From a4bbcbc7fffb8fed9a9d9a04e35f962232da6293 Mon Sep 17 00:00:00 2001
From: rudolfkoenig <>
Date: Sun, 15 Apr 2018 18:44:05 +0000
Subject: [PATCH] FHEM/DevIo.pm: add some more comments (Forum #85258)

git-svn-id: https://svn.fhem.de/fhem/trunk@16623 2b470e98-0d58-463d-a4d8-8e2adae1ed80
---
 fhem/FHEM/DevIo.pm | 48 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 10 deletions(-)

diff --git a/fhem/FHEM/DevIo.pm b/fhem/FHEM/DevIo.pm
index f30d96776..7f85bc7e8 100644
--- a/fhem/FHEM/DevIo.pm
+++ b/fhem/FHEM/DevIo.pm
@@ -21,6 +21,8 @@ DevIo_setStates($$)
 }
 
 ########################
+# Try to read once from the device.
+# "private" function
 sub
 DevIo_DoSimpleRead($)
 {
@@ -54,7 +56,9 @@ DevIo_DoSimpleRead($)
 }
 
 ########################
-# If called directly after a select, it should not block.
+# This is the function to read data, to be called in ReadFn.
+# If there is no data, sets the device to disconnected, which results in
+# polling via ReadyFn, trying to open it.
 sub
 DevIo_SimpleRead($)
 {
@@ -77,7 +81,7 @@ DevIo_SimpleRead($)
 ########################
 # wait at most timeout seconds until the file handle gets ready
 # for reading; returns undef on timeout
-# NOTE1: FHEM can be blocked for $timeout seconds!
+# NOTE1: FHEM can be blocked for $timeout seconds, DO NOT USE IT!
 # NOTE2: This works on Windows only for TCP connections
 sub
 DevIo_SimpleReadWithTimeout($$)
@@ -92,8 +96,9 @@ DevIo_SimpleReadWithTimeout($$)
 }
 
 ########################
-# Read until you get the timeout. Use it with care since it waits _at least_
-# timeout seconds, and it works on Windows only for TCP/IP connections
+# Read until the timeout occures
+# NOTE1: FHEM WILL be blocked for $timeout seconds, DO NOT USE IT!
+# NOTE2: This works on Windows only for TCP connections
 sub
 DevIo_TimeoutRead($$)
 {
@@ -113,7 +118,7 @@ DevIo_TimeoutRead($$)
 }
 
 ########################
-# Input is HEX, with header and CRC
+# Function to write data
 sub
 DevIo_SimpleWrite($$$;$)
 {
@@ -144,6 +149,7 @@ DevIo_SimpleWrite($$$;$)
 ########################
 # Write something, then read something
 # reopen device if timeout occurs and write again, then read again
+# NOTE1: FHEM can be blocked for $timeout seconds, DO NOT USE IT!
 sub
 DevIo_Expect($$$)
 {
@@ -194,9 +200,19 @@ DevIo_Expect($$$)
   return undef; # undef means ultimate failure
 }
 
+
 ########################
-# callback is only meaningful for TCP/IP (Nonblocking connect), but can used in
-# every cases. It will be called with $hash and a (potential) error message
+# Open a device for reading/writing data.
+# Possible values for $hash->{DeviceName}:
+# - device@baud[78][NEO][012] => open device, set serial-line parameters
+# - hostname:port => TCP/IP client connection
+# - device@directio => open device without additional "magic"
+# - UNIX:(SEQPACKET|STREAM):filename => Open filename as a UNIX socket
+# - FHEM:DEVIO:IoDev[:IoPort] => Cascade I/O over another FHEM Device
+#
+# callback is only meaningful for TCP/IP (in which case a nonblocking connect
+# is executed) every cases. It will be called with $hash and a (potential)
+# error message. If $hash->{SSL} is set, SSL encryption is activated.
 sub
 DevIo_OpenDev($$$;$)
 {
@@ -209,6 +225,7 @@ DevIo_OpenDev($$$;$)
   my ($databits, $parity, $stopbits) = (8, 'none', 1);
   my $nextOpenDelay = ($hash->{nextOpenDelay} ? $hash->{nextOpenDelay} : 60);
 
+  # Call the callback if specified, simply return in other cases
   my $doCb = sub ($) {
     my ($r) = @_;
     Log3 $name, 1, "$name: Can't connect to $dev: $r" if(!$reopen && $r);
@@ -216,6 +233,9 @@ DevIo_OpenDev($$$;$)
     return $r;
   };
 
+  # Call initFn
+  # if fails: disconnect, schedule the next polltime for reopen
+  # if ok: log message, trigger CONNECTED on reopen
   my $doTailWork = sub {
     DevIo_setStates($hash, "opened");
 
@@ -317,6 +337,11 @@ DevIo_OpenDev($$$;$)
 
     delete($readyfnlist{"$name.$dev"});
     my $timeout = $hash->{TIMEOUT} ? $hash->{TIMEOUT} : 3;
+
+    
+    # Do common TCP/IP "afterwork":
+    # if connected: set keepalive, fill selectlist, FD, TCPDev.
+    # if not: report the error and schedule reconnect
     my $doTcpTail = sub($) {
       my ($conn) = @_;
       if($conn) {
@@ -337,7 +362,7 @@ DevIo_OpenDev($$$;$)
       return 1;
     };
 
-    if($callback) {
+    if($callback) { # reuse the nonblocking connect from HttpUtils.
       use HttpUtils;
       my $err = HttpUtils_Connect({     # Nonblocking
         timeout => $timeout,
@@ -353,7 +378,7 @@ DevIo_OpenDev($$$;$)
       return &$doCb($err) if($err);
       return undef;     # no double callback: connect is running in bg now
 
-    } else {
+    } else {    # blocking connect
       my $conn = $haveInet6 ? 
           IO::Socket::INET6->new(PeerAddr => $dev, Timeout => $timeout) :
           IO::Socket::INET ->new(PeerAddr => $dev, Timeout => $timeout);
@@ -460,6 +485,8 @@ DevIo_SetHwHandshake($)
 }
 
 ########################
+# close the device, remove it from selectlist, 
+# delete DevIo specific internals from $hash
 sub
 DevIo_CloseDev($@)
 {
@@ -514,6 +541,8 @@ DevIo_IsOpen($)
           $hash->{IODevPort});
 }
 
+
+# Close the device, schedule the reopen via ReadyFn, trigger DISCONNECTED
 sub
 DevIo_Disconnected($)
 {
@@ -535,5 +564,4 @@ DevIo_Disconnected($)
   DoTrigger($name, "DISCONNECTED");
 }
 
-
 1;