[XeTeX] VIQR pre-processor wrotten in (Xe)TeX ?

[Philip TAYLOR]

Does anyone have (or know of) a VIQR ("Vietnamese Quoted-Readable")
pre-processor, written in (Xe)TeX, that would allow me to input
documents of the form :

1.	Ba’nh pho^`ng to^m | Prawn Crackers (£1.00)
2.	Rong bie^?n | Crispy seaweed (£2.50)

and to have these VIQR forms internally converted to Unicode
such that I get (in the typeset output) :

1.	Bánh phồng pôm | Prawn Crackers (£1.00)
2.	Rong biển | Crispy seaweed (£2.50)

I can perform the conversion externally, of course, but would
far prefer to perform it within XeTeX.

** Phil.