mirror of
https://github.com/JakeHillion/object-introspection.git
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77 lines
2.0 KiB
C++
77 lines
2.0 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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/*
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* TypeCheckingWalker
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*
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* Walks a dynamic data segment type simultaneously with the contents of the
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* data segment, providing context to each extracted element.
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*
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* The dynamic types are implemented as a stack machine. Handling a type
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* pops the top element, handles it which may involve pushing more types onto
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* the stack, and returns an element from the data segment if appropriate or
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* recurses. See the implementation for details.
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*/
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#include <cstdint>
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#include <optional>
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#include <span>
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#include <stack>
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#include <stdexcept>
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#include <variant>
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#include "oi/types/dy.h"
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namespace oi::detail::exporters {
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class TypeCheckingWalker {
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public:
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struct VarInt {
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uint64_t value;
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};
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struct SumIndex {
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uint64_t index;
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};
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struct ListLength {
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uint64_t length;
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};
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using Element = std::variant<VarInt, SumIndex, ListLength>;
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TypeCheckingWalker(types::dy::Dynamic rootType,
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std::span<const uint64_t> buffer)
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: stack({rootType}), buf(buffer) {
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}
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std::optional<Element> advance();
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private:
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std::stack<types::dy::Dynamic> stack;
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std::span<const uint64_t> buf;
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private:
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uint64_t popFront() {
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if (buf.empty()) {
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throw std::runtime_error("unexpected end of data segment");
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}
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auto el = buf.front();
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buf = buf.last(buf.size() - 1);
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return el;
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}
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};
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} // namespace oi::detail::exporters
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