Expanding Man (Mar 08 2021 at 23:42): Expanding Man (Mar 08 2021 at 23:42):The documentation claims that take!(::IOBuffer) does not copying, but it's clearly lying:
julia> io = IOBuffer(zeros(UInt8, 2^18));
julia> v = take!(io);
julia> io.data[1] = 0xff
0xff
julia> v[1]
0x00
julia> @btime take!($io);
17.486 μs (2 allocations: 256.14 KiB)
As far as I can tell this happens whenever the buffer is not writable. I guess because it assumes in those cases the data in the buffer has to be preserved at all costs?
Takafumi Arakaki (tkf) (Mar 09 2021 at 00:08):take!'s docstring is correct. it just does not say that it will also create a new array
julia> io = IOBuffer();
julia> data = io.data;
julia> take!(io) === data
true
julia> io.data === data
false
so where are you saying it's creating an array here?
Takafumi Arakaki (tkf) (Mar 09 2021 at 00:26):take!(io) === data indicates that it returns the internal buffer as-is. io.data !== data indicates that the internal buffer is re-allocated. You can also see the code here: https://github.com/JuliaLang/julia/blob/970edc7d7734ce0175177699e474ffc8f7b9eb27/base/iobuffer.jl#L391
Expanding Man (Mar 09 2021 at 00:26):Ok, I was so confused about the internal buffer being re-allocated I just kind of dind't believe it lol
Expanding Man (Mar 09 2021 at 00:26):I mean, I guess it's for the same reason I said above, to preserve the data, it's just really confusing
Last updated: Nov 06 2024 at 04:40 UTC