Savepoint Problem - Mailing list pgsql-general

Hello,

I have a function, which stores some Data. Sometimes this function is
called within a transaction an sometimes not. But I need to set a
savepoint in this function. But this is my problem, when I'm not in a
transaction I get this error:

ERROR:  SAVEPOINT may only be used in transaction blocks

How can I check, if there is an transaction?

Thanks for your help,
Stefan Sturm