Source/JavaScriptCore/wasm/WasmSections.h

/*
 * 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)

#if !ASSERT_ENABLED
IGNORE_RETURN_TYPE_WARNINGS_BEGIN
#endif

namespace JSC { namespace Wasm {

#define FOR_EACH_KNOWN_WASM_SECTION(macro) \
    macro(Type,       1, "Function signature declarations") \
    macro(Import,     2, "Import declarations") \
    macro(Function,   3, "Function declarations") \
    macro(Table,      4, "Indirect function table and other tables") \
    macro(Memory,     5, "Memory attributes") \
    macro(Global,     6, "Global declarations") \
    macro(Export,     7, "Exports") \
    macro(Start,      8, "Start function declaration") \
    macro(Element,    9, "Elements section") \
    macro(Code,      10, "Function bodies (code)") \
    macro(Data,      11, "Data segments") \
    macro(DataCount, 12, "Data count") \
    macro(Exception, 13, "Exception declarations") \

enum class Section : uint8_t {
    // It's important that Begin is less than every other section number and that Custom is greater.
    // This only works because section numbers are currently monotonically increasing.
    // Also, Begin is not a real section but is used as a marker for validating the ordering
    // of sections.
    Begin = 0,
#define DEFINE_WASM_SECTION_ENUM(NAME, ID, DESCRIPTION) NAME = ID,
    FOR_EACH_KNOWN_WASM_SECTION(DEFINE_WASM_SECTION_ENUM)
#undef DEFINE_WASM_SECTION_ENUM
    Custom
};
static_assert(static_cast<uint8_t>(Section::Begin) < static_cast<uint8_t>(Section::Type), "Begin should come before the first known section.");

template<typename Int>
inline bool isKnownSection(Int section)
{
    switch (section) {
#define VALIDATE_SECTION(NAME, ID, DESCRIPTION) case static_cast<Int>(Section::NAME): return true;
        FOR_EACH_KNOWN_WASM_SECTION(VALIDATE_SECTION)
#undef VALIDATE_SECTION
    default:
        return false;
    }
}

inline bool decodeSection(uint8_t sectionByte, Section& section)
{
    section = Section::Custom;
    if (!sectionByte)
        return true;

    if (!isKnownSection(sectionByte))
        return false;

    section = static_cast<Section>(sectionByte);
    return true;
}

inline bool validateOrder(Section previousKnown, Section next)
{
    ASSERT(isKnownSection(previousKnown) || previousKnown == Section::Begin);
    if (previousKnown == Section::DataCount && next == Section::Code)
        return true;
    if (previousKnown == Section::Exception)
        return next >= Section::Global;
    if (next == Section::Exception)
        return previousKnown <= Section::Memory;
    return static_cast<uint8_t>(previousKnown) < static_cast<uint8_t>(next);
}

inline const char* makeString(Section section)
{
    switch (section) {
    case Section::Begin:
        return "Begin";
    case Section::Custom:
        return "Custom";
#define STRINGIFY_SECTION_NAME(NAME, ID, DESCRIPTION) case Section::NAME: return #NAME;
        FOR_EACH_KNOWN_WASM_SECTION(STRINGIFY_SECTION_NAME)
#undef STRINGIFY_SECTION_NAME
    }
    ASSERT_NOT_REACHED();
}

} } // namespace JSC::Wasm

#if !ASSERT_ENABLED
IGNORE_RETURN_TYPE_WARNINGS_END
#endif

#endif // ENABLE(WEBASSEMBLY)