103 lines
3.1 KiB
C
103 lines
3.1 KiB
C
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// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#ifndef GOOGLE_PROTOBUF_ARENA_CLEANUP_H__
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#define GOOGLE_PROTOBUF_ARENA_CLEANUP_H__
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#include <cstddef>
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#include <cstring>
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#include <vector>
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#include "absl/base/attributes.h"
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#include "absl/base/prefetch.h"
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// Must be included last.
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#include "google/protobuf/port_def.inc"
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namespace google {
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namespace protobuf {
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namespace internal {
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class SerialArena;
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namespace cleanup {
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// Helper function invoking the destructor of `object`
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template <typename T>
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void arena_destruct_object(void* object) {
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reinterpret_cast<T*>(object)->~T();
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}
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// CleanupNode contains the object (`elem`) that needs to be
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// destroyed, and the function to destroy it (`destructor`)
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// elem must be aligned at minimum on a 4 byte boundary.
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struct CleanupNode {
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// Optimization: performs a prefetch on the elem for the cleanup node. We
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// explicitly use NTA prefetch here to avoid polluting remote caches: we are
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// destroying these instances, there is no purpose for these cache lines to
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// linger around in remote caches.
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ABSL_ATTRIBUTE_ALWAYS_INLINE void Prefetch() {
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// TODO: we should also prefetch the destructor code once
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// processors support code prefetching.
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absl::PrefetchToLocalCacheNta(elem);
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}
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// Destroys the object referenced by the cleanup node.
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ABSL_ATTRIBUTE_ALWAYS_INLINE void Destroy() { destructor(elem); }
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void* elem;
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void (*destructor)(void*);
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};
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// Manages the list of cleanup nodes in a chunked linked list. Chunks grow by
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// factors of two up to a limit. Trivially destructible, but Cleanup() must be
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// called before destruction.
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class ChunkList {
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public:
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PROTOBUF_ALWAYS_INLINE void Add(void* elem, void (*destructor)(void*),
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SerialArena& arena) {
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if (PROTOBUF_PREDICT_TRUE(next_ < limit_)) {
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AddFromExisting(elem, destructor);
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return;
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}
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AddFallback(elem, destructor, arena);
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}
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// Runs all inserted cleanups and frees allocated chunks. Must be called
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// before destruction.
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void Cleanup(const SerialArena& arena);
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private:
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struct Chunk;
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friend class internal::SerialArena;
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void AddFallback(void* elem, void (*destructor)(void*), SerialArena& arena);
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ABSL_ATTRIBUTE_ALWAYS_INLINE void AddFromExisting(void* elem,
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void (*destructor)(void*)) {
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*next_++ = CleanupNode{elem, destructor};
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}
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// Returns the pointers to the to-be-cleaned objects.
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std::vector<void*> PeekForTesting();
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Chunk* head_ = nullptr;
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CleanupNode* next_ = nullptr;
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CleanupNode* limit_ = nullptr;
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// Current prefetch position. Data from `next_` up to but not including
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// `prefetch_ptr_` is software prefetched. Used in SerialArena prefetching.
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const char* prefetch_ptr_ = nullptr;
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};
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} // namespace cleanup
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} // namespace internal
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} // namespace protobuf
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} // namespace google
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#include "google/protobuf/port_undef.inc"
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#endif // GOOGLE_PROTOBUF_ARENA_CLEANUP_H__
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