Don't compute the strlen() of the string we're comparing against first.
This can save a lot of time if we're comparing against something that
already fails to match in the first few characters.
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.
The symbol name insertion scheme is different from objdump -d's.
Compare the output on Build/Userland/id:
* disasm:
...
_start (08048305-0804836b):
08048305 push ebp
...
08048366 call 0x0000df56
0804836b o16 nop
0804836d o16 nop
0804836f nop
(deregister_tm_clones (08048370-08048370))
08048370 mov eax, 0x080643e0
...
_ZN2AK8Utf8ViewC1ERKNS_6StringE (0805d9b2-0805d9b7):
_ZN2AK8Utf8ViewC2ERKNS_6StringE (0805d9b2-0805d9b7):
0805d9b2 jmp 0x00014ff2
0805d9b7 nop
* objdump -d:
08048305 <_start>:
8048305: 55 push %ebp
...
8048366: e8 9b dc 00 00 call 8056006 <exit>
804836b: 66 90 xchg %ax,%ax
804836d: 66 90 xchg %ax,%ax
804836f: 90 nop
08048370 <deregister_tm_clones>:
8048370: b8 e0 43 06 08 mov $0x80643e0,%eax
...
0805d9b2 <_ZN2AK8Utf8ViewC1ERKNS_6StringE>:
805d9b2: e9 eb f6 ff ff jmp 805d0a2 <_ZN2AK10StringViewC1ERKNS_6StringE>
805d9b7: 90 nop
Differences:
1. disasm can show multiple symbols that cover the same instructions.
I've only seen this happen for C1/C2 (and D1/D2) ctor/dtor pairs,
but it could conceivably happen with ICF as well.
2. disasm separates instructions that do not belong to a symbol with
a newline, so that nop padding isn't shown as part of a function
when it technically isn't.
3. disasm shows symbols that are skipped (due to having size 0)
in parenthesis, separated from preceding and following instructions.
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
StringUtils::equals_ignoring_case() already operates on a StringView&,
so StringView should have the method directly without having to go
through a temporary String (which also has the method).
This allows easy creation of a new string from an existing StringView.
Can be used e.g. for output with printf(..., view.to_string().characters())
instead of writing printf(..., String{view}.characters()).
These methods search from the beginning or end of a string for the
first character in the input StringView and returns the position in
the string of the first match. Note that this is not a substring match.
Each comes with single char overloads for efficiency.
Due to us using size_t for the length, the actual value will always be positive.
If, for example, we calculate the length as "0 - 1", we'll get SIZE_T_MAX. What
we can do is check that adding the characters pointer and the length together
doesn't overflow.
FlyString is a flyweight string class that wraps a RefPtr<StringImpl>
known to be unique among the set of FlyStrings. The class is very
unoptimized at the moment.
When to use FlyString:
- When you want O(1) string comparison
- When you want to deduplicate a lot of identical strings
When not to use FlyString:
- For strings that don't need either of the above features
- For strings that are likely to be unique
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.
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.
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 a shameless copy-paste of String::to_int(). We should find some
way to share this code between String and StringView instead of having
two duplicate copies like this.
Without this function, comparing a String to a const char* will instantiate
a temporary String which is obviously not great.
Also add some missing null checks to StringView::operator==(const char*).
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
