# Memcpy in julia
**URL:** https://discourse.julialang.org/t/memcpy-in-julia/67791
**Category:** Performance
**Tags:** question
**Created:** [September 7, 2021, 7:01am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791 "2021-09-07T07:01:09Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Beh123](https://discourse.julialang.org/u/Beh123)
#### Post date: [September 7, 2021, 7:01am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/1 "2021-09-07T07:01:09Z")
Hi everyone
I have a vector which contains 5 uint8 elements. How do I copy them to two int32 variables ? we can do it with memcpy in c. Is there similar command in julia?
```julia
x=[0x3 0x00 0x11 0x00 0x80]
m= convert(Int32, signed(x[3])&0x0f)<<16 | convert( Int32, signed(x[2]))<<8 | convert( Int32, signed(x[1]));
n= convert(Int32, signed(x[5]))<<16 |convert(Int32, signed(x[4]))<<8 | convert (Int32, signed(x[3])>>4);
```
This code is run but it isn’t optimal. Is there other way? Thanks alot.
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [September 7, 2021, 7:09am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/2 "2021-09-07T07:09:03Z")
Use `reinterpret`.
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### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [September 7, 2021, 7:29am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/3 "2021-09-07T07:29:02Z")
I see now that you’ve edited your question (which was about 4 `UInt8` instead of 5).
If you show code, please surround it in triple backticks (```) to make it easier to read & follow, and ultimately to [make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757).
* * *
I’m not sure using `memcpy` to interpret 5 bytes as two `Int32` works in C either - you’ll interpret bytes outside of the array as part of the last `Int32`, which is a dangerous thing (and probably undefined behavior as well). Where do you get those bytes from? What do you want to do with them?
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [September 7, 2021, 7:37am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/4 "2021-09-07T07:37:45Z")
Assuming you want to have the top 3 bytes to be `0x00`, you can just
```julia
while length(x) % 4 != 0
push!(x, zero(UInt8))
end
```
(or calculate the new size statically and `append!` the correct amount directly) and then do `reinterpret(Int32, x)`.
---
### Author:  [@Beh123](https://discourse.julialang.org/u/Beh123)
#### Post date: [September 7, 2021, 8:27am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/5 "2021-09-07T08:27:16Z")
I recieve data from udp network. Each 20 bits is a variable. How do I spilit data?
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### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [September 7, 2021, 8:45am UTC](https://discourse.julialang.org/t/memcpy-in-julia/67791/6 "2021-09-07T08:45:57Z")
With bit shifts, something along the lines of your original post.