snprintf format string encountered std :: string containing \ problem 0

When transmitting data with the signature, using snprintf formatted data, where the signature data is sometimes found to have missed

as follows:

char AuthBidirection[320] = { '\0' };
snprintf(AuthBidirection, 320, "Bidirection algorithm=\"%s\",random1=\"%s\",random2=\"%s\",deviceid=\"%s\",serverid=\"%s\",sign1=\"%s\"

", strAlgorithm.c_str(), m_strRandom1.c_str(), strRandom2.c_str(), m_strGbID.c_str(), m_strGbServerID.c_str(), sign1.c_str());

Read:

char AuthBidirection[320] = { '\0' };
snprintf(AuthBidirection, 320, "Bidirection algorithm=\"%s\",random1=\"%s\",random2=\"%s\",deviceid=\"%s\",serverid=\"%s\",sign1=\"",
strAlgorithm.c_str(), m_strRandom1.c_str(), strRandom2.c_str(), m_strGbID.c_str(), m_strGbServerID.c_str());
//added sign1
memcpy(AuthBidirection + strlen(AuthBidirection), sign1.c_str(), sign1.size());
//added " end
strcat(AuthBidirection,"\"");

Alternative use memcpy

The reason: After the signed data, type std :: sign into the string of data may encounter character \ 0,

Then, then, then. . . , Sign1.c_str () returns the starting address of a character array, which put into sprintf naturally when the \ 0 is over, the back of the data is directly missing. . . . . .

Carry out alone to test:

    char *buf = new char[5];
    memcpy(buf,(void *)"abc\0d", 5);
    string strSig;
    strSig.assign(buf, 5);
    int len = strSig.size();
    std::cout << strSig.size() << std::endl;     //5
    std::cout << strSig[4] << std::endl;         //d

    char AuthBidirection[320] = { '\0' };
    the snprintf (AuthBidirection, 320. , " strSig =% S " , strSig.c_str ());
     STD :: COUT << AuthBidirection [ . 11 ] << STD :: endl; // print null characters, because no go into, both behind It is empty

    char AuthBidirection1[320] = { '\0' };
    snprintf(AuthBidirection1, 320, "strSig=%s", "");
    memcpy(AuthBidirection1 + strlen(AuthBidirection1), strSig.c_str(),len);
    std::cout << AuthBidirection1[11] << std::endl; //d

Output:

5
d'

The final went into a d, a no

Thus, when using string data processing, the size of the size needs special attention, in particular, relates to a network when the contract, pay special attention to the use of strSig.c_str () to process, strSig.c_str () is only a start address,

Thus encountered string manipulation functions, such as snprintf, etc., are to \ numerals 0 to end processing, it is necessary to carefully again. It had also experienced similar, so in order to quickly identify problems and record it. . . .

snprintf format string encountered std :: string containing \ problem 0

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