Issue 4125 - [emscripten] Convert filter classes to C++

compiled/String.h

-#ifndef ADBLOCK_PLUS_STRING_H
-#define ADBLOCK_PLUS_STRING_H
+#pragma once
 
 #include <cstddef>
 #include <cstring>
 #include <algorithm>
 
+#include <emscripten.h>
+
 #include "debug.h"
 
+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;
 
   // Type flags, stored in the top 2 bits of the mLen member
-  static constexpr size_type OWNBUFFER = 0xC0000000;
-  static constexpr size_type INVALID = 0x80000000;
-  static constexpr size_type DELETED = 0x40000000;
-  static constexpr size_type DEPENDENT = 0x00000000;
+  static constexpr size_type INVALID = 0xC0000000;
+  static constexpr size_type DELETED = 0x80000000;
+  static constexpr size_type READ_ONLY = 0x40000000;
+  static constexpr size_type READ_WRITE = 0x00000000;
+
   static constexpr size_type FLAGS_MASK = 0xC0000000;
   static constexpr size_type LENGTH_MASK = 0x3FFFFFFF;
 
   static constexpr size_type npos = -1;
 
-private:
+protected:
   value_type* mBuf;
   size_type mLen;
 
-  value_type* allocate(size_type len)
-  {
-    if (len)
-      return new value_type[len];
-    else
-      return nullptr;
-  }
-
-  void resize(size_type newLength, bool copy)
-  {
-    bool owningOldBuffer = owns_buffer();
-    size_type oldLength = length();
-    value_type* oldBuffer = mBuf;
-
-    newLength &= LENGTH_MASK;
-    mBuf = allocate(newLength);
-    annotate_address(mBuf, "String");
-    mLen = OWNBUFFER | newLength;
-
-    if (copy && oldLength)
-      memcpy(mBuf, oldBuffer, sizeof(value_type) * std::min(oldLength, newLength));
-    if (owningOldBuffer)
-      delete[] oldBuffer;
+  explicit String(value_type* buf, size_type len, size_type flags)
+      : mBuf(buf), mLen((len & LENGTH_MASK) | flags)
+  {
+  }
+
+  ~String()
+  {
+  }
+
+  void reset(value_type* buf, size_type len, size_type flags)
+  {
+    mBuf = buf;
+    mLen = (len & LENGTH_MASK) | flags;
   }
 
 public:
-  String() : mBuf(nullptr), mLen(INVALID) {}
-
-  String(size_type len)
-      : mBuf(allocate(len & LENGTH_MASK)), mLen(OWNBUFFER | (len & LENGTH_MASK))
-  {
-    annotate_address(mBuf, "String");
-  }
-
-  String(value_type* buf, size_type len)
-      : mBuf(buf), mLen(DEPENDENT | (buf ? len & LENGTH_MASK: 0))
-  {
-  }
-
-  String(const String& str, size_type pos = 0, size_type len = npos)
-      : mBuf(str.mBuf + std::min(pos, str.length())),
-        mLen(DEPENDENT | std::min(len, str.length() - (mBuf - str.mBuf)))
-  {
-  }
-
-  String(String&& str)
-  {
-    *this = std::move(str);
-  }
-
-  String(const char* source, size_type len)
-      : String(len)
-  {
-    for (size_type i = 0; i < len; i++)
-      mBuf[i] = source[i];
-  }
-
-  void operator=(const String& str)
-  {
-    mBuf = str.mBuf;
-    mLen = DEPENDENT | str.length();
-  }
-
-  void operator=(String& str)
-  {
-    reset(str);
-  }
-
-  String& operator=(String&& str)
-  {
-    mBuf = str.mBuf;
-    mLen = str.mLen;
-    str.mBuf = nullptr;
-    str.mLen = INVALID;
-    ensure_own_buffer();
-    return *this;
-  }
-
-  ~String()
-  {
-    if (owns_buffer())
-      delete[] mBuf;
-  }
-
-  void reset(value_type* buf, size_type len)
-  {
-    mBuf = buf;
-    mLen = (DEPENDENT | (buf ? len & LENGTH_MASK: 0));
-  }
-
-  void reset(const String& str, size_type pos = 0, size_type len = npos)
-  {
-    pos = std::min(pos, str.length());
-    len = std::min(len, str.length() - pos);
-    reset(str.mBuf + pos, len);
-  }
-
   size_type length() const
   {
     return mLen & LENGTH_MASK;
   }
 
