abstract WHC and pull it out of core DDSI code

Signed-off-by: Erik Boasson <eb@ilities.com>

src/core/ddsc/.fileids

@@ -31,3 +31,4 @@
 69  src/dds_report.c
 70  src/dds_builtin.c
 72  src/dds_guardcond.c
+73  src/dds_whc.c

src/core/ddsc/CMakeLists.txt

@@ -41,6 +41,7 @@ PREPEND(srcs_ddsc "${CMAKE_CURRENT_LIST_DIR}/src"
     dds_guardcond.c
     dds_subscriber.c
     dds_write.c
+    dds_whc.c
 )
  
 PREPEND(hdrs_public_ddsc "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include/ddsc>$<INSTALL_INTERFACE:include/ddsc>"
@@ -80,6 +81,7 @@ PREPEND(hdrs_private_ddsc "${CMAKE_CURRENT_LIST_DIR}/src"
     dds__types.h
     dds__write.h
     dds__writer.h
+    dds__whc.h
     q__osplser.h
 )
 

src/core/ddsc/src/dds__types.h

@@ -190,6 +190,7 @@ typedef struct dds_writer
   struct nn_xpack * m_xp;
   struct writer * m_wr;
   os_mutex m_call_lock;
+  struct whc *m_whc; /* FIXME: ownership still with underlying DDSI writer (cos of DDSI built-in writers )*/
 
   /* Status metrics */
 

src/core/ddsc/src/dds__whc.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright(c) 2006 to 2018 ADLINK Technology Limited and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Eclipse Distribution License
+ * v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+ */
+#ifndef DDS__WHC_H
+#define DDS__WHC_H
+
+#include "ddsi/q_whc.h"
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+struct whc *whc_new (int is_transient_local, unsigned hdepth, unsigned tldepth);
+
+#if defined (__cplusplus)
+}
+#endif
+
+#endif /* Q_WHC_H */

src/core/ddsc/src/dds_whc.c

@@ -17,10 +17,95 @@
 #include "ddsi/ddsi_ser.h"
 #include "ddsi/q_unused.h"
 #include "ddsi/q_config.h"
-#include "ddsi/q_whc.h"
 #include "q__osplser.h"
+#include "dds__whc.h"
 #include "dds__tkmap.h"
 
+#include "util/ut_avl.h"
+#include "util/ut_hopscotch.h"
+#include "ddsi/q_time.h"
+#include "ddsi/q_rtps.h"
+#include "ddsi/q_freelist.h"
+
+#define USE_EHH 0
+
+struct whc_node {
+  struct whc_node *next_seq; /* next in this interval */
+  struct whc_node *prev_seq; /* prev in this interval */
+  struct whc_idxnode *idxnode; /* NULL if not in index */
+  unsigned idxnode_pos; /* index in idxnode.hist */
+  seqno_t seq;
+  uint64_t total_bytes; /* cumulative number of bytes up to and including this node */
+  size_t size;
+  struct nn_plist *plist; /* 0 if nothing special */
+  unsigned unacked: 1; /* counted in whc::unacked_bytes iff 1 */
+  unsigned borrowed: 1; /* at most one can borrow it at any time */
+  nn_mtime_t last_rexmit_ts;
+  unsigned rexmit_count;
+  struct serdata *serdata;
+};
+
+struct whc_intvnode {
+  ut_avlNode_t avlnode;
+  seqno_t min;
+  seqno_t maxp1;
+  struct whc_node *first; /* linked list of seqs with contiguous sequence numbers [min,maxp1) */
+  struct whc_node *last; /* valid iff first != NULL */
+};
+
+struct whc_idxnode {
+  int64_t iid;
+  seqno_t prune_seq;
+  struct tkmap_instance *tk;
+  unsigned headidx;
+#if __STDC_VERSION__ >= 199901L
+  struct whc_node *hist[];
+#else
+  struct whc_node *hist[1];
+#endif
+};
+
+#if USE_EHH
+struct whc_seq_entry {
+  seqno_t seq;
+  struct whc_node *whcn;
+};
+#endif
+
+struct whc_impl {
+  struct whc common;
+  os_mutex lock;
+  unsigned seq_size;
+  size_t unacked_bytes;
+  size_t sample_overhead;
+  uint64_t total_bytes; /* total number of bytes pushed in */
+  unsigned is_transient_local: 1;
+  unsigned hdepth; /* 0 = unlimited */
+  unsigned tldepth; /* 0 = disabled/unlimited (no need to maintain an index if KEEP_ALL <=> is_transient_local + tldepth=0) */
+  unsigned idxdepth; /* = max(hdepth, tldepth) */
+  seqno_t max_drop_seq; /* samples in whc with seq <= max_drop_seq => transient-local */
+  struct whc_intvnode *open_intv; /* interval where next sample will go (usually) */
+  struct whc_node *maxseq_node; /* NULL if empty; if not in open_intv, open_intv is empty */
+  struct nn_freelist freelist; /* struct whc_node *; linked via whc_node::next_seq */
+#if USE_EHH
+  struct ut_ehh *seq_hash;
+#else
+  struct ut_hh *seq_hash;
+#endif
+  struct ut_hh *idx_hash;
+  ut_avlTree_t seq;
+};
+
+struct whc_sample_iter_impl {
+  struct whc_impl *whc;
+  bool first;
+};
+
+/* check that our definition of whc_sample_iter fits in the type that callers allocate */
+struct whc_sample_iter_sizecheck {
+  char fits_in_generic_type[sizeof(struct whc_sample_iter_impl) <= sizeof(struct whc_sample_iter) ? 1 : -1];
+};
+
 /* Avoiding all nn_log-related activities when LC_WHC is not set
    (and it hardly ever is, as it is not even included in "trace")
    saves a couple of % CPU on a high-rate publisher - that's worth
@@ -47,14 +132,45 @@ static int trace_whc (const char *fmt, ...)
  * - cleaning up after ACKs has additional pruning stage for same case
  */
 
-static void insert_whcn_in_hash (struct whc *whc, struct whc_node *whcn);
+static struct whc_node *whc_findseq (const struct whc_impl *whc, seqno_t seq);
-static void whc_delete_one (struct whc *whc, struct whc_node *whcn);
+static void insert_whcn_in_hash (struct whc_impl *whc, struct whc_node *whcn);
+static void whc_delete_one (struct whc_impl *whc, struct whc_node *whcn);
 static int compare_seq (const void *va, const void *vb);
-static unsigned whc_remove_acked_messages_full (struct whc *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list);
+static unsigned whc_remove_acked_messages_full (struct whc_impl *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list);
+static void free_deferred_free_list (struct whc_impl *whc, struct whc_node *deferred_free_list);
+static void get_state_locked(const struct whc_impl *whc, struct whc_state *st);
+
+static unsigned whc_remove_acked_messages (struct whc *whc, seqno_t max_drop_seq, struct whc_state *whcst, struct whc_node **deferred_free_list);
+static void whc_free_deferred_free_list (struct whc *whc, struct whc_node *deferred_free_list);
+static void whc_get_state(const struct whc *whc, struct whc_state *st);
+static int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, serdata_t serdata, struct tkmap_instance *tk);
+static seqno_t whc_next_seq (const struct whc *whc, seqno_t seq);
+static bool whc_borrow_sample (const struct whc *whc, seqno_t seq, struct whc_borrowed_sample *sample);
+static bool whc_borrow_sample_key (const struct whc *whc, const struct serdata *serdata_key, struct whc_borrowed_sample *sample);
+static void whc_return_sample (struct whc *whc, struct whc_borrowed_sample *sample, bool update_retransmit_info);
+static unsigned whc_downgrade_to_volatile (struct whc *whc, struct whc_state *st);
+static void whc_sample_iter_init (const struct whc *whc, struct whc_sample_iter *opaque_it);
+static bool whc_sample_iter_borrow_next (struct whc_sample_iter *opaque_it, struct whc_borrowed_sample *sample);
+static void whc_free (struct whc *whc);
 
 static const ut_avlTreedef_t whc_seq_treedef =
   UT_AVL_TREEDEF_INITIALIZER (offsetof (struct whc_intvnode, avlnode), offsetof (struct whc_intvnode, min), compare_seq, 0);
 
