Adding upstream version 1.52.0.upstream/1.52.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1018 insertions, 0 deletions

diff --git a/lib/nghttp2_stream.c b/lib/nghttp2_stream.c
new file mode 100644
index 0000000..b3614a0
--- /dev/null
+++ b/lib/nghttp2_stream.c
@@ -0,0 +1,1018 @@
+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2012 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "nghttp2_stream.h"
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "nghttp2_session.h"
+#include "nghttp2_helper.h"
+#include "nghttp2_debug.h"
+#include "nghttp2_frame.h"
+
+/* Maximum distance between any two stream's cycle in the same
+   priority queue.  Imagine stream A's cycle is A, and stream B's
+   cycle is B, and A < B.  The cycle is unsigned 32 bit integer, it
+   may get overflow.  Because of how we calculate the next cycle
+   value, if B - A is less than or equals to
+   NGHTTP2_MAX_CYCLE_DISTANCE, A and B are in the same scale, in other
+   words, B is really greater than or equal to A.  Otherwise, A is a
+   result of overflow, and it is actually A > B if we consider that
+   fact. */
+#define NGHTTP2_MAX_CYCLE_DISTANCE                                             \
+  ((uint64_t)NGHTTP2_MAX_FRAME_SIZE_MAX * 256 + 255)
+
+static int stream_less(const void *lhsx, const void *rhsx) {
+  const nghttp2_stream *lhs, *rhs;
+
+  lhs = nghttp2_struct_of(lhsx, nghttp2_stream, pq_entry);
+  rhs = nghttp2_struct_of(rhsx, nghttp2_stream, pq_entry);
+
+  if (lhs->cycle == rhs->cycle) {
+    return lhs->seq < rhs->seq;
+  }
+
+  return rhs->cycle - lhs->cycle <= NGHTTP2_MAX_CYCLE_DISTANCE;
+}
+
+void nghttp2_stream_init(nghttp2_stream *stream, int32_t stream_id,
+                         uint8_t flags, nghttp2_stream_state initial_state,
+                         int32_t weight, int32_t remote_initial_window_size,
+                         int32_t local_initial_window_size,
+                         void *stream_user_data, nghttp2_mem *mem) {
+  nghttp2_pq_init(&stream->obq, stream_less, mem);
+
+  stream->stream_id = stream_id;
+  stream->flags = flags;
+  stream->state = initial_state;
+  stream->shut_flags = NGHTTP2_SHUT_NONE;
+  stream->stream_user_data = stream_user_data;
+  stream->item = NULL;
+  stream->remote_window_size = remote_initial_window_size;
+  stream->local_window_size = local_initial_window_size;
+  stream->recv_window_size = 0;
+  stream->consumed_size = 0;
+  stream->recv_reduction = 0;
+  stream->window_update_queued = 0;
+
+  stream->dep_prev = NULL;
+  stream->dep_next = NULL;
+  stream->sib_prev = NULL;
+  stream->sib_next = NULL;
+
+  stream->closed_prev = NULL;
+  stream->closed_next = NULL;
+
+  stream->weight = weight;
+  stream->sum_dep_weight = 0;
+
+  stream->http_flags = NGHTTP2_HTTP_FLAG_NONE;
+  stream->content_length = -1;
+  stream->recv_content_length = 0;
+  stream->status_code = -1;
+
+  stream->queued = 0;
+  stream->descendant_last_cycle = 0;
+  stream->cycle = 0;
+  stream->pending_penalty = 0;
+  stream->descendant_next_seq = 0;
+  stream->seq = 0;
+  stream->last_writelen = 0;
+
+  stream->extpri = stream->http_extpri = NGHTTP2_EXTPRI_DEFAULT_URGENCY;
+}
+
+void nghttp2_stream_free(nghttp2_stream *stream) {
+  nghttp2_pq_free(&stream->obq);
+  /* We don't free stream->item.  If it is assigned to aob, then
+     active_outbound_item_reset() will delete it.  Otherwise,
+     nghttp2_stream_close() or session_del() will delete it. */
+}
+
+void nghttp2_stream_shutdown(nghttp2_stream *stream, nghttp2_shut_flag flag) {
+  stream->shut_flags = (uint8_t)(stream->shut_flags | flag);
+}
+
+/*
+ * Returns nonzero if |stream| is active.  This function does not take
+ * into account its descendants.
