Merge pull request #1017 from mefyl/fix/to-string-trim

Fix assertion in `Parser.Source.to_string_trim`.

CHANGES.md

@@ -1,3 +1,7 @@
+## Unreleased
+
+- http: Fix assertion in `Source.to_string_trim` when `pos <> 0` (mefyl #1017)
+
 ## v6.0.0~beta2 (2024-01-05)
 
 - cohttp-eio: Don't blow up Server on client disconnections. (mefyl #1011)

http/src/http.ml

@@ -944,7 +944,7 @@ module Parser = struct
              "Http_parser.Source.substring: Index out of bounds., Requested \
               off: %d, len: %d"
              pos len);
-      let last = ref (t.pos + len - 1) in
+      let last = ref (t.pos + pos + len - 1) in
       let pos = ref (t.pos + pos) in
       while is_space (String.unsafe_get t.buffer !pos) do
         incr pos
@@ -953,7 +953,7 @@ module Parser = struct
         decr last
       done;
       let len = !last - !pos + 1 in
-      String.sub t.buffer !pos len
+      if len < 0 then "" else String.sub t.buffer !pos len
 
     let rec index_rec t ch idx len =
       if idx = len then -1

http/test/test_parser.ml

@@ -15,6 +15,7 @@ let req =
    Cookie: wp_ozh_wsa_visits=2; wp_ozh_wsa_visit_lasttime=xxxxxxxxxx; \
    __utma=xxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.x; \
    __utmz=xxxxxxxxx.xxxxxxxxxx.x.x.utmccn=(referral)|utmcsr=reader.livedoor.com|utmcct=/reader/|utmcmd=referral\r\n\
+   Empty:    \r\n\
    \r\n"
 
 let assert_req_success ~here ~expected_req ~expected_consumed ?pos ?len buf =
@@ -69,13 +70,14 @@ let req_expected =
               __utma=xxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.xxxxxxxxxx.x; \
               __utmz=xxxxxxxxx.xxxxxxxxxx.x.x.utmccn=(referral)|utmcsr=reader.livedoor.com|utmcct=/reader/|utmcmd=referral"
            );
+           ("Empty", "");
          ])
     `GET "/wp-content/uploads/2010/03/hello-kitty-darth-vader-pink.jpg"
 
 let parse_single_request () =
   assert_req_success
     ~here:[ [%here] ]
-    ~expected_req:req_expected ~expected_consumed:706 req
+    ~expected_req:req_expected ~expected_consumed:718 req
 
 let reject_headers_with_space_before_colon () =
   let req =