Bitmap class

Provides a bitmap c++ class implementation. A bitmap is essentially an array of bits.

Usage and compilation

To use the class, just add #include "path/to/bitmap.hpp" to your own header file.

When compiling, make sure to use at least c++17 and include bitmap.cpp on your command. It should look something like this:

g++ -std=c++17 <your-files> bitmap.cpp -o <output-file>

Interface

Assume n is a positive integer and b is a BitMap of the same size as the the subject Bitmap.

Member functions

• Bitmap(n) constructs a new bitmap that can store 𝑛 bits. All bits are initially set to 0.
• Bitmap(n, b) constructs a copy of b1. If 𝑛 is smaller than the size of b1, the bitmap is truncated to the first 𝑛 bits of b1. If 𝑛 is greater than the size of b1, additional bits are set to 0.
• 0-based indexing with the [] operator:
  • bool operation[](n) const returns a bool, which is true if the 𝑛th bit of b1 is 1 and false otherwise.
  • BitRef operation[](n) returns a special proxy class BitRef, as C++ does not allow references to bool. This class is described below.
  • The [] operation does not do any bounds checking, the result is unspecified (and can be a crash) if 𝑛 is greater or equal to the size of b1.
• at(n) returns (*this)[n], but additionally does bounds checking, and throws exception std::out_of_range if 𝑛 is greater or equal to the size of the bitmap.
• size() returns the number of bits in the array.
• operator!() returns a new bitmap that is the negation of b1, i.e. the 𝑛th bit of the result is 1 iff the 𝑛th bit of b1 is 0.
• operator+(b) returns a new bitmap that is the union of b1 and b2, i.e. the 𝑛th bit of the result is 1 iff the 𝑛th bit is set (i.e. equals 1) in b1, b2, or both.
• operator*(b) returns a new bitmap that is the intersection of b1 and b2, i.e. the 𝑛th bit of the result is 1 iff the 𝑛th bit is set in both b1 and b2.
• operator-(b) returns a new bitmap that is the set difference (or relative complement) of b1 and b2, i.e. the 𝑛th bit of the result is 1 iff the 𝑛th bit is set in b1 but not in b2.
• operator^(b) returns a new bitmap that is the symmetric difference (or disjunctive union) of b1 and b2, i.e. the 𝑛th bit of the result is 1 iff the 𝑛th bit of b1 or b2 is set, but not both.
• operator*(n) returns a bitmap that repeats the sequence of bits 𝑛 times, e.g. if it contains 100110, then b * 3 should return a bitmap that contains 100110 100110 100110. See also non-member function operator*(n, b), which provides comutativity to this operation.

Non-member functions

• operator<<(ostream, b) prints b as a text sequence of 0s and 1s on the output stream, where b[0] appears as the rightmost bit.
• operator*(n, b) returns a bitmap that repeats 𝑛 times the sequence of bits in b. See also member function operator*(n).