+static const struct whc_ops whc_ops = {
+  .insert = whc_insert,
+  .remove_acked_messages = whc_remove_acked_messages,
+  .free_deferred_free_list = whc_free_deferred_free_list,
+  .get_state = whc_get_state,
+  .next_seq = whc_next_seq,
+  .borrow_sample = whc_borrow_sample,
+  .borrow_sample_key = whc_borrow_sample_key,
+  .return_sample = whc_return_sample,
+  .sample_iter_init = whc_sample_iter_init,
+  .sample_iter_borrow_next = whc_sample_iter_borrow_next,
+  .downgrade_to_volatile = whc_downgrade_to_volatile,
+  .free = whc_free
+};
+
 #if USE_EHH
 static uint32_t whc_seq_entry_hash (const void *vn)
 {
@@ -111,7 +227,7 @@ static int compare_seq (const void *va, const void *vb)
   return (*a == *b) ? 0 : (*a < *b) ? -1 : 1;
 }
 
-static struct whc_node *whc_findmax_procedurally (const struct whc *whc)
+static struct whc_node *whc_findmax_procedurally (const struct whc_impl *whc)
 {
   if (whc->seq_size == 0)
     return NULL;
@@ -128,7 +244,7 @@ static struct whc_node *whc_findmax_procedurally (const struct whc *whc)
   }
 }
 
-static void check_whc (const struct whc *whc)
+static void check_whc (const struct whc_impl *whc)
 {
   /* there's much more we can check, but it gets expensive quite
      quickly: all nodes but open_intv non-empty, non-overlapping and
@@ -155,7 +271,7 @@ static void check_whc (const struct whc *whc)
   }
   assert (whc->maxseq_node == whc_findmax_procedurally (whc));
 
-#if 1 && !defined(NDEBUG)
+#if !defined(NDEBUG)
   {
     struct whc_intvnode *firstintv;
     struct whc_node *cur;
@@ -174,7 +290,7 @@ static void check_whc (const struct whc *whc)
 #endif
 }
 
-static void insert_whcn_in_hash (struct whc *whc, struct whc_node *whcn)
+static void insert_whcn_in_hash (struct whc_impl *whc, struct whc_node *whcn)
 {
   /* precondition: whcn is not in hash */
 #if USE_EHH
@@ -187,7 +303,7 @@ static void insert_whcn_in_hash (struct whc *whc, struct whc_node *whcn)
 #endif
 }
 
-static void remove_whcn_from_hash (struct whc *whc, struct whc_node *whcn)
+static void remove_whcn_from_hash (struct whc_impl *whc, struct whc_node *whcn)
 {
   /* precondition: whcn is in hash */
 #if USE_EHH
@@ -200,7 +316,7 @@ static void remove_whcn_from_hash (struct whc *whc, struct whc_node *whcn)
 #endif
 }
 
-struct whc_node *whc_findseq (const struct whc *whc, seqno_t seq)
+static struct whc_node *whc_findseq (const struct whc_impl *whc, seqno_t seq)
 {
 #if USE_EHH
   struct whc_seq_entry e = { .seq = seq }, *r;
@@ -215,15 +331,36 @@ struct whc_node *whc_findseq (const struct whc *whc, seqno_t seq)
 #endif
 }
 
-
+static struct whc_node *whc_findkey (const struct whc_impl *whc, const struct serdata *serdata_key)
-struct whc *whc_new (int is_transient_local, unsigned hdepth, unsigned tldepth, size_t sample_overhead)
 {
-  struct whc *whc;
+  union {
+    struct whc_idxnode idxn;
+    char pad[sizeof(struct whc_idxnode) + sizeof(struct whc_node *)];
+  } template;
+  struct whc_idxnode *n;
+  check_whc (whc);
+  template.idxn.iid = dds_tkmap_lookup(gv.m_tkmap, serdata_key);
+  n = ut_hhLookup (whc->idx_hash, &template.idxn);
+  if (n == NULL)
+    return NULL;
+  else
+  {
+    assert (n->hist[n->headidx]);
+    return n->hist[n->headidx];
+  }
+}
+
+struct whc *whc_new (int is_transient_local, unsigned hdepth, unsigned tldepth)
+{
+  size_t sample_overhead = 80; /* INFO_TS, DATA (estimate), inline QoS */
+  struct whc_impl *whc;
   struct whc_intvnode *intv;
 
   assert((hdepth == 0 || tldepth <= hdepth) || is_transient_local);
 
   whc = os_malloc (sizeof (*whc));
+  whc->common.ops = &whc_ops;
+  os_mutexInit (&whc->lock);
   whc->is_transient_local = is_transient_local ? 1 : 0;
   whc->hdepth = hdepth;
   whc->tldepth = tldepth;
@@ -257,10 +394,10 @@ struct whc *whc_new (int is_transient_local, unsigned hdepth, unsigned tldepth,
   nn_freelist_init (&whc->freelist, UINT32_MAX, offsetof (struct whc_node, next_seq));
 
   check_whc (whc);
-  return whc;
+  return (struct whc *)whc;
 }
 
-static void free_whc_node_contents (struct whc *whc, struct whc_node *whcn)
+static void free_whc_node_contents (struct whc_node *whcn)
 {
   ddsi_serdata_unref (whcn->serdata);
   if (whcn->plist) {
@@ -269,9 +406,10 @@ static void free_whc_node_contents (struct whc *whc, struct whc_node *whcn)
   }
 }
 
-void whc_free (struct whc *whc)
+void whc_free (struct whc *whc_generic)
 {
   /* Freeing stuff without regards for maintaining data structures */
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
   check_whc (whc);
 
   if (whc->idx_hash)
@@ -292,7 +430,7 @@ void whc_free (struct whc *whc)
 OS_WARNING_MSVC_OFF(6001);
       whcn = whcn->prev_seq;
 OS_WARNING_MSVC_ON(6001);
-      free_whc_node_contents (whc, tmp);
+      free_whc_node_contents (tmp);
       os_free (tmp);
     }
   }
@@ -305,45 +443,41 @@ OS_WARNING_MSVC_ON(6001);
 #else
   ut_hhFree (whc->seq_hash);
 #endif
+  os_mutexDestroy (&whc->lock);
   os_free (whc);
 }
 
