✨ 新增select语句

magicoca/__init__.py

@@ -1,5 +1,25 @@
 from multiprocessing import set_start_method
+from typing import Any, Callable, Generator
 
-from magicoca.chan import Chan, T
+from magicoca.chan import Chan, T, NoRecvValue
 
-set_start_method("spawn", force=True)
+__all__ = [
+    "Chan",
+    "select"
+]
+
+set_start_method("spawn", force=True)
+
+def select(*args: Chan[T]) -> Generator[T, None, None]:
+    """
+    Return a yield, when a value is received from one of the channels.
+    Args:
+        args: channels
+    """
+    while True:
+        for ch in args:
+            if ch.is_closed:
+                continue
+
+            if not isinstance(value := ch.recv(0), NoRecvValue):
+                yield value

magicoca/chan.py

@@ -6,6 +6,12 @@ from typing import TypeVar, Generic, Any
 
 T = TypeVar("T")
 
+class NoRecvValue(Exception):
+    """
+    Exception raised when there is no value to receive.
+    """
+    pass
+
 
 class Chan(Generic[T]):
     """
@@ -31,6 +37,8 @@ class Chan(Generic[T]):
         """
         self.send_conn, self.recv_conn = Pipe()
 
+        self.is_closed = False
+
     def send(self, value: T):
         """
         Send a value to the channel.
@@ -39,7 +47,7 @@ class Chan(Generic[T]):
         """
         self.send_conn.send(value)
 
-    def recv(self, timeout: float | None = None) -> T | None:
+    def recv(self, timeout: float | None = None) -> T | None | NoRecvValue:
         """Receive a value from the channel.
         If the timeout is None, it will block until a value is received.
         If the timeout is a positive number, it will wait for the specified time, and if no value is received, it will return None.
@@ -56,15 +64,17 @@ class Chan(Generic[T]):
         """
         if timeout is not None:
             if not self.recv_conn.poll(timeout):
-                return None
+                return NoRecvValue("No value to receive.")
         return self.recv_conn.recv()
 
+
     def close(self):
         """
         Close the channel. destructor
         """
         self.send_conn.close()
         self.recv_conn.close()
+        self.is_closed = True
 
     def __iter__(self) -> "Chan[T]":
         """

tests/test_chan.py

@@ -1,4 +1,5 @@
 import time
+from select import select
 
 from magicoca.chan import Chan
 from multiprocessing import Process, set_start_method
@@ -21,6 +22,7 @@ def p2f(chan: Chan[int]):
     if recv_ans != list(range(10)) + [-1]:
         raise ValueError("Chan Shift Test Failed")
 
+
 class TestChan:
 
     def test_test(self):
@@ -63,3 +65,6 @@ class TestChan:
         p2.start()
         p1.join()
         p2.join()
+
+
+

tests/test_select.py

@@ -0,0 +1,42 @@
+from multiprocessing import Process
+
+from magicoca import Chan, select
+
+
+def sp1(chan: Chan[int]):
+    for i in range(10):
+        chan << i
+
+
+def sp2(chan: Chan[int]):
+    for i in range(10):
+        chan << i
+
+
+def rp(chans: list[Chan[int]]):
+    rl = []
+    for t in select(*chans):
+        rl.append(t)
+        if len(rl) == 20:
+            break
+    print(rl)
+    assert len(rl) == 20
+
+
+class TestSelect:
+    def test_select(self):
+        chan1 = Chan[int]()
+        chan2 = Chan[int]()
+
+        print("Test Chan Select")
+
+        p1 = Process(target=sp1, args=(chan1,))
+        p2 = Process(target=sp2, args=(chan2,))
+        p3 = Process(target=rp, args=([chan1, chan2],))
+        p3.start()
+        p1.start()
+        p2.start()
+
+        p1.join()
+        p2.join()
+        p3.join()