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75 lines
3.2 KiB
C
75 lines
3.2 KiB
C
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//===- Layout.h -----------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// Convenience macros for obtaining offsets of members in structs.
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//
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// Usage:
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//
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// #define FOR_EACH_FOO_FIELD(DO) \
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// DO(Ptr, bar) \
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// DO(uint32_t, baz) \
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// CREATE_LAYOUT_CLASS(Foo, FOR_EACH_FOO_FIELD)
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// #undef FOR_EACH_FOO_FIELD
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//
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// This will generate
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//
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// struct FooLayout {
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// uint32_t barOffset;
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// uint32_t bazOffset;
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// uint32_t totalSize;
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//
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// FooLayout(size_t wordSize) {
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// if (wordSize == 8)
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// init<uint64_t>();
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// else {
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// assert(wordSize == 4);
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// init<uint32_t>();
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// }
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// }
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//
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// private:
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// template <class Ptr> void init() {
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// FOR_EACH_FIELD(_INIT_OFFSET);
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// barOffset = offsetof(Layout<Ptr>, bar);
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// bazOffset = offsetof(Layout<Ptr>, baz);
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// totalSize = sizeof(Layout<Ptr>);
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// }
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// template <class Ptr> struct Layout {
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// Ptr bar;
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// uint32_t baz;
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// };
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// };
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#define _OFFSET_FOR_FIELD(_, name) uint32_t name##Offset;
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#define _INIT_OFFSET(type, name) name##Offset = offsetof(Layout<Ptr>, name);
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#define _LAYOUT_ENTRY(type, name) type name;
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#define CREATE_LAYOUT_CLASS(className, FOR_EACH_FIELD) \
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struct className##Layout { \
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FOR_EACH_FIELD(_OFFSET_FOR_FIELD) \
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uint32_t totalSize; \
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\
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className##Layout(size_t wordSize) { \
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if (wordSize == 8) \
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init<uint64_t>(); \
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else { \
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assert(wordSize == 4); \
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init<uint32_t>(); \
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} \
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} \
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\
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private: \
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template <class Ptr> void init() { \
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FOR_EACH_FIELD(_INIT_OFFSET); \
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totalSize = sizeof(Layout<Ptr>); \
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} \
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template <class Ptr> struct Layout { \
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FOR_EACH_FIELD(_LAYOUT_ENTRY) \
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}; \
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}
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