How to implement a bitset in C?

Question

I have been using the Bitset class in Java and I would like to do something similar in C. I suppose I would have to do it manually as most stuff in C. What would be an effic

Answer 1

You can give my PackedArray code a try with a bitsPerItem of 1.

It implements a random access container where items are packed at the bit-level. In other words, it acts as if you were able to manipulate a e.g. uint9_t or uint17_t array:

PackedArray principle:
  . compact storage of <= 32 bits items
  . items are tightly packed into a buffer of uint32_t integers

PackedArray requirements:
  . you must know in advance how many bits are needed to hold a single item
  . you must know in advance how many items you want to store
  . when packing, behavior is undefined if items have more than bitsPerItem bits

PackedArray general in memory representation:
  |-------------------------------------------------- - - -
  |       b0       |       b1       |       b2       |
  |-------------------------------------------------- - - -
  | i0 | i1 | i2 | i3 | i4 | i5 | i6 | i7 | i8 | i9 |
  |-------------------------------------------------- - - -

  . items are tightly packed together
  . several items end up inside the same buffer cell, e.g. i0, i1, i2
  . some items span two buffer cells, e.g. i3, i6