+ */
+static int stream_active(nghttp2_stream *stream) {
+  return stream->item &&
+         (stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_ALL) == 0;
+}
+
+/*
+ * Returns nonzero if |stream| or one of its descendants is active
+ */
+static int stream_subtree_active(nghttp2_stream *stream) {
+  return stream_active(stream) || !nghttp2_pq_empty(&stream->obq);
+}
+
+/*
+ * Returns next cycle for |stream|.
+ */
+static void stream_next_cycle(nghttp2_stream *stream, uint64_t last_cycle) {
+  uint64_t penalty;
+
+  penalty = (uint64_t)stream->last_writelen * NGHTTP2_MAX_WEIGHT +
+            stream->pending_penalty;
+
+  stream->cycle = last_cycle + penalty / (uint32_t)stream->weight;
+  stream->pending_penalty = (uint32_t)(penalty % (uint32_t)stream->weight);
+}
+
+static int stream_obq_push(nghttp2_stream *dep_stream, nghttp2_stream *stream) {
+  int rv;
+
+  for (; dep_stream && !stream->queued;
+       stream = dep_stream, dep_stream = dep_stream->dep_prev) {
+    stream_next_cycle(stream, dep_stream->descendant_last_cycle);
+    stream->seq = dep_stream->descendant_next_seq++;
+
+    DEBUGF("stream: stream=%d obq push cycle=%lu\n", stream->stream_id,
+           stream->cycle);
+
+    DEBUGF("stream: push stream %d to stream %d\n", stream->stream_id,
+           dep_stream->stream_id);
+
+    rv = nghttp2_pq_push(&dep_stream->obq, &stream->pq_entry);
+    if (rv != 0) {
+      return rv;
+    }
+    stream->queued = 1;
+  }
+
+  return 0;
+}
+
+/*
+ * Removes |stream| from parent's obq.  If removal of |stream| makes
+ * parent's obq empty, and parent is not active, then parent is also
+ * removed.  This process is repeated recursively.
+ */
+static void stream_obq_remove(nghttp2_stream *stream) {
+  nghttp2_stream *dep_stream;
+
+  dep_stream = stream->dep_prev;
+
+  if (!stream->queued) {
+    return;
+  }
+
+  for (; dep_stream; stream = dep_stream, dep_stream = dep_stream->dep_prev) {
+    DEBUGF("stream: remove stream %d from stream %d\n", stream->stream_id,
+           dep_stream->stream_id);
+
+    nghttp2_pq_remove(&dep_stream->obq, &stream->pq_entry);
+
+    assert(stream->queued);
+
+    stream->queued = 0;
+    stream->cycle = 0;
+    stream->pending_penalty = 0;
+    stream->descendant_last_cycle = 0;
+    stream->last_writelen = 0;
+
+    if (stream_subtree_active(dep_stream)) {
+      return;
+    }
+  }
+}
+
+/*
+ * Moves |stream| from |src|'s obq to |dest|'s obq.  Removal from
+ * |src|'s obq is just done calling nghttp2_pq_remove(), so it does
+ * not recursively remove |src| and ancestors, like
+ * stream_obq_remove().
