how to convert std::string to NSData and vice versa?

Question

I am using google protocol buffer to send and receive data in cocos2d-x multiplayer game via Google Play Games Services iOS sdk.

Protocol buffer converts data to std::string but GPGS iOS sdk sends data via NSData hence I have to convert from std::string to NSData and then back to std::string after receiving data.

I am currently using following method:

( std::string to NSData and NSData to std::string will be done in different functions at different times. Following code just summarise what I am doing overall)

//PlayerData is protocol buffer class
PlayerData data, temp;

std::string dataStr;
data.SerializeToString(&dataStr);

NSString* nsDataStr = [NSString stringWithCString:dataStr.c_str()
                        encoding:[NSString defaultCStringEncoding]];

NSData* nsData = [nsDataStr dataUsingEncoding:NSUTF8StringEncoding];

NSString* dataStr_2 = [[NSString alloc] initWithData:nsData
                        encoding:NSUTF8StringEncoding];

std::string foo = [dataStr_2 UTF8String];

temp.ParseFromString(foo);

Initial string ie dataStr after serializing

"\\r\\x95n\\x99D\\x158\\xddNDJ\\nUmar SaeedR\\x12p_CPH64oqq2K-TXxAB"

size: 42

Final string ie foo before parsing

"\\r\\xc3\\xafn\\xc3\\xb4D\\x158\\xe2\\x80\\xbaNDJ\\nUmar SaeedR\\x12p_CPH64oqq2K-TXxAB"

size: 46

the ParseFromString function of protocol buffer does not parse foo and returns false.

How to do string conversions so that string remains same?

Answer 1

I know this is old, but... Could you use protobufs ParseFromArray instead of ParseFromString?

IE

const void *bytes = [parseData bytes];
int byteLen = (int)[parseData length];

protobufMessage.ParseFromArray(bytes, byteLen);

Just a thought.

Answer 2

Try this:

std::string str = "123";
NSData *data = [NSData dataWithBytes:str.data() length:str.length()];