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AK+LibRegex: Add Utf16View::code_point_at and use it in RegexStringView

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The current method of iterating through the string to access a code
point hurts performance quite badly for very large strings. The test262
test "RegExp/property-escapes/generated/Any.js" previously took 3 hours
to complete; this one change brings it down to under 10 seconds.
This commit is contained in:
Timothy Flynn 2021-08-01 18:56:52 -04:00 • committed by Andreas Kling
parent bed51d856a
commit 510bbcd8e0
3 changed files with 21 additions and 0 deletions
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17
AK/Utf16View.cpp
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@ -111,6 +111,23 @@ u16 Utf16View::code_unit_at(size_t index) const
return m_code_units[index];
}
u32 Utf16View::code_point_at(size_t index) const
{
VERIFY(index < length_in_code_units());
u32 code_point = code_unit_at(index);
if (!is_high_surrogate(code_point) && !is_low_surrogate(code_point))
return code_point;
if (is_low_surrogate(code_point) || (index + 1 == length_in_code_units()))
return code_point;
auto second = code_unit_at(index + 1);
if (!is_low_surrogate(second))
return code_point;
return decode_surrogate_pair(code_point, second);
}
size_t Utf16View::code_point_offset_of(size_t code_unit_offset) const
{
size_t code_point_offset = 0;