Issue with circular shift BITMASK - iphone

Question

i'm having one enum
typedef NS_ENUM(NSInteger, Node) {
NodeTop ,
NodeLeft ,
NodeBottom ,
NodeRight ,
} ;
and property as,
#property Node node;
now in my controller i'm assigning node multiple values using pipeline,
node =top | left | bottom | right ;
(Q-1 does node have 0000,0011 kind of values using NodeTop,Left OR simply final result of ORing of top|left|bottom|right?)
this way NSLog("%d",node); giving result 1.
now if node contains 0001 , i want to left shift it by 1 so i tried
node<<1;
which changes node value 1 to 2 but is it does not seem really changing 0001 to 0010?
in short i want node to have value like 0001,
and later on i want to shift its value like,
0010
0100
1000
0001
0010
...
Any help? let me know if question is not clear!

Answer 1

You can use NS_OPTIONS to create a bit mask where each value is defined as 1<<n. This NSHipster post explain the usage of both NS_ENUM and NS_OPTIONS.
typedef NS_OPTIONS(NSInteger, Node) {
NodeTop = 1 << 0, // 1
NodeLeft = 1 << 1, // 2
NodeBottom = 1 << 2, // 4
NodeRight = 1 << 3 // 8
};
That way when you write
NodeTop | NodeBottom
it will be the same as
...0001 | ...0100 = ....0101
And shifting the bit will move it to the next option
Node node = NodeBottom<<1; // = NodeRight
since ...0100 << ...1000.

Answer 2

which changes node value 1 to 2 but is it does not seem really changing 0001 to 0010?
It does. 0010 binary is 2 decimal.

Answer 3

You can only bitwise OR these values together in a meaningful way if you make each value correspond to a different bit, e.g.
typedef NS_ENUM(NSInteger, Node) {
NodeTop = 1,
NodeLeft = 2,
NodeBottom = 4,
NodeRight = 8
};
node = NodeTop; // 0b0001 = 0x01 = 1
node <<= 1; // 0b0010 = 0x02 = 2 = NodeLeft
node <<= 1; // 0b0100 = 0x04 = 4 = NodeBottom

Answer 4

Well as for the circular bit shifting, I think the best you can do is something like this (quickly thrown together C code)
enum test {
test1 = 1,
test2 = 2,
test4 = 4,
test8 = 8
};
static enum test val(enum test input) {
while(input >= 16) //Or whatever max bit you want
input = input >> 4; //Be sure to shift by the appropriate number
return input;
}
Then when you run this code:
enum test foo = test1;
foo = val(foo << 5);
foo will be test2