I have defined my own primitive type as below which works. import Base: >>, >(x::UInt24, y) = Base.lshr_int(x, y) <<(x::UInt24, y) = Base.shl_int(x, y) I then tried to define a masking operation using & the below works pretty well but I can’t figure out how to define my own bits e.g. if I want to set z = 0xffffff it turns z into UInt32 with 0x00ffffff. But I want 24 bits of 1’s. How can I acheive that? Or more generally how do I define arbitrary bit patters for my new type. Help appreciated! This will help make a much faster string sorting algorithm in pure Julia! x = unsafe_load(Ptr{UInt24}(pointer("abc"))) y = unsafe_load(Ptr{UInt24}(pointer("def"))) Base.and_int(x,y)

I think I got a working solution. Just not sure if it’s the most efficient. z = UInt(16^5*15 + 16^4*15 + 16^3*15 + 16^2*15 + 16*15+ 15) unsafe_load(Ptr{UInt24}(pointer_from_objref(z)))

This may help: [image] Convert to and from Int24 General Usage I am want to try an Int24 type, purely for storage. It is easy to declare one with primitive type Int24 <: Signed 24 end but I am not sure how to access its value. I only need conversion to and from Int32, but I don’t think I can use reinterpret because they don’t have the same number of bits. How can I convert to and from Int32? (BTW, I am aware that I destroy alignment and it will degrade performance; it is an experiment)

This topic might also be of interest (this isn’t the first time people have wanted to use a 24-bit primitive type): [image] Regression between v0.6 and master with reinterpret from #21831 Internals & Design On v0.6.0-rc2, this works: julia> primitive type Foo 24 end ; reinterpret(Foo, b"123") 1-element Array{Foo,1}: Foo(0x333231) On v0.7.0-DEV.427, it fails: julia> primitive type Foo 24 end ; reinterpret(Foo, b"123") ERROR: ArgumentError: reinterpret from alignment 1 bytes to alignment 4 bytes not allowed Stacktrace: [1] reinterpret(::Type{Foo}, ::Array{UInt8,1}, ::Tuple{Int64}) at ./array.jl:160 [2] reinterpret(::Type{Foo}, ::Array{UInt8,1}) at ./array.jl:139 This seems to be another regres…

How to write bits into a user-defined primitive type?

General Usage

Tamas_Papp December 29, 2017, 7:21am 3

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How to write bits into a user-defined primitive type?

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