Comment #5 on issue 469 by wuy...@gmail.com: how to write/read more than
one piece of message to/from a text file in c++
http://code.google.com/p/protobuf/issues/detail?id=469
Yes,it is just binary data chunk. When I open the file stored some protobuf
messages, it seems like that the SerializeToString method forms a c++
string with '\n' as the last character. And when debugging, the first
character of the serielized string is '\n' whose ASCII code is 0x0A.
if you try parse it in this way,it will work: head a character '\n' at the
buffer that receive the parsed binary data chunk gotten from readline.the
c++ example code is like:
string fPath("message.txt");
string strMsg;
char buf[1024] = {0};
fstream f;
f.open(fPath.c_str(),std::ios_base::in | std::ios_base::binary);
f.seekg(std::ios_base::beg);
while(!f.eof())
{
buf[0] = '\n';
f.getline(buf+1,sizeof(buf) - sizeof(char));
string strTmp(buf);
if(!strTmp.empty())
{
msg.ParseFromString(buf);
//msg.ParsePartialFromString(strTmp);
cout<<"name:\t\t"<<msg.name()<<std::endl;
cout<<"state:\t\t"<<static_cast<int>(msg.state())<<std::endl;
}
msg.Clear();
memset(buf,'\0',sizeof(buf));
}
At most of the time, it will work, yet there is a problem: when it failed
to parse, you can do nothing, reading source code, it's a much lot of work.
And I have come across this problem. In other words, the parsing method by
heading a character '\n' is unreliable or unstable.
Any one have other Feasible way to read/write messages from/to a file?
Thanks.
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