Compare :lang value case-insensitive in ASCII range

Source/wtf/text/StringImpl.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 486 matching lines @@
 inline bool equalIgnoringCase(const char* a, const LChar* b, unsigned length) { return equalIgnoringCase(b, reinterpret_cast<const LChar*>(a), length); }
 inline bool equalIgnoringCase(const UChar* a, const UChar* b, int length)
 {
     ASSERT(length >= 0);
     return !Unicode::umemcasecmp(a, b, length);
 }
 WTF_EXPORT bool equalIgnoringCaseNonNull(const StringImpl*, const StringImpl*);
 
 WTF_EXPORT bool equalIgnoringNullity(StringImpl*, StringImpl*);
 
+template<typename CharacterTypeA, typename CharacterTypeB>
+inline bool equalIgnoringASCIICase(const CharacterTypeA* a, const CharacterTypeB* b, unsigned length)
+{
+    for (unsigned i = 0; i < length; ++i) {
+        if (toASCIILower(a[i]) != toASCIILower(b[i]))
+            return false;
+    }
+    return true;
+}
+
+template<typename CharacterTypeA, typename CharacterTypeB>
+bool startsWithIgnoringASCIICase(const CharacterTypeA& reference, const CharacterTypeB& prefix)
+{
+    unsigned prefixLength = prefix.length();
+    if (prefixLength > reference.length())
+        return false;
+
+    if (reference.is8Bit()) {
+        if (prefix.is8Bit())
+            return equalIgnoringASCIICase(reference.characters8(), prefix.characters8(), prefixLength);
+        return equalIgnoringASCIICase(reference.characters8(), prefix.characters16(), prefixLength);
+    }
+    if (prefix.is8Bit())
+        return equalIgnoringASCIICase(reference.characters16(), prefix.characters8(), prefixLength);
+    return equalIgnoringASCIICase(reference.characters16(), prefix.characters16(), prefixLength);
+}
+
 template<typename CharacterType>
 inline size_t find(const CharacterType* characters, unsigned length, CharacterType matchCharacter, unsigned index = 0)
 {
     while (index < length) {
         if (characters[index] == matchCharacter)
             return index;
         ++index;
     }
     return kNotFound;
 }
@@ skipping 226 matching lines @@
 }
 
 using WTF::StringImpl;
 using WTF::equal;
 using WTF::equalNonNull;
 using WTF::TextCaseSensitivity;
 using WTF::TextCaseSensitive;
 using WTF::TextCaseInsensitive;
 
 #endif