C and C++

dasyad · 2 Sep 2011 at 08:43

Trying to teach myself C++ and running into a few questions so I thought maybe some of you guys could help me out here

I come from a C# background so some of the syntax is rather familiar(obviously), in fact I think the biggest learning curve is learning what libraries I need to include for the purposes I need!

Anyway my question is, can I use a C header file in C++? More specifically could I simply include http://developer.spotify.com/en/libspotify/overview/ in a C++ project and it would just simply "work"? Or do I need some sort of wrapper for it?

mistercrabb · 2 Sep 2011 at 08:51

It should work fine IIRC..

animatronic · 2 Sep 2011 at 15:05

Differences in name mangeling will mean you will have to use extern "C" see http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html. Also when using third party libraries you will need get the right version for your compiler/linker.

Emphacy · 2 Sep 2011 at 16:02

Ideally it should work fine. Since C++ runs off the .NET framework all the libraries you will ever need should be included.
This could be somewhat different however if you're writing for linux.

dasyad · 2 Sep 2011 at 17:40

Thanks for the answers guys much appreciated

[EDIT]Will be using non-CLR C++ so things should get "fun"

azteched · 3 Sep 2011 at 18:55

Emphacy said:
Since C++ runs off the .NET framework all the libraries you will ever need should be included.

Only C++/CLI or whatever it's called. Otherwise it doesn't.

dasyad · 4 Sep 2011 at 10:29

Had some problems getting this to work in C++, but I put it down to my inexperience

So I tried getting it working in C thinking it would all slot together a bit smoother, however I now get compilation issues to do with things within their library.

This is harder than I thought it was going to be

Haydz · 5 Sep 2011 at 11:37

I only started using/learning c++ about a year and a half ago, coming from a 4 year C# background, so I kinda know the situation your in.

I would be happy to help if I can

dasyad · 5 Sep 2011 at 12:34

Haydz said:
I only started using/learning c++ about a year and a half ago, coming from a 4 year C# background, so I kinda know the situation your in.

I would be happy to help if I can

Really appreciate the offer thanks

When I get home I'll post the code I've got so far, I think the main issue I have is with the function pointers. I believe they are the equivalent of delegates and events in .NET. The issue appears to be that they are not "firing" or at least If they are I cannot seem to get them to hit break points.

Anyway I think it will be all clearer once I post some code up tonight

dasyad · 7 Sep 2011 at 18:08

Better late than never

and I'm still stumped.

Code:

#include <cstring>
extern "C" {
	#include <libspotify/api.h>
}
#include <stdint.h>
#include <iostream>
using namespace std;

const uint8_t g_appkey [] = {
/*api key*/
	};

const size_t g_appkey_size = sizeof(g_appkey);

static sp_session *session;

static void (SP_CALLCONV logged_in)(sp_session *session, sp_error error)
{
	if(error != SP_ERROR_OK)
	{
		cout << "Error on log in\r\n";
	}
	else
	{
		cout << "Logged in\r\n";
	}
}
static void (SP_CALLCONV logged_out)(sp_session* session)
{

}
static void (SP_CALLCONV connection_error)(sp_session *session, sp_error error)
{

}
static void (SP_CALLCONV notify_main_thread)(sp_session *sess)
{

}

static sp_session_callbacks sessionCallbacks = {
	&logged_in,
	&logged_out,
    NULL,
    &connection_error,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL
};
static sp_session_config sessionConfig = {
		SPOTIFY_API_VERSION,
		"/tmp",
		"/tmp",
		g_appkey,
		g_appkey_size,
		"Test Client",
		&sessionCallbacks,
		NULL,
		TRUE,
		FALSE,
		TRUE
};

int main() {
	cout << "Hello World";
	sp_error err;

	err = sp_session_create(&sessionConfig, &session);

	if(err != SP_ERROR_OK )
	{
		return -1;
	}
	else
	{
		sp_session_login(session, /*username*/, /*password*/, 1);

		sp_session_logout(session);
	}
	string str;

	cin >> str;
	return 0;
}

Now if I put a break point on:

Code:

static void (SP_CALLCONV logged_in)(sp_session *session, sp_error error)

It never hits the break point which leads to me believe that it isn't hitting that block for whatever reason.

animatronic · 8 Sep 2011 at 23:57

With out knowing anything about the api, my guess would be that sp_session_login doesn't block so you have to wait for the login process to complete.

e.g.

Code:

bool gbLoginError = false;
volatile bool gbLoginCompleted = false; 

static void (SP_CALLCONV logged_in)(sp_session *session, sp_error error)
{
        gbLoginError  = error != SP_ERROR_OK;
	gbLoginCompleted = true;
}

int main() 
{
...
	{
		sp_session_login(session, /*username*/, /*password*/, 1);

                while(!gbLoginCompleted)
                {
                         Sleep(0);
                }

                if(gbLoginError)
	        {
		        cout << "Error on log in\r\n";
	        }
	        else
	        {
		        cout << "Logged in\r\n";
	        }

		sp_session_logout(session);
	}
...
}

(completly untested)

dasyad · 9 Sep 2011 at 07:44

Thanks for the tip I'll give it a whirl!

Doing some more reading and the library isn't thread safe in parts, which I had not realised. I need to pay more attention

So the way I seemingly hook up to the function pointers is fine?