1 files changed, 101 insertions, 0 deletions
diff --git a/Source/JavaScriptCore/wasm/WasmPageCount.h b/Source/JavaScriptCore/wasm/WasmPageCount.h
new file mode 100644
index 000000000..e43847c01
--- /dev/null
+++ b/Source/JavaScriptCore/wasm/WasmPageCount.h
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2016 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#if ENABLE(WEBASSEMBLY)
+
+#include <limits.h>
+
+namespace WTF {
+class PrintStream;
+}
+
+namespace JSC { namespace Wasm {
+
+class PageCount {
+
+public:
+    PageCount()
+        : m_pageCount(UINT_MAX)
+    {
+        static_assert(maxPageCount < UINT_MAX, "We rely on this here.");
+    }
+
+    PageCount(uint32_t pageCount)
+        : m_pageCount(pageCount)
+    { }
+
+    void dump(WTF::PrintStream&) const;
+
+    uint64_t bytes() const { return static_cast<uint64_t>(m_pageCount) * static_cast<uint64_t>(pageSize); }
+    uint32_t pageCount() const { return m_pageCount; }
+
+    static bool isValid(uint32_t pageCount)
+    {
+        return pageCount <= maxPageCount;
+    }
+
+    static PageCount fromBytes(uint64_t bytes)
+    {
+        RELEASE_ASSERT(bytes % pageSize == 0);
+        uint32_t numPages = bytes / pageSize;
+        RELEASE_ASSERT(PageCount::isValid(numPages));
+        return PageCount(numPages);
+    }
+
+    static PageCount max()
+    {
+        return PageCount(maxPageCount);
+    }
+
+    explicit operator bool() const
+    {
+        return m_pageCount != UINT_MAX;
+    }
+
+    bool operator<(const PageCount& other) const { return m_pageCount < other.m_pageCount; }
+    bool operator>(const PageCount& other) const { return m_pageCount > other.m_pageCount; }
+    bool operator>=(const PageCount& other) const { return m_pageCount >= other.m_pageCount; }
+    PageCount operator+(const PageCount& other) const
+    {
+        if (sumOverflows<uint32_t>(m_pageCount, other.m_pageCount))
+            return PageCount();
+        uint32_t newCount = m_pageCount + other.m_pageCount;
+        if (!PageCount::isValid(newCount))
+            return PageCount();
+        return PageCount(newCount);
+    }
+
+    static constexpr uint32_t pageSize = 64 * KB;
+private:
+    static constexpr uint32_t maxPageCount = static_cast<uint32_t>((1ull << 32) / pageSize);
+
+    uint32_t m_pageCount;
+};
+
+} } // namespace JSC::Wasm
+
+#endif // ENABLE(WASM)