Diff: main.cpp

Revision:

0:0f1c0f6579ab

diff -r 000000000000 -r 0f1c0f6579ab main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Nov 10 16:08:43 2017 +0000
@@ -0,0 +1,50 @@
+#include "mbed.h"
+
+UARTSerial pc(USBTX, USBRX);
+UARTSerial device(MBED_CONF_APP_UART1_TX, MBED_CONF_APP_UART1_RX);
+
+static void copy_some(FileHandle *out, FileHandle *in) {
+    // To ensure performance, allow to read multiple bytes at once, although
+    // we don't expect to read many in practice.
+
+    // read() will return immediately, as we've already
+    // checked that `in` is ready with poll()
+    char buffer[32];
+    ssize_t read = in->read(buffer, sizeof buffer);
+    if (read <= 0) {
+        error("Input error");
+    }
+
+    // Then write them all out. Assuming output port is similar speed to input,
+    // this may block briefly, but not significantly.
+    ssize_t written = 0;
+    while (written < read) {
+        ssize_t w = out->write(buffer + written, read - written);
+        if (w <= 0) {
+            error("Output error");
+        }
+        written += w;
+    }
+}
+
+int main() {
+    char buffer[32];
+    pollfh fds[2];
+
+    fds[0].fh = &pc;
+    fds[0].events = POLLIN;
+    fds[1].fh = &device;
+    fds[1].events = POLLIN;
+
+    while (1) {
+        // Block until either of the 2 ports is readable (or has an error)
+        poll(fds, 2, -1);
+
+        if (fds[0].revents) {
+            copy_some(fds[1].fh, fds[0].fh);
+        }
+        if (fds[1].revents) {
+            copy_some(fds[0].fh, fds[1].fh);
+        }
+    }
+}