unicode - How To Convert An Elixir Binary To A String?

Question

So I'm trying to convert a binary to a string. This code:

t = [{<<71,0,69,0,84,0>>}]
String.from_char_list(t)

But I'm getting this when I try this conversion:

** (ArgumentError) argument error
    (stdlib) :unicode.characters_to_binary([{<<70, 0, 73, 0, 78, 0>>}])
    (elixir) lib/string.ex:1161: String.from_char_list/1

I'm assuming the <<70, 0, etc. is likely a list of graphemes (it's the return from an API call and the API is not quite documented) but do I need to specify the encoding somehow?

I know I'm likely missing something obvious (maybe that's not the right function to use?) but I can't seem to figure out what to do here.

---

EDIT:

For what it's worth, the binary above is the return value of an Erlang ODBC call. After a little more digging I found that the binary in question is actually a "Unicode binary encoded as UTF16 little endian" (see here: http://www.erlang.org/doc/apps/odbc/odbc.pdf pg. 9 re: SQL_WVARCHAR) Doesn't really change the issue but it does add some context.

Answer 1

There's a couple of things here:

1.) You have a list with a tuple containing one element, a binary. You can probably just extract the binary and have your string. Passing the current data structure to to_string is not going to work.

2.) The binary you used in your example contains 0, an unprintable character. In the shell, this will not be printed properly as a string, due to the fact that Elixir can't tell the difference between just a binary, and a binary representing a string, when the binary representing a string contains unprintable characters.

3.) You can use pattern matching to convert a binary to a particular type. For instance:

iex> raw = <<71,32,69,32,84,32>>
...> Enum.join(for <<c::utf8 <- raw>>, do: <<c::utf8>>)
"G E T "
...> <<c::utf8, _::binary>> = raw
"G"

Also, if you are getting binary data from a network connection, you probably want to use :erlang.iolist_to_binary, since the data will be an iolist, not a charlist. The difference is that iolists can contain binaries, nested lists, as well as just be a list of integers. Charlists are always just a flat list of integers. If you call to_string, on an iolist, it will fail.