Issue 4128, 5138 - Add Parser and Serializer implemented in C++

compiled/storage/Parser.cpp

+/*
+* This file is part of Adblock Plus <https://adblockplus.org/>,
+* Copyright (C) 2006-present eyeo GmbH
+*
+* Adblock Plus is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 3 as
+* published by the Free Software Foundation.
+*
+* Adblock Plus is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with Adblock Plus. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "Parser.h"
+#include "../subscription/DownloadableSubscription.h"
+#include "../subscription/UserDefinedSubscription.h"
+#include "../filter/Filter.h"
+
+namespace
+{
+  bool IsSection(const String& value, const String& expectedSectionName)
+  {
+    auto valueLength = value.length();
+    // fast check whether it's a section and if its length is expected
+    if (!(valueLength == expectedSectionName.length() + 2 && value[0] == u'[' && value[valueLength - 1] == u']'))
+      return false;
+    OwnedString sectionName(DependentString(value, 1, valueLength - 2));
+    sectionName.toLower();
+    return sectionName == expectedSectionName;
+  }
+
+  bool IsSubscriptionSection(const String& value)
+  {
+    return IsSection(value, u"subscription"_str);
+  }
+
+  bool IsSubscriptionFiltersSection(const String& value)
+  {
+    return ::IsSection(value, u"subscription filters"_str);

[Wladimir Palant, 2017/12/21 10:30:37]

Does :: make sense here? You don't use it above.

+  }
+
+  Subscription::KeyValue CreateKeyValue(const std::pair<DependentString, DependentString>& pair)
+  {
+    Subscription::KeyValue retValue;
+    retValue.first = TrimSpaces(pair.first);
+    retValue.second = TrimSpaces(pair.second);
+    return retValue;
+  }
+
+  void DecodeOpeningBracket(DependentString& value)
+  {
+    String::size_type skippedChars = 0;
+    for (String::size_type i = 1; i < value.length(); ++i)
+    {
+      if (value[i - 1] == u'\\' && value[i] == u'[')
+        ++skippedChars;
+      value[i - skippedChars] = value[i];
+    }
+    if (skippedChars > 0)
+      value.reset(value, 0, value.length() - skippedChars);
+  }
+}
+
+Parser::Parser()
+  : mCurrentState{State::Initial}
+{
+}
+
+void Parser::Process(const String& untrimmedLine)
+{
+  auto line = TrimSpaces(untrimmedLine);
+  // skip empty lines
+  if (line.length() == 0)
+    return;
+
+  if (IsSubscriptionSection(line))
+  {
+    Finalize();
+    mCurrentState = State::SubscriptionSection;
+    return;
+  }
+
+  switch (mCurrentState)
+  {
+  case State::Initial:
+    Initial_processLine(line);
+    break;
+  case State::SubscriptionSection:
+    SubscriptionSection_processLine(line);
+    break;
+  case State::SubscriptionFiltersSection:
+    SubscriptionFiltersSection_processLine(line);
+    break;
+  default:
+    ;
+  }
+}
+
+void Parser::Finalize()
+{
+  switch (mCurrentState)
+  {
+  case State::Initial:
+    // don't clear file properties because they are also the parser member
+    break;
+  case State::SubscriptionSection:
+    onSubscription(createSubscriptionFromProperties());
+    mSubscriptionProperties.clear();
+    break;
+  case State::SubscriptionFiltersSection:
+    onSubscription(std::move(mSubscription));
+    break;
+  default:
+    ;
+  }
+}
+
+Parser::Subscriptions::size_type Parser::GetSubscriptionCount() const
+{
+  return mSubscriptions.size();
+}
+
+Subscription* Parser::SubscriptionAt(Subscriptions::size_type index)
+{
+  if (index >= mSubscriptions.size())
+    return nullptr;
+  return SubscriptionPtr(mSubscriptions[index]).release();
+}
+
+SubscriptionPtr Parser::createSubscriptionFromProperties() const
+{
+  return Subscription::FromProperties(mSubscriptionProperties);
+}
+
+void Parser::Initial_processLine(const String& line)
+{
+  // skip # Adblock Plus preferences
+  if (line[0] == u'#')
+    return;
+
+  String::size_type assignSignPos = line.find(u'=');
+  if (assignSignPos != String::npos)
+  {
+    mFileProperties.emplace_back(CreateKeyValue(SplitString(line, assignSignPos)));
+    return;
+  }
+  onFail("Unexpected line value, it should be either a file property or the [Subscription] section");
+}
+
+void Parser::SubscriptionSection_processLine(const String& line)
+{
+  String::size_type assignSignPos = line.find(u'=');
+  if (assignSignPos != String::npos)
+  {
+    mSubscriptionProperties.emplace_back(CreateKeyValue(SplitString(line, assignSignPos)));
+    return;
+  }
+  if (IsSubscriptionFiltersSection(line))
+  {
+    mSubscription = createSubscriptionFromProperties();
+    mCurrentState = State::SubscriptionFiltersSection;
+    return;
+  }
+  onFail("Unexpected line value, it should be either a subscription property, the [Subscription filters] section or the [Subscription] section");
+}
+
+void Parser::SubscriptionFiltersSection_processLine(const String& line)
+{
+  OwnedString lineCopy{line};

[Wladimir Palant, 2017/12/21 10:30:37]

I assume that you create a copy so that DecodeOpeningBracket doesn't mess with
the input buffer? We should rather require a non-const input buffer that we can
mess with, this will prevent the temporary allocation here. For me, this would
produce 200k temporary allocations, that isn't cheap and will increase memory
fragmentation massively (note that the temporary buffer is only released after
memory for the filter and its copy of the text has been allocated).

+  DependentString lineForFilter{lineCopy};
+  DecodeOpeningBracket(lineForFilter);

[Wladimir Palant, 2017/12/21 10:30:37]

Copying all data around unconditionally seems wasteful, it isn't the fastest
operation and in 99.9% of the cases it should be unnecessary. Maybe call this
conditionally: `if (lineForFilter.find(u'\\') != String::npos)`

+  mSubscription->AddFilter(*FilterPtr(Filter::FromText(lineForFilter)));
+  // any line is considered as a filter, there can be no error
+}
+
+void Parser::onSubscription(SubscriptionPtr subscription)
+{
+  mSubscriptions.emplace_back(std::move(subscription));
+}