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// 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 <map>
#include <stubs/logging.h>
#include <stubs/common.h>
#include <descriptor.h>
#include <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) {}
const SCC* GetSCC(const Descriptor* descriptor) {
if (cache_.count(descriptor)) return cache_[descriptor].scc;
return DFS(descriptor).scc;
}
private:
struct NodeData {
const SCC* scc; // if null it means its still on the stack
int index;
int lowlink;
};
std::map<const Descriptor*, 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) {
// Must not have visited already.
GOOGLE_DCHECK_EQ(cache_.count(descriptor), 0);
// Mark visited by inserting in map.
NodeData& result = cache_[descriptor];
// Initialize data structures.
result.index = result.lowlink = index_++;
stack_.push_back(descriptor);
// Recurse the fields / nodes in graph
for (auto dep : DepsGenerator()(descriptor)) {
GOOGLE_CHECK(dep);
if (cache_.count(dep) == 0) {
// unexplored node
NodeData child_data = DFS(dep);
result.lowlink = std::min(result.lowlink, child_data.lowlink);
} else {
NodeData child_data = cache_[dep];
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) {
std::set<const SCC*> seen;
for (auto descriptor : scc->descriptors) {
for (auto child_msg : DepsGenerator()(descriptor)) {
GOOGLE_CHECK(child_msg);
const SCC* child = GetSCC(child_msg);
if (child == scc) continue;
if (seen.insert(child).second) {
scc->children.push_back(child);
}
}
}
}
// This is necessary for compiler bug in msvc2015.
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(SCCAnalyzer);
};
} // namespace compiler
} // namespace protobuf
} // namespace google
#include <port_undef.inc>
#endif // GOOGLE_PROTOBUF_COMPILER_SCC_H__
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