   bool empty() const
   {
     return !(mLen & LENGTH_MASK);
   }
 
   const value_type* data() const
   {
     return mBuf;
   }
 
   value_type* data()
   {
+    String_assert_readonly(is_readOnly());
     return mBuf;
   }
 
   const value_type& operator[](size_type pos) const
   {
     return mBuf[pos];
   }
 
   value_type& operator[](size_type pos)
   {
+    String_assert_readonly(is_readOnly());
     return mBuf[pos];
   }
 
+  bool is_readOnly() const
+  {
+    return (mLen & FLAGS_MASK) != READ_WRITE;
+  }
+
   bool equals(const String& other) const
   {
-    if (mLen != other.mLen)
+    if (length() != other.length())
       return false;
 
-    return memcmp(mBuf, other.mBuf, sizeof(value_type) * length()) == 0;
+    return std::memcmp(mBuf, other.mBuf, sizeof(value_type) * length()) == 0;
   }
 
   size_type find(value_type c, size_type pos = 0) const
   {
     for (size_type i = pos; i < length(); ++i)
       if (mBuf[i] == c)
         return i;
     return npos;
   }
 
   size_type find(const String& str, size_type pos = 0) const
   {
+    if (pos > LENGTH_MASK || pos + str.length() > length())
+      return npos;
+
     if (!str.length())
       return pos;
 
-    if (length() - pos < str.length())
-      return npos;
-
-    for (; pos < length() - str.length(); ++pos)
+    for (; pos + str.length() <= length(); ++pos)
     {
       if (mBuf[pos] == str[0] &&
-          memcmp(mBuf + pos, str.mBuf, sizeof(value_type) * str.length()) == 0)
+          std::memcmp(mBuf + pos, str.mBuf, sizeof(value_type) * str.length()) == 0)
       {
         return pos;
       }
     }
 
     return npos;
   }
 
   size_type rfind(value_type c, size_type pos = npos) const
   {
     if (length() == 0)
       return npos;
 
-    if (pos == npos)
+    if (pos >= length())
       pos = length() - 1;
 
     for (int i = pos; i >= 0; --i)
       if (mBuf[i] == c)
         return i;
     return npos;
   }
 
