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.
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 :^)
These are guarded with #ifndef KERNEL, since doubles (and floats) are
not allowed in KERNEL mode.
In StringUtils there is convert_to_floating_point which does have a
template parameter incase you have a templated type.
During the removal of StringView(char const*), all users of these
functions were removed, and they are of dubious value (relying on
implicit StringView conversion).
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
Apologies for the enormous commit, but I don't see a way to split this
up nicely. In the vast majority of cases it's a simple change. A few
extra places can use TRY instead of manual error checking though. :^)
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
This removes the awkward String::replace API which was the only String
API which mutated the String and replaces it with a new immutable
version that returns a new String with the replacements applied. This
also fixes a couple of UAFs that were caused by the use of this API.
As an optimization an equivalent StringView::replace API was also added
to remove an unnecessary String allocations in the format of:
`String { view }.replace(...);`
This was needlessly copying StringView arguments, and was also using
strstr internally, which meant it was doing a bunch of unnecessary
strlen calls on it. This also moves the implementation to StringUtils
to allow API consistency between String and StringView.
This adds the String::find_last() as wrapper for StringUtils::find_last,
which is another step in harmonizing the String and StringView APIs
where possible.
This also inlines the find() methods, as they are simple wrappers around
StringUtils functions without any additional logic.
This implements the StringView::find_all() method by re-implemeting the
current method existing for String in StringUtils, and using that
implementation for both String and StringView.
The rewrite uses memmem() instead of strstr(), so the String::find_all()
argument type has been changed from String to StringView, as the null
byte is no longer required.
This patch reimplements the StringView::find methods in StringUtils, so
they can also be used by String. The methods now also take an optional
start parameter, which moves their API in line with String's respective
methods.
This also implements a StringView::find_ast(char) method, which is
currently functionally equivalent to find_last_of(char). This is because
find_last_of(char) will be removed in a further commit.
We had two functions for doing mostly the same thing. Combine both
of them into String::find() and use that everywhere.
Also add some tests to cover basic behavior.
This allows everybody to create a String version of their number
in a arbitrary bijective base. Bijective base meaning that the mapping
doesn't have a 0. In the usual mapping to the alphabet the follower
after 'Z' is 'AA'.
The mapping using the (uppercase) alphabet is used as a standard but
can be overridden specifying 'base' and 'map'.
The code was directly yanked from the Spreadsheet.
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 *
We had an unusual optimization in AK::StringView where constructing
a StringView from a String would cause it to remember the internal
StringImpl pointer of the String.
This was used to make constructing a String from a StringView fast
and copy-free.
I tried removing this optimization and indeed we started seeing a
ton of allocation traffic. However, all of it was due to a silly
pattern where functions would take a StringView and then go on
to create a String from it.
I've gone through most of the code and updated those functions to
simply take a String directly instead, which now makes this
optimization unnecessary, and indeed a source of bloat instead.
So, let's get rid of it and make StringView a little smaller. :^)
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
This is an improved version of WrapperGenerator's snake_name(), which
seems like the kind of thing that could be useful elsewhere but would
end up getting duplicated - so let's add this to AK::String instead,
like to_{lowercase,uppercase}().
Arbitrarily split up to make git bisect easier.
These unnecessary #include's were found by combining an automated tool (which
determined likely candidates) and some brain power (which decided whether
the #include is also semantically superfluous).
Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
Use SFINAE to enforce the fact that it's supposed to only be called for
Arithmetic types, rather than counting on the linker to tell us that an
instantiation of String::number(my_arg) was not found. This also adds
String::number for floating point types as a side-effect.
This is a convenience API when you just want the rest of the string
starting at some index. We already had substring_view() in the same
flavor, so this is a complement to that.
With this commit, <AK/Format.h> has a more supportive role and isn't
used directly.
Essentially, there now is a public 'vformat' function ('v' for vector)
which takes already type erased parameters. The name is choosen to
indicate that this function behaves similar to C-style functions taking
a va_list equivalent.
The interface for frontend users are now 'String::formatted' and
'StringBuilder::appendff'.
This is a strcpy()-like method with actually sane semantics:
* It accepts a non-empty buffer along with its size in bytes.
* It copies as much of the string as fits into the buffer.
* It always null-terminates the result.
* It returns, as a non-discardable boolean, whether the whole string has been
copied.
Intended usage looks like this:
bool fits = string.copy_characters_to_buffer(buffer, sizeof(buffer));
and then either
if (!fits) {
fprintf(stderr, "The name does not fit!!11");
return nullptr;
}
or, if you're sure the buffer is large enough,
// I'm totally sure it fits because [reasons go here].
ASSERT(fits);
or if you're feeling extremely adventurous,
(void)fits;
but don't do that, please.
Get rid of the weird old signature:
- int StringType::to_int(bool& ok) const
And replace it with sensible new signature:
- Optional<int> StringType::to_int() const
FileSystemPath::has_extension was jumping through hoops and allocating
memory to do a case insensitive comparison needlessly. Extend the
existing String::ends_with method to allow the caller to specify the
case sensitivity required.
As suggested by @awesomekling in a code review and (initially) ignored
by me :^)
Implementation is roughly based on LibJS's trim_string(), but with a fix
for trimming all-whitespace strings.
This adds a replace functionality that replaces a string that contains
occurences of a "needle" by a "replacement" value. With "all_occurences"
enabled, all occurences are being replaced, otherwise only the first
occurence is being replaced.
Move the "fast memcpy" stuff out of StdLibExtras.h and into Memory.h.
This will break a ton of things that were relying on StdLibExtras.h
to include a bunch of other headers. Fix will follow immediately after.
This makes it possible to include StdLibExtras.h from Types.h, which is
the main point of this exercise.
You can now #include <AK/Forward.h> to get most of the AK types as
forward declarations.
Header dependency explosion is one of the main contributors to compile
times at the moment, so this is a step towards smaller include graphs.
Now that we're trying to be more portable, we can't only rely on using
i32/u32 and i64/u64 since different systems have different combinations
of int/long/long long and unsigned/unsigned long/unsigned long long.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
If the last character was the separator and keep_empty is true, the
previous if statement would have already appended the last empty part,
so no need to do this again.
This was even more problematic, because the result of split_view() is
expected to consist of true substrings that are usable with the
StringView::substring_view_starting_*_substring() methods, not of
equal strings located elsewhere.
Fixes https://github.com/SerenityOS/serenity/issues/970
See https://github.com/SerenityOS/serenity/pull/938
Using int was a mistake. This patch changes String, StringImpl,
StringView and StringBuilder to use size_t instead of int for lengths.
Obviously a lot of code needs to change as a result of this.
This is just a wrapper around strstr() for now. There are many better
ways to search for a string within a string, but I'm just adding a nice
API at the moment. :^)
This kind of thing is a bit annoying. On Serenity, size_t is the same
size as u32, but not the same type. Because of "long" or whatever.
This patch makes String not complain about duplicate overloads.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
