Parsing XML at the Speed of Light
This chapter describes various performance tricks that allowed the author to write a very high-performing parser in C++: pugixml. While the techniques were used for an XML parser, most of them can be applied to parsers of other formats or even unrelated software (e.g., memory management algorithms are widely applicable beyond parsers).
Found out about this gem, recommended by the author of “Writing a Really, Really Fast JSON Parser”. This is a really good post as well.