位图源码实现

位图：就是用每一位存放某种状态，适用于海量数据，数据无重复场景，通常是用来判断某个数据存在不存在。

#include<iostream>
using namespace std;
#include<vector>

namespace leb {
	class bitmap {

	public:
		bitmap(size_t bitc) :m_bitc(bitc / 32 + 1), m_bitCount(bitc) {

		}
		void set(size_t pos) {
			if (pos > m_bitCount) {
				return;
			}

			size_t index = pos / 32;
			size_t bits = pos % 32;
			m_bitc[index] |= 1u << bits;   //将1标记为unsigned类型。
		//置0 位 |   置1  用与非     置反为异或

		}
		void reset(size_t pos) {
			if (pos > m_bitCount) {
				return;
			}

			size_t index = pos / 32;
			size_t bits = pos % 32;
			m_bitc[index] &= ~(1u << bits);
		}

		bool get(size_t pos) {
			if (pos > m_bitCount) {
				return false;
			}

			size_t index = pos / 32;
			size_t bits = pos % 32;
			return m_bitc[index] >> bits & 1;
		}

		size_t size() {
			return m_bitCount;
		}
		size_t count() {
			//8进制
			size_t bittable[16] = { 0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4 };
			size_t size = m_bitc.size();
			size_t count = 0;
			size_t i;
			for (i = 0; i < size; i++) {
				int value = m_bitc[i];
				int j = 0;
				for (j = 0; j < sizeof(m_bitc[0]); j++, value >>= 8) {
					char c = value;
					count += bittable[c & 0x0f];
					c >>=4;
					count += bittable[c & 0x0f];
				}
			}
			return count;
		}

	private:
		vector<int>  m_bitc;
		size_t m_bitCount; //相当于capacity；
		//size可选项。

	};

}
int main() {

	leb::bitmap bt(10);
	bt.set(3);
	bt.set(5);
	bt.set(8);
	bt.set(0);
	bt.set(7);
	bt.reset(5);

	cout << bt.count() << endl;
	system("pause");
	return 0;
}