Getting Content-Length header of response, for allocating Vec::with_capacity before downloading

[Boscop]

Getting Content-Length header of response, for allocating Vec::with_capacity before downloading

[SonnyX]

Thanks for the interest of the crate.
I don't see a way to manipulate the API of the crate which would allow you to receive the headers, set the size of the vec beforehand and then return to downloading, in a way that makes sense.
Currently you could use/abuse the Progress trait, as when the content-length is set, the set_file_size function of that trait is called, in which you can do whatever you wish with that information, such as potentially manipulating the size of the Vec (albeit probably through the use of unsafe rust at this point).
Although it could have been a nice optimization to set the file-size beforehand using with_capacity, any service is not guaranteed to set the content-length header, rendering it useless in those cases.