103 lines
3.0 KiB
C
103 lines
3.0 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_ALLOCATION_POLICY_H__
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#define GOOGLE_PROTOBUF_ARENA_ALLOCATION_POLICY_H__
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#include <cstddef>
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#include <cstdint>
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namespace google {
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namespace protobuf {
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namespace internal {
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// `AllocationPolicy` defines `Arena` allocation policies. Applications can
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// customize the initial and maximum sizes for arena allocation, as well as set
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// custom allocation and deallocation functions. `AllocationPolicy` is for
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// protocol buffer internal use only, and typically created from a user facing
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// public configuration class such as `ArenaOptions`.
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struct AllocationPolicy {
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static constexpr size_t kDefaultStartBlockSize = 256;
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static constexpr size_t kDefaultMaxBlockSize = 32 << 10;
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size_t start_block_size = kDefaultStartBlockSize;
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size_t max_block_size = kDefaultMaxBlockSize;
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void* (*block_alloc)(size_t) = nullptr;
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void (*block_dealloc)(void*, size_t) = nullptr;
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bool IsDefault() const {
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return start_block_size == kDefaultStartBlockSize &&
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max_block_size == kDefaultMaxBlockSize && block_alloc == nullptr &&
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block_dealloc == nullptr;
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}
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};
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// Tagged pointer to an AllocationPolicy.
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class TaggedAllocationPolicyPtr {
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public:
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constexpr TaggedAllocationPolicyPtr() : policy_(0) {}
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explicit TaggedAllocationPolicyPtr(AllocationPolicy* policy)
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: policy_(reinterpret_cast<uintptr_t>(policy)) {}
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void set_policy(AllocationPolicy* policy) {
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auto bits = policy_ & kTagsMask;
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policy_ = reinterpret_cast<uintptr_t>(policy) | bits;
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}
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AllocationPolicy* get() {
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return reinterpret_cast<AllocationPolicy*>(policy_ & kPtrMask);
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}
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const AllocationPolicy* get() const {
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return reinterpret_cast<const AllocationPolicy*>(policy_ & kPtrMask);
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}
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AllocationPolicy& operator*() { return *get(); }
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const AllocationPolicy& operator*() const { return *get(); }
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AllocationPolicy* operator->() { return get(); }
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const AllocationPolicy* operator->() const { return get(); }
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bool is_user_owned_initial_block() const {
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return static_cast<bool>(get_mask<kUserOwnedInitialBlock>());
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}
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void set_is_user_owned_initial_block(bool v) {
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set_mask<kUserOwnedInitialBlock>(v);
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}
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uintptr_t get_raw() const { return policy_; }
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private:
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enum : uintptr_t {
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kUserOwnedInitialBlock = 1,
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};
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static constexpr uintptr_t kTagsMask = 7;
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static constexpr uintptr_t kPtrMask = ~kTagsMask;
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template <uintptr_t kMask>
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uintptr_t get_mask() const {
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return policy_ & kMask;
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}
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template <uintptr_t kMask>
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void set_mask(bool v) {
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if (v) {
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policy_ |= kMask;
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} else {
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policy_ &= ~kMask;
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}
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}
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uintptr_t policy_;
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};
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} // namespace internal
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} // namespace protobuf
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} // namespace google
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#endif // GOOGLE_PROTOBUF_ARENA_ALLOCATION_POLICY_H__
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