= cowboy_req:read_part_body(3)
== Name
cowboy_req:read_part_body - Read the current part's body
== Description
[source,erlang]
----
read_part_body(Req :: cowboy_req:req())
-> read_part_body(Req, #{})
read_part_body(Req :: cowboy_req:req(), Opts)
-> {ok, Data :: binary(), Req}
| {more, Data :: binary(), Req}
Opts :: cowboy_req:read_body_opts()
----
Read the body of the current part of the multipart message.
This function reads the request body and parses it as
multipart. Each parts of a multipart representation have
their own headers and body. This function returns the
body of the current part. Examples of multipart media types
are `multipart/form-data` and `multipart/byteranges`.
This function reads a chunk of the part's body. A `more` tuple
is returned when more data remains to be read. Call the function
repeatedly until an `ok` tuple is returned to read the entire body.
Once a part has been read, it can not be read again.
Once the body has been read, Cowboy sets the content-length
header if it was not previously provided.
// @todo Limit the maximum size of multipart headers.
== Arguments
Req::
The Req object.
Opts::
A map of body reading options. Please refer to
link:man:cowboy_req:read_body(3)[cowboy_req:read_body(3)]
for details about each option.
+
This function uses the same default options as the
link:man:cowboy_req:read_body(3)[cowboy_req:read_body(3)]
function.
== Return value
A `more` tuple is returned when there are more data to be read.
An `ok` tuple is returned when there are no more data to be read.
The data is always returned as a binary.
The Req object returned in the tuple must be used for that point
onward. It contains a more up to date representation of the request.
For example it may have an added content-length header once the
body has been read.
== Changelog
* *2.0*: Function introduced. Replaces `part_body/1,2`.
== Examples
.Read a full part's body
[source,erlang]
----
stream_body(Req0, Acc) ->
case cowboy_req:read_part_body(Req0) of
{more, Data, Req} ->
stream_body(Req, << Acc/binary, Data/binary >>);
{ok, Data, Req} ->
{ok, << Acc/binary, Data/binary >>, Req}
end.
----
.Ensure a part's body is smaller than 64KB
[source,erlang]
----
{ok, Body, Req} = cowboy_req:read_part_body(Req0, #{length => 64000}).
----
== See also
link:man:cowboy_req(3)[cowboy_req(3)],
link:man:cowboy_req:has_body(3)[cowboy_req:has_body(3)],
link:man:cowboy_req:body_length(3)[cowboy_req:body_length(3)],
link:man:cowboy_req:read_body(3)[cowboy_req:read_body(3)],
link:man:cowboy_req:read_urlencoded_body(3)[cowboy_req:read_urlencoded_body(3)],
link:man:cowboy_req:read_part(3)[cowboy_req:read_part(3)]