-int whc_empty (const struct whc *whc)
+static void get_state_locked(const struct whc_impl *whc, struct whc_state *st)
 {
-  return whc->seq_size == 0;
+  if (whc->seq_size == 0)
+  {
+    st->min_seq = st->max_seq = -1;
+    st->unacked_bytes = 0;
   }
-
+  else
-seqno_t whc_min_seq (const struct whc *whc)
   {
-  /* precond: whc not empty */
     const struct whc_intvnode *intv;
-  check_whc (whc);
-  assert (!whc_empty (whc));
     intv = ut_avlFindMin (&whc_seq_treedef, &whc->seq);
-  assert (intv);
     /* not empty, open node may be anything but is (by definition)
      findmax, and whc is claimed to be non-empty, so min interval
      can't be empty */
     assert (intv->maxp1 > intv->min);
-  return intv->min;
+    st->min_seq = intv->min;
+    st->max_seq = whc->maxseq_node->seq;
+    st->unacked_bytes = whc->unacked_bytes;
+  }
 }
 
-struct whc_node *whc_findmax (const struct whc *whc)
+static void whc_get_state(const struct whc *whc_generic, struct whc_state *st)
 {
+  const struct whc_impl * const whc = (const struct whc_impl *)whc_generic;
+  os_mutexLock ((struct os_mutex *)&whc->lock);
   check_whc (whc);
-  return (struct whc_node *) whc->maxseq_node;
+  get_state_locked(whc, st);
+  os_mutexUnlock ((struct os_mutex *)&whc->lock);
 }
 
-seqno_t whc_max_seq (const struct whc *whc)
+static struct whc_node *find_nextseq_intv (struct whc_intvnode **p_intv, const struct whc_impl *whc, seqno_t seq)
-{
-  /* precond: whc not empty */
-  check_whc (whc);
-  assert (!whc_empty (whc));
-  assert (whc->maxseq_node != NULL);
-  return whc->maxseq_node->seq;
-}
-
-static struct whc_node *find_nextseq_intv (struct whc_intvnode **p_intv, const struct whc *whc, seqno_t seq)
 {
   struct whc_node *n;
   struct whc_intvnode *intv;
@@ -385,25 +519,23 @@ static struct whc_node *find_nextseq_intv (struct whc_intvnode **p_intv, const s
   }
 }
 
-seqno_t whc_next_seq (const struct whc *whc, seqno_t seq)
+static seqno_t whc_next_seq (const struct whc *whc_generic, seqno_t seq)
 {
+  const struct whc_impl * const whc = (const struct whc_impl *)whc_generic;
   struct whc_node *n;
   struct whc_intvnode *intv;
+  seqno_t nseq;
+  os_mutexLock ((struct os_mutex *)&whc->lock);
   check_whc (whc);
   if ((n = find_nextseq_intv (&intv, whc, seq)) == NULL)
-    return MAX_SEQ_NUMBER;
+    nseq = MAX_SEQ_NUMBER;
   else
-    return n->seq;
+    nseq = n->seq;
+  os_mutexUnlock ((struct os_mutex *)&whc->lock);
+  return nseq;
 }
 
-struct whc_node* whc_next_node(const struct whc *whc, seqno_t seq)
+static void delete_one_sample_from_idx (struct whc_impl *whc, struct whc_node *whcn)
-{
-    struct whc_intvnode *intv;
-    check_whc (whc);
-    return find_nextseq_intv(&intv, whc, seq);
-}
-
-static void delete_one_sample_from_idx (struct whc *whc, struct whc_node *whcn)
 {
   struct whc_idxnode * const idxn = whcn->idxnode;
   assert (idxn != NULL);
@@ -426,7 +558,7 @@ static void delete_one_sample_from_idx (struct whc *whc, struct whc_node *whcn)
   whcn->idxnode = NULL;
 }
 
-static void free_one_instance_from_idx (struct whc *whc, seqno_t max_drop_seq, struct whc_idxnode *idxn)
+static void free_one_instance_from_idx (struct whc_impl *whc, seqno_t max_drop_seq, struct whc_idxnode *idxn)
 {
   unsigned i;
   for (i = 0; i < whc->idxdepth; i++)
@@ -446,14 +578,14 @@ static void free_one_instance_from_idx (struct whc *whc, seqno_t max_drop_seq, s
   os_free(idxn);
 }
 
-static void delete_one_instance_from_idx (struct whc *whc, seqno_t max_drop_seq, struct whc_idxnode *idxn)
+static void delete_one_instance_from_idx (struct whc_impl *whc, seqno_t max_drop_seq, struct whc_idxnode *idxn)
 {
   if (!ut_hhRemove (whc->idx_hash, idxn))
     assert (0);
   free_one_instance_from_idx (whc, max_drop_seq, idxn);
 }
 
-static int whcn_in_tlidx (const struct whc *whc, const struct whc_idxnode *idxn, unsigned pos)
+static int whcn_in_tlidx (const struct whc_impl *whc, const struct whc_idxnode *idxn, unsigned pos)
 {
   if (idxn == NULL)
     return 0;
@@ -465,19 +597,24 @@ static int whcn_in_tlidx (const struct whc *whc, const struct whc_idxnode *idxn,
   }
 }
 
-void whc_downgrade_to_volatile (struct whc *whc)
+static unsigned whc_downgrade_to_volatile (struct whc *whc_generic, struct whc_state *st)
 {
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
   seqno_t old_max_drop_seq;
   struct whc_node *deferred_free_list;
+  unsigned cnt;
 
   /* We only remove them from whc->tlidx: we don't remove them from
      whc->seq yet.  That'll happen eventually.  */
+  os_mutexLock (&whc->lock);
   check_whc (whc);
 
   if (whc->idxdepth == 0)
   {
     /* if not maintaining an index at all, this is nonsense */
-    return;
+    get_state_locked(whc, st);
+    os_mutexUnlock (&whc->lock);
+    return 0;
   }
 
   assert (!whc->is_transient_local);
@@ -502,18 +639,21 @@ void whc_downgrade_to_volatile (struct whc *whc)
      them all. */
   old_max_drop_seq = whc->max_drop_seq;
   whc->max_drop_seq = 0;
-  whc_remove_acked_messages_full (whc, old_max_drop_seq, &deferred_free_list);
+  cnt = whc_remove_acked_messages_full (whc, old_max_drop_seq, &deferred_free_list);
-  whc_free_deferred_free_list (whc, deferred_free_list);
+  whc_free_deferred_free_list (whc_generic, deferred_free_list);
   assert (whc->max_drop_seq == old_max_drop_seq);
+  get_state_locked(whc, st);
+  os_mutexUnlock (&whc->lock);
+  return cnt;
 }
 
-static size_t whcn_size (const struct whc *whc, const struct whc_node *whcn)
+static size_t whcn_size (const struct whc_impl *whc, const struct whc_node *whcn)
 {
   size_t sz = ddsi_serdata_size (whcn->serdata);
   return sz + ((sz + config.fragment_size - 1) / config.fragment_size) * whc->sample_overhead;
 }
 
-static void whc_delete_one_intv (struct whc *whc, struct whc_intvnode **p_intv, struct whc_node **p_whcn)
+static void whc_delete_one_intv (struct whc_impl *whc, struct whc_intvnode **p_intv, struct whc_node **p_whcn)
 {
   /* Removes *p_whcn, possibly deleting or splitting *p_intv, as the
      case may be.  Does *NOT* update whc->seq_size.  *p_intv must be
@@ -612,7 +752,7 @@ static void whc_delete_one_intv (struct whc *whc, struct whc_intvnode **p_intv,
   }
 }
 
