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::currentInputChar()
+{
+    if (m_offset >= m_string.length())

[eseidel, 2014/03/11 20:14:19]

Same here.  Looks like thsi could be implemented in terms of peek?

+        return kEndOfFileMarker;
+    return m_string[m_offset];
+}
+
+UChar MediaQueryInputStream::peek(unsigned lookaheadOffset)
+{
+    if ((m_offset + lookaheadOffset) >= m_string.length())

[eseidel, 2014/03/11 20:14:19]

This is a bit odd.  EOF should only be length + 1, anything else should ASSERT,
IMO.

+        return kEndOfFileMarker;
+    return m_string[m_offset + lookaheadOffset];
+}
+
+void MediaQueryInputStream::advance(unsigned offset)
+{
+    ASSERT(m_offset + offset <= m_string.length() + 1);

[eseidel, 2014/03/11 20:14:19]

Maybe we need a lengthIncludingEOF() helper, or just a length() helper which
returns m_string.length() + 1?

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