storing char[], int16, int32 in double array

[AutoC]

Hi,

Here's my scenario. I am given records and the datastructure of each column in the records at runtime. A sample looks like this,

char[] | int16 | int32 | double
abcd   | 2     | 96    | 1024 
ghi    | 3     | 104   | 2048

I cannot predefine a structure because I dont know what data types I am gonna be given.How can I store the records? I was thinking of declaring a multidimensional double array and typecasting all the records and then casting back whenever necessary. Does this seem sensible? Is there a better solution?

[NicAx64]

Well that's where union's are there.

Read a chapter on a C++ book about unions.

http://www.codeguru.com/cpp/tic/tic0085.shtml

[AutoC]

I dont understand. How do unions help?

[NicAx64]

for a example here , you declare a union like this.

union DataStructure
{
  char mCharPtr[20];
  short mInt16;
  int   mInt32;
  double mDouble;
};

and the size of the DataStructure is just 20. not 20+2+4+8 =40.

and if you still can't understand just go and do a exercises on this
page.
http://www.yolinux.com/TUTORIALS/LinuxTutorialC++Structures.html
you will understand why so.And still not understood just ask.

[NicAx64]

read this page too:
http://www.cplusplus.com/doc/tutorial/other_data_types/

[mrnutty]

look into boost::any

>>I cannot predefine a structure because I dont know what data types I am gonna be given

Why not? Well do you at least know if its a string or a number?

This seems like a ridiculous task. What about taking the input, and sorting it into different vectors depending on what column it's in? You could probably catch all possibilities with a std::string vector, a double vector, and a int64 vector. Route all strings to the string vector, all floats and double to the double vector, and every size of integer to the int64 vector.