This will make it easier to support both string types at the same time
while we convert code, and tracking down remaining uses.
One big exception is Value::to_string() in LibJS, where the name is
dictated by the ToString AO.
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 :^)
Instead of concatenating string data every time you add two strings
together in JavaScript, we now create a new PrimitiveString that points
to the two concatenated strings instead.
This turns concatenated strings into a tree structure that doesn't have
to be serialized until someone wants the characters in the string.
This *dramatically* reduces the peak memory footprint when running
the SunSpider benchmark (from ~6G to ~1G on my machine). It's also
significantly faster (1.39x) :^)
This helps make the overall codebase consistent. `class_name()` in
`Kernel` is always `StringView`, but not elsewhere.
Additionally, this results in the `strlen` (which needs to be done
when printing or other operations) always being computed at
compile-time.
When performing GetValue on a primitive type we do not need to perform
the ToObject conversion as it will resolve to a property on the
prototype object.
To avoid this we skip the initial ToObject conversion on the base value
as it only serves to get the primitive's boxed prototype. We further
specialize on PrimitiveString in order to get efficient behaviour
behaviour for the direct properties.
Depending on the tests anywhere from 20 to 60%, with significant loop
overhead.
When appending two strings together to form a new string, if both of the
strings are already UTF-16, create the new string as UTF-16 as well.
This shaves about 0.5 seconds off the following test262 test:
RegExp/property-escapes/generated/General_Category_-_Decimal_Number.js
This commit does not go out of its way to reduce copying of the string
data yet, but is a minimum set of changes to compile LibJS after making
PrimitiveString hold a Utf16String.
PrimitiveString may currently only be created with a UTF-8 string, and
it transcodes on the fly when a UTF-16 string is needed. Allow creating
a PrimitiveString from a UTF-16 string to avoid unnecessary transcoding
when the caller only wants UTF-16.
LibJS parses JavaScript as UTF-8, so when creating a string, we must
transcode it to UTF-16 to handle encoded surrogate pairs.
For example, consider the following string:
"\ud83d\ude00"
The UTF-8 encoding of this surrogate pair is:
0xf0 0x9f 0x98 0x80
However, LibJS will currently store the two surrogates individually as
UTF-8 encoded bytes, rather than combining the pair:
0xed 0xa0 0xb8, 0xed 0xb8 0x80
These are not equivalent. So, as String.prototype becomes UTF-16 aware,
this encoding will no longer work for abstractions like strict equality.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
