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// 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"
#include "components/tracing/tracing_export.h"
namespace tracing {
namespace v2 {
namespace proto {
// See https://developers.google.com/protocol-buffers/docs/encoding wire types.
enum FieldType : uint32_t {
kFieldTypeVarInt = 0,
kFieldTypeFixed64 = 1,
kFieldTypeLengthDelimited = 2,
kFieldTypeFixed32 = 5,
};
class ProtoFieldDescriptor {
public:
enum Type {
TYPE_INVALID = 0,
TYPE_DOUBLE = 1,
TYPE_FLOAT = 2,
TYPE_INT64 = 3,
TYPE_UINT64 = 4,
TYPE_INT32 = 5,
TYPE_FIXED64 = 6,
TYPE_FIXED32 = 7,
TYPE_BOOL = 8,
TYPE_STRING = 9,
TYPE_MESSAGE = 11,
// TYPE_GROUP = 10 is not supported.
TYPE_BYTES = 12,
TYPE_UINT32 = 13,
TYPE_ENUM = 14,
TYPE_SFIXED32 = 15,
TYPE_SFIXED64 = 16,
TYPE_SINT32 = 17,
TYPE_SINT64 = 18,
};
ProtoFieldDescriptor(const char* name,
Type type,
uint32_t number,
bool is_repeated)
: name_(name), type_(type), number_(number), is_repeated_(is_repeated) {
}
const char* name() const {
return name_;
}
Type type() const {
return type_;
}
uint32_t number() const {
return number_;
}
bool is_repeated() const {
return is_repeated_;
}
bool is_valid() const {
return type_ != Type::TYPE_INVALID;
}
private:
const char* const name_;
const Type type_;
const uint32_t number_;
const bool is_repeated_;
DISALLOW_COPY_AND_ASSIGN(ProtoFieldDescriptor);
};
// 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;
// Proto types: (int|uint|sint)(32|64), bool, enum.
constexpr uint32_t MakeTagVarInt(uint32_t field_id) {
return (field_id << 3) | kFieldTypeVarInt;
}
// Proto types: fixed64, sfixed64, fixed32, sfixed32, double, float.
template <typename T>
constexpr uint32_t MakeTagFixed(uint32_t field_id) {
static_assert(sizeof(T) == 8 || sizeof(T) == 4, "Value must be 4 or 8 bytes");
return (field_id << 3) |
(sizeof(T) == 8 ? kFieldTypeFixed64 : kFieldTypeFixed32);
}
// Proto types: string, bytes, embedded messages.
constexpr uint32_t MakeTagLengthDelimited(uint32_t field_id) {
return (field_id << 3) | kFieldTypeLengthDelimited;
}
// Proto tipes: sint64, sint32.
template <typename T>
inline typename std::make_unsigned<T>::type ZigZagEncode(T value) {
return (value << 1) ^ (value >> (sizeof(T) * 8 - 1));
}
template <typename T>
inline uint8_t* WriteVarInt(T value, uint8_t* target) {
// Avoid arithmetic (sign expanding) shifts.
typedef typename std::make_unsigned<T>::type unsigned_T;
unsigned_T unsigned_value = static_cast<unsigned_T>(value);
while (unsigned_value >= 0x80) {
*target++ = static_cast<uint8_t>(unsigned_value) | 0x80;
unsigned_value >>= 7;
}
*target = static_cast<uint8_t>(unsigned_value);
return target + 1;
}
// Writes a fixed-size redundant encoding of the given |value|. This is
// used to backfill fixed-size reservations for the length field using a
// non-canonical varint encoding (e.g. \x81\x80\x80\x00 instead of \x01).
// See https://github.com/google/protobuf/issues/1530.
// In particular, this is used for nested messages. The size of a nested message
// is not known until all its field have been written. |kMessageLengthFieldSize|
// bytes are reserved to encode the size field and backfilled at the end.
inline void WriteRedundantVarInt(uint32_t value, uint8_t* buf) {
for (size_t i = 0; i < kMessageLengthFieldSize; ++i) {
const uint8_t msb = (i < kMessageLengthFieldSize - 1) ? 0x80 : 0;
buf[i] = static_cast<uint8_t>(value) | msb;
value >>= 7;
}
DCHECK_EQ(0u, value) << "Message is too long";
}
template <uint32_t field_id>
void StaticAssertSingleBytePreamble() {
static_assert(field_id < 16,
"Proto field id too big to fit in a single byte preamble");
};
// Parses a VarInt from the encoded buffer [start, end). |end| is STL-style and
// points one byte past the end of buffer.
// The parsed int value is stored in the output arg |value|. Returns a pointer
// to the next unconsumed byte (so start < retval <= end).
TRACING_EXPORT const uint8_t* ParseVarInt(const uint8_t* start,
const uint8_t* end,
uint64_t* value);
// Parses a protobuf field and computes its id, type and value.
// Returns a pointer to the next unconsumed byte (|start| < retval <= end) that
// is either the beginning of the next field or the end of the parent message.
// In the case of a kFieldTypeLengthDelimited field, |field_intvalue| will store
// the length of the payload (either a string or a nested message). In this
// case, the start of the payload will be at (return value) - |field_intvalue|.
TRACING_EXPORT const uint8_t* ParseField(const uint8_t* start,
const uint8_t* end,
uint32_t* field_id,
FieldType* field_type,
uint64_t* field_intvalue);
} // namespace proto
} // namespace v2
} // namespace tracing
#endif // COMPONENTS_TRACING_CORE_PROTO_UTILS_H_
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