protobuf: refactor proto visitor pattern. #9807
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| #include "common/protobuf/visitor.h" | ||
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| namespace Envoy { | ||
| namespace ProtobufMessage { | ||
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| void traverseMutableMessage(ProtoVisitor& visitor, Protobuf::Message& message, const void* ctxt) { | ||
| visitor.onMessage(message, ctxt); | ||
| const Protobuf::Descriptor* descriptor = message.GetDescriptor(); | ||
| const Protobuf::Reflection* reflection = message.GetReflection(); | ||
| for (int i = 0; i < descriptor->field_count(); ++i) { | ||
| const Protobuf::FieldDescriptor* field = descriptor->field(i); | ||
| const void* field_ctxt = visitor.onField(message, *field, ctxt); | ||
| // If this is a message, recurse to scrub deprecated fields in the sub-message. | ||
| if (field->cpp_type() == Protobuf::FieldDescriptor::CPPTYPE_MESSAGE) { | ||
| if (field->is_repeated()) { | ||
| const int size = reflection->FieldSize(message, field); | ||
| for (int j = 0; j < size; ++j) { | ||
| traverseMutableMessage(visitor, *reflection->MutableRepeatedMessage(&message, field, j), | ||
| field_ctxt); | ||
| } | ||
| } else if (reflection->HasField(message, field)) { | ||
| traverseMutableMessage(visitor, *reflection->MutableMessage(&message, field), field_ctxt); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| void traverseMessage(ConstProtoVisitor& visitor, const Protobuf::Message& message, | ||
| const void* ctxt) { | ||
| visitor.onMessage(message, ctxt); | ||
| const Protobuf::Descriptor* descriptor = message.GetDescriptor(); | ||
| const Protobuf::Reflection* reflection = message.GetReflection(); | ||
| for (int i = 0; i < descriptor->field_count(); ++i) { | ||
| const Protobuf::FieldDescriptor* field = descriptor->field(i); | ||
| const void* field_ctxt = visitor.onField(message, *field, ctxt); | ||
| // If this is a message, recurse to scrub deprecated fields in the sub-message. | ||
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| if (field->cpp_type() == Protobuf::FieldDescriptor::CPPTYPE_MESSAGE) { | ||
| if (field->is_repeated()) { | ||
| const int size = reflection->FieldSize(message, field); | ||
| for (int j = 0; j < size; ++j) { | ||
| traverseMessage(visitor, reflection->GetRepeatedMessage(message, field, j), field_ctxt); | ||
| } | ||
| } else if (reflection->HasField(message, field)) { | ||
| traverseMessage(visitor, reflection->GetMessage(message, field), field_ctxt); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| } // namespace ProtobufMessage | ||
| } // namespace Envoy | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| #pragma once | ||
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| #include "common/protobuf/protobuf.h" | ||
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| namespace Envoy { | ||
| namespace ProtobufMessage { | ||
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| class ProtoVisitor { | ||
| public: | ||
| virtual ~ProtoVisitor() = default; | ||
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| // Invoked when a field is visited, with the message, field descriptor and context. Returns a new | ||
| // context for use when traversing the sub-message in a field. | ||
| virtual const void* onField(Protobuf::Message&, const Protobuf::FieldDescriptor&, | ||
| const void* ctxt) { | ||
| return ctxt; | ||
| } | ||
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| // Invoked when a message is visited, with the message and a context. | ||
| virtual void onMessage(Protobuf::Message&, const void*){}; | ||
| }; | ||
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| class ConstProtoVisitor { | ||
| public: | ||
| virtual ~ConstProtoVisitor() = default; | ||
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| // Invoked when a field is visited, with the message, field descriptor and context. Returns a new | ||
| // context for use when traversing the sub-message in a field. | ||
| virtual const void* onField(const Protobuf::Message&, const Protobuf::FieldDescriptor&, | ||
| const void* ctxt) { | ||
| return ctxt; | ||
| } | ||
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| // Invoked when a message is visited, with the message and a context. | ||
| virtual void onMessage(const Protobuf::Message&, const void*){}; | ||
| }; | ||
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| void traverseMutableMessage(ProtoVisitor& visitor, Protobuf::Message& message, const void* ctxt); | ||
| void traverseMessage(ConstProtoVisitor& visitor, const Protobuf::Message& message, | ||
| const void* ctxt); | ||
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| } // namespace ProtobufMessage | ||
| } // namespace Envoy |
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optional, but it seems like this might be useful enough to make part of the onField call. I'd think folks would either want to be traversing structure (not care) or looking at valid fields (care) and if they care it's easy enough to get this wrong.
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Surprisingly tricky, since what is counted as used/unused is subtle for scalar fields. This can be seen in this code, since it first performs the scalar enum check before conditioning on whether the field is set in some sense.