A thread-safe Media Query Parser

Source/core/css/parser/MediaQueryInputStream.cpp

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/css/parser/MediaQueryInputStream.h"
+
+#include "core/html/parser/InputStreamPreprocessor.h"
+
+namespace WebCore {
+
+MediaQueryInputStream::MediaQueryInputStream(String input)
+    : m_offset(0)
+    , m_string(input)
+{
+}
+
+UChar MediaQueryInputStream::peek(unsigned lookaheadOffset)
+{
+    ASSERT((m_offset + lookaheadOffset) <= maxLength());
+    if ((m_offset + lookaheadOffset) >= m_string.length())
+        return kEndOfFileMarker;
+    return m_string[m_offset + lookaheadOffset];
+}
+
+void MediaQueryInputStream::advance(unsigned offset)
+{
+    ASSERT(m_offset + offset <= maxLength());
+    m_offset += offset;
+}
+
+void MediaQueryInputStream::pushBack(UChar cc)
+{
+    --m_offset;
+    ASSERT(currentInputChar() == cc);
+}
+
+unsigned long long MediaQueryInputStream::getUInt(unsigned start, unsigned end)
+{
+    ASSERT(start <= end && ((m_offset + end) <= m_string.length()));
+    bool isResultOK = false;
+    if (start < end) {
+        unsigned long long result;
+        if (m_string.is8Bit())
+            result = charactersToUInt64Strict(m_string.characters8() + m_offset + start, end - start, &isResultOK);
+        else
+            result = charactersToUInt64Strict(m_string.characters16() + m_offset + start, end - start, &isResultOK);
+        if (isResultOK)

[eseidel, 2014/03/13 17:22:07]

nit: I might have written this as a ternary at the end.
return isResultOK ? result : 0;

+            return result;
+    }
+    return 0;
+}
+
+double MediaQueryInputStream::getDouble(unsigned start, unsigned end)
+{
+    ASSERT(start <= end && ((m_offset + end) <= m_string.length()));
+    bool isResultOK = false;
+    if (start < end) {
+        double result;
+        if (m_string.is8Bit())
+            result = charactersToDouble(m_string.characters8() + m_offset + start, end - start, &isResultOK);

[eseidel, 2014/03/13 17:22:07]

Sigh.  If we had a StringView class then the caller would just do this:
inputStream.stringView(start, end).toDouble(isOK);
One of these years we'll add something like that.

+        else
+            result = charactersToDouble(m_string.characters16() + m_offset + start, end - start, &isResultOK);
+        if (isResultOK)
+            return result;
+    }
+    return 0.0;
+}
+
+} // namespace WebCore