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Improve performance of ncodeunits(::Char) #54001

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merged 3 commits into from
Apr 9, 2024
Merged

Improve performance of ncodeunits(::Char) #54001

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3e9520a
Improve performance of `ncodeunits(::Char)`
Seelengrab Apr 9, 2024
19b29df
Fix use with malformed `Char`
Seelengrab Apr 9, 2024
409e7e7
Incorporate code review
Seelengrab Apr 9, 2024
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15 changes: 14 additions & 1 deletion base/char.jl
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Expand Up @@ -62,7 +62,20 @@ to an output stream, or `ncodeunits(string(c))` but computed efficiently.
This method requires at least Julia 1.1. In Julia 1.0 consider
using `ncodeunits(string(c))`.
"""
ncodeunits(c::Char) = write(devnull, c) # this is surprisingly efficient
function ncodeunits(c::Char)
# All Char are 4 byte wide, and since unicode encoding
# doesn't have null bytes (except for \0), we can just
# count non-zero bytes
char_data = reinterpret(UInt32, c)
mask = 0xff % UInt32
nbytes = !iszero(char_data & mask)
Base.Cartesian.@nexprs 3 i -> begin
m <<= 0x8
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nbytes += !iszero(char_data & mask)
end
# We have to account for `\0`, which is encoded as all zeros
nbytes + iszero(uc)
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end

"""
codepoint(c::AbstractChar) -> Integer
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