2 N-Power rounding method in Concurrenthashmap

Recently see the source code of the Concurrenthashmap class in the JDK, which has a function:

/*** Returns a power of both table size for the given desired capacity. * See Hackers Delight, SEC 3.2*  /private static final int tablesizefor (int c) { int n = c-1; n |= N >>> ; 1 n|= n >>> 2 n|= n >>> 4 n|= n >>> 8 n|= n >>>
                   
                    return (n < 0)? 1: (n >= maximum_capacity)? Maximum_capacity:n + 1
                    ;} 
                                

I can't see what this is, but then I looked at the book "Hackers Delight" (the Mystery of the efficient program), only to know that this function is used to calculate the n power of C rounded up to 2. The functions in the book are as follows:

"Hackers delight" has been added to the book list.

Http://www.cnblogs.com/katsura/p/4134737.html

2 N-Power rounding method in Concurrenthashmap (RPM)