+  bool is_invalid() const
+  {
+    return (mLen & FLAGS_MASK) == INVALID;
+  }
+
+  bool is_deleted() const
+  {
+    return (mLen & FLAGS_MASK) == DELETED;
+  }
+
+  void toLower()
+  {
+    size_type len = length();
+    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);
+      }
+    }
+  }
+};
+
+class DependentString : public String
+{
+public:
+  explicit DependentString()
+      : String(nullptr, 0, INVALID)
+  {
+  }
+
+  explicit DependentString(value_type* buf, size_type len)
+      : String(buf, len, READ_WRITE)
+  {
+  }
+
+  explicit DependentString(const value_type* buf, size_type len)
+      : String(const_cast<value_type*>(buf), len, READ_ONLY)
+  {
+  }
+
+  explicit DependentString(String& str, size_type pos = 0, size_type len = npos)
+      : String(
+          str.mBuf + std::min(pos, str.length()),
+          std::min(len, str.length() - std::min(pos, str.length())),
+          str.is_readOnly() ? READ_ONLY : READ_WRITE
+        )
+  {
+  }
+
+  explicit DependentString(const String& str, size_type pos = 0,
+      size_type len = npos)
+      : String(
+          str.mBuf + std::min(pos, str.length()),
+          std::min(len, str.length() - std::min(pos, str.length())),
+          READ_ONLY
+        )
+  {
+  }
+
+  void reset(value_type* buf, size_type len)
+  {
+    *this = DependentString(buf, len);
+  }
+
+  void reset(const value_type* buf, size_type len)
+  {
+    *this = DependentString(buf, len);
+  }
+
+  void reset(String& str, size_type pos = 0, size_type len = npos)
+  {
+    *this = DependentString(str, pos, len);
+  }
+
+  void reset(const String& str, size_type pos = 0, size_type len = npos)
+  {
+    *this = DependentString(str, pos, len);
+  }
+
+  void erase()
+  {
+    *this = DependentString();
+    mLen = DELETED;
+  }
+};
+
+inline DependentString operator "" _str(const String::value_type* str,
+    String::size_type len)
+{
+  return DependentString(str, len);
+}
+
+inline void String_assert_readonly(bool readOnly)
+{
+  assert(!readOnly, u"Writing access to a read-only string"_str);
+}
+
+class OwnedString : public String
+{
+private:
+  void grow(size_type additionalSize)
+  {
+    OwnedString newValue(length() + additionalSize);
+    if (length() > 0)
+      std::memcpy(newValue.mBuf, mBuf, sizeof(value_type) * length());
+    *this = std::move(newValue);
+  }
+
+public:
+  explicit OwnedString(size_type len = 0)
+      : String(nullptr, len, READ_WRITE)
+  {
+    if (len)
+    {
+      mBuf = new value_type[length()];
+      annotate_address(mBuf, "String");
+    }
+    else
+      mBuf = nullptr;
+  }
+
+  explicit OwnedString(const String& str)
+      : OwnedString(str.length())
+  {
+    if (length())
+      std::memcpy(mBuf, str.mBuf, sizeof(value_type) * length());
+  }
+
+  OwnedString(const OwnedString& str)
+      : OwnedString(static_cast<const String&>(str))
+  {
+  }
+
+  explicit OwnedString(const value_type* str, size_type len)
+      : OwnedString(DependentString(str, len))
+  {
+  }
+
+  explicit OwnedString(OwnedString&& str)
+      : OwnedString(0)
+  {
+    mBuf = str.mBuf;
+    mLen = str.mLen;
+    str.mBuf = nullptr;
+    str.mLen = READ_WRITE | 0;
+  }
+
+  ~OwnedString()
+  {
+    if (mBuf)
+      delete[] mBuf;
+  }
+
+  OwnedString& operator=(const String& str)
+  {
+    *this = std::move(OwnedString(str));
+    return *this;
+  }
+
+  OwnedString& operator=(const OwnedString& str)
+  {
+    *this = std::move(OwnedString(str));
+    return *this;
+  }
+
+  OwnedString& operator=(OwnedString&& str)
+  {
+    std::swap(mBuf, str.mBuf);
+    std::swap(mLen, str.mLen);
+    return *this;
+  }
+
   void append(const value_type* source, size_type sourceLen)
   {
     if (!sourceLen)
       return;
 
+    assert(source, u"Null buffer passed to OwnedString.append()"_str);
     size_t oldLength = length();
-    resize(oldLength + sourceLen, true);
-    memcpy(mBuf + oldLength, source, sizeof(value_type) * sourceLen);
+    grow(sourceLen);
+    std::memcpy(mBuf + oldLength, source, sizeof(value_type) * sourceLen);
   }
 
   void append(const String& str)
   {
     append(str.mBuf, str.length());
   }
 
   void append(value_type c)
   {
     append(&c, 1);
   }
-
-  bool owns_buffer() const
-  {
-    return mBuf && (mLen & FLAGS_MASK) == OWNBUFFER;
-  }
-
-  void ensure_own_buffer()
-  {
-    size_type len = length();
-    if (len && !owns_buffer())
-      resize(len, true);
-  }
-
-  bool is_dependent() const
-  {
-    return (mLen & FLAGS_MASK) == DEPENDENT;
-  }
-
-  bool is_invalid() const
-  {
-    return (mLen & FLAGS_MASK) == INVALID;
-  }
-
-  bool is_deleted() const
-  {
-    return (mLen & FLAGS_MASK) == DELETED;
-  }
 };
-
-inline String operator "" _str(const String::value_type* str,
-    String::size_type len)
-{
-  return String(const_cast<String::value_type*>(str), len);
-}
-#endif