InternetReadFile返回末尾带有额外字符的文本

时间:2016-09-13 12:11:06

标签: c++ c ftp wininet

HINTERNET hInternet, hFtpSession, hFile;

    hInternet = InternetOpen(NULL, INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0);
    hFtpSession = InternetConnect(hInternet, FTPHOST, INTERNET_DEFAULT_FTP_PORT,
        FTPUSER, FTPPASS, INTERNET_SERVICE_FTP, INTERNET_FLAG_PASSIVE, 0);
    hFile = FtpOpenFile(hFtpSession, argv[1], GENERIC_READ, FTP_TRANSFER_TYPE_ASCII, 0);

    DWORD rSize;
    char tmp[2048];
    string buffer;

    while(InternetReadFile(hFile, tmp, 2048, &rSize) && rSize > 0)
    {
        buffer += (string)tmp;
    }

    cout << buffer;

    InternetCloseHandle(hFile);
    InternetCloseHandle(hFtpSession);
    InternetCloseHandle(hInternet);

我有这个小程序从FTP服务器读取文本文件到字符串,但在读取字符串的末尾有一些额外的字符。我想问题是文字的大小,但我无法弄明白。

例如,我想下载一个加密的文本,它会像这样被破坏

MIICIDANBgkqhkiG9w0BAQEFAAOCAg0AMIICCAKCAgEAp2q+92EQPncY0sN6SMTC0yh05GpZ
FUEGATvUx/zcUrzdDTva5JKz0MztuCn3lnHmaUB6L97w8fuVOhJjj90ItH4FdUk4R9m50son
DSZ4ad5ZKi7WE7GApIq21vgM0zoG5sr0Xb6X41IQgvYF7i9nX4zKO2znRyD3uzBqkqkhWzbS
HI2euCdhmXfx2az0ynNKrcnQINaWowipc0LrW0Q9PWI1McCs4V5sz8GkBMpKENb3m/LBlSqz
TboC/9hiD9Yfclvk3wFeNGvsnUUDpwZipF9cBMVzmfyjA1gBDNLV8qcTXSortHaGeHdLpqIg
Qn3SpDol8gPRis7A7Hy4KjRS8Y/iZa8Nv9EmEeful6u3IHY0Qror/wOeST5WhaTynVBT0wgP
6GSMWsofwA3NttsFCw55z5c8GBEGP6Uo+jP/rdiYvednT0iV8Grp+XJ6zMFqYlVcLqAzQWLw
dfqve/lr8+OKfR9WvG6hvrVduTnoy+LBFF/QEVxAlZqymlXMm/hcO/TUoE1Kmon6FwID4Mek
nV1eb1aCmUIzxFHtPkMO0KFitmxa5EGwAFHRAjXrp2lUHIQSaWwVnsfoQgmrG9ux2I27w+WR
8kFdkqWrutFz2xn6ovVwla7Oj0iL2f9azNO2Z2KT/sBPwGmI67M9Ceih0YLD0w7Woy32H2aM
mIeK368CARE=
8

8最后不应该在那里。

2 个答案:

答案 0 :(得分:4)

函数InternetReadFile不会使null终止缓冲区,因此数组tmp的内容不是字符串,而是将其视为字符串。

行为未定义。

删除此行:

buffer += (string)tmp;

而是使用字符串函数append的重载,它接受一个数组及其大小:

buffer.append( tmp , rSize );

答案 1 :(得分:2)

2501表示你没有考虑到NULL终止符,所以你想做的就是这样的

DWORD rSize;
char tmp[2048+1];
string buffer;

while(InternetReadFile(hFile, tmp, 2048, &rSize) && rSize > 0)
{
    tmp[rSize] = '\0';
    buffer += (string)tmp;
}