const std = @import("../std.zig");
const builtin = @import("builtin");
const assert = std.debug.assert;
const testing = std.testing;
const mem = std.mem;
const Loop = std.event.Loop;
pub const Lock = struct {
mutex: std.Thread.Mutex = std.Thread.Mutex{},
head: usize = UNLOCKED,
const UNLOCKED = 0;
const LOCKED = 1;
const global_event_loop = Loop.instance orelse
@compileError("std.event.Lock currently only works with event-based I/O");
const Waiter = struct {
next: ?*Waiter align(2),
tail: *Waiter,
node: Loop.NextTickNode,
};
pub fn initLocked() Lock {
return Lock{ .head = LOCKED };
}
pub fn acquire(self: *Lock) Held {
self.mutex.lock();
if (self.head == UNLOCKED) {
self.head = LOCKED;
self.mutex.unlock();
return Held{ .lock = self };
}
var waiter: Waiter = undefined;
waiter.next = null;
waiter.tail = &waiter;
const head = switch (self.head) {
UNLOCKED => unreachable,
LOCKED => null,
else => @intToPtr(*Waiter, self.head),
};
if (head) |h| {
h.tail.next = &waiter;
h.tail = &waiter;
} else {
self.head = @ptrToInt(&waiter);
}
suspend {
waiter.node = Loop.NextTickNode{
.prev = undefined,
.next = undefined,
.data = @frame(),
};
self.mutex.unlock();
}
return Held{ .lock = self };
}
pub const Held = struct {
lock: *Lock,
pub fn release(self: Held) void {
const waiter = blk: {
self.lock.mutex.lock();
defer self.lock.mutex.unlock();
switch (self.lock.head) {
UNLOCKED => {
unreachable;
},
LOCKED => {
self.lock.head = UNLOCKED;
break :blk null;
},
else => {
const waiter = @intToPtr(*Waiter, self.lock.head);
self.lock.head = if (waiter.next == null) LOCKED else @ptrToInt(waiter.next);
if (waiter.next) |next|
next.tail = waiter.tail;
break :blk waiter;
},
}
};
if (waiter) |w| {
global_event_loop.onNextTick(&w.node);
}
}
};
};
test "std.event.Lock" {
if (!std.io.is_async) return error.SkipZigTest;
if (builtin.single_threaded) return error.SkipZigTest;
if (builtin.os.tag == .freebsd) return error.SkipZigTest;
var lock = Lock{};
testLock(&lock);
const expected_result = [1]i32{3 * @intCast(i32, shared_test_data.len)} ** shared_test_data.len;
try testing.expectEqualSlices(i32, &expected_result, &shared_test_data);
}
fn testLock(lock: *Lock) void {
var handle1 = async lockRunner(lock);
var handle2 = async lockRunner(lock);
var handle3 = async lockRunner(lock);
await handle1;
await handle2;
await handle3;
}
var shared_test_data = [1]i32{0} ** 10;
var shared_test_index: usize = 0;
fn lockRunner(lock: *Lock) void {
Lock.global_event_loop.yield();
var i: usize = 0;
while (i < shared_test_data.len) : (i += 1) {
const handle = lock.acquire();
defer handle.release();
shared_test_index = 0;
while (shared_test_index < shared_test_data.len) : (shared_test_index += 1) {
shared_test_data[shared_test_index] = shared_test_data[shared_test_index] + 1;
}
}
}