C语言实现的bitmap位图代码分享

#define WORD 32
#define SHIFT 5 ////移动5个位,左移则相当于乘以32,右移相当于除以32取整
#define MASK 0x1F //16进制下的31
#define N 10000000
int bitmap[1 + N / WORD];
/*
 * 置位函数——用"|"操作符,i&MASK相当于mod操作
 * m mod n 运算，当n = 2的X次幂的时候,m mod n = m&(n-1)
 */
void set(int i) {
 bitmap[i >> SHIFT] |= (1 << (i & MASK));
}
/* 清除位操作，用&~操作符 */
void clear(int i) {
 bitmap[i >> SHIFT] &= ~(1 << (i & MASK));
}
/* 测试位操作用&操作符 */
int test(int i) {
 return bitmap[i >> SHIFT] & (1 << (i & MASK));
}

int main(void) {
 FILE *in = fopen("in.txt", "r");
 FILE *out = fopen("out.txt", "w");
 if (in == NULL || out == NULL) {
 exit(-1);
 }
 int i = 0;
 int m;
 for (i = 0; i < N; i++) {
 clear(i);
 }
 while (!feof(in)) {
 fscanf(in, "%d", &m);
 printf("%d/n", m);
 set(m);
 }
 printf("abnother");
 for (i = 0; i < N; i++) {
 if (test(i)) {
  printf("%d/n", i);
  fprintf(out, "%d/n", i);
 }
 }
 fclose(in);
 fclose(out);
 return EXIT_SUCCESS;
}