output in microsoft visual studio - winforms

Question

i'm making an app wich shows the output of a php page using libcurl
in terminal mode this app works great
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, "www.sglroostermail.nl/api/getChanges.php?y=1);
res = curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
}
but now i want to make a gui app.
For the GUI i use microsoft visual studio 2015 --> CLR empty project.
but the terminal code gives his own output
and i want to show the output in a textbox or a label.
for example: (this is the part of the MYForm.h
#pragma endregion
private: System::Void MyForm_Load(System::Object^ sender, System::EventArgs^ e) {
}
private: System::Void textBox1_TextChanged_1(System::Object^ sender, System::EventArgs^ e) {
}
private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e) {
String ^ klas = textBox1->Text;
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, "www.sglroostermail.nl/api/getChanges.php?y=", klas);
res = curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
}
}
can anyone tell me how to store the output of the first code in a variable, label or textbox?

Answer 1

You need to tell libcurl what to do with the output it receives from the remote server.
There are two options to use here:
CURLOPT_WRITEFUNCTION: This tells libcurl which function to call when it receives data.
CURLOPT_WRITEDATA: This is a void* that will be passed to the write function.
By default, these are set to fwrite and stdout, which is why libcurl writes the output to the terminal. (Note: The options are named 'write' because a common operation is to download the file and write it to disk. Think of it as what to do with the data after you receive it, don't think of it as 'reading' from the server.)
If you want to capture the data, here's what I would do:
Allocate a container of some sort: Have a byte buffer, and set CURLOPT_WRITEDATA to a pointer to that buffer.
Create a method to copy the data to the buffer, and set that as CURLOPT_WRITEFUNCTION.
Because libcurl is an unmanaged library, I'd use std::vector<uint8_t> as the buffer. The write callback must have the prototype size_t write_callback(char *ptr, size_t size, size_t nmemb, void *userdata);, and I think it's easier to deal with the unmanaged vector than it is to pin a managed buffer & deal with that properly.