+ */
+static int stream_obq_move(nghttp2_stream *dest, nghttp2_stream *src,
+                           nghttp2_stream *stream) {
+  if (!stream->queued) {
+    return 0;
+  }
+
+  DEBUGF("stream: remove stream %d from stream %d (move)\n", stream->stream_id,
+         src->stream_id);
+
+  nghttp2_pq_remove(&src->obq, &stream->pq_entry);
+  stream->queued = 0;
+
+  return stream_obq_push(dest, stream);
+}
+
+void nghttp2_stream_reschedule(nghttp2_stream *stream) {
+  nghttp2_stream *dep_stream;
+
+  assert(stream->queued);
+
+  dep_stream = stream->dep_prev;
+
+  for (; dep_stream; stream = dep_stream, dep_stream = dep_stream->dep_prev) {
+    nghttp2_pq_remove(&dep_stream->obq, &stream->pq_entry);
+
+    stream_next_cycle(stream, dep_stream->descendant_last_cycle);
+    stream->seq = dep_stream->descendant_next_seq++;
+
+    nghttp2_pq_push(&dep_stream->obq, &stream->pq_entry);
+
+    DEBUGF("stream: stream=%d obq resched cycle=%lu\n", stream->stream_id,
+           stream->cycle);
+
+    dep_stream->last_writelen = stream->last_writelen;
+  }
+}
+
+void nghttp2_stream_change_weight(nghttp2_stream *stream, int32_t weight) {
+  nghttp2_stream *dep_stream;
+  uint64_t last_cycle;
+  int32_t old_weight;
+  uint64_t wlen_penalty;
+
+  if (stream->weight == weight) {
+    return;
+  }
+
+  old_weight = stream->weight;
+  stream->weight = weight;
+
+  dep_stream = stream->dep_prev;
+
+  if (!dep_stream) {
+    return;
+  }
+
+  dep_stream->sum_dep_weight += weight - old_weight;
+
+  if (!stream->queued) {
+    return;
+  }
+
+  nghttp2_pq_remove(&dep_stream->obq, &stream->pq_entry);
+
+  wlen_penalty = (uint64_t)stream->last_writelen * NGHTTP2_MAX_WEIGHT;
+
+  /* Compute old stream->pending_penalty we used to calculate
+     stream->cycle */
+  stream->pending_penalty =
+      (uint32_t)((stream->pending_penalty + (uint32_t)old_weight -
+                  (wlen_penalty % (uint32_t)old_weight)) %
+                 (uint32_t)old_weight);
+
+  last_cycle = stream->cycle -
+               (wlen_penalty + stream->pending_penalty) / (uint32_t)old_weight;
+
+  /* Now we have old stream->pending_penalty and new stream->weight in
+     place */
+  stream_next_cycle(stream, last_cycle);
+
+  if (dep_stream->descendant_last_cycle - stream->cycle <=
+      NGHTTP2_MAX_CYCLE_DISTANCE) {
+    stream->cycle = dep_stream->descendant_last_cycle;
+  }
+
+  /* Continue to use same stream->seq */
+
+  nghttp2_pq_push(&dep_stream->obq, &stream->pq_entry);
+
+  DEBUGF("stream: stream=%d obq resched cycle=%lu\n", stream->stream_id,
+         stream->cycle);
+}
+
+static nghttp2_stream *stream_last_sib(nghttp2_stream *stream) {
+  for (; stream->sib_next; stream = stream->sib_next)
+    ;
+
+  return stream;
+}
+
+int32_t nghttp2_stream_dep_distributed_weight(nghttp2_stream *stream,
+                                              int32_t weight) {
+  weight = stream->weight * weight / stream->sum_dep_weight;
+
+  return nghttp2_max(1, weight);
+}
+
+#ifdef STREAM_DEP_DEBUG
+
+static void ensure_inactive(nghttp2_stream *stream) {
+  nghttp2_stream *si;
+
+  if (stream->queued) {
+    fprintf(stderr, "stream(%p)=%d, stream->queued = 1; want 0\n", stream,
+            stream->stream_id);
+    assert(0);
+  }
+
+  if (stream_active(stream)) {
+    fprintf(stderr, "stream(%p)=%d, stream_active(stream) = 1; want 0\n",
+            stream, stream->stream_id);
+    assert(0);
+  }
+
+  if (!nghttp2_pq_empty(&stream->obq)) {
+    fprintf(stderr, "stream(%p)=%d, nghttp2_pq_size() = %zu; want 0\n", stream,
+            stream->stream_id, nghttp2_pq_size(&stream->obq));
+    assert(0);
+  }
+
+  for (si = stream->dep_next; si; si = si->sib_next) {
+    ensure_inactive(si);
+  }
+}
+
+static void check_queued(nghttp2_stream *stream) {
+  nghttp2_stream *si;
+  int queued;
+
+  if (stream->queued) {
+    if (!stream_subtree_active(stream)) {
+      fprintf(stderr,
