A couple headers expected names to be in the global namespace, qualify
those names to make sure they're resolved even when the names are not
exported.
One header placed its functions in the global namespace, move those to
the AK namespace to make the concepts resolve.
Implement insertion sort in AK. The cutoff value 7 is a magic number
here, values [5, 15] should work well. Main idea of the cutoff is to
reduce recursion performed by quicksort to speed up sorting
of small partitions.
Note that Jakt only allows StringView creation from string literals, so
none of the invariants in the class are broken by this (if used only
from within Jakt).
This allows the user to transform the contents of the optional (if any
exists), without manually unwrapping and then rewrapping it.
This is needed by the Jakt runtime.
This is used in Jakt, and providing that value from Jakt's side is more
trouble than doing this.
Considering this class is bound to go away, a little
backwards-compatible API change is just fine.
The previous moved-from state was the null string. This violates both
our invariant that String is never null, and also the C++ contract that
the moved-from state must be valid but unspecified. The empty short
string state is of course valid, so it satisfies both invariants. It
also allows us to remove any extra checks for the null state.
The reason this change is made is primarily because swap() requires
moved-from objects to be reassignable (C++ allows this). Because the
move assignment of String would not check the null state, it crashed
trying to increment the data reference count (nullptr signals a
non-short string). This meant that e.g. quick_sort'ing String would
crash immediately.
s p a c e s h i p o p e r a t o r
Comparing UTF-8 can be done by simple byte lexicographic comparison per
definition, so we just piggy-back on StringView's high-performance
comparator.
Similar to how LibJS and LibSQL used to behave, the boolean constructor
of JsonValue is currently allowing pointers to be used to construct a
boolean value. Explicitly disallow such construction.
This allows us to pass the new String type to functions that take a
StringView directly, having to call bytes_as_string_view() every time
gets old quickly.
DeprecatedString (formerly String) has been with us since the start,
and it has served us well. However, it has a number of shortcomings
that I'd like to address.
Some of these issues are hard if not impossible to solve incrementally
inside of DeprecatedString, so instead of doing that, let's build a new
String class and then incrementally move over to it instead.
Problems in DeprecatedString:
- It assumes string allocation never fails. This makes it impossible
to use in allocation-sensitive contexts, and is the reason we had to
ban DeprecatedString from the kernel entirely.
- The awkward null state. DeprecatedString can be null. It's different
from the empty state, although null strings are considered empty.
All code is immediately nicer when using Optional<DeprecatedString>
but DeprecatedString came before Optional, which is how we ended up
like this.
- The encoding of the underlying data is ambiguous. For the most part,
we use it as if it's always UTF-8, but there have been cases where
we pass around strings in other encodings (e.g ISO8859-1)
- operator[] and length() are used to iterate over DeprecatedString one
byte at a time. This is done all over the codebase, and will *not*
give the right results unless the string is all ASCII.
How we solve these issues in the new String:
- Functions that may allocate now return ErrorOr<String> so that ENOMEM
errors can be passed to the caller.
- String has no null state. Use Optional<String> when needed.
- String is always UTF-8. This is validated when constructing a String.
We may need to add a bypass for this in the future, for cases where
you have a known-good string, but for now: validate all the things!
- There is no operator[] or length(). You can get the underlying data
with bytes(), but for iterating over code points, you should be using
an UTF-8 iterator.
Furthermore, it has two nifty new features:
- String implements a small string optimization (SSO) for strings that
can fit entirely within a pointer. This means up to 3 bytes on 32-bit
platforms, and 7 bytes on 64-bit platforms. Such small strings will
not be heap-allocated.
- String can create substrings without making a deep copy of the
substring. Instead, the superstring gets +1 refcount from the
substring, and it acts like a view into the superstring. To make
substrings like this, use the substring_with_shared_superstring() API.
One caveat:
- String does not guarantee that the underlying data is null-terminated
like DeprecatedString does today. While this was nifty in a handful of
places where we were calling C functions, it did stand in the way of
shared-superstring substrings.
Previously we allowed the end_offset to be larger than the chunk itself,
which made it so that certain input sizes would make the logic attempt
to delete a nonexistent object.
Fixes#16308.
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 :^)
