From 24c79977c7974d5415b6d4f7085a651ce1048e6a Mon Sep 17 00:00:00 2001
From: Siri Hansen <siri@erlang.org>
Date: Tue, 17 Oct 2017 19:23:58 +0200
Subject: [observer] Don't crash on empty binary

Commit e1310b8f introduced a bug which caused the observer tool (and
crashdump_viewer) to crash when trying to display an empty binary. The
same change would also cause leading zeros in a binary to disappear in
the preview. The bug is now corrected.
---
 lib/observer/src/cdv_bin_cb.erl        | 2 ++
 lib/observer/src/observer_html_lib.erl | 6 +++---
 lib/observer/src/observer_lib.erl      | 8 ++++----
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/lib/observer/src/cdv_bin_cb.erl b/lib/observer/src/cdv_bin_cb.erl
index 5502869973..a4a542297c 100644
--- a/lib/observer/src/cdv_bin_cb.erl
+++ b/lib/observer/src/cdv_bin_cb.erl
@@ -71,6 +71,8 @@ hex_binary_fun(Bin) ->
 	    plain_html(io_lib:format("~s",[S]))
     end.
 
+format_hex(<<>>,_) ->
+    [];
 format_hex(<<B1:4,B2:4>>,_) ->
     [integer_to_list(B1,16),integer_to_list(B2,16)];
 format_hex(<<B1:4,B2:4,Bin/binary>>,0) ->
diff --git a/lib/observer/src/observer_html_lib.erl b/lib/observer/src/observer_html_lib.erl
index a85808a472..22b4714d63 100644
--- a/lib/observer/src/observer_html_lib.erl
+++ b/lib/observer/src/observer_html_lib.erl
@@ -355,11 +355,11 @@ href_proc_bin(From, T, Acc, LTB) ->
                                 PreviewStr
                         end
                 end;
-	    [PreviewIntStr,SizeStr,Md5] when From =:= obs ->
+	    [PreviewIntStr,PreviewBitSizeStr,SizeStr,Md5] when From =:= obs ->
 		Size = list_to_integer(SizeStr),
                 PreviewInt = list_to_integer(PreviewIntStr),
-		PrevSize = (trunc(math:log2(PreviewInt)/8)+1)*8,
-		PreviewStr = preview_string(Size,<<PreviewInt:PrevSize>>),
+                PreviewBitSize = list_to_integer(PreviewBitSizeStr),
+		PreviewStr = preview_string(Size,<<PreviewInt:PreviewBitSize>>),
 		if LTB ->
 			href("TARGET=\"expanded\"",
 			     ["#OBSBinary?key1="++PreviewIntStr++
diff --git a/lib/observer/src/observer_lib.erl b/lib/observer/src/observer_lib.erl
index 29f4f9fabc..94d199e688 100644
--- a/lib/observer/src/observer_lib.erl
+++ b/lib/observer/src/observer_lib.erl
@@ -810,7 +810,7 @@ progress_dialog_destroy({Dialog,_,_}) ->
 
 make_obsbin(Bin,Tab) ->
     Size = byte_size(Bin),
-    Preview =
+    {Preview,PreviewBitSize} =
         try
             %% The binary might be a unicode string, in which case we
             %% don't want to split it in the middle of a grapheme
@@ -819,14 +819,14 @@ make_obsbin(Bin,Tab) ->
             PB1 = string:slice(Bin,0,PL1),
             PS1 = byte_size(PB1) * 8,
             <<P1:PS1>> = PB1,
-            P1
+            {P1,PS1}
         catch _:_ ->
                 %% Probably not a string, so just split anywhere
                 PS2 = min(Size, 10) * 8,
                 <<P2:PS2, _/binary>> = Bin,
-                P2
+                {P2,PS2}
         end,
     Hash = erlang:phash2(Bin),
     Key = {Preview, Size, Hash},
     ets:insert(Tab, {Key,Bin}),
-    ['#OBSBin',Preview,Size,Hash].
+    ['#OBSBin',Preview,PreviewBitSize,Size,Hash].
-- 
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