+              "stream(%p)=%d, stream->queued == 1, but "
+              "stream_active() == %d and nghttp2_pq_size(&stream->obq) = %zu\n",
+              stream, stream->stream_id, stream_active(stream),
+              nghttp2_pq_size(&stream->obq));
+      assert(0);
+    }
+    if (!stream_active(stream)) {
+      queued = 0;
+      for (si = stream->dep_next; si; si = si->sib_next) {
+        if (si->queued) {
+          ++queued;
+        }
+      }
+      if (queued == 0) {
+        fprintf(stderr,
+                "stream(%p)=%d, stream->queued == 1, and "
+                "!stream_active(), but no descendants is queued\n",
+                stream, stream->stream_id);
+        assert(0);
+      }
+    }
+
+    for (si = stream->dep_next; si; si = si->sib_next) {
+      check_queued(si);
+    }
+  } else {
+    if (stream_active(stream) || !nghttp2_pq_empty(&stream->obq)) {
+      fprintf(stderr,
+              "stream(%p) = %d, stream->queued == 0, but "
+              "stream_active(stream) == %d and "
+              "nghttp2_pq_size(&stream->obq) = %zu\n",
+              stream, stream->stream_id, stream_active(stream),
+              nghttp2_pq_size(&stream->obq));
+      assert(0);
+    }
+    for (si = stream->dep_next; si; si = si->sib_next) {
+      ensure_inactive(si);
+    }
+  }
+}
+
+static void check_sum_dep(nghttp2_stream *stream) {
+  nghttp2_stream *si;
+  int32_t n = 0;
+  for (si = stream->dep_next; si; si = si->sib_next) {
+    n += si->weight;
+  }
+  if (n != stream->sum_dep_weight) {
+    fprintf(stderr, "stream(%p)=%d, sum_dep_weight = %d; want %d\n", stream,
+            stream->stream_id, n, stream->sum_dep_weight);
+    assert(0);
+  }
+  for (si = stream->dep_next; si; si = si->sib_next) {
+    check_sum_dep(si);
+  }
+}
+
+static void check_dep_prev(nghttp2_stream *stream) {
+  nghttp2_stream *si;
+  for (si = stream->dep_next; si; si = si->sib_next) {
+    if (si->dep_prev != stream) {
+      fprintf(stderr, "si->dep_prev = %p; want %p\n", si->dep_prev, stream);
+      assert(0);
+    }
+    check_dep_prev(si);
+  }
+}
+
+#endif /* STREAM_DEP_DEBUG */
+
+#ifdef STREAM_DEP_DEBUG
+static void validate_tree(nghttp2_stream *stream) {
+  nghttp2_stream *si;
+
+  if (!stream) {
+    return;
+  }
+
+  for (; stream->dep_prev; stream = stream->dep_prev)
+    ;
+
+  assert(stream->stream_id == 0);
+  assert(!stream->queued);
+
+  fprintf(stderr, "checking...\n");
+  if (nghttp2_pq_empty(&stream->obq)) {
+    fprintf(stderr, "root obq empty\n");
+    for (si = stream->dep_next; si; si = si->sib_next) {
+      ensure_inactive(si);
+    }
+  } else {
+    for (si = stream->dep_next; si; si = si->sib_next) {
+      check_queued(si);
+    }
+  }
+
+  check_sum_dep(stream);
+  check_dep_prev(stream);
+}
+#else  /* !STREAM_DEP_DEBUG */
+static void validate_tree(nghttp2_stream *stream) { (void)stream; }
+#endif /* !STREAM_DEP_DEBUG*/
+
+static int stream_update_dep_on_attach_item(nghttp2_stream *stream) {
+  int rv;
+
+  rv = stream_obq_push(stream->dep_prev, stream);
+  if (rv != 0) {
+    return rv;
+  }
+
+  validate_tree(stream);
+  return 0;
+}
+
+static int stream_update_dep_on_detach_item(nghttp2_stream *stream) {
+  if (nghttp2_pq_empty(&stream->obq)) {
+    stream_obq_remove(stream);
+  }
+
+  validate_tree(stream);
+
+  return 0;
+}
+
+int nghttp2_stream_attach_item(nghttp2_stream *stream,
+                               nghttp2_outbound_item *item) {
+  int rv;
+
+  assert((stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_ALL) == 0);
+  assert(stream->item == NULL);
+
+  DEBUGF("stream: stream=%d attach item=%p\n", stream->stream_id, item);
+
+  stream->item = item;
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES) {
+    return 0;
+  }
+
+  rv = stream_update_dep_on_attach_item(stream);
+  if (rv != 0) {
+    /* This may relave stream->queued == 1, but stream->item == NULL.
