protobuf

protobuf定义了一种数据交换格式，具有性能高，有代码生成机制，兼容性好等优点，广泛应用在游戏开发领域，常常用它来定义客户端与服务器之间的通信协议。

常用接口:

序列化与反序列化相关:

bool SerializeToArray(void* data, int size) const;

bool ParseFromArray(const void* data, int size);

 

bool SerializeToString(string* output) const;

bool ParseFromString(const string& data);

 

bool SerializeToFileDescriptor(int file_descriptor) const;

bool ParseFromFileDescriptor(int file_descriptor);

 

bool SerializeToOstream(ostream* output) const;

bool ParseFromIstream(istream* input);

 

 

size相关:

message test_proto {

    optional uint32 test = 1;

    repeated uint32 test2 = 2;

}

test_proto msg;

msg.set_test(2);

for (int i = 1; i < 10; ++i)  {

    msg.add_test2(i);

}

(1)msg.test2_size()

test2字段的大小

(2)msg.ByteSize()

msg消息的大小

(3)msg.GetCachedSize();

string buf;

int size = address_book.ByteSize();

void *buffer = malloc(size);

msg.SerializeToString(&buf); 或者msg.SerializeToArray(buffer, size);

这个时候使用msg.GetCachedSize();可以获取msg消息的大小，与(2)求出来的大小一样。

 

设置与获取数据相关:

message test_proto2 {

    optional uint32 test = 1;

    repeated uint32 test2 = 2;

    optional test_proto test3 = 3;

    repeated test_proto test4 = 4; 

}

test_proto2 msg2;

1. 被optional关键字修饰

(1) 系统类型

设置:

msg2.set_test(2);

获取:

uint32_t tmp = msg2.test();

(2) 自定义类型

设置:

auto tmp = msg2.mutable_test3();

tmp->set_test(3);

获取:

auto &it  = msg2.test3();

uint32_t tmp = it.test();

 

2. 被repeated关键字修饰

(1) 系统类型

设置:

for (int i = 1; i < 10; i+) {

    msg2.add_test2(2);

}

获取:

for (auto &it : msg2.test2()) {

    tmp_vec.push_back(it);

}

(2) 自定义类型

设置:

auto tmp = msg2.add_test4();

tmp->set_test(2);

获取:

for (int i = 0; i < msg2.test4_size(); ++i) {

    auto &tmp = msg2.test4(i);

    uint32_t value = tmp.test();

}

或者:

for (auto &it : msg2.test4()) {

    uint32_t tmp = it.test();

}

 

 

参考资料:

https://blog.youkuaiyun.com/tennysonsky/article/details/73920767

https://cloud.tencent.com/developer/article/1504465

https://blog.youkuaiyun.com/sealyao/article/details/6940245

https://blog.youkuaiyun.com/tennysonsky/article/details/73810180

https://blog.youkuaiyun.com/benny5609/article/details/7592301

https://blog.youkuaiyun.com/linxinfa/article/details/90515593