string to ptr uint8

[bunkford]

I'm trying to port [zint](https://github.com/zint/zint) to nim so I can 
generate barcodes.

I'm stuck on this: 
    
    
    input: ptr uint8;
    
    Run

how do I take a string and pass it to input.

zint.h:
    
    
    int ZBarcode_Encode_and_Print(struct zint_symbol *symbol, uint8_t *input, 
int length, int rotate_angle);
    
    Run

c2nim nim output:
    
    
    proc ZBarcode_Encode_and_Print*(symbol: ptr zint_symbol; input: ptr uint8; 
length: cint; rotate_angle: cint): cint {.cdecl, importc: 
"ZBarcode_Encode_and_Print", dynlib: libzint.}
    
    Run