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#pragma once
template<typename T>
class queue
{
public:
queue(size_t count)
{
assert(count >= 6);
sema = CreateSemaphore(0, 0, 1, 0);
waiting.store(false, std::memory_order_relaxed);
deq_node = 0;
block = new node [count];
block->next.store(0, std::memory_order_relaxed);
full_tail = block;
full_head.store(block, std::memory_order_relaxed);
free_head = block + 1;
free_tail.store(block + count - 1, std::memory_order_relaxed);
free_tail.load(std::memory_order_relaxed)->next.store(0, std::memory_order_relaxed);
for (size_t i = 1; i != count - 1; i += 1)
block[i].next.store(block + i + 1, std::memory_order_relaxed);
}
~queue()
{
CloseHandle(sema);
delete [] block;
}
VAR_T(T)& enqueue_prepare()
{
return full_tail->data;
}
void enqueue_commit()
{
node* n = get_free_node();
n->next.store(0, std::memory_order_release);
full_tail->next.store(n, std::memory_order_seq_cst);
bool signal = waiting.load(std::memory_order_seq_cst);
full_tail = n;
if (signal)
{
waiting.store(false, std::memory_order_relaxed);
ReleaseSemaphore(sema, 1, 0);
}
}
VAR_T(T)& dequeue_prepare()
{
deq_node = get_full_node();
return deq_node->data;
}
void dequeue_commit()
{
deq_node->next.store(0, std::memory_order_release);
node* prev = free_tail.exchange(deq_node, std::memory_order_acq_rel);
prev->next.store(deq_node, std::memory_order_release);
}
private:
struct node
{
std::atomic<node*> next;
VAR_T(T) data;
};
node* block;
node* full_tail;
node* free_head;
node* deq_node;
char pad [64];
std::atomic<node*> full_head;
std::atomic<node*> free_tail;
std::atomic<bool> waiting;
HANDLE sema;
node* get_free_node()
{
for (;;)
{
node* n = free_head;
node* next = n->next.load(std::memory_order_acquire);
if (next)
{
free_head = next;
return n;
}
n = full_head.load(std::memory_order_acquire);
next = n->next.load(std::memory_order_acquire);
if (next)
{
if (full_head.compare_exchange_strong(n, next, std::memory_order_seq_cst))
{
//node* n2 = free_head;
//node* next2 = n2->next.load(std::memory_order_acquire);
//if (next2)
//{
// n->next.store(0, std::memory_order_release);
// node* prev = free_tail.exchange(n, std::memory_order_acq_rel);
// prev->next.store(n, std::memory_order_release);
// free_head = next2;
// return n2;
//}
//else
{
return n;
}
}
}
}
}
node* get_full_node()
{
node* n = full_head.load(std::memory_order_acquire);
for (;;)
{
node* next = n->next.load(std::memory_order_acquire);
if (next == 0)
{
waiting.store(true, std::memory_order_seq_cst);
n = full_head.load(std::memory_order_seq_cst);
next = n->next.load(std::memory_order_acquire);
if (next)
{
waiting.store(false, std::memory_order_relaxed);
}
else
{
WaitForSingleObject(sema, INFINITE);
n = full_head.load(std::memory_order_acquire);
continue;
}
}
if (full_head.compare_exchange_strong(n, next, std::memory_order_acq_rel))
return n;
}
}
};
unsigned RL_STDCALL consumer_thread(void* ctx)
{
queue<int>* q = (queue<int>*)ctx;
int prev_data = -1;
for (;;)
{
VAR_T(int)& data0 = q->dequeue_prepare();
int data = VAR(data0);
assert(data > prev_data);
prev_data = data;
q->dequeue_commit();
//printf("%d\n", prev_data);
if (prev_data == 11)
break;
//Sleep(5);
}
return 0;
}
unsigned RL_STDCALL producer_thread(void* ctx)
{
queue<int>* q = (queue<int>*)ctx;
for (int i = 0; i != 12; i += 1)
{
VAR_T(int)& data = q->enqueue_prepare();
VAR(data) = i;
q->enqueue_commit();
//Sleep(1);
}
return 0;
}
void spsc_overwrite_queue_test()
{
queue<int> q (6);
HANDLE th [2];
th[0] = (HANDLE)_beginthreadex(0, 0, consumer_thread, &q, 0, 0);
th[1] = (HANDLE)_beginthreadex(0, 0, producer_thread, &q, 0, 0);
WaitForMultipleObjects(2, th, 1, INFINITE);
for (int i = 100; i != 104; i += 1)
{
VAR_T(int)& data = q.enqueue_prepare();
VAR(data) = i;
q.enqueue_commit();
}
for (int i = 100; i != 104; i += 1)
{
VAR_T(int)& data0 = q.dequeue_prepare();
int data = VAR(data0);
assert(data == i);
q.dequeue_commit();
}
}
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