How can I pack and access multiple uint8 values into one bigger uint?

Question

I currently have a situation where I have variables like this:

uint8 _variable1 = 4;
uint8 _variable2 = 2;
uint8 _variable3 = 99;
uint8 _variable4 = 1;
uint8 _variable5 = 0;
uint8 _variable6 = 2;
uint8 _variable7 = 1;
uint8 _variable8 = 34;

When I have to pass or return these values (since Solidity doesn't report Structs as parameters or return values) I keep running into this issue:

CompilerError: Stack too deep, try removing local variables.

The usage of the function to retrieve these values looks like this:

uint8 _variable1;
uint8 _variable2;
uint8 _variable3;
uint8 _variable4;
uint8 _variable5;
uint8 _variable6;
uint8 _variable7;
uint8 _variable8;

(_variable1, _variable2, _variable3, _variable4, _variable5, _variable6) = dataContract.getData(_id);

What I would like to do instead is store a single variable such as uint64 data = 0402990100020134

How would I correctly define that in solidity?

If I wanted to get the value of variable 6, how would I do that?

Answer 1

You can use bit shift operators to pack data from smaller integers to bigger integers.

E.g.

uint8 a = 1, b = 2;
uint16 foo = (b << 16) | a;