value::TYPE_INT_DEC:
    case Res_value::TYPE_INT_HEX:
    case Res_value::TYPE_INT_BOOLEAN: {
      return std::to_string(value.data);
    }
  }
  return Error(R"(Failed to convert attribute "%s" value to a string)", label.c_str());
}

Result<Res_value> XmlParser::Node::GetAttributeValue(ResourceId attr,
                                                     const std::string& label) const {
  return FindAttribute(parser_, label, [&](size_t index) -> bool {
    return parser_.getAttributeNameResID(index) == attr;
  });
}

Result<Res_value> XmlParser::Node::GetAttributeValue(const std::string& name) const {
  String16 name16;
  return FindAttribute(parser_, name, [&](size_t index) -> bool {
    if (name16.empty()) {
        name16 = String16(name.c_str(), name.size());
    }
    size_t key_len;
    const auto key16 = parser_.getAttributeName(index, &key_len);
    return key16 && name16.size() == key_len && name16 == key16;
  });
}

Result<std::string> XmlParser::Node::GetAttributeStringValue(ResourceId attr,
                                                             const std::string& label) const {
  auto value = GetAttributeValue(attr, label);
  return value ? GetStringValue(parser_, *value, label) : value.GetError();
}

Result<std::string> XmlParser::Node::GetAttributeStringValue(const std::string& name) const {
  auto value = GetAttributeValue(name);
  return value ? GetStringValue(parser_, *value, name) : value.GetError();
}

XmlParser::XmlParser(std::unique_ptr<ResXMLTree> tree) : tree_(std::move(tree)) {
}

Result<XmlParser> XmlParser::Create(const void* data, size_t size, bool copy_data) {
  auto tree = std::make_unique<ResXMLTree>();
  if (tree->setTo(data, size, copy_data) != NO_ERROR) {
    return Error("Malformed xml block");
  }

  // Find the beginning of the first tag.
  XmlParser::Event event;
  while ((event = tree->next()) != XmlParser::Event::BAD_DOCUMENT &&
         event != XmlParser::Event::END_DOCUMENT && event != XmlParser::Event::START_TAG) {
  }

  if (event == XmlParser::Event::END_DOCUMENT) {
    return Error("Root tag was not be found");
  }

  if (event == XmlParser::Event::BAD_DOCUMENT) {
    return Error("Bad xml document");
  }

  return XmlParser{std::move(tree)};
}

}  // namespace android::idmap2