1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef GOOGLE_PROTOBUF_COMPILER_SCC_H__
#define GOOGLE_PROTOBUF_COMPILER_SCC_H__
#include <memory>
#include "y_absl/container/flat_hash_map.h"
#include "y_absl/container/flat_hash_set.h"
#include "y_absl/log/absl_check.h"
#include "y_absl/memory/memory.h"
#include "google/protobuf/descriptor.h"
// Must be included last.
#include "google/protobuf/port_def.inc"
namespace google {
namespace protobuf {
namespace compiler {
// Description of each strongly connected component. Note that the order
// of both the descriptors in this SCC and the order of children is
// deterministic.
struct SCC {
std::vector<const Descriptor*> descriptors;
std::vector<const SCC*> children;
const Descriptor* GetRepresentative() const { return descriptors[0]; }
// All messages must necessarily be in the same file.
const FileDescriptor* GetFile() const { return descriptors[0]->file(); }
};
// This class is used for analyzing the SCC for each message, to ensure linear
// instead of quadratic performance, if we do this per message we would get
// O(V*(V+E)).
template <class DepsGenerator>
class PROTOC_EXPORT SCCAnalyzer {
public:
explicit SCCAnalyzer() : index_(0) {}
SCCAnalyzer(const SCCAnalyzer&) = delete;
SCCAnalyzer& operator=(const SCCAnalyzer&) = delete;
const SCC* GetSCC(const Descriptor* descriptor) {
auto it = cache_.find(descriptor);
if (it == cache_.end()) {
return DFS(descriptor).scc;
}
return it->second->scc;
}
private:
struct NodeData {
const SCC* scc; // if null it means its still on the stack
int index;
int lowlink;
};
y_absl::flat_hash_map<const Descriptor*, std::unique_ptr<NodeData>> cache_;
std::vector<const Descriptor*> stack_;
int index_;
std::vector<std::unique_ptr<SCC>> garbage_bin_;
SCC* CreateSCC() {
garbage_bin_.emplace_back(new SCC());
return garbage_bin_.back().get();
}
// Tarjan's Strongly Connected Components algo
NodeData DFS(const Descriptor* descriptor) {
// Mark visited by inserting in map.
auto ins = cache_.try_emplace(descriptor, y_absl::make_unique<NodeData>());
// Must not have visited already.
Y_ABSL_DCHECK(ins.second);
NodeData& result = *ins.first->second;
// Initialize data structures.
result.index = result.lowlink = index_++;
stack_.push_back(descriptor);
// Recurse the fields / nodes in graph
for (const auto* dep : DepsGenerator()(descriptor)) {
Y_ABSL_CHECK(dep);
auto it = cache_.find(dep);
if (it == cache_.end()) {
// unexplored node
NodeData child_data = DFS(dep);
result.lowlink = std::min(result.lowlink, child_data.lowlink);
} else {
NodeData& child_data = *it->second;
if (child_data.scc == nullptr) {
// Still in the stack_ so we found a back edge
result.lowlink = std::min(result.lowlink, child_data.index);
}
}
}
if (result.index == result.lowlink) {
// This is the root of a strongly connected component
SCC* scc = CreateSCC();
while (true) {
const Descriptor* scc_desc = stack_.back();
scc->descriptors.push_back(scc_desc);
// Remove from stack
stack_.pop_back();
cache_[scc_desc]->scc = scc;
if (scc_desc == descriptor) break;
}
// The order of descriptors is random and depends how this SCC was
// discovered. In-order to ensure maximum stability we sort it by name.
std::sort(scc->descriptors.begin(), scc->descriptors.end(),
[](const Descriptor* a, const Descriptor* b) {
return a->full_name() < b->full_name();
});
AddChildren(scc);
}
return result;
}
// Add the SCC's that are children of this SCC to its children.
void AddChildren(SCC* scc) {
y_absl::flat_hash_set<const SCC*> seen;
for (auto descriptor : scc->descriptors) {
for (auto child_msg : DepsGenerator()(descriptor)) {
Y_ABSL_CHECK(child_msg);
const SCC* child = GetSCC(child_msg);
if (child == scc) continue;
if (seen.insert(child).second) {
scc->children.push_back(child);
}
}
}
}
};
} // namespace compiler
} // namespace protobuf
} // namespace google
#include "google/protobuf/port_undef.inc"
#endif // GOOGLE_PROTOBUF_COMPILER_SCC_H__
|
