From 8ec8af12439c951987202d4aed6d7f7f12257d79 Mon Sep 17 00:00:00 2001
From: Prashanth Mundkur <prashanth.mundkur@gmail.com>
Date: Mon, 5 Nov 2012 17:12:23 -0800
Subject: [PATCH] Fix 0-length range responses.

There were two issues:

- file:pread() returns eof in the case when the length of the
  read is 0 bytes, for any offset.  This causes badarg exceptions
  later in iolist_size when the 'eof' atom is encountered instead
  of a binary

- The range-length computation is off by 1 for 0-length ranges:
  {Skip, Skip + Length - 1, PartialBody} would result in e.g.
  {0, -1, eof}. {0, -1} is invalid HTTP according to

  http://tools.ietf.org/html/rfc2616#section-14.16

     A byte-content-range-spec with a byte-range-resp-spec whose
     last-byte-pos value is less than its first-byte-pos value,
     or whose instance-length value is less than or equal to its
     last-byte-pos value, is invalid.

This patch fixes both issues.
---
 src/mochiweb_request.erl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/mochiweb_request.erl b/src/mochiweb_request.erl
index aeeeb1b5..9a8f28d1 100644
--- a/src/mochiweb_request.erl
+++ b/src/mochiweb_request.erl
@@ -652,7 +652,12 @@ range_parts({file, IoDevice}, Ranges) ->
     LocNums = lists:foldr(F, [], Ranges),
     {ok, Data} = file:pread(IoDevice, LocNums),
     Bodies = lists:zipwith(fun ({Skip, Length}, PartialBody) ->
-                                   {Skip, Skip + Length - 1, PartialBody}
+                                   case Length of
+                                       0 ->
+                                           {Skip, Skip, <<>>};
+                                       _ ->
+                                           {Skip, Skip + Length - 1, PartialBody}
+                                   end
                            end,
                            LocNums, Data),
     {Bodies, Size};