mm-coding-system-p

mm-coding-system-p is a compiled Lisp function in `mm-util.el'.

(mm-coding-system-p CS)

Return non-nil if CS is a symbol naming a coding system.
In XEmacs, also return non-nil if CS is a coding system object.
If CS is available, return CS itself in Emacs, and return a coding
system object in XEmacs.