static uint32_t next_gen_id() { static uint32_t gNextGenID = 0; uint32_t genID; // Loop in case our global wraps around, as we never want to return a 0. do { genID = sk_atomic_fetch_add(&gNextGenID, 2u) + 2; // Never set the low bit. } while (0 == genID); return genID; }
uint32_t SkNextID::ImageID() { static uint32_t gID = 0; uint32_t id; // Loop in case our global wraps around, as we never want to return a 0. do { id = sk_atomic_fetch_add(&gID, 2u) + 2; // Never set the low bit. } while (0 == id); return id; }
void unref() const { SkASSERT(fRefCnt > 0); // A release here acts in place of all releases we "should" have been doing in ref(). if (1 == sk_atomic_fetch_add(&fRefCnt, -1, sk_memory_order_acq_rel)) { // Like unique(), the acquire is only needed on success. SkBufferBlock* block = fBlock.fNext; sk_free((void*)this); while (block) { SkBufferBlock* next = block->fNext; sk_free(block); block = next; } } }
uint32_t SkPicture::uniqueID() const { static uint32_t gNextID = 1; uint32_t id = sk_atomic_load(&fUniqueID, sk_memory_order_relaxed); while (id == 0) { uint32_t next = sk_atomic_fetch_add(&gNextID, 1u); if (sk_atomic_compare_exchange(&fUniqueID, &id, next, sk_memory_order_relaxed, sk_memory_order_relaxed)) { id = next; } else { // sk_atomic_compare_exchange replaced id with the current value of fUniqueID. } } return id; }
void SkBaseSemaphore::signal(int n) { SkASSERT(n >= 0); // We only want to call the OS semaphore when our logical count crosses // from <= 0 to >0 (when we need to wake sleeping threads). // // This is easiest to think about with specific examples of prev and n. // If n == 5 and prev == -3, there are 3 threads sleeping and we signal // SkTMin(-(-3), 5) == 3 times on the OS semaphore, leaving the count at 2. // // If prev >= 0, no threads are waiting, SkTMin(-prev, n) is always <= 0, // so we don't call the OS semaphore, leaving the count at (prev + n). int prev = sk_atomic_fetch_add(&fCount, n, sk_memory_order_release); int toSignal = SkTMin(-prev, n); if (toSignal > 0) { this->osSignal(toSignal); } }