Exceptional C++ Style 40 New Engineering Puzzles, Programming Problems, and Solutions

Chapter 27. Data Formats and Efficiency, Part 2: (Even Less) Bit-Twiddling

Difficulty: 8

Time to consider even more highly compact and memory-efficient data formats and get down to writing some bit-twiddling code.

Guru Question

1. To implement solution Item 26-2(e), you decide to create the following class that manages a buffer of bits. Implement it portably so that it will work correctly on all conforming C++ compilers regardless of platform.

   class BitBuffer {
   public:
    // … add other functions as needed …
   
    // Append num bits starting with the first bit of p.
    //
    void Append(unsigned char* p, size_t num);
   
    // Query #bits in use (initially zero).
    //
    size_t Size() const;
   
    // Get num bits starting with the start-th bit,
    // and store the result starting with ...