Diff: mbed-os/platform/mbed_poll.cpp

Revision:

0:6bf0743ece18

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os/platform/mbed_poll.cpp	Sat Mar 28 15:28:19 2020 +0000
@@ -0,0 +1,75 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "mbed_poll.h"
+#include "FileHandle.h"
+#include "Timer.h"
+#ifdef MBED_CONF_RTOS_PRESENT
+#include "rtos/Thread.h"
+#endif
+
+namespace mbed {
+
+// timeout -1 forever, or milliseconds
+int poll(pollfh fhs[], unsigned nfhs, int timeout)
+{
+    /**
+     * TODO Proper wake-up mechanism.
+     * In order to correctly detect availability of read/write a FileHandle, we needed
+     * a select or poll mechanisms. We opted for poll as POSIX defines in
+     * http://pubs.opengroup.org/onlinepubs/009695399/functions/poll.html Currently,
+     * mbed::poll() just spins and scans filehandles looking for any events we are
+     * interested in. In future, his spinning behaviour will be replaced with
+     * condition variables.
+     */
+    Timer timer;
+    if (timeout > 0) {
+        timer.start();
+    }
+
+    int count = 0;
+    for (;;) {
+        /* Scan the file handles */
+        for (unsigned n = 0; n < nfhs; n++) {
+            FileHandle *fh = fhs[n].fh;
+            short mask = fhs[n].events | POLLERR | POLLHUP | POLLNVAL;
+            if (fh) {
+                fhs[n].revents = fh->poll(mask) & mask;
+            } else {
+                fhs[n].revents = POLLNVAL;
+            }
+            if (fhs[n].revents) {
+                count++;
+            }
+        }
+
+        if (count) {
+            break;
+        }
+
+        /* Nothing selected - this is where timeout handling would be needed */
+        if (timeout == 0 || (timeout > 0 && timer.read_ms() > timeout)) {
+            break;
+        }
+#ifdef MBED_CONF_RTOS_PRESENT
+        // TODO - proper blocking
+        // wait for condition variable, wait queue whatever here
+        rtos::Thread::wait(1);
+#endif
+    }
+    return count;
+}
+
+} // namespace mbed