ChannelUtil function GetChannelNumber

Add function GetChannelNumber to retrieve the channel number
for a given video source ID and the channel name.
The channel name is truncated to the first 64 characters because
that is the length of the name field in table channel.

mythtv/libs/libmythtv/channelutil.cpp

@@ -988,6 +988,29 @@ int ChannelUtil::GetChannelValueInt(const QString &channel_field,
     return (retval) ? retval : -1;
 }
 
+QString ChannelUtil::GetChannelNumber(uint sourceid, const QString &channel_name)
+{
+    if (channel_name.isEmpty())
+        return {};
+
+    MSqlQuery query(MSqlQuery::InitCon());
+    query.prepare("SELECT channum FROM channel WHERE sourceid = :SOURCEID "
+                  "AND name = :NAME "
+                  "AND deleted IS NULL;" );
+    query.bindValue(":SOURCEID", sourceid);
+    query.bindValue(":NAME", channel_name.left(64));    // Field channel.name is 64 characters
+    if (!query.exec())
+    {
+        MythDB::DBError("GetChannelNumber", query);
+        return {};
+    }
+
+    if (!query.next())
+        return {};
+
+    return query.value(0).toString();
+}
+
 bool ChannelUtil::IsOnSameMultiplex(uint srcid,
                                     const QString &new_channum,
                                     const QString &old_channum)

mythtv/libs/libmythtv/channelutil.h

@@ -289,6 +289,9 @@ class MTV_PUBLIC ChannelUtil
                                       uint           sourceid,
                                       const QString &channum);
 
+    static QString GetChannelNumber(uint           sourceid,
+                                    const QString &channel_name);
+
     static bool    IsOnSameMultiplex(uint srcid,
                                      const QString &new_channum,
                                      const QString &old_channum);