how to convert a char buffer to a struct in c++ ?

[RLeePlusPlus]

Hi there,

So i have a struct:

struct stinfo{
 
  char info1[19];
  char info2[5];
  char info3[2];

}struct_info;

and a char buffer:

                 
char buf[] = "info1datainfo2i3";

i want to cast buf to stInfo... What is the best (and safe) way to do this in C++??


thank you!

[laserlight]

After you have performed this operation, what will the contents of the stinfo object be?

[RLeePlusPlus]

i will use the first field to identify a tag and then according to the tag process the other fields. Its just a way to separate things to process.

[laserlight]

I would then write a constructor that accepts this buf argument, inspects the tags and populates the other members.

[RLeePlusPlus]

I see... The idea was cast and then evalue in the struct fields, using they sizes and etc... Its really not safe to do this?

[laserlight]

Since you are going to process the other fields according to the tag, I do not see a point in trying a cast.

[RLeePlusPlus]

i forgot to say that the stInfo will be inserted into a vector of stInfo's... So it have to be a stInfo. And when i say tags i mean ID's like "001" or "002". It will be easier to do if a just cast the buffer, but the way you said works too, process, identify, put on stInfo and the insert in the vector.

[laserlight]

i forgot to say that the stInfo will be inserted into a vector of stInfo's... So it have to be a stInfo.

Well, I did not say that you should not use stInfo objects.

And when i say tags i mean ID's like "001" or "002".

Yes, I understand.

It will be easier to do if a just cast the buffer, but the way you said works too, process, identify, put on stInfo and the insert in the vector.

I do not see what is so difficult about:

char buf[] = "info1datainfo2i3";
std::vector<stInfo> stInfoObjects;
stInfoObjects.push_back(stInfo(buf));
// Now stInfoObjects[0] has everything identified and processed.

Also, have you considered using std::string objects?

[RLeePlusPlus]

Thx for suggestions laserlight, i just have one more question...

if i make a constructor in the struct, it will affect the result of sizeof(struct)???

thank you!

[Elkvis]

sizeof(struct) should not be affected, as long as there are no virtual methods. a simple constructor should not have any effect on the in-memory size of the struct.

[manasij7479]

if i make a constructor in the struct, it will affect the result of sizeof(struct)???

Though not strictly relevant, if you are into binary I/O and/or serialization; do not rely on anything related sizeof, for anything non POD.