-static void whc_delete_one (struct whc *whc, struct whc_node *whcn)
+static void whc_delete_one (struct whc_impl *whc, struct whc_node *whcn)
 {
   struct whc_intvnode *intv;
   struct whc_node *whcn_tmp = whcn;
@@ -624,11 +764,11 @@ static void whc_delete_one (struct whc *whc, struct whc_node *whcn)
   if (whcn_tmp->next_seq)
     whcn_tmp->next_seq->prev_seq = whcn_tmp->prev_seq;
   whcn_tmp->next_seq = NULL;
-  whc_free_deferred_free_list (whc, whcn_tmp);
+  free_deferred_free_list (whc, whcn_tmp);
   whc->seq_size--;
 }
 
-void whc_free_deferred_free_list (struct whc *whc, struct whc_node *deferred_free_list)
+static void free_deferred_free_list (struct whc_impl *whc, struct whc_node *deferred_free_list)
 {
   if (deferred_free_list)
   {
@@ -637,7 +777,8 @@ void whc_free_deferred_free_list (struct whc *whc, struct whc_node *deferred_fre
     for (cur = deferred_free_list, last = NULL; cur; last = cur, cur = cur->next_seq)
     {
       n++;
-      free_whc_node_contents (whc, cur);
+      if (!cur->borrowed)
+        free_whc_node_contents (cur);
     }
     cur = nn_freelist_pushmany (&whc->freelist, deferred_free_list, last, n);
     while (cur)
@@ -649,7 +790,13 @@ void whc_free_deferred_free_list (struct whc *whc, struct whc_node *deferred_fre
   }
 }
 
-static unsigned whc_remove_acked_messages_noidx (struct whc *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list)
+static void whc_free_deferred_free_list (struct whc *whc_generic, struct whc_node *deferred_free_list)
+{
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
+  free_deferred_free_list(whc, deferred_free_list);
+}
+
+static unsigned whc_remove_acked_messages_noidx (struct whc_impl *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list)
 {
   struct whc_intvnode *intv;
   struct whc_node *whcn;
@@ -725,7 +872,7 @@ static unsigned whc_remove_acked_messages_noidx (struct whc *whc, seqno_t max_dr
   return ndropped;
 }
 
-static unsigned whc_remove_acked_messages_full (struct whc *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list)
+static unsigned whc_remove_acked_messages_full (struct whc_impl *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list)
 {
   struct whc_intvnode *intv;
   struct whc_node *whcn;
@@ -859,49 +1006,36 @@ static unsigned whc_remove_acked_messages_full (struct whc *whc, seqno_t max_dro
   return ndropped;
 }
 
-unsigned whc_remove_acked_messages (struct whc *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list)
+static unsigned whc_remove_acked_messages (struct whc *whc_generic, seqno_t max_drop_seq, struct whc_state *whcst, struct whc_node **deferred_free_list)
 {
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
+  unsigned cnt;
+
+  os_mutexLock (&whc->lock);
   assert (max_drop_seq < MAX_SEQ_NUMBER);
   assert (max_drop_seq >= whc->max_drop_seq);
 
+  if (config.enabled_logcats & LC_WHC)
+  {
+    struct whc_state whcst;
+    get_state_locked(whc, &whcst);
     TRACE_WHC(("whc_remove_acked_messages(%p max_drop_seq %"PRId64")\n", (void *)whc, max_drop_seq));
     TRACE_WHC(("  whc: [%"PRId64",%"PRId64"] max_drop_seq %"PRId64" h %u tl %u\n",
-             whc_empty(whc) ? (seqno_t)-1 : whc_min_seq(whc),
+               whcst.min_seq, whcst.max_seq, whc->max_drop_seq, whc->hdepth, whc->tldepth));
-             whc_empty(whc) ? (seqno_t)-1 : whc_max_seq(whc),
+  }
-             whc->max_drop_seq, whc->hdepth, whc->tldepth));
 
   check_whc (whc);
 
   if (whc->idxdepth == 0)
-  {
+    cnt = whc_remove_acked_messages_noidx (whc, max_drop_seq, deferred_free_list);
-    return whc_remove_acked_messages_noidx (whc, max_drop_seq, deferred_free_list);
-  }
   else
-  {
+    cnt = whc_remove_acked_messages_full (whc, max_drop_seq, deferred_free_list);
-    return whc_remove_acked_messages_full (whc, max_drop_seq, deferred_free_list);
+  get_state_locked(whc, whcst);
-  }
+  os_mutexUnlock (&whc->lock);
+  return cnt;
 }
 
-struct whc_node *whc_findkey (const struct whc *whc, const struct serdata *serdata_key)
+static struct whc_node *whc_insert_seq (struct whc_impl *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, serdata_t serdata)
-{
-  union {
-    struct whc_idxnode idxn;
-    char pad[sizeof(struct whc_idxnode) + sizeof(struct whc_node *)];
-  } template;
-  struct whc_idxnode *n;
-  check_whc (whc);
-  template.idxn.iid = dds_tkmap_lookup(gv.m_tkmap, serdata_key);
-  n = ut_hhLookup (whc->idx_hash, &template.idxn);
-  if (n == NULL)
-    return NULL;
-  else
-  {
-    assert (n->hist[n->headidx]);
-    return n->hist[n->headidx];
-  }
-}
-
-static struct whc_node *whc_insert_seq (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, serdata_t serdata)
 {
   struct whc_node *newn = NULL;
 
@@ -910,6 +1044,7 @@ static struct whc_node *whc_insert_seq (struct whc *whc, seqno_t max_drop_seq, s
   newn->seq = seq;
   newn->plist = plist;
   newn->unacked = (seq > max_drop_seq);
+  newn->borrowed = 0;
   newn->idxnode = NULL; /* initial state, may be changed */
   newn->idxnode_pos = 0;
   newn->last_rexmit_ts.v = 0;
@@ -961,21 +1096,27 @@ static struct whc_node *whc_insert_seq (struct whc *whc, seqno_t max_drop_seq, s
   return newn;
 }
 
-int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, serdata_t serdata, struct tkmap_instance *tk)
+static int whc_insert (struct whc *whc_generic, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, serdata_t serdata, struct tkmap_instance *tk)
 {
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
   struct whc_node *newn = NULL;
   struct whc_idxnode *idxn;
   union {
     struct whc_idxnode idxn;
     char pad[sizeof(struct whc_idxnode) + sizeof(struct whc_node *)];
   } template;
+
+  os_mutexLock (&whc->lock);
   check_whc (whc);
 
+  if (config.enabled_logcats & LC_WHC)
+  {
+    struct whc_state whcst;
+    get_state_locked(whc, &whcst);
     TRACE_WHC(("whc_insert(%p max_drop_seq %"PRId64" seq %"PRId64" plist %p serdata %p:%x)\n", (void *)whc, max_drop_seq, seq, (void*)plist, (void*)serdata, *(unsigned *)serdata->v.keyhash.m_hash));
     TRACE_WHC(("  whc: [%"PRId64",%"PRId64"] max_drop_seq %"PRId64" h %u tl %u\n",
-             whc_empty(whc) ? (seqno_t)-1 : whc_min_seq(whc),
+               whcst.min_seq, whcst.max_seq, whc->max_drop_seq, whc->hdepth, whc->tldepth));
-             whc_empty(whc) ? (seqno_t)-1 : whc_max_seq(whc),
+  }
-             whc->max_drop_seq, whc->hdepth, whc->tldepth));
 
   assert (max_drop_seq < MAX_SEQ_NUMBER);
   assert (max_drop_seq >= whc->max_drop_seq);
@@ -983,7 +1124,7 @@ int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_pl
   /* Seq must be greater than what is currently stored. Usually it'll
      be the next sequence number, but if there are no readers
      temporarily, a gap may be among the possibilities */
-  assert (whc_empty (whc) || seq > whc_max_seq (whc));
+  assert (whc->seq_size == 0 || seq > whc->maxseq_node->seq);
 
