Requesting JSON data through WinInet duplicates some parts of data - c++

Question

I have some API URL that returns JSON data like this:
{"data":[{"id":"1","param":"value1"},{"id":"2","param":"value2"}, ... {"id":"N","param":"valueN"}]}
Every id should be unique.
When i'm requesting this API URL through browser (Firefox or Chrome) it returns valid data, i.e. every id is unique and non of the parts of data is duplicated.
But when i'm requesting this API URL through my own function based on WinInet it duplicates some parts of data. It still is valid JSON, but some of id's are duplicated and some of them not. Just like this:
{"data":[{"id":"1","param":"value1"},{"id":"1","param":"value1"},{"id":"2","param":"value2"},{"id":"3","param":"value3"},{"id":"3","param":"value3"} ... {"id":"N","param":"valueN"}]}
I'm using GET method. Here is my WinInet function:
using namespace std;
enum EMethod {M_UNKNOWN, M_POST, M_GET, M_DELETE};
enum EProtocol {P_UNKNOWN, P_HTTP, P_HTTPS};
// |example:|
/*
string responce = SendInetRequest(
P_HTTPS, M_GET, "www.site.com", "page.php", "param1=val1&param2=val2");
*/
string SendInetRequest(const EProtocol _eProtocol,
const EMethod _eMethod,
const string& _server,
const string& _page,
const string& _params = "")
{
char szData[1024];
string recvStr;
// initialize WinInet
HINTERNET hInternet = ::InternetOpenA("WinInet Test",
INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
if (hInternet != NULL)
{
INTERNET_PORT port = NULL;
DWORD flags = NULL;
switch (_eProtocol)
{
case P_HTTP:
port = INTERNET_DEFAULT_HTTP_PORT;
flags = /*INTERNET_FLAG_KEEP_CONNECTION*/
INTERNET_FLAG_NO_CACHE_WRITE | INTERNET_FLAG_PRAGMA_NOCACHE;
break;
case P_HTTPS:
port = INTERNET_DEFAULT_HTTPS_PORT;
flags = INTERNET_FLAG_SECURE |
INTERNET_FLAG_NO_CACHE_WRITE | INTERNET_FLAG_PRAGMA_NOCACHE;
break;
default:
return NULL;
}
// open HTTP session
HINTERNET hConnect = ::InternetConnectA(hInternet,
_server.c_str(), port, NULL,NULL, INTERNET_SERVICE_HTTP, 0, 1);
if (hConnect != NULL)
{
string request;
string method;
string headers;
string data;
switch (_eMethod)
{
case M_GET:
method = "GET";
request = _page +
(_params.empty() ? "" : ("?" + _params));
break;
case M_POST:
method = "POST";
request = _page;
headers = "Content-Type: application/x-www-form-urlencoded";
data = _params.empty() ? "" : _params;
break;
case M_DELETE:
method = "DELETE";
request = _page +
(_params.empty() ? "" : ("?" + _params));
break;
default:
return NULL;
}
// open request
HINTERNET hRequest = ::HttpOpenRequestA(hConnect, method.c_str(),
(LPCSTR)request.c_str() ,NULL, NULL, 0, flags, 1);
if (hRequest != NULL)
{
// send request
BOOL isSend = ::HttpSendRequestA(hRequest, headers.c_str(),
headers.length(), (LPVOID)data.c_str(), data.length());
if (isSend)
{
for(;;)
{
// reading data
DWORD dwByteRead;
BOOL isRead = ::InternetReadFile(hRequest,
szData, sizeof(szData) - 1, &dwByteRead);
// break cycle if error or end
if (isRead == FALSE || dwByteRead == 0)
break;
// saving result
recvStr.append(szData, dwByteRead);
szData[dwByteRead] = 0;
}
}
// close request
::InternetCloseHandle(hRequest);
}
// close session
::InternetCloseHandle(hConnect);
}
// close WinInet
::InternetCloseHandle(hInternet);
}
return recvStr;
}
So what is wrong with my function? Why does it duplicate some parts of responce JSON data unlike normal browsers?

Answer 1

You need to add the null terminator byte to szData before you append it to recvStr, so that you only append the data that was just received.
// saving result
szData[dwByteRead] = 0;
recvStr.append(szData, dwByteRead);