html/template: fix quadratic performance with special tags
The current implementation of the tSpecialTagEnd function
is inefficient since it generates plenty of memory allocations
and converts the whole buffer to lowercase at each call.
If the number of special tags increases linearly with the
template size, the complexity becomes quadratic.
This CL provides an alternative implementation.
While the algorithm is probably still not optimal, it avoids
the quadratic behavior and the memory allocations.
benchmark old ns/op new ns/op delta
BenchmarkTemplateSpecialTags-4
19326431 532190 -97.25%
benchmark old allocs new allocs delta
BenchmarkTemplateSpecialTags-4 2650 190 -92.83%
benchmark old bytes new bytes delta
BenchmarkTemplateSpecialTags-4
4106460 46568 -98.87%
While we are there, make sure we respect the HTML tokenization algorithm.
An end tag needs to be followed by a space, tab, CR, FF, /, or > as described
in https://html.spec.whatwg.org/multipage/syntax.html#tokenization
Explicitly add this check.
Fixes #10605
Change-Id: Ia33ddee164ab608a69ac4183e16ec506bbeaa54c
Reviewed-on: https://go-review.googlesource.com/9502
Reviewed-by: Rob Pike <r@golang.org>