I*******g
发帖数: 7600 | 1 Imagine the following compare_and_swap (CAS) primitive function is available
to
you. Using this function, write an integer counter class providing increment,
decrement, set and get APIs in an atomic and thread-safe way in a context
subject to
periodic highly intensive concurrent activity .
/* In a critical section, if (*dest) == old_val, then updates dest to new_
val and returns true otherwise leaves dest unchanged and returns false.
*/
bool compare_and_swap(int* dest, int old_val, int new_val) | I*******g
发帖数: 7600 | 2 要求用C++
available
increment,
【在 I*******g 的大作中提到】
: Imagine the following compare_and_swap (CAS) primitive function is available
: to
: you. Using this function, write an integer counter class providing increment,
: decrement, set and get APIs in an atomic and thread-safe way in a context
: subject to
: periodic highly intensive concurrent activity .
: /* In a critical section, if (*dest) == old_val, then updates dest to new_
: val and returns true otherwise leaves dest unchanged and returns false.
: */
: bool compare_and_swap(int* dest, int old_val, int new_val)
| z******g
发帖数: 271 | 3 class AtomicCounter {
private:
volatile int mem;
public:
AtomicCounter(): mem(0) {}
int get() { return mem; }
void inc() {
int new_val, old_val;
do {
old_val = mem;
new_val = old_val + 1;
} while(!compare_and_swap(&mem, old_val, new_val));
}
void dec() {
// same
}
}; |
|
