Tracing V2: Proto fields reflection.

components/tracing/core/proto_utils.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_TRACING_CORE_PROTO_UTILS_H_
 #define COMPONENTS_TRACING_CORE_PROTO_UTILS_H_
 
 #include <inttypes.h>
 
 #include <type_traits>
 
 #include "base/logging.h"
 
 namespace tracing {
 namespace v2 {
 namespace proto {
 
 // See https://developers.google.com/protocol-buffers/docs/encoding wire types.
 
 enum : uint32_t {
   kFieldTypeVarInt = 0,
   kFieldTypeFixed64 = 1,
   kFieldTypeLengthDelimited = 2,
   kFieldTypeFixed32 = 5,
 };
 
+enum ProtoType : uint32_t {
+  kProtoTypeInvalid = 0,
+  kProtoTypeBool = 1,
+  kProtoTypeInt32 = 2,
+  kProtoTypeInt64 = 3,
+  kProtoTypeUint32 = 4,
+  kProtoTypeUint64 = 5,
+  kProtoTypeSint32 = 6,
+  kProtoTypeSint64 = 7,
+  kProtoTypeFixed32 = 8,
+  kProtoTypeFixed64 = 9,
+  kProtoTypeSfixed32 = 10,
+  kProtoTypeSfixed64 = 11,
+  kProtoTypeFloat = 12,
+  kProtoTypeDouble = 13,
+  kProtoTypeEnum = 14,
+  kProtoTypeString = 15,
+  kProtoTypeBytes = 16,
+  kProtoTypeMessage = 17,
+};
+
+struct FieldReflection {

[Primiano Tucci (use gerrit), 2016/08/31 09:04:07]

Can this have the same shape of 
https://developers.google.com/protocol-buffers/docs/reference/cpp/google.prot...
which means

- make this a class FieldDescriptor (not struct)
- make the num above an inner public enum of this class and call it "Type"
- use the same name and values of that one, e.g.:
  TYPE_DOUBLE =  1,
  TYPE_FLOAT = 2,
 etc. You just need the one that we support.

 - add a Type type() const {...} getter
- add a uint32_t number() getter;
- add a const char* name() getter (no need to use std::string)
- ditto for is_repeated()

[kraynov, 2016/08/31 17:43:33]

Done.

+  FieldReflection(const std::string& name,
+                  ProtoType type,
+                  uint32_t number,
+                  bool repeated) : name(name),
+                                   type(type),
+                                   number(number),
+                                   repeated(repeated) {
+  }
+
+  static FieldReflection CreateInvalid() {
+    return FieldReflection("<INVALID>", kProtoTypeInvalid, 0, false);
+  }
+  bool IsValid() const {
+    return type != kProtoTypeInvalid && number > 0 && name != "<INVALID>";
+  }
+
+  const std::string name;

[Primiano Tucci (use gerrit), 2016/08/31 09:04:07]

const char* const

[kraynov, 2016/08/31 17:43:33]

Done.

+  const ProtoType type;
+  const uint32_t number;
+  const bool repeated;
+};

[Primiano Tucci (use gerrit), 2016/08/31 09:04:07]

DISALLOW_COPY_AND_ASSIGN

[kraynov, 2016/08/31 17:43:33]

Done.

+
 // Maximum message size supported: 256 MiB (4 x 7-bit due to varint encoding).
 constexpr size_t kMessageLengthFieldSize = 4;
 constexpr size_t kMaxMessageLength = (1u << (kMessageLengthFieldSize * 7)) - 1;
 
 // Field tag is encoded as 32-bit varint (5 bytes at most).
 // Largest value of simple (not length-delimited) field is 64-bit varint
 // (10 bytes at most). 15 bytes buffer is enough to store a simple field.
 constexpr size_t kMaxTagEncodedSize = 5;
 constexpr size_t kMaxSimpleFieldEncodedSize = kMaxTagEncodedSize + 10;
 
@@ skipping 55 matching lines @@
 void StaticAssertSingleBytePreamble() {
   static_assert(field_id < 16,
                 "Proto field id too big to fit in a single byte preamble");
 };
 
 }  // namespace proto
 }  // namespace v2
 }  // namespace tracing
 
 #endif  // COMPONENTS_TRACING_CORE_PROTO_UTILS_H_