src/google/protobuf/compiler/cpp/field.h

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
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// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.

#ifndef GOOGLE_PROTOBUF_COMPILER_CPP_FIELD_H__
#define GOOGLE_PROTOBUF_COMPILER_CPP_FIELD_H__

#include <cstdint>
#include <map>
#include <memory>
#include <string>

#include <google/protobuf/descriptor.h>
#include <google/protobuf/compiler/cpp/helpers.h>
#include <google/protobuf/compiler/cpp/options.h>

namespace google {
namespace protobuf {
namespace io {
class Printer;  // printer.h
}
}  // namespace protobuf
}  // namespace google

namespace google {
namespace protobuf {
namespace compiler {
namespace cpp {

// Helper function: set variables in the map that are the same for all
// field code generators.
// ['name', 'index', 'number', 'classname', 'declared_type', 'tag_size',
// 'deprecation'].
void SetCommonFieldVariables(const FieldDescriptor* descriptor,
                             std::map<std::string, std::string>* variables,
                             const Options& options);

void SetCommonOneofFieldVariables(
    const FieldDescriptor* descriptor,
    std::map<std::string, std::string>* variables);

class FieldGenerator {
 public:
  explicit FieldGenerator(const FieldDescriptor* descriptor,
                          const Options& options)
      : descriptor_(descriptor), options_(options) {}
  virtual ~FieldGenerator();
  virtual void GenerateSerializeWithCachedSizes(
      io::Printer* printer) const final{};
  // Generate lines of code declaring members fields of the message class
  // needed to represent this field.  These are placed inside the message
  // class.
  virtual void GeneratePrivateMembers(io::Printer* printer) const = 0;

  // Generate static default variable for this field. These are placed inside
  // the message class. Most field types don't need this, so the default
  // implementation is empty.
  virtual void GenerateStaticMembers(io::Printer* /*printer*/) const {}

  // Generate prototypes for all of the accessor functions related to this
  // field.  These are placed inside the class definition.
  virtual void GenerateAccessorDeclarations(io::Printer* printer) const = 0;

  // Generate inline definitions of accessor functions for this field.
  // These are placed inside the header after all class definitions.
  virtual void GenerateInlineAccessorDefinitions(
      io::Printer* printer) const = 0;

  // Generate definitions of accessors that aren't inlined.  These are
  // placed somewhere in the .cc file.
  // Most field types don't need this, so the default implementation is empty.
  virtual void GenerateNonInlineAccessorDefinitions(
      io::Printer* /*printer*/) const {}

  // Generate declarations of accessors that are for internal purposes only.
  // Most field types don't need this, so the default implementation is empty.
  virtual void GenerateInternalAccessorDefinitions(
      io::Printer* /*printer*/) const {}

  // Generate definitions of accessors that are for internal purposes only.
  // Most field types don't need this, so the default implementation is empty.
  virtual void GenerateInternalAccessorDeclarations(
      io::Printer* /*printer*/) const {}

  // Generate lines of code (statements, not declarations) which clear the
  // field.  This is used to define the clear_$name$() method
  virtual void GenerateClearingCode(io::Printer* printer) const = 0;

  // Generate lines of code (statements, not declarations) which clear the
  // field as part of the Clear() method for the whole message.  For message
  // types which have field presence bits, MessageGenerator::GenerateClear
  // will have already checked the presence bits.
  //
  // Since most field types can re-use GenerateClearingCode, this method is
  // not pure virtual.
  virtual void GenerateMessageClearingCode(io::Printer* printer) const {
    GenerateClearingCode(printer);
  }

  // Generate lines of code (statements, not declarations) which merges the
  // contents of the field from the current message to the target message,
  // which is stored in the generated code variable "from".
  // This is used to fill in the MergeFrom method for the whole message.
  // Details of this usage can be found in message.cc under the
  // GenerateMergeFrom method.
  virtual void GenerateMergingCode(io::Printer* printer) const = 0;

  // Generates a copy constructor
  virtual void GenerateCopyConstructorCode(io::Printer* printer) const;

  // Generate lines of code (statements, not declarations) which swaps
  // this field and the corresponding field of another message, which
  // is stored in the generated code variable "other". This is used to
  // define the Swap method. Details of usage can be found in
  // message.cc under the GenerateSwap method.
  virtual void GenerateSwappingCode(io::Printer* printer) const = 0;

  // Generate initialization code for private members declared by
  // GeneratePrivateMembers(). These go into the message class's SharedCtor()
  // method, invoked by each of the generated constructors.
  virtual void GenerateConstructorCode(io::Printer* printer) const = 0;

  // Generate initialization code for private members in the cold struct.
  virtual void GenerateCreateSplitMessageCode(io::Printer* printer) const {}

