I'm trying to implement deserialization where the mapping to field/member is only known at runtime (its complicated). Anyway what I'm trying to do is something like the following:
Class A
{
public:
int a; // index 0
float b; // index 1
char c; // index 2
}
Then I have two arrays, one with the index of the field and the other with something that indicates the type. I then want to iterate over the arrays and write to the fields from a byte stream.
Sorry for the crappy description but I just don't know how to implement it in code. Any ideas would be appreciated thanks!
Yes you can, the there are two things you need to look out for when doing it though.
First of all make sure you start writing from (const char*)&A.a because all compilers append stuff that doesn't really concern you at the start of an object (visualc puts the vtable there for instance) and you won't be writing what you think you are if you start from the address of the object.
Second you might want to do a #pragma pack(1) before declaring any class that needs to be written to disk because the compilers usually align class members to make DMA transfers more efficient and you might end up having problems with this as well.
On the dynamic part of it, if making one class definition for each field combination you want to have is acceptable, then it's ok to do it like this, otherwise you'd be better off including a hash table in your class and serializing/deserializing its' contents by writing key-value pairs to the file