This is a strictly UTF-16 string with some optimizations for ASCII.
* If created from a short UTF-8 or UTF-16 string that is also ASCII,
then the string is stored in an inlined byte buffer.
* If created with a long UTF-8 or UTF-16 string that is also ASCII,
then the string is stored in an outlined char buffer.
* If created with a short or long UTF-8 or UTF-16 string that is not
ASCII, then the string is stored in an outlined char16 buffer.
We do not store short non-ASCII text in the inlined buffer to avoid
confusion with operations such as `length_in_code_units` and
`code_unit_at`. For example, "😀" would be stored as 4 UTF-8 bytes
in short string form. But we still want `length_in_code_units` to
be 2, and `code_unit_at(0)` to be 0xD83D.
This was a mistake. Consider U+201C (LEFT DOUBLE QUOTATION MARK). This
code point is encoded as the bytes 0x1c 0x20 in UTF-16LE. Both of these
bytes are ASCII if interpreted as UTF-8. But the string itself is most
certainly not ASCII.
By definition, the web allows lonely surrogates by default. Let's have
our string APIs reflect this, so we don't have to pass an allow option
all over the place.
To prepare for an upcoming Utf16String, this migrates Utf16View to store
its data as a char16_t. Most function definitions are moved inline and
made constexpr.
This also adds a UDL to construct a Utf16View from a string literal:
auto string = u"hello"sv;
This let's us remove the NTTP Utf16View constructor, as we have found
that such constructors bloat binary size quite a bit.
These were mostly removed in 7628ddfaf7.
This removes the few remaining cases, as no callers are providing any
non-host endianness. This is just to prevent weird API dissymmetry
between Utf16View and an upcoming Utf16String.
Much of the web requires us to allow lonely surrogates in UTF-16 data.
The default behavior to disallow such code units has not been changed
here - that will be changed in an upcoming commit.
By piggybacking on the already-optimized implementation in
StringBuilder, we can get simdutf for the AllowInvalidCodeUnits::Yes
case here as well.
1.03x speedup on Speedometer's TodoMVC-jQuery.
For the slight cost of counting code points when converting between
encodings and a teeny bit of memory, this commit adds a fast path for
all-happy utf-16 substrings and code point operations.
This seems to be a significant chunk of time spent in many regex
benchmarks.
This is preparation for removing the endianness override, since it was
only used by a single client: LibTextCodec.
While here, add helpers and make use of simdutf for fast conversion.
The underlying CPU-specific instructions for operating on UTF-16 strings
behave differently for null inputs. Add an explicit check for this state
for consistency.
Utf16View currently assumes host endianness. Add support for specifying
either big or little endianness (which we mostly just pipe through to
simdutf). This will allow using simdutf facilities with LibTextCodec.
The one behavior difference is that we will now actually fail on invalid
code units with Utf16View::to_utf8(AllowInvalidCodeUnits::No). It was
arguably a bug that this wasn't already the case.
The [UTF-8](https://datatracker.ietf.org/doc/html/rfc3629#page-5)
standard says to reject strings with upper or lower surrogates. However,
in many standards, ECMAScript included, unpaired surrogates (and
therefore UTF-8 surrogates) are allowed in strings. So, this commit
extends the UTF-8 validation API with `AllowSurrogates`, which will
reject upper and lower surrogate characters.
This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).
This commit is auto-generated:
$ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
Meta Ports Ladybird Tests Kernel)
$ perl -pie 's/\bDeprecatedString\b/ByteString/g;
s/deprecated_string/byte_string/g' $xs
$ clang-format --style=file -i \
$(git diff --name-only | grep \.cpp\|\.h)
$ gn format $(git ls-files '*.gn' '*.gni')
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
It's very common to encounter single-character strings in JavaScript on
the web. We can make such strings significantly lighter by having a
1-character inline capacity on the Vectors.
The current method of iterating through the string to access a code
point hurts performance quite badly for very large strings. The test262
test "RegExp/property-escapes/generated/Any.js" previously took 3 hours
to complete; this one change brings it down to under 10 seconds.
To be used as a RegexStringView variant, Utf16View must provide a couple
more helper methods. It must also not default its assignment operators,
because that implicitly deletes move/copy constructors.