+       But only consequence of this error is fatal one, and session
+       destruction.  In that execution path, these inconsistency does
+       not matter. */
+    stream->item = NULL;
+    return rv;
+  }
+
+  return 0;
+}
+
+int nghttp2_stream_detach_item(nghttp2_stream *stream) {
+  DEBUGF("stream: stream=%d detach item=%p\n", stream->stream_id, stream->item);
+
+  stream->item = NULL;
+  stream->flags = (uint8_t)(stream->flags & ~NGHTTP2_STREAM_FLAG_DEFERRED_ALL);
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES) {
+    return 0;
+  }
+
+  return stream_update_dep_on_detach_item(stream);
+}
+
+int nghttp2_stream_defer_item(nghttp2_stream *stream, uint8_t flags) {
+  assert(stream->item);
+
+  DEBUGF("stream: stream=%d defer item=%p cause=%02x\n", stream->stream_id,
+         stream->item, flags);
+
+  stream->flags |= flags;
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES) {
+    return 0;
+  }
+
+  return stream_update_dep_on_detach_item(stream);
+}
+
+int nghttp2_stream_resume_deferred_item(nghttp2_stream *stream, uint8_t flags) {
+  assert(stream->item);
+
+  DEBUGF("stream: stream=%d resume item=%p flags=%02x\n", stream->stream_id,
+         stream->item, flags);
+
+  stream->flags = (uint8_t)(stream->flags & ~flags);
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_ALL) {
+    return 0;
+  }
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES) {
+    return 0;
+  }
+
+  return stream_update_dep_on_attach_item(stream);
+}
+
+int nghttp2_stream_check_deferred_item(nghttp2_stream *stream) {
+  return stream->item && (stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_ALL);
+}
+
+int nghttp2_stream_check_deferred_by_flow_control(nghttp2_stream *stream) {
+  return stream->item &&
+         (stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_FLOW_CONTROL);
+}
+
+static int update_initial_window_size(int32_t *window_size_ptr,
+                                      int32_t new_initial_window_size,
+                                      int32_t old_initial_window_size) {
+  int64_t new_window_size = (int64_t)(*window_size_ptr) +
+                            new_initial_window_size - old_initial_window_size;
+  if (INT32_MIN > new_window_size ||
+      new_window_size > NGHTTP2_MAX_WINDOW_SIZE) {
+    return -1;
+  }
+  *window_size_ptr = (int32_t)new_window_size;
+  return 0;
+}
+
+int nghttp2_stream_update_remote_initial_window_size(
+    nghttp2_stream *stream, int32_t new_initial_window_size,
+    int32_t old_initial_window_size) {
+  return update_initial_window_size(&stream->remote_window_size,
+                                    new_initial_window_size,
+                                    old_initial_window_size);
+}
+
+int nghttp2_stream_update_local_initial_window_size(
+    nghttp2_stream *stream, int32_t new_initial_window_size,
+    int32_t old_initial_window_size) {
+  return update_initial_window_size(&stream->local_window_size,
+                                    new_initial_window_size,
+                                    old_initial_window_size);
+}
+
