Bitwise flag issue

Question

I have a series of bit flags that order something like {none=0x00, puppies=0x01, kittens=0x02, cute=0x04, funny=0x08, scary=0x10} and so forth.

Whenever a user does a search, I just |= each of the flags that they wish, e.g. if a user wants something of cute kittens, I would just search |= cute and search |= kittens.

Yet, when I carry out the search operation, by looping through and checking all my items where that item's (flag & search) != 0, it instead returns items that have cute attributes OR kittens. How can I change this so it returns cute attributes AND kittens?

score 4 · Accepted Answer · answered Jun 23 '11 at 17:21

4

You've masked out irrelevant flags with your (flag & search) expression. Now you just have to ensure that all requested flags are present. So, instead of doing (flag & search) != 0, do (flag & search) == search.

answered Jun 23 '11 at 17:21

John Bartholomew

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Thanks a bunch! That made some sense now! – Jun 23 '11 at 17:23

score 1 · Answer 2 · answered Jun 23 '11 at 17:21

1

if((flags&cute) && (flags&kittens))

answered Jun 23 '11 at 17:21

Hernán Eche

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score 1 · Answer 3 · answered Jun 23 '11 at 17:22

1

Instead of looping and checking each flag one at a time, check the search against all the flags combined:

((flag1 | flag2 | flag3) & search) == search

answered Jun 23 '11 at 17:22

ean5533

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Bitwise flag issue

3 Answers3