   /* Always insert in seq admin */
   newn = whc_insert_seq (whc, max_drop_seq, seq, plist, serdata);
@@ -994,6 +1135,7 @@ int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_pl
   if (ddsi_serdata_is_empty(serdata) || whc->idxdepth == 0)
   {
     TRACE_WHC((" empty or no hist\n"));
+    os_mutexUnlock (&whc->lock);
     return 0;
   }
 
@@ -1089,10 +1231,123 @@ int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_pl
     }
     TRACE_WHC(("\n"));
   }
+  os_mutexUnlock (&whc->lock);
   return 0;
 }
 
-size_t whc_unacked_bytes (struct whc *whc)
+static void make_borrowed_sample(struct whc_borrowed_sample *sample, struct whc_node *whcn)
 {
-  return whc->unacked_bytes;
+  assert(!whcn->borrowed);
+  whcn->borrowed = 1;
+  sample->seq = whcn->seq;
+  sample->plist = whcn->plist;
+  sample->serdata = whcn->serdata;
+  sample->unacked = whcn->unacked;
+  sample->rexmit_count = whcn->rexmit_count;
+  sample->last_rexmit_ts = whcn->last_rexmit_ts;
+}
+
+static bool whc_borrow_sample (const struct whc *whc_generic, seqno_t seq, struct whc_borrowed_sample *sample)
+{
+  const struct whc_impl * const whc = (const struct whc_impl *)whc_generic;
+  struct whc_node *whcn;
+  bool found;
+  os_mutexLock ((os_mutex *)&whc->lock);
+  if ((whcn = whc_findseq(whc, seq)) == NULL)
+    found = false;
+  else
+  {
+    make_borrowed_sample(sample, whcn);
+    found = true;
+  }
+  os_mutexUnlock ((os_mutex *)&whc->lock);
+  return found;
+}
+
+static bool whc_borrow_sample_key (const struct whc *whc_generic, const struct serdata *serdata_key, struct whc_borrowed_sample *sample)
+{
+  const struct whc_impl * const whc = (const struct whc_impl *)whc_generic;
+  struct whc_node *whcn;
+  bool found;
+  os_mutexLock ((os_mutex *)&whc->lock);
+  if ((whcn = whc_findkey(whc, serdata_key)) == NULL)
+    found = false;
+  else
+  {
+    make_borrowed_sample(sample, whcn);
+    found = true;
+  }
+  os_mutexUnlock ((os_mutex *)&whc->lock);
+  return found;
+}
+
+static void return_sample_locked (struct whc_impl *whc, struct whc_borrowed_sample *sample, bool update_retransmit_info)
+{
+  struct whc_node *whcn;
+  if ((whcn = whc_findseq (whc, sample->seq)) == NULL)
+  {
+    /* data no longer present in WHC - that means ownership for serdata, plist shifted to the borrowed copy and "returning" it really becomes "destroying" it */
+    ddsi_serdata_unref (sample->serdata);
+    if (sample->plist) {
+      nn_plist_fini (sample->plist);
+      os_free (sample->plist);
+    }
+  }
+  else
+  {
+    assert(whcn->borrowed);
+    whcn->borrowed = 0;
+    if (update_retransmit_info)
+    {
+      whcn->rexmit_count = sample->rexmit_count;
+      whcn->last_rexmit_ts = sample->last_rexmit_ts;
+    }
+  }
+}
+
+static void whc_return_sample (struct whc *whc_generic, struct whc_borrowed_sample *sample, bool update_retransmit_info)
+{
+  struct whc_impl * const whc = (struct whc_impl *)whc_generic;
+  os_mutexLock (&whc->lock);
+  return_sample_locked (whc, sample, update_retransmit_info);
+  os_mutexUnlock (&whc->lock);
+}
+
+static void whc_sample_iter_init (const struct whc *whc_generic, struct whc_sample_iter *opaque_it)
+{
+  const struct whc_impl * const whc = (const struct whc_impl *)whc_generic;
+  struct whc_sample_iter_impl *it = (struct whc_sample_iter_impl *)opaque_it->opaque.opaque;
+  it->whc = (struct whc_impl *)whc;
+  it->first = true;
+}
+
+static bool whc_sample_iter_borrow_next (struct whc_sample_iter *opaque_it, struct whc_borrowed_sample *sample)
+{
+  struct whc_sample_iter_impl * const it = (struct whc_sample_iter_impl *)opaque_it->opaque.opaque;
+  struct whc_impl * const whc = it->whc;
+  struct whc_node *whcn;
+  struct whc_intvnode *intv;
+  seqno_t seq;
+  bool valid;
+  os_mutexLock (&whc->lock);
+  check_whc (whc);
+  if (!it->first)
+  {
+    seq = sample->seq;
+    return_sample_locked(whc, sample, false);
+  }
+  else
+  {
+    it->first = false;
+    seq = 0;
+  }
+  if ((whcn = find_nextseq_intv (&intv, whc, seq)) == NULL)
+    valid = false;
+  else
+  {
+    make_borrowed_sample(sample, whcn);
+    valid = true;
+  }
+  os_mutexUnlock (&whc->lock);
+  return valid;
 }

src/core/ddsc/src/dds_writer.c

@@ -21,6 +21,7 @@
 #include "dds__err.h"
 #include "dds__init.h"
 #include "dds__tkmap.h"
+#include "dds__whc.h"
 #include "dds__report.h"
 #include "ddsc/ddsc_project.h"
 
@@ -233,6 +234,8 @@ dds_writer_delete(
     assert(e);
     assert(thr);
 
+    /* FIXME: not freeing WHC here because it is owned by the DDSI entity */
+
     if (asleep) {
         thread_state_awake(thr);
     }
@@ -338,6 +341,62 @@ dds_writer_qos_set(
     return ret;
 }
 
+static struct whc *make_whc(const dds_qos_t *qos)
+{
+  bool startup_mode;
+  bool handle_as_transient_local;
+  unsigned hdepth, tldepth;
+  /* Startup mode causes the writer to treat data in its WHC as if
+   transient-local, for the first few seconds after startup of the
+   DDSI service. It is done for volatile reliable writers only
+   (which automatically excludes all builtin writers) or for all
+   writers except volatile best-effort & transient-local ones.
+
+   Which one to use depends on whether merge policies are in effect
+   in durability. If yes, then durability will take care of all
+   transient & persistent data; if no, DDSI discovery usually takes
+   too long and this'll save you.
+
+   Note: may still be cleared, if it turns out we are not maintaining
+   an index at all (e.g., volatile KEEP_ALL) */
+  if (config.startup_mode_full) {
+    startup_mode = gv.startup_mode &&
+      (qos->durability.kind >= DDS_DURABILITY_TRANSIENT ||
+       (qos->durability.kind == DDS_DURABILITY_VOLATILE &&
+        qos->reliability.kind != DDS_RELIABILITY_BEST_EFFORT));
+  } else {
+    startup_mode = gv.startup_mode &&
+      (qos->durability.kind == DDS_DURABILITY_VOLATILE &&
+       qos->reliability.kind != DDS_RELIABILITY_BEST_EFFORT);
+  }
+
+  /* Construct WHC -- if aggressive_keep_last1 is set, the WHC will
+    drop all samples for which a later update is available.  This
+    forces it to maintain a tlidx.  */
+  handle_as_transient_local = (qos->durability.kind == DDS_DURABILITY_TRANSIENT_LOCAL);
+  if (!config.aggressive_keep_last_whc || qos->history.kind == DDS_HISTORY_KEEP_ALL)
+    hdepth = 0;
+  else
+    hdepth = (unsigned)qos->history.depth;
+  if (handle_as_transient_local) {
+    if (qos->durability_service.history.kind == DDS_HISTORY_KEEP_ALL)
+      tldepth = 0;
+    else
+      tldepth = (unsigned)qos->durability_service.history.depth;
+  } else if (startup_mode) {
+    tldepth = (hdepth == 0) ? 1 : hdepth;
+  } else {
+    tldepth = 0;
+  }
+  if (hdepth == 0 && tldepth == 0)
+  {
+    /* no index at all - so no need to bother with startup mode */
+    startup_mode = 0;
+  }
+
+  return whc_new (handle_as_transient_local, hdepth, tldepth);
+}
+
 