+void nghttp2_stream_promise_fulfilled(nghttp2_stream *stream) {
+  stream->state = NGHTTP2_STREAM_OPENED;
+  stream->flags = (uint8_t)(stream->flags & ~NGHTTP2_STREAM_FLAG_PUSH);
+}
+
+int nghttp2_stream_dep_find_ancestor(nghttp2_stream *stream,
+                                     nghttp2_stream *target) {
+  for (; stream; stream = stream->dep_prev) {
+    if (stream == target) {
+      return 1;
+    }
+  }
+  return 0;
+}
+
+int nghttp2_stream_dep_insert(nghttp2_stream *dep_stream,
+                              nghttp2_stream *stream) {
+  nghttp2_stream *si;
+  int rv;
+
+  DEBUGF("stream: dep_insert dep_stream(%p)=%d, stream(%p)=%d\n", dep_stream,
+         dep_stream->stream_id, stream, stream->stream_id);
+
+  stream->sum_dep_weight = dep_stream->sum_dep_weight;
+  dep_stream->sum_dep_weight = stream->weight;
+
+  if (dep_stream->dep_next) {
+    for (si = dep_stream->dep_next; si; si = si->sib_next) {
+      si->dep_prev = stream;
+      if (si->queued) {
+        rv = stream_obq_move(stream, dep_stream, si);
+        if (rv != 0) {
+          return rv;
+        }
+      }
+    }
+
+    if (stream_subtree_active(stream)) {
+      rv = stream_obq_push(dep_stream, stream);
+      if (rv != 0) {
+        return rv;
+      }
+    }
+
+    stream->dep_next = dep_stream->dep_next;
+  }
+
+  dep_stream->dep_next = stream;
+  stream->dep_prev = dep_stream;
+
+  validate_tree(stream);
+
+  return 0;
+}
+
+static void set_dep_prev(nghttp2_stream *stream, nghttp2_stream *dep) {
+  for (; stream; stream = stream->sib_next) {
+    stream->dep_prev = dep;
+  }
+}
+
+static void link_dep(nghttp2_stream *dep_stream, nghttp2_stream *stream) {
+  dep_stream->dep_next = stream;
+  if (stream) {
+    stream->dep_prev = dep_stream;
+  }
+}
+
+static void link_sib(nghttp2_stream *a, nghttp2_stream *b) {
+  a->sib_next = b;
+  if (b) {
+    b->sib_prev = a;
+  }
+}
+
+static void insert_link_dep(nghttp2_stream *dep_stream,
+                            nghttp2_stream *stream) {
+  nghttp2_stream *sib_next;
+
+  assert(stream->sib_prev == NULL);
+
+  sib_next = dep_stream->dep_next;
+
+  link_sib(stream, sib_next);
+
+  link_dep(dep_stream, stream);
+}
+
+static void unlink_sib(nghttp2_stream *stream) {
+  nghttp2_stream *prev, *next, *dep_next;
+
+  prev = stream->sib_prev;
+  dep_next = stream->dep_next;
+
+  assert(prev);
+
+  if (dep_next) {
+    /*
+     *  prev--stream(--sib_next--...)
+     *         |
+     *        dep_next
+     */
+
+    link_sib(prev, dep_next);
+
+    set_dep_prev(dep_next, stream->dep_prev);
+
+    if (stream->sib_next) {
+      link_sib(stream_last_sib(dep_next), stream->sib_next);
+    }
+  } else {
+    /*
+     *  prev--stream(--sib_next--...)
+     */
+    next = stream->sib_next;
+
+    prev->sib_next = next;
+
+    if (next) {
+      next->sib_prev = prev;
+    }
+  }
+}
+
+static void unlink_dep(nghttp2_stream *stream) {
+  nghttp2_stream *prev, *next, *dep_next;
+
+  prev = stream->dep_prev;
+  dep_next = stream->dep_next;
+
+  assert(prev);
+
+  if (dep_next) {
+    /*
+     * prev
+     *   |
+     * stream(--sib_next--...)
