Fixing a bug in the unix write code which may have prevented it from writing in some cases, and updating some of the comments and error messages in the write function that still read like the read function

src/impl/unix.cc

@@ -523,7 +523,7 @@ Serial::SerialImpl::write (const uint8_t *data, size_t length)
     get_time_now(start);
 #endif
     // Do the select
-    int r = select (fd_ + 1, &writefds, NULL, NULL, &timeout);
+    int r = select (fd_ + 1, NULL, &writefds, NULL, &timeout);
 #if !defined(__linux__)
     // Calculate difference and update the structure
     get_time_now(end);
@@ -558,43 +558,42 @@ Serial::SerialImpl::write (const uint8_t *data, size_t length)
     if (r == 0) {
       break;
     }
-    /** Something ready to read **/
+    /** Port ready to write **/
     if (r > 0) {
-      // Make sure our file descriptor is in the ready to read list
+      // Make sure our file descriptor is in the ready to write list
       if (FD_ISSET (fd_, &writefds)) {
-        // This should be non-blocking returning only what is avaialble now
+        // This will write some
-        //  Then returning so that select can block again.
         ssize_t bytes_written_now =
           ::write (fd_, data + bytes_written, length - bytes_written);
-        // read should always return some data as select reported it was
+        // write should always return some data as select reported it was
-        // ready to read when we get to this point.
+        // ready to write when we get to this point.
         if (bytes_written_now < 1) {
           // Disconnected devices, at least on Linux, show the
-          // behavior that they are always ready to read immediately
+          // behavior that they are always ready to write immediately
-          // but reading returns nothing.
+          // but writing returns nothing.
           throw SerialExecption ("device reports readiness to write but "
                                  "returned no data (device disconnected?)");
         }
-        // Update bytes_read
+        // Update bytes_written
         bytes_written += static_cast<size_t> (bytes_written_now);
-        // If bytes_read == size then we have read everything we need
+        // If bytes_written == size then we have written everything we need to
         if (bytes_written == length) {
           break;
         }
-        // If bytes_read < size then we have more to read
+        // If bytes_written < size then we have more to write
         if (bytes_written < length) {
           continue;
         }
-        // If bytes_read > size then we have over read, which shouldn't happen
+        // If bytes_written > size then we have over written, which shouldn't happen
         if (bytes_written > length) {
-          throw SerialExecption ("read over read, too many bytes where "
+          throw SerialExecption ("write over wrote, too many bytes where "
-                                 "read, this shouldn't happen, might be "
+                                 "written, this shouldn't happen, might be "
                                  "a logical error!");
         }
       }
       // This shouldn't happen, if r > 0 our fd has to be in the list!
-      THROW (IOException, "select reports ready to read, but our fd isn't"
+      THROW (IOException, "select reports ready to write, but our fd isn't"
-             " in the list, this shouldn't happen!");
+                          " in the list, this shouldn't happen!");
     }
   }
   return bytes_written;