mirror of
https://github.com/JakeHillion/object-introspection.git
synced 2024-11-09 21:24:14 +00:00
77 lines
2.5 KiB
C++
77 lines
2.5 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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#include <oi/exporters/ParsedData.h>
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#include <cassert>
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#include <stdexcept>
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#include <type_traits>
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template <typename T>
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constexpr bool always_false_v = false;
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namespace oi::exporters {
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namespace {
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uint64_t parseVarint(std::vector<uint8_t>::const_iterator& it);
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}
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ParsedData ParsedData::parse(std::vector<uint8_t>::const_iterator& it,
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types::dy::Dynamic dy) {
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return std::visit(
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[&it](const auto el) -> ParsedData {
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auto ty = el.get();
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using T = std::decay_t<decltype(ty)>;
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if constexpr (std::is_same_v<T, types::dy::Unit>) {
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return ParsedData::Unit{};
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} else if constexpr (std::is_same_v<T, types::dy::VarInt>) {
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return ParsedData::VarInt{.value = parseVarint(it)};
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} else if constexpr (std::is_same_v<T, types::dy::Pair>) {
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return ParsedData::Pair{
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.first = Lazy{it, ty.first},
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.second = Lazy{it, ty.second},
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};
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} else if constexpr (std::is_same_v<T, types::dy::List>) {
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return ParsedData::List{
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.length = parseVarint(it),
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.values = {it, ty.element},
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};
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} else if constexpr (std::is_same_v<T, types::dy::Sum>) {
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auto index = parseVarint(it);
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assert(index < ty.variants.size());
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return ParsedData::Sum{
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.index = parseVarint(it),
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.value = {it, ty.variants[index]},
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};
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} else {
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static_assert(always_false_v<T>, "non-exhaustive visitor!");
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}
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},
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dy);
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}
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namespace {
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uint64_t parseVarint(std::vector<uint8_t>::const_iterator& it) {
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uint64_t v = 0;
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int shift = 0;
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while (*it >= 0x80) {
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v |= static_cast<uint64_t>(*it++ & 0x7f) << shift;
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shift += 7;
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}
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v |= static_cast<uint64_t>(*it++ & 0x7f) << shift;
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return v;
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}
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} // namespace
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} // namespace oi::exporters
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