Combining Bitwise Operators and Enums

$\newcommand{\N}{\mathbb N} \newcommand{\Z}{\mathbb Z} \newcommand{\Q}{\mathbb Q} \newcommand{\R}{\mathbb R} \newcommand{\lt}{<} \newcommand{\gt}{>} \newcommand{\amp}{&} \definecolor{fillinmathshade}{gray}{0.9} \newcommand{\fillinmath}[1]{\mathchoice{\colorbox{fillinmathshade}{$\displaystyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\textstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptscriptstyle\phantom{\,#1\,}$}}} $

Section 32.3 Combining Bitwise Operators and Enums

Bitwise operators and enums pair especially well together when each enum constant represents a single bit— a technique often used to represent a set of independent on/off options (called flags) packed into a single integer. For example:

admin.....open in new window

Since READ, WRITE, and EXECUTE each occupy a different bit position ($0001\text{,}$ $0010\text{,}$ $0100$), we can combine several permissions into one integer using bitwise OR (|), and later test whether a specific permission is set using bitwise AND (&)— all without needing a separate variable for each flag.

Prev Top Next