- Use string concatenation instead of `Sprintf`, as this is much faster, and the
call to `Sprintf` is responsible for 30% of the CPU time of the function
- Anchor the youtube regex, to allow it to bail early, as this also account for
another 30% of the CPU time. It might be worth chaining calls to `TrimPrefix`
and check if the string has been trimmed instead of using a regex, to speed
things up even more, but this needs to be benchmarked properly.
- Use `token.String()` instead of `html.EscapeString(token.Data)`
- Refactor conditions to highlight their similitude, enabling further
refactoring
This refactoring brings forth at least one bug: `tagStack` is never emptied.
The `isAnchor` function's first parameter was always `a`, instead of being
passed `tagName`. As this function is a single line and was only called in a
single place, it can be inlined.
This function takes around 1.5% of the total CPU time on my instance, and most
of it is spent in `mapassign_faststr` to initialize the `map`. This is replaced
with a switch-case construct, that should be both significantly faster as well
as pretty dull in term of memory consumption.
- allow youtube urls to start with `www`
- use `strings.Builder` instead of a `bytes.Buffer`
- use a `strings.NewReader` instead of a `bytes.NewBufferString`
- sprinkles a couple of `continue` to make the code-flow more obvious
- inline calls to `inList`, and put their parameters in the right order
- simplify isPixelTracker
- simplify `isValidIframeSource`, by extracting the hostname and comparing it
directly, instead of using the full url and checking if it starts with
multiple variations of the same one (`//`, `http:`, `https://` multiplied by
``/`www.`)
- add a benchmark
Instead of having to allocate a ~100 keys map containing possibly dynamic
values (at least to the go compiler), allocate it once in a global variable.
This significantly speeds things up, by reducing the garbage
collector/allocator involvements.
Local synthetic benchmarks have shown a improvements from 38% of wall time to only
12%.
- Use constant time access for maps instead of iterating on them
- Build a ~large whitelist map inline instead of constructing it item by item
(and remove a duplicate key/value pair)
- Use `slices` instead of hand-rolled loops