 _Pre_satisfies_(((participant_or_publisher & DDS_ENTITY_KIND_MASK) == DDS_KIND_PUBLISHER) || \
                 ((participant_or_publisher & DDS_ENTITY_KIND_MASK) == DDS_KIND_PARTICIPANT))
@@ -426,6 +485,7 @@ dds_create_writer(
     wr->m_entity.m_deriver.set_qos = dds_writer_qos_set;
     wr->m_entity.m_deriver.validate_status = dds_writer_status_validate;
     wr->m_entity.m_deriver.get_instance_hdl = dds_writer_instance_hdl;
+    wr->m_whc = make_whc (wqos);
 
     /* Extra claim of this writer to make sure that the delete waits until DDSI
      * has deleted its writer as well. This can be known through the callback. */
@@ -439,8 +499,7 @@ dds_create_writer(
     if (asleep) {
         thread_state_awake(thr);
     }
-    wr->m_wr = new_writer(&wr->m_entity.m_guid, NULL, &pub->m_participant->m_guid, ((dds_topic*)tp)->m_stopic,
+    wr->m_wr = new_writer(&wr->m_entity.m_guid, NULL, &pub->m_participant->m_guid, ((dds_topic*)tp)->m_stopic, wqos, wr->m_whc, dds_writer_status_cb, wr);
-                          wqos, dds_writer_status_cb, wr);
     os_mutexLock(&pub->m_mutex);
     os_mutexLock(&tp->m_mutex);
     assert(wr->m_wr);

src/core/ddsi/.fileids

@@ -33,7 +33,6 @@
 32  src/q_thread_inlines.c
 33  src/q_time.c
 34  src/q_transmit.c
-35  src/q_whc.c
 36  src/q_xevent.c
 37  src/q_xmsg.c
 38  src/q_freelist.c

src/core/ddsi/CMakeLists.txt

@@ -50,7 +50,6 @@ PREPEND(srcs_ddsi "${CMAKE_CURRENT_LIST_DIR}/src"
     q_time.c
     q_transmit.c
     q_inverse_uint32_set.c
-    q_whc.c
     q_xevent.c
     q_xmsg.c
     q_freelist.c

src/core/ddsi/include/ddsi/q_entity.h

@@ -474,34 +474,15 @@ struct writer *get_builtin_writer (const struct participant *pp, unsigned entity
    GUID "ppguid". May return NULL if participant unknown or
    writer/reader already known. */
 
-struct writer * new_writer
+struct writer * new_writer (struct nn_guid *wrguid, const struct nn_guid *group_guid, const struct nn_guid *ppguid, const struct sertopic *topic, const struct nn_xqos *xqos, struct whc * whc, status_cb_t status_cb, void * status_cb_arg);
-(
-  struct nn_guid *wrguid,
-  const struct nn_guid *group_guid,
-  const struct nn_guid *ppguid,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  status_cb_t status_cb,
-  void * status_cb_arg
-);
 
-struct reader * new_reader
+struct reader * new_reader (struct nn_guid *rdguid, const struct nn_guid *group_guid, const struct nn_guid *ppguid, const struct sertopic *topic, const struct nn_xqos *xqos, struct rhc * rhc, status_cb_t status_cb, void * status_cb_arg);
-(
-  struct nn_guid *rdguid,
-  const struct nn_guid *group_guid,
-  const struct nn_guid *ppguid,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  struct rhc * rhc,
-  status_cb_t status_cb,
-  void * status_cb_arg
-);
 
 struct whc_node;
-unsigned remove_acked_messages (struct writer *wr, struct whc_node **deferred_free_list);
+struct whc_state;
-unsigned remove_acked_messages_and_free (struct writer *wr);
+unsigned remove_acked_messages (struct writer *wr, struct whc_state *whcst, struct whc_node **deferred_free_list);
 seqno_t writer_max_drop_seq (const struct writer *wr);
-int writer_must_have_hb_scheduled (const struct writer *wr);
+int writer_must_have_hb_scheduled (const struct writer *wr, const struct whc_state *whcst);
 void writer_set_retransmitting (struct writer *wr);
 void writer_clear_retransmitting (struct writer *wr);
 

src/core/ddsi/include/ddsi/q_hbcontrol.h

@@ -17,6 +17,7 @@ extern "C" {
 #endif
 
 struct writer;
+struct whc_state;
 
 struct hbcontrol {
   nn_mtime_t t_of_last_write;
@@ -28,12 +29,12 @@ struct hbcontrol {
 };
 
 void writer_hbcontrol_init (struct hbcontrol *hbc);
-int64_t writer_hbcontrol_intv (const struct writer *wr, nn_mtime_t tnow);
+int64_t writer_hbcontrol_intv (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow);
-void writer_hbcontrol_note_asyncwrite (struct writer *wr, nn_mtime_t tnow);
+void writer_hbcontrol_note_asyncwrite (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow);
-int writer_hbcontrol_ack_required (const struct writer *wr, nn_mtime_t tnow);
+int writer_hbcontrol_ack_required (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow);
-struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, nn_mtime_t tnow, unsigned packetid, int *hbansreq);
+struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow, unsigned packetid, int *hbansreq);
-int writer_hbcontrol_must_send (const struct writer *wr, nn_mtime_t tnow);
+int writer_hbcontrol_must_send (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow);
-struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, nn_mtime_t tnow, int hbansreq, int issync);
+struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow, int hbansreq, int issync);
 
 #if defined (__cplusplus)
 }

src/core/ddsi/include/ddsi/q_transmit.h

@@ -22,6 +22,7 @@ extern "C" {
 struct nn_xpack;
 struct nn_xmsg;
 struct writer;
+struct whc_state;
 struct proxy_reader;
 struct serdata;
 struct tkmap_instance;
@@ -41,7 +42,7 @@ int write_sample_nogc_notk (struct nn_xpack *xp, struct writer *wr, struct serda
 /* When calling the following functions, wr->lock must be held */
 int create_fragment_message (struct writer *wr, seqno_t seq, const struct nn_plist *plist, struct serdata *serdata, unsigned fragnum, struct proxy_reader *prd,struct nn_xmsg **msg, int isnew);
 int enqueue_sample_wrlock_held (struct writer *wr, seqno_t seq, const struct nn_plist *plist, struct serdata *serdata, struct proxy_reader *prd, int isnew);
-void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, int hbansreq, nn_entityid_t dst, int issync);
+void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, const struct whc_state *whcst, int hbansreq, nn_entityid_t dst, int issync);
 
