Line data Source code
1 : // Protocol Buffers - Google's data interchange format
2 : // Copyright 2008 Google Inc. All rights reserved.
3 : // https://developers.google.com/protocol-buffers/
4 : //
5 : // Redistribution and use in source and binary forms, with or without
6 : // modification, are permitted provided that the following conditions are
7 : // met:
8 : //
9 : // * Redistributions of source code must retain the above copyright
10 : // notice, this list of conditions and the following disclaimer.
11 : // * Redistributions in binary form must reproduce the above
12 : // copyright notice, this list of conditions and the following disclaimer
13 : // in the documentation and/or other materials provided with the
14 : // distribution.
15 : // * Neither the name of Google Inc. nor the names of its
16 : // contributors may be used to endorse or promote products derived from
17 : // this software without specific prior written permission.
18 : //
19 : // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 : // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 : // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 : // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 : // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 : // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 : // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 : // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 : // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 : // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 : // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 :
31 : // This header file defines an internal class that encapsulates internal message
32 : // metadata (Unknown-field set, Arena pointer, ...) and allows its
33 : // representation to be made more space-efficient via various optimizations.
34 : //
35 : // Note that this is distinct from google::protobuf::Metadata, which encapsulates
36 : // Descriptor and Reflection pointers.
37 :
38 : #ifndef GOOGLE_PROTOBUF_METADATA_H__
39 : #define GOOGLE_PROTOBUF_METADATA_H__
40 :
41 : #include <google/protobuf/stubs/common.h>
42 : #include <google/protobuf/arena.h>
43 : #include <google/protobuf/unknown_field_set.h>
44 :
45 : namespace google {
46 : namespace protobuf {
47 : namespace internal {
48 :
49 : // This is the representation for messages that support arena allocation. It
50 : // uses a tagged pointer to either store the Arena pointer, if there are no
51 : // unknown fields, or a pointer to a block of memory with both the Arena pointer
52 : // and the UnknownFieldSet, if there are unknown fields. This optimization
53 : // allows for "zero-overhead" storage of the Arena pointer, relative to the
54 : // above baseline implementation.
55 : //
56 : // The tagged pointer uses the LSB to disambiguate cases, and uses bit 0 == 0 to
57 : // indicate an arena pointer and bit 0 == 1 to indicate a UFS+Arena-container
58 : // pointer.
59 : class LIBPROTOBUF_EXPORT InternalMetadataWithArena {
60 : public:
61 : InternalMetadataWithArena() : ptr_(NULL) {}
62 7611174 : explicit InternalMetadataWithArena(Arena* arena)
63 7684960 : : ptr_ (arena) {}
64 :
65 7683124 : ~InternalMetadataWithArena() {
66 7683608 : if (have_unknown_fields() && arena() == NULL) {
67 968 : delete PtrValue<Container>();
68 : }
69 7688172 : ptr_ = NULL;
70 7688172 : }
71 :
72 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE const UnknownFieldSet& unknown_fields() const {
73 1579 : if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
74 1305 : return PtrValue<Container>()->unknown_fields_;
75 : } else {
76 274 : return *UnknownFieldSet::default_instance();
77 : }
78 : }
79 :
80 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE UnknownFieldSet* mutable_unknown_fields() {
81 960 : if (GOOGLE_PREDICT_TRUE(have_unknown_fields())) {
82 476 : return &PtrValue<Container>()->unknown_fields_;
83 : } else {
84 484 : return mutable_unknown_fields_slow();
85 : }
86 : }
87 :
88 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE Arena* arena() const {
89 3960875 : if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
90 484 : return PtrValue<Container>()->arena_;
91 : } else {
92 3960391 : return PtrValue<Arena>();
93 : }
94 : }
95 :
96 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE bool have_unknown_fields() const {
97 11573854 : return PtrTag() == kTagContainer;
98 : }
99 :
100 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE void Swap(InternalMetadataWithArena* other) {
101 : // Semantics here are that we swap only the unknown fields, not the arena
102 : // pointer. We cannot simply swap ptr_ with other->ptr_ because we need to
103 : // maintain our own arena ptr. Also, our ptr_ and other's ptr_ may be in
104 : // different states (direct arena pointer vs. container with UFS) so we
105 : // cannot simply swap ptr_ and then restore the arena pointers. We reuse
106 : // UFS's swap implementation instead.
107 156 : if (have_unknown_fields() || other->have_unknown_fields()) {
108 0 : mutable_unknown_fields()->Swap(other->mutable_unknown_fields());
109 : }
110 : }
111 :
112 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE void* raw_arena_ptr() const {
113 : return ptr_;
114 : }
115 :
116 : private:
117 : void* ptr_;
118 :
119 : // Tagged pointer implementation.
120 : enum {
121 : // ptr_ is an Arena*.
122 : kTagArena = 0,
123 : // ptr_ is a Container*.
124 : kTagContainer = 1,
125 : };
126 : static const intptr_t kPtrTagMask = 1;
127 : static const intptr_t kPtrValueMask = ~kPtrTagMask;
128 :
129 : // Accessors for pointer tag and pointer value.
130 : GOOGLE_ATTRIBUTE_ALWAYS_INLINE int PtrTag() const {
131 11688523 : return reinterpret_cast<intptr_t>(ptr_) & kPtrTagMask;
132 : }
133 :
134 3958286 : template<typename T> T* PtrValue() const {
135 : return reinterpret_cast<T*>(
136 3958770 : reinterpret_cast<intptr_t>(ptr_) & kPtrValueMask);
137 : }
138 :
139 : // If ptr_'s tag is kTagContainer, it points to an instance of this struct.
140 968 : struct Container {
141 : UnknownFieldSet unknown_fields_;
142 : Arena* arena_;
143 : };
144 :
145 484 : GOOGLE_ATTRIBUTE_NOINLINE UnknownFieldSet* mutable_unknown_fields_slow() {
146 484 : Arena* my_arena = arena();
147 484 : Container* container = Arena::Create<Container>(my_arena);
148 : ptr_ = reinterpret_cast<void*>(
149 484 : reinterpret_cast<intptr_t>(container) | kTagContainer);
150 484 : container->arena_ = my_arena;
151 484 : return &(container->unknown_fields_);
152 : }
153 : };
154 :
155 : // Temporary compatibility typedef. Remove once this is released in components
156 : // and upb CL is submitted.
157 : typedef InternalMetadataWithArena InternalMetadata;
158 :
159 : } // namespace internal
160 : } // namespace protobuf
161 :
162 : } // namespace google
163 : #endif // GOOGLE_PROTOBUF_METADATA_H__
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