[llvm] [llvm][Support] Implement raw_socket_stream::read with optional timeout (PR #92308)

[Michael Spencer via llvm-commits]

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@@ -177,43 +178,51 @@ Expected<ListeningSocket> ListeningSocket::createUnix(StringRef SocketPath,
 #endif // _WIN32
 }
 
-Expected<std::unique_ptr<raw_socket_stream>>
-ListeningSocket::accept(std::chrono::milliseconds Timeout) {
-
-  struct pollfd FDs[2];
-  FDs[0].events = POLLIN;
+// If a file descriptor being monitored by poll is closed by another thread, the
+// result is unspecified. In the case poll does not unblock and return when
+// ActiveFD is closed you can provide another file descriptor via CancelFD that
+// when written to will cause poll to return. Typically CancelFD is the read end
+// of a unidirectional pipe.
+static llvm::Error manageTimeout(std::chrono::milliseconds Timeout,
+                                 std::function<int()> getActiveFD,
+                                 std::optional<int> CancelFD = std::nullopt) {
+  struct pollfd FD[2];
+  FD[0].events = POLLIN;
 #ifdef _WIN32
-  SOCKET WinServerSock = _get_osfhandle(FD);
-  FDs[0].fd = WinServerSock;
+  SOCKET WinServerSock = _get_osfhandle(getActiveFD());
+  FD[0].fd = WinServerSock;
 #else
-  FDs[0].fd = FD;
+  FD[0].fd = getActiveFD();
 #endif
-  FDs[1].events = POLLIN;
-  FDs[1].fd = PipeFD[0];
+  uint8_t FDCount = 1;
+  if (CancelFD.has_value()) {
+    FD[1].events = POLLIN;
+    FD[1].fd = CancelFD.value();
+    FDCount++;
+  }
 
-  // Keep track of how much time has passed in case poll is interupted by a
-  // signal and needs to be recalled
+  // Keep track of how much time has passed in case ::poll or WSAPoll are
+  // interupted by a signal and need to be recalled
   int RemainingTime = Timeout.count();
   std::chrono::milliseconds ElapsedTime = std::chrono::milliseconds(0);
   int PollStatus = -1;
 
   while (PollStatus == -1 && (Timeout.count() == -1 || ElapsedTime < Timeout)) {
     if (Timeout.count() != -1)
       RemainingTime -= ElapsedTime.count();
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Bigcheese wrote:

This over counts ElapsedTime because it includes previous loop iterations.

https://github.com/llvm/llvm-project/pull/92308