unikernel/duniverse/ocaml-h2/lib/priority.ml

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+(*----------------------------------------------------------------------------
+ *  Copyright (c) 2019 António Nuno Monteiro
+ *
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *  this list of conditions and the following disclaimer.
+ *
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *  notice, this list of conditions and the following disclaimer in the
+ *  documentation and/or other materials provided with the distribution.
+ *
+ *  3. Neither the name of the copyright holder nor the names of its
+ *  contributors may be used to endorse or promote products derived from this
+ *  software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ *---------------------------------------------------------------------------*)
+
+open Util
+
+type t =
+  { exclusive : bool
+  ; stream_dependency : Stream_identifier.t
+  ; weight : int
+  }
+
+(* From RFC7540§5.3.5:
+ *   All streams are initially assigned a non-exclusive dependency on stream
+ *   0x0. Pushed streams (Section 8.2) initially depend on their associated
+ *   stream. In both cases, streams are assigned a default weight of 16. *)
+let default_priority =
+  { exclusive = false; stream_dependency = 0l; weight = 16 }
+
+(* From RFC7540§5.4.1:
+ *   All dependent streams are allocated an integer weight between 1 and 256
+ *   (inclusive). *)
+let highest_priority =
+  { exclusive = false; stream_dependency = 0l; weight = 256 }
+
+(* --- Exclusive flag ---
+ *
+ * From RFC7540§5.4.1:
+ *   +-+-------------------------------------------------------------+
+ *   |E|                  Stream Dependency (31)                     |
+ *   +-+-------------+-----------------------------------------------+
+ *   |   Weight (8)  |
+ *   +-+-------------+
+ *)
+
+let test_exclusive n = test_bit_int32 n 31
+let set_exclusive n = set_bit_int32 n 31
+let clear_exclusive n = clear_bit_int32 n 31
+
+let equal p1 p2 =
+  p1.weight = p2.weight
+  && Int32.equal p1.stream_dependency p2.stream_dependency
+  && p1.exclusive = p2.exclusive