Checking if AmfItemPtr isn't Null

[adammankowski1]

Hello, i'm writing to ask if construction:

if(amf::AmfItemPtr != amf::AmfNull())

Is right? I have to verify if AmfItemPtr is not null before doing something with it.

[Ventero]

No, amf::AmfNull() is an instance of the AMF null type. To check if an amf::AmfItemPtr is null, use something like if (item_ptr.get() != nullptr).

However, you shouldn't really be using AmfItemPtr other than handling the return value of calls to Deserializer::deserialize, which guarantees to always return a non-null AmfItemPtr. What exactly is the use-case you have where a null-check for the itemptr is required?

[adammankowski1]

I'm working with Qt, i see that i'm not working with your latest version of amf-cpp. First I'm working on received amf packet (read version, header count, message count etc), then i'm looking for Content (there is always another "body" array which i have to check if is null or not).

vstd::map<std::string, amf::AmfItemPtr> *data
amf::AmfItemPtr body_ptr = data->find("body")->second;
amf::AmfArray body_array;
 if(body_ptr != amf::AmfNull())
     body_array = body_ptr.as<amf::AmfArray>();
else
     throw 0;

[Ventero]

So if I understand you correctly, you're manually deserializing a AmfPacket? If that's the case, I've added deserialization support for it to amf-cpp yesterday, maybe see if you can use that instead. Note that since AmfPacket is not an AMF object type (as e.g. AmfNull and AmfArray are), you can't use Deserializer::deserialize to deserialize it.

Instead, you'll have to use something like the following:

// assuming this contains your data, v8 is a typedef for std::vector<unsigned char>
// the first to bytes in this vector should be the packet version, i.e. 0x00, 0x03
amf::v8 data; 
auto it = data.begin();
amf::DeserializationContext ctx;
amf::AmfPacket deserialized = amf::AmfPacket::deserialize(it, data.end(), ctx);

Afterwards, the range [it, data.end()) contains any remaining unparsed data (i.e., it points to the first unparsed byte after the AmfPacket). deserialized is the deserialized AmfPacket, which allows you to access the corresponding headers and messages through the .headers and .messages members (vectors of amf::AmfHeader and amf::AmfMessage, respectively). See src/amfpacket.hpp for more details.

But to answer the original question: in general, you would have to use if (body_ptr.get() != nullptr) to check if the body_ptr is null or not.