WinINet trouble downloading file to client? - c++

Question

I'm curious why I'm having trouble with this function. I'm downloading a PNG file on the web to a destination path. For example, downloading the Google image to the C: drive:
netDownloadData("http://www.google.com/intl/en_ALL/images/srpr/logo1w.png", "c:\file.png");
The file size is correct after downloading. Nothing returning false. When I try opening it it won't show the image. Any ideas are helpful. Thanks!
Here's the code:
bool netDownloadData(const char *strSourceUrl, const char *strDestPath)
{
HINTERNET hINet = NULL;
HINTERNET hFile = NULL;
char buffer[1024];
DWORD dwRead;
String sTemp;
FILE *fp = NULL;
DWORD size = 0;
// Open a new internet session
hINet = netInit();
if (hINet == NULL) {
sprintf(buffer, "Initializing WinINet failed.", strSourceUrl);
utilLog(buffer);
netCloseHandle(hINet);
return false;
}
// Open the requested url.
hFile = netOpenUrl(hINet, strSourceUrl);
if (hFile == NULL) {
sprintf(buffer, "URL failed upon loading: %s\n", strSourceUrl);
utilLog(buffer);
netCloseHandle(hINet);
return false;
}
// Read file.
while (InternetReadFile(hFile, buffer, 1023, &dwRead))
{
if (dwRead == 0)
break;
buffer[dwRead] = 0;
sTemp += buffer;
size += dwRead;
}
// Load information to file.
fp = fopen(strDestPath, "wb");
if (fp == NULL)
return false;
fwrite(sTemp, size, 1, fp);
fclose(fp);
InternetCloseHandle(hFile);
InternetCloseHandle(hINet);
return true;
}

Answer 1

What data type is String? Avoid storing binary data in strings because NULLs in the data can potentially cause problems. Just write the buffer as and when you read it:
// Load information to file.
fp = fopen(strDestPath, "wb");
if (fp == NULL)
return false;
// Read file.
while (InternetReadFile(hFile, buffer, 1024, &dwRead))
{
if (dwRead == 0)
break;
fwrite(buffer, dwRead, 1, fp);
}
fclose(fp);

Answer 2

It looks like your second and third args to fwrite are transposed. See fwrite docs for explanation.
try:
fwrite(sTemp, 1, size, fp);