 #if defined (__cplusplus)
 }

src/core/ddsi/include/ddsi/q_whc.h

@@ -12,108 +12,83 @@
 #ifndef Q_WHC_H
 #define Q_WHC_H
 
-#include "util/ut_avl.h"
-#include "util/ut_hopscotch.h"
-#include "ddsi/q_time.h"
-#include "ddsi/q_rtps.h"
-#include "ddsi/q_freelist.h"
-
 #if defined (__cplusplus)
 extern "C" {
 #endif
 
 struct serdata;
 struct nn_plist;
-struct whc_idxnode;
+struct tkmap_instance;
+struct whc_node; /* opaque, but currently used for deferred free lists */
+struct whc;
 
-#define USE_EHH 0
+struct whc_borrowed_sample {
-
-struct whc_node {
-  struct whc_node *next_seq; /* next in this interval */
-  struct whc_node *prev_seq; /* prev in this interval */
-  struct whc_idxnode *idxnode; /* NULL if not in index */
-  unsigned idxnode_pos; /* index in idxnode.hist */
   seqno_t seq;
-  uint64_t total_bytes; /* cumulative number of bytes up to and including this node */
+  struct serdata *serdata;
-  size_t size;
+  struct nn_plist *plist;
-  struct nn_plist *plist; /* 0 if nothing special */
+  bool unacked;
-  unsigned unacked: 1; /* counted in whc::unacked_bytes iff 1 */
   nn_mtime_t last_rexmit_ts;
   unsigned rexmit_count;
-  struct serdata *serdata;
 };
 
-struct whc_intvnode {
+struct whc_state {
-  ut_avlNode_t avlnode;
+  seqno_t min_seq; /* -1 if WHC empty, else > 0 */
-  seqno_t min;
+  seqno_t max_seq; /* -1 if WHC empty, else >= min_seq */
-  seqno_t maxp1;
-  struct whc_node *first; /* linked list of seqs with contiguous sequence numbers [min,maxp1) */
-  struct whc_node *last; /* valid iff first != NULL */
-};
-
-struct whc_idxnode {
-  int64_t iid;
-  seqno_t prune_seq;
-  struct tkmap_instance *tk;
-  unsigned headidx;
-#if __STDC_VERSION__ >= 199901L
-  struct whc_node *hist[];
-#else
-  struct whc_node *hist[1];
-#endif
-};
-
-#if USE_EHH
-struct whc_seq_entry {
-  seqno_t seq;
-  struct whc_node *whcn;
-};
-#endif
-
-struct whc {
-  unsigned seq_size;
   size_t unacked_bytes;
-  size_t sample_overhead;
+};
-  uint64_t total_bytes; /* total number of bytes pushed in */
+#define WHCST_ISEMPTY(whcst) ((whcst)->max_seq == -1)
-  unsigned is_transient_local: 1;
+
-  unsigned hdepth; /* 0 = unlimited */
+/* Adjust SIZE and alignment stuff as needed: they are here simply so we can allocate
-  unsigned tldepth; /* 0 = disabled/unlimited (no need to maintain an index if KEEP_ALL <=> is_transient_local + tldepth=0) */
+   an iter on the stack without specifying an implementation. If future changes or
-  unsigned idxdepth; /* = max(hdepth, tldepth) */
+   implementations require more, these can be adjusted.  An implementation should check
-  seqno_t max_drop_seq; /* samples in whc with seq <= max_drop_seq => transient-local */
+   things fit at compile time. */
-  struct whc_intvnode *open_intv; /* interval where next sample will go (usually) */
+#define WHC_SAMPLE_ITER_SIZE (2*sizeof(void *))
-  struct whc_node *maxseq_node; /* NULL if empty; if not in open_intv, open_intv is empty */
+struct whc_sample_iter {
-  struct nn_freelist freelist; /* struct whc_node *; linked via whc_node::next_seq */
+  union {
-#if USE_EHH
+    char opaque[WHC_SAMPLE_ITER_SIZE];
-  struct ut_ehh *seq_hash;
+    /* cover alignment requirements: */
-#else
+    uint64_t x;
-  struct ut_hh *seq_hash;
+    double y;
-#endif
+    void *p;
-  struct ut_hh *idx_hash;
+  } opaque;
-  ut_avlTree_t seq;
 };
 
-struct whc *whc_new (int is_transient_local, unsigned hdepth, unsigned tldepth, size_t sample_overhead);
+typedef seqno_t (*whc_next_seq_t)(const struct whc *whc, seqno_t seq);
-void whc_free (struct whc *whc);
+typedef void (*whc_get_state_t)(const struct whc *whc, struct whc_state *st);
-int whc_empty (const struct whc *whc);
+typedef bool (*whc_borrow_sample_t)(const struct whc *whc, seqno_t seq, struct whc_borrowed_sample *sample);
-seqno_t whc_min_seq (const struct whc *whc);
+typedef bool (*whc_borrow_sample_key_t)(const struct whc *whc, const struct serdata *serdata_key, struct whc_borrowed_sample *sample);
-seqno_t whc_max_seq (const struct whc *whc);
+typedef void (*whc_return_sample_t)(struct whc *whc, struct whc_borrowed_sample *sample, bool update_retransmit_info);
-seqno_t whc_next_seq (const struct whc *whc, seqno_t seq);
+typedef void (*whc_sample_iter_init_t)(const struct whc *whc, struct whc_sample_iter *it);
-size_t whc_unacked_bytes (struct whc *whc);
+typedef bool (*whc_sample_iter_borrow_next_t)(struct whc_sample_iter *it, struct whc_borrowed_sample *sample);
-
+typedef void (*whc_free_t)(struct whc *whc);
-struct whc_node *whc_findseq (const struct whc *whc, seqno_t seq);
-struct whc_node *whc_findmax (const struct whc *whc);
-struct whc_node *whc_findkey (const struct whc *whc, const struct serdata *serdata_key);
-
-struct whc_node *whc_next_node (const struct whc *whc, seqno_t seq);
 
 /* min_seq is lowest sequence number that must be retained because of
    reliable readers that have not acknowledged all data */
 /* max_drop_seq must go soon, it's way too ugly. */
 /* plist may be NULL or os_malloc'd, WHC takes ownership of plist */
-int whc_insert (struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, struct serdata *serdata, struct tkmap_instance *tk);
+typedef int (*whc_insert_t)(struct whc *whc, seqno_t max_drop_seq, seqno_t seq, struct nn_plist *plist, struct serdata *serdata, struct tkmap_instance *tk);
-void whc_downgrade_to_volatile (struct whc *whc);
+typedef unsigned (*whc_downgrade_to_volatile_t)(struct whc *whc, struct whc_state *st);
-unsigned whc_remove_acked_messages (struct whc *whc, seqno_t max_drop_seq, struct whc_node **deferred_free_list);
+typedef unsigned (*whc_remove_acked_messages_t)(struct whc *whc, seqno_t max_drop_seq, struct whc_state *whcst, struct whc_node **deferred_free_list);
-void whc_free_deferred_free_list (struct whc *whc, struct whc_node *deferred_free_list);
+typedef void (*whc_free_deferred_free_list_t)(struct whc *whc, struct whc_node *deferred_free_list);
+
+struct whc_ops {
+  whc_insert_t insert;
+  whc_remove_acked_messages_t remove_acked_messages;
+  whc_free_deferred_free_list_t free_deferred_free_list;
+  whc_get_state_t get_state;
+  whc_next_seq_t next_seq;
+  whc_borrow_sample_t borrow_sample;
+  whc_borrow_sample_key_t borrow_sample_key;
+  whc_return_sample_t return_sample;
+  whc_sample_iter_init_t sample_iter_init;
+  whc_sample_iter_borrow_next_t sample_iter_borrow_next;
+  whc_downgrade_to_volatile_t downgrade_to_volatile;
+  whc_free_t free;
+};
+
+struct whc {
+  const struct whc_ops *ops;
+};
 