+     *   |
+     * dep_next
+     */
+    link_dep(prev, dep_next);
+
+    set_dep_prev(dep_next, stream->dep_prev);
+
+    if (stream->sib_next) {
+      link_sib(stream_last_sib(dep_next), stream->sib_next);
+    }
+
+  } else if (stream->sib_next) {
+    /*
+     * prev
+     *   |
+     * stream--sib_next
+     */
+    next = stream->sib_next;
+
+    next->sib_prev = NULL;
+
+    link_dep(prev, next);
+  } else {
+    prev->dep_next = NULL;
+  }
+}
+
+void nghttp2_stream_dep_add(nghttp2_stream *dep_stream,
+                            nghttp2_stream *stream) {
+  DEBUGF("stream: dep_add dep_stream(%p)=%d, stream(%p)=%d\n", dep_stream,
+         dep_stream->stream_id, stream, stream->stream_id);
+
+  dep_stream->sum_dep_weight += stream->weight;
+
+  if (dep_stream->dep_next == NULL) {
+    link_dep(dep_stream, stream);
+  } else {
+    insert_link_dep(dep_stream, stream);
+  }
+
+  validate_tree(stream);
+}
+
+int nghttp2_stream_dep_remove(nghttp2_stream *stream) {
+  nghttp2_stream *dep_prev, *si;
+  int32_t sum_dep_weight_delta;
+  int rv;
+
+  DEBUGF("stream: dep_remove stream(%p)=%d\n", stream, stream->stream_id);
+
+  /* Distribute weight of |stream| to direct descendants */
+  sum_dep_weight_delta = -stream->weight;
+
+  for (si = stream->dep_next; si; si = si->sib_next) {
+    si->weight = nghttp2_stream_dep_distributed_weight(stream, si->weight);
+
+    sum_dep_weight_delta += si->weight;
+
+    if (si->queued) {
+      rv = stream_obq_move(stream->dep_prev, stream, si);
+      if (rv != 0) {
+        return rv;
+      }
+    }
+  }
+
+  assert(stream->dep_prev);
+
+  dep_prev = stream->dep_prev;
+
+  dep_prev->sum_dep_weight += sum_dep_weight_delta;
+
+  if (stream->queued) {
+    stream_obq_remove(stream);
+  }
+
+  if (stream->sib_prev) {
+    unlink_sib(stream);
+  } else {
+    unlink_dep(stream);
+  }
+
+  stream->sum_dep_weight = 0;
+
+  stream->dep_prev = NULL;
+  stream->dep_next = NULL;
+  stream->sib_prev = NULL;
+  stream->sib_next = NULL;
+
+  validate_tree(dep_prev);
+
+  return 0;
+}
+
+int nghttp2_stream_dep_insert_subtree(nghttp2_stream *dep_stream,
+                                      nghttp2_stream *stream) {
+  nghttp2_stream *last_sib;
+  nghttp2_stream *dep_next;
+  nghttp2_stream *si;
+  int rv;
+
+  DEBUGF("stream: dep_insert_subtree dep_stream(%p)=%d stream(%p)=%d\n",
+         dep_stream, dep_stream->stream_id, stream, stream->stream_id);
+
+  stream->sum_dep_weight += dep_stream->sum_dep_weight;
+  dep_stream->sum_dep_weight = stream->weight;
+
+  if (dep_stream->dep_next) {
+    dep_next = dep_stream->dep_next;
+
+    link_dep(dep_stream, stream);
+
+    if (stream->dep_next) {
+      last_sib = stream_last_sib(stream->dep_next);
+
+      link_sib(last_sib, dep_next);
+    } else {
+      link_dep(stream, dep_next);
+    }
+
+    for (si = dep_next; si; si = si->sib_next) {
+      si->dep_prev = stream;
+      if (si->queued) {
+        rv = stream_obq_move(stream, dep_stream, si);
+        if (rv != 0) {
+          return rv;
+        }
+      }
+    }
+  } else {
+    link_dep(dep_stream, stream);
+  }
+
+  if (stream_subtree_active(stream)) {
+    rv = stream_obq_push(dep_stream, stream);
+    if (rv != 0) {
+      return rv;
+    }
+  }
+
+  validate_tree(dep_stream);
+
+  return 0;
+}
+
+int nghttp2_stream_dep_add_subtree(nghttp2_stream *dep_stream,
+                                   nghttp2_stream *stream) {
+  int rv;
+
+  DEBUGF("stream: dep_add_subtree dep_stream(%p)=%d stream(%p)=%d\n",
