What's the easiest way to encode a String to utf-8?

[sa-]

I have a String and I would like to convert it into a byte array (so presumably a DynamicVector[UI8])

[czheo]

maybe this

from Vector import DynamicVector
from String import String

let vec : DynamicVector[SI8] = String("hello world").buffer

[sa-]

Nice, thanks!

[survuvi]

and how to print the vec variable, we need builtins module?

from Vector import DynamicVector
from String import String
from PythonInterface import Python

let vec : DynamicVector[SI8] = String("hello world").buffer

let builtins = Python.import_module("builtins")
builtins.print(vec)

error: Expression [4]:23:19: invalid call to 'call': argument #1 cannot be converted from 'DynamicVector[SIMD[si8, 1]]' to 'PythonObject'
builtins.print(vec)
~~~~~~~~~~~~~~^~~~~

/.modular/Kernels/mojo/Python/PythonObject.mojo:210:5: function declared here
fn call(self, *args: PythonObject) raises -> PythonObject:
^

[survuvi]

from Vector import DynamicVector
from String import String

fn conversion_to_utf(my_string) -> str:
    let vec : DynamicVector[SI8] = String(my_string).buffer
    return vec
    
conversion_to_utf("hello world")

_error: Expression [13]:8:36: use of unknown declaration 'str', 'fn' declarations require explicit variable declarations
fn conversion_to_utf(my_string) -> str:
^~~

error: Expression [13]:8:22: 'fn' parameter type must be specified
fn conversion_to_utf(my_string) -> str:_

[abhinav-upadhyay]

You are returning DynamicVector[SI8] so you need to declare that as the return type of the function.
fn conversion_to_utf(my_string) -> DynamicVector[SI8]:

The other problem is that when writing Mojo functions (fn) -- you need to declare the types of all the arguments to the function. So it should be something like

fn conversion_to_utf(my_string: String) -> DynamicVector[SI8]:

Your final code will look like this:

from Vector import DynamicVector
from String import String

fn conversion_to_utf(my_string: String) -> DynamicVector[SI8]:
    let vec : DynamicVector[SI8] = my_string.buffer
    return vec
    
conversion_to_utf("hello world")

[survuvi]

why it doesn't show any output value?

[mfranzon]

From my understanding, at the moment there is not a method to stored the object itself into the dynamic vector but just its reference. So, if you print the return of that function, you end up in an error because you can only get the reference using the __getitem__ for example in this way:

from Vector import DynamicVector
from String import String

fn conversion_to_utf(my_string: String) -> DynamicVector[SI8]:
    let vec : DynamicVector[SI8] = my_string.buffer
    return vec
    
print(conversion_to_utf("hello world")[0])

And it return the reference to the 0 element of the String, but not the value.
You can have a look on these issues in which is better explained :)
-> #126
-> #113

[d3v3us]

hey @czheo, how do opposite, convert DynamicVector[SI8] into String?

[mfranzon]

From my understanding using fn you should declare the string as immutable object:

from Vector import DynamicVector
from String import String
fn into_utf8(data:String) -> DynamicVector[SI8]:
        let vec:DynamicVector[SI8] = data.buffer
        return vec
fn from_utf8(vec:DynamicVector[SI8]) -> String:
        let p = String(vec.data, len(vec))
        return p

let s : String = "temp"
let bt=into_utf8(s)
print(from_utf8(bt))

[d3v3us]

thank you @mfranzon, works like a charm)

[d3v3us]

hey @czheo @mfranzon, do you know whats the difference between Pointer.alloc and stack_allocation?

[sa-]

I'm not either of them, but I would Pointer.alloc allocates memory on the heap, and stack_allocation does it on the stack as the name suggests

[d3v3us]

make sense, my bad, just curious how to use memory.stack_allocation)

[iamtimdavis]

Closing this out given there is a clear answer above

[taalhaataahir0102]

Can you please share how you wrote SI8?