  // Generate any code that needs to go in the class's SharedDtor() method,
  // invoked by the destructor.
  // Most field types don't need this, so the default implementation is empty.
  virtual void GenerateDestructorCode(io::Printer* /*printer*/) const {}

  // Generate a manual destructor invocation for use when the message is on an
  // arena. The code that this method generates will be executed inside a
  // shared-for-the-whole-message-class method registered with
  // OwnDestructor().
  virtual void GenerateArenaDestructorCode(io::Printer* printer) const {
    GOOGLE_CHECK(NeedsArenaDestructor() == ArenaDtorNeeds::kNone)
        << descriptor_->cpp_type_name();
  }

  // Generate initialization code for private members declared by
  // GeneratePrivateMembers(). These go into the SharedCtor's
  // aggregate initialization of the _impl_ struct and must follow the syntax
  // (e.g. `decltype($field$){$default$}`). Does not include `:` or `,`
  // separators.  Default values should be specified here when possible.
  //
  // Note: We use `decltype($field$)` for both explicit construction and the
  // fact that it's self-documenting.  Pre-C++17, copy elision isn't guaranteed
  // in aggregate initialization so a valid copy/move constructor must exist
  // (even though it's not used).  Because of this, we need to comment out the
  // decltype and fallback to implicit construction.
  virtual void GenerateAggregateInitializer(io::Printer* printer) const;

  // Generate constinit initialization code for private members declared by
  // GeneratePrivateMembers(). These go into the constexpr constructor's
  // aggregate initialization of the _impl_ struct and must follow the syntax
  // (e.g. `/*decltype($field$)*/{}`, see above). Does not
  // include `:` or `,` separators.
  virtual void GenerateConstexprAggregateInitializer(
      io::Printer* printer) const;

  // Generate copy initialization code for private members declared by
  // GeneratePrivateMembers(). These go into the copy constructor's
  // aggregate initialization of the _impl_ struct and must follow the syntax
  // (e.g. `decltype($field$){from.$field$}`, see above). Does not
  // include `:` or `,` separators.
  virtual void GenerateCopyAggregateInitializer(io::Printer* printer) const;

  // Generate lines to serialize this field directly to the array "target",
  // which are placed within the message's SerializeWithCachedSizesToArray()
  // method. This must also advance "target" past the written bytes.
  virtual void GenerateSerializeWithCachedSizesToArray(
      io::Printer* printer) const = 0;

  // Generate lines to compute the serialized size of this field, which
  // are placed in the message's ByteSize() method.
  virtual void GenerateByteSize(io::Printer* printer) const = 0;

  // Generates lines to call IsInitialized() for eligible message fields. Non
  // message fields won't need to override this function.
  virtual void GenerateIsInitialized(io::Printer* printer) const {}

  virtual bool IsInlined() const { return false; }

  virtual ArenaDtorNeeds NeedsArenaDestructor() const {
    return ArenaDtorNeeds::kNone;
  }

  void SetHasBitIndex(int32_t has_bit_index);
  void SetInlinedStringIndex(int32_t inlined_string_index);

 protected:
  const FieldDescriptor* descriptor_;
  const Options& options_;
  std::map<std::string, std::string> variables_;

 private:
  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldGenerator);
};

// Convenience class which constructs FieldGenerators for a Descriptor.
class FieldGeneratorMap {
 public:
  FieldGeneratorMap(const Descriptor* descriptor, const Options& options,
                    MessageSCCAnalyzer* scc_analyzer);
  ~FieldGeneratorMap();

  const FieldGenerator& get(const FieldDescriptor* field) const;

  void SetHasBitIndices(const std::vector<int>& has_bit_indices_) {
    for (int i = 0; i < descriptor_->field_count(); ++i) {
      field_generators_[i]->SetHasBitIndex(has_bit_indices_[i]);
    }
  }

  void SetInlinedStringIndices(const std::vector<int>& inlined_string_indices) {
    for (int i = 0; i < descriptor_->field_count(); ++i) {
      field_generators_[i]->SetInlinedStringIndex(inlined_string_indices[i]);
    }
  }

 private:
  const Descriptor* descriptor_;
  std::vector<std::unique_ptr<FieldGenerator>> field_generators_;

  static FieldGenerator* MakeGoogleInternalGenerator(
      const FieldDescriptor* field, const Options& options,
      MessageSCCAnalyzer* scc_analyzer);
  static FieldGenerator* MakeGenerator(const FieldDescriptor* field,
                                       const Options& options,
                                       MessageSCCAnalyzer* scc_analyzer);

  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldGeneratorMap);
};

}  // namespace cpp
}  // namespace compiler
}  // namespace protobuf
}  // namespace google

#endif  // GOOGLE_PROTOBUF_COMPILER_CPP_FIELD_H__