Issue 5201 - [emscripten] Replace EM_ASM calls by a custom JavaScript library

compiled/String.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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/>.
  */
 
 #pragma once
 
 #include <algorithm>
 #include <cstddef>
 #include <cstring>
 #include <type_traits>
 
 #include <emscripten.h>
 
 #include "debug.h"
 
+extern "C"
+{
+  // It seems that calling JS is the easiest solution for lowercasing Unicode
+  // characters.
+  char16_t CharToLower(char16_t charCode);
+}
+
 inline void String_assert_readonly(bool readOnly);
 
 class String
 {
   friend class DependentString;
   friend class OwnedString;
 
 public:
   typedef char16_t value_type;
   typedef size_t size_type;
@@ skipping 142 matching lines @@
     for (size_type i = 0; i < len; ++i)
     {
       value_type currChar = mBuf[i];
 
       // This should be more efficient with a lookup table but I couldn't measure
       // any performance difference.
       if (currChar >= u'A' && currChar <= u'Z')
         mBuf[i] = currChar + u'a' - u'A';
       else if (currChar >= 128)
       {
-        // It seems that calling JS is the easiest solution for lowercasing
-        // Unicode characters.
-        mBuf[i] = EM_ASM_INT({
-          return String.fromCharCode($0).toLowerCase().charCodeAt(0);
-        }, currChar);
+        mBuf[i] = CharToLower(currChar);
       }
     }
   }
 };
 
 class DependentString : public String
 {
 public:
   explicit DependentString()
       : String(nullptr, 0, INVALID)
@@ skipping 197 matching lines @@
     if (negative)
       mBuf[pos++] = '-';
 
     for (int i = size - 1; i >= 0; i--)
     {
       mBuf[pos + i] = '0' + (num % 10);
       num /= 10;
     }
   }
 };