(base64-substring->u8vector str start end)

Decodes a base64 encoded substring and returns a u8vector.

Parameter	Description
str	string to decode
start	string start index
end	string end index

Example

> (base64-substring->u8vector "TEST:HcoDVdC7Sds=" 5 17)
#u8(29 202 3 85 208 187 73 219)