+         dep_stream, dep_stream->stream_id, stream, stream->stream_id);
+
+  dep_stream->sum_dep_weight += stream->weight;
+
+  if (dep_stream->dep_next) {
+    insert_link_dep(dep_stream, stream);
+  } else {
+    link_dep(dep_stream, stream);
+  }
+
+  if (stream_subtree_active(stream)) {
+    rv = stream_obq_push(dep_stream, stream);
+    if (rv != 0) {
+      return rv;
+    }
+  }
+
+  validate_tree(dep_stream);
+
+  return 0;
+}
+
+void nghttp2_stream_dep_remove_subtree(nghttp2_stream *stream) {
+  nghttp2_stream *next, *dep_prev;
+
+  DEBUGF("stream: dep_remove_subtree stream(%p)=%d\n", stream,
+         stream->stream_id);
+
+  assert(stream->dep_prev);
+
+  dep_prev = stream->dep_prev;
+
+  if (stream->sib_prev) {
+    link_sib(stream->sib_prev, stream->sib_next);
+  } else {
+    next = stream->sib_next;
+
+    link_dep(dep_prev, next);
+
+    if (next) {
+      next->sib_prev = NULL;
+    }
+  }
+
+  dep_prev->sum_dep_weight -= stream->weight;
+
+  if (stream->queued) {
+    stream_obq_remove(stream);
+  }
+
+  validate_tree(dep_prev);
+
+  stream->sib_prev = NULL;
+  stream->sib_next = NULL;
+  stream->dep_prev = NULL;
+}
+
+int nghttp2_stream_in_dep_tree(nghttp2_stream *stream) {
+  return stream->dep_prev || stream->dep_next || stream->sib_prev ||
+         stream->sib_next;
+}
+
+nghttp2_outbound_item *
+nghttp2_stream_next_outbound_item(nghttp2_stream *stream) {
+  nghttp2_pq_entry *ent;
+  nghttp2_stream *si;
+
+  for (;;) {
+    if (stream_active(stream)) {
+      /* Update ascendant's descendant_last_cycle here, so that we can
+         assure that new stream is scheduled based on it. */
+      for (si = stream; si->dep_prev; si = si->dep_prev) {
+        si->dep_prev->descendant_last_cycle = si->cycle;
+      }
+      return stream->item;
+    }
+    ent = nghttp2_pq_top(&stream->obq);
+    if (!ent) {
+      return NULL;
+    }
+    stream = nghttp2_struct_of(ent, nghttp2_stream, pq_entry);
+  }
+}
+
+nghttp2_stream_proto_state nghttp2_stream_get_state(nghttp2_stream *stream) {
+  if (stream->flags & NGHTTP2_STREAM_FLAG_CLOSED) {
+    return NGHTTP2_STREAM_STATE_CLOSED;
+  }
+
+  if (stream->flags & NGHTTP2_STREAM_FLAG_PUSH) {
+    if (stream->shut_flags & NGHTTP2_SHUT_RD) {
+      return NGHTTP2_STREAM_STATE_RESERVED_LOCAL;
+    }
+
+    if (stream->shut_flags & NGHTTP2_SHUT_WR) {
+      return NGHTTP2_STREAM_STATE_RESERVED_REMOTE;
+    }
+  }
+
+  if (stream->shut_flags & NGHTTP2_SHUT_RD) {
+    return NGHTTP2_STREAM_STATE_HALF_CLOSED_REMOTE;
+  }
+
+  if (stream->shut_flags & NGHTTP2_SHUT_WR) {
+    return NGHTTP2_STREAM_STATE_HALF_CLOSED_LOCAL;
+  }
+
+  if (stream->state == NGHTTP2_STREAM_IDLE) {
+    return NGHTTP2_STREAM_STATE_IDLE;
+  }
+
+  return NGHTTP2_STREAM_STATE_OPEN;
+}
+
+nghttp2_stream *nghttp2_stream_get_parent(nghttp2_stream *stream) {
+  return stream->dep_prev;
+}
+
+nghttp2_stream *nghttp2_stream_get_next_sibling(nghttp2_stream *stream) {
+  return stream->sib_next;
+}
+
+nghttp2_stream *nghttp2_stream_get_previous_sibling(nghttp2_stream *stream) {
+  return stream->sib_prev;
+}
+
+nghttp2_stream *nghttp2_stream_get_first_child(nghttp2_stream *stream) {
+  return stream->dep_next;
+}
+
+int32_t nghttp2_stream_get_weight(nghttp2_stream *stream) {
+  return stream->weight;
+}
+
+int32_t nghttp2_stream_get_sum_dependency_weight(nghttp2_stream *stream) {
+  return stream->sum_dep_weight;
+}
+
+int32_t nghttp2_stream_get_stream_id(nghttp2_stream *stream) {
+  return stream->stream_id;
+}