Originally I added this to use it in Utf16View::ends_with(), but the
final implementation ended up a lot simpler. I chose to keep this anyway
since it mirrors Span::starts_with().
RegExp was the only caller relying on being able to provide an offset
larger than the string length. So let's do a pre-check in RegExp and
then enforce that the offsets we receive in Utf16View are valid.
There were a couple of issues here, including the following computation
could actually overflow to NumericLimits<size_t>::max():
code_unit_offset -= it.length_in_code_units();
And do the same for Utf8View::code_point_offset_of(). Some of these
`VERIFY`s of the view's length were introduced recently, but they caused
the parsing of named capture groups in RegexParser to crash in some
situations.
Instead, allow indexing at the view's length: the byte offset of code
point `length()` is known, even though that code point does not exist in
the view. Similarly, we know the code point offset at byte offset
`byte_length()`. Beyond those offsets, we still crash.
Fixes 13 failures in test262's `language/literals/regexp/named-groups`.
Utf16FlyString more or less works exactly the same as FlyString. It will
store the raw encoded data of the string instance. If the string is a
short ASCII string, Utf16FlyString holds the ShortString bytes; else,
Utf16FlyString holds a pointer to the Utf16StringData.
The underlying storage used during string formatting is StringBuilder.
To support UTF-16 strings, this patch allows callers to specify a mode
during StringBuilder construction. The default mode is UTF-8, for which
StringBuilder remains unchanged.
In UTF-16 mode, we treat the StringBuilder's internal ByteBuffer as a
series of u16 code units. Appending a single character will append 2
bytes for that character (cast to a char16_t). Appending a StringView
will transcode the string to UTF-16.
Utf16String also gains the same memory optimization that we added for
String, where we hand-off the underlying buffer to Utf16String to avoid
having to re-allocate.
In the future, we may want to further optimize for ASCII strings. For
example, we could defer committing to the u16-esque storage until we
see a non-ASCII code point.
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.
To enable storing it in a hashmap. 13 is a somewhat arbitrary
value, something like 0 is not appropriate since a lot of types
return 0 as a hash for an invalid / empty state.
* Error and ErrorOr are not themelves constexpr, so a function returning
these types cannot be constexpr.
* The UDL was trying to call Utf16View::validate, which is not constexpr
itself. The compiler will actually already raise an error if a UTF-16
literal is invalid, so let's just avoid the call altogether.
Our floating point number parser was based on the fast_float library:
https://github.com/fastfloat/fast_float
However, our implementation only supports 8-bit characters. To support
UTF-16, we will need to be able to convert char16_t-based strings to
numbers as well. This works out-of-the-box with fast_float.
We can also use fast_float for integer parsing.
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.
