Although up to 10x slower for general parsing, this module improves the performance of the aeson module's string unescaper by between 10% and 50%.
This gives about a 3% improvement in Aeson parsing with GHC 6.12.3, and 5% with 7. But it makes the internals almost incomprehensible :-p
This saves us a ton of intermediate copies.
This saves us a lot of needless bytestring copying.