C++ 如何使用 Google Protocol Buffers 序列化为 char*？
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How to serialize to char* using Google Protocol Buffers?
提问by Eamorr
I want to serialize my protocol buffer to a char*. Is this possible? I know one can serialize to file as per:
我想将我的协议缓冲区序列化为 char*。这可能吗？我知道可以按以下方式序列化到文件：
fstream output("/home/eamorr/test.bin", ios::out | ios::trunc | ios::binary);
if (!address_book.SerializeToOstream(&output)) {
cerr << "Failed to write address book." << endl;
return -1;
}
But I'd like to serialize to a C-style char* for transmission across a network.
但我想序列化为 C 风格的 char* 以通过网络传输。
How to do this? Please bear in mind that I'm very new to C++.
这该怎么做？请记住，我对 C++ 很陌生。
回答by Evgen Bodunov
That's easy:
这很容易：
size_t size = address_book.ByteSizeLong();
void *buffer = malloc(size);
address_book.SerializeToArray(buffer, size);
Check documentation of MessageLite classalso, it's parent class of Message and it contains useful methods.
检查MessageLite 类的文档，它是 Message 的父类，它包含有用的方法。
回答by Fox32
You can serailze the output to a ostringstreamand use stream.str()to get the string and then access the c-string with string.c_str().
您可以将输出序列化为 aostringstream并用于stream.str()获取字符串，然后使用string.c_str().
std::ostringstream stream;
address_book.SerializeToOstream(&stream);
string text = stream.str();
char* ctext = text.c_str();
Don't forget to include sstreamfor std::ostringstream.
不要忘记包含sstreamfor std::ostringstream。
回答by David Schwartz
You can use ByteSizeLong()to get the number of bytes the message will occupy and then SerializeToArray()to populate an array with the encoded message.
您可以使用ByteSizeLong()来获取消息将占用的字节数，然后SerializeToArray()使用编码的消息填充数组。
回答by Hemaolle
Solution with a smart pointer for the array:
使用数组智能指针的解决方案：
size_t size = address_book.ByteSizeLong();
std::unique_ptr<char[]> serialized(new char[size]);
address_book.SerializeToArray(&serialized[0], static_cast<int>(size));
回答by GhislainS
Still one more line of code to take care of the fact that the serialized data can contain zero's.
还有一行代码来处理序列化数据可以包含零的事实。
std::ostringstream stream;
address_book.SerializeToOstream(&stream);
string text = stream.str();
char* ctext = text.c_str(); // ptr to serialized data buffer
// strlen(ctext) would wrongly stop at the 1st 0 it encounters.
int data_len = text.size(); // length of serialized data
