Issue 5174 - Allow '{' and '}' in selectors

compiled/filter/ElemHideBase.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
@@ skipping 85 matching lines @@
     return Type::UNKNOWN;
 
   // Selector part
 
   // Selector shouldn't be empty
   seenSpaces |= scanner.skip(u' ');
   if (scanner.done())
     return Type::UNKNOWN;
 
   data.mSelectorStart = scanner.position() + 1;
-  while (!scanner.done())
-  {
-    switch (scanner.next())
-    {
-      case u'{':
-      case u'}':
-        return Type::UNKNOWN;
-    }
-  }
 
   // We are done validating, now we can normalize whitespace and the domain part
   if (seenSpaces)
     NormalizeWhitespace(text, data.mDomainsEnd, data.mSelectorStart);
   DependentString(text, 0, data.mDomainsEnd).toLower();
 
   if (exception)
     return Type::ELEMHIDEEXCEPTION;
 
   if (text.find(u"[-abp-properties="_str, data.mSelectorStart) != text.npos)
     return Type::ELEMHIDEEMULATION;
 
   return Type::ELEMHIDE;
 }
 
+namespace {

[Wladimir Palant, 2017/10/18 09:24:02]

Please put the opening curly on the next line and indent the code inside this
block.

[hub, 2017/10/18 12:53:47]

Done.

+
+static constexpr size_t REPLACE_SIZE = 5;

[Wladimir Palant, 2017/10/18 09:24:02]

This name doesn't quite make it clear what this constant is about.
CURLY_REPLACEMENT_SIZE maybe?

Also, it would be nice if we wouldn't hardcode the value. Maybe something like:

static constexpr String::value_type[] OPENING_CURLY_REPLACEMENT = u"\\x7B ";
static constexpr String::value_type[] CLOSING_CURLY_REPLACEMENT = u"\\x7D ";
static constexpt size_t CURLY_REPLACEMENT_SIZE =
sizeof(OPENING_CURLY_REPLACEMENT) / sizeof(OPENING_CURLY_REPLACEMENT[0]) - 1;

[hub, 2017/10/18 12:53:48]

Done.

+
+OwnedString EscapeCurlies(String::size_type count, const DependentString& str)
+{
+  OwnedString result(str.length() + (count * (REPLACE_SIZE - 1)));

[Wladimir Palant, 2017/10/18 09:24:02]

Nit: the parentheses around `count * ...` are unnecessary, multiplication is
evaluated before addition.

[hub, 2017/10/18 12:53:47]

Done.

+
+  String::size_type start = 0;
+  String::size_type i = 0;
+  String::value_type* current = result.data();
+  for (; i < str.length(); i++)
+  {
+    if (str[i] == '}' || str[i] == '{')
+    {
+      if (i != start)
+      {
+        std::memcpy(current, str.data() + start,
+                    sizeof(String::value_type) * (i - start));
+        current += i - start;

[Wladimir Palant, 2017/10/18 09:24:02]

The logic here got unnecessarily complicated. I'd rather go with:

  for (String::size_type i = 0, j = 0; i < str.length(); i++, j++)
  {
    if (str[i] == u'{')
      ...
    else if (str[i] == u'}')
      ...
    else
      result[j] = str[i];
  }

[hub, 2017/10/18 12:53:48]

Done.

+      }
+      start = i + 1;
+      switch(str[i])
+      {
+      case '}':

[Wladimir Palant, 2017/10/18 09:24:02]

Nit: I'd probably say u'}' to indicate that we are dealing with char16_t here.

[hub, 2017/10/18 12:53:47]

Done.

+        std::memcpy(current, u"\\x7D ",
+                    sizeof(String::value_type) * REPLACE_SIZE);

[Wladimir Palant, 2017/10/18 09:24:02]

You need to include <cstring> explicitly to use std::memcpy.

[hub, 2017/10/18 12:53:47]

Done.

+        current += REPLACE_SIZE;
+        break;
+      case '{':
+        std::memcpy(current, u"\\x7B ",
+                    sizeof(String::value_type) * REPLACE_SIZE);
+        current += REPLACE_SIZE;
+        break;
+      default:
+        break;
+      }
+    }
+  }
+  if (start < i)
+    std::memcpy(current, str.data() + start,
+                sizeof(String::value_type) * (i - start));
+  return result;
+}
+
+}
+
+OwnedString ElemHideBase::GetSelector() const
+{
+  DependentString selector = mData.GetSelector(mText);
+  String::size_type count = 0;

[Wladimir Palant, 2017/10/18 09:24:02]

Nit: Somewhat less generic name such as replacementCount maybe?

[hub, 2017/10/18 12:53:47]

Done.

+  for (String::size_type i = 0; i < selector.length(); i++)
+    if (selector[i] == '}' || selector[i] == '{')
+      count++;
+  if (count)
+    return EscapeCurlies(count, selector);
+
+  return OwnedString(selector);
+}
+
 OwnedString ElemHideBase::GetSelectorDomain() const
 {
   /* TODO this is inefficient */
   OwnedString result;
   if (mDomains)
   {
     for (const auto& item : *mDomains)
     {
       if (item.second && !item.first.empty())
       {
         if (!result.empty())
           result.append(u',');
         result.append(item.first);
       }
     }
   }
   return result;
 }