 #if defined (__cplusplus)
 }

src/core/ddsi/src/q_debmon.c

@@ -22,7 +22,6 @@
 #include "ddsi/q_time.h"
 #include "ddsi/q_misc.h"
 #include "ddsi/q_log.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_plist.h"
 #include "q__osplser.h"
 #include "ddsi/q_ephash.h"
@@ -39,7 +38,7 @@
 #include "ddsi/ddsi_tcp.h"
 
 #include "ddsi/sysdeps.h"
-
+#include "dds__whc.h"
 
 struct plugin {
   debug_monitor_plugin_t fn;
@@ -185,14 +184,14 @@ static int print_participants (struct thread_state1 *self, ddsi_tran_conn_t conn
       {
         ut_avlIter_t rdit;
         struct wr_prd_match *m;
+        struct whc_state whcst;
         if (w->c.pp != p)
           continue;
         os_mutexLock (&w->e.lock);
         print_endpoint_common (conn, "wr", &w->e, &w->c, w->xqos, w->topic);
+        w->whc->ops->get_state(w->whc, &whcst);
         x += cpf (conn, "    whc [%lld,%lld] unacked %"PRIuSIZE"%s [%u,%u] seq %lld seq_xmit %lld cs_seq %lld\n",
-                  whc_empty (w->whc) ? -1 : whc_min_seq (w->whc),
+                  whcst.min_seq, whcst.max_seq, whcst.unacked_bytes,
-                  whc_empty (w->whc) ? -1 : whc_max_seq (w->whc),
-                  whc_unacked_bytes (w->whc),
                   w->throttling ? " THROTTLING" : "",
                   w->whc_low, w->whc_high,
                   w->seq, READ_SEQ_XMIT(w), w->cs_seq);

src/core/ddsi/src/q_entity.c

@@ -22,7 +22,6 @@
 #include "ddsi/q_misc.h"
 #include "ddsi/q_log.h"
 #include "util/ut_avl.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_plist.h"
 #include "ddsi/q_lease.h"
 #include "q__osplser.h"
@@ -42,6 +41,7 @@
 #include "ddsi/ddsi_mcgroup.h"
 
 #include "ddsi/sysdeps.h"
+#include "dds__whc.h"
 
 struct deleted_participant {
   ut_avlNode_t avlnode;
@@ -84,27 +84,8 @@ static const unsigned prismtech_builtin_writers_besmask =
   NN_DISC_BUILTIN_ENDPOINT_CM_PUBLISHER_WRITER |
   NN_DISC_BUILTIN_ENDPOINT_CM_SUBSCRIBER_WRITER;
 
-static struct writer * new_writer_guid
+static struct writer * new_writer_guid (const struct nn_guid *guid, const struct nn_guid *group_guid, struct participant *pp, const struct sertopic *topic, const struct nn_xqos *xqos, struct whc *whc, status_cb_t status_cb, void *status_cbarg);
-(
+static struct reader * new_reader_guid (const struct nn_guid *guid, const struct nn_guid *group_guid, struct participant *pp, const struct sertopic *topic, const struct nn_xqos *xqos, struct rhc *rhc, status_cb_t status_cb, void *status_cbarg);
-  const struct nn_guid *guid,
-  const struct nn_guid *group_guid,
-  struct participant *pp,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  status_cb_t status_cb,
-  void *status_cbarg
-);
-static struct reader * new_reader_guid
-(
-  const struct nn_guid *guid,
-  const struct nn_guid *group_guid,
-  struct participant *pp,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  struct rhc *rhc,
-  status_cb_t status_cb,
-  void *status_cbarg
-);
 static struct participant *ref_participant (struct participant *pp, const struct nn_guid *guid_of_refing_entity);
 static void unref_participant (struct participant *pp, const struct nn_guid *guid_of_refing_entity);
 static void delete_proxy_group_locked (struct proxy_group *pgroup, nn_wctime_t timestamp, int isimplicit);
@@ -466,7 +447,7 @@ int new_participant_guid (const nn_guid_t *ppguid, unsigned flags, const nn_plis
   if (!(flags & RTPS_PF_NO_BUILTIN_WRITERS))
   {
     subguid.entityid = to_entityid (NN_ENTITYID_SPDP_BUILTIN_PARTICIPANT_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.spdp_endpoint_xqos, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.spdp_endpoint_xqos, whc_new(1, 1, 1), LAST_WR_PARAMS);
     /* But we need the as_disc address set for SPDP, because we need to
        send it to everyone regardless of the existence of readers. */
     {
@@ -489,23 +470,23 @@ int new_participant_guid (const nn_guid_t *ppguid, unsigned flags, const nn_plis
   if (!(flags & RTPS_PF_NO_BUILTIN_WRITERS))
   {
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_SUBSCRIPTIONS_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->bes |= NN_DISC_BUILTIN_ENDPOINT_SUBSCRIPTION_ANNOUNCER;
 
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_PUBLICATIONS_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->bes |= NN_DISC_BUILTIN_ENDPOINT_PUBLICATION_ANNOUNCER;
 
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_CM_PARTICIPANT_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->prismtech_bes |= NN_DISC_BUILTIN_ENDPOINT_CM_PARTICIPANT_WRITER;
 
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_CM_PUBLISHER_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->prismtech_bes |= NN_DISC_BUILTIN_ENDPOINT_CM_PUBLISHER_WRITER;
 
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_CM_SUBSCRIBER_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->prismtech_bes |= NN_DISC_BUILTIN_ENDPOINT_CM_SUBSCRIBER_WRITER;
   }
 
@@ -513,7 +494,7 @@ int new_participant_guid (const nn_guid_t *ppguid, unsigned flags, const nn_plis
   {
     /* TODO: make this one configurable, we don't want all participants to publish all topics (or even just those that they use themselves) */
     subguid.entityid = to_entityid (NN_ENTITYID_SEDP_BUILTIN_TOPIC_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->bes |= NN_DISC_BUILTIN_ENDPOINT_TOPIC_ANNOUNCER;
   }
 
@@ -521,7 +502,7 @@ int new_participant_guid (const nn_guid_t *ppguid, unsigned flags, const nn_plis
   if (!(flags & RTPS_PF_NO_BUILTIN_WRITERS))
   {
     subguid.entityid = to_entityid (NN_ENTITYID_P2P_BUILTIN_PARTICIPANT_MESSAGE_WRITER);
-    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, LAST_WR_PARAMS);
+    new_writer_guid (&subguid, &group_guid, pp, NULL, &gv.builtin_endpoint_xqos_wr, whc_new(1, 1, 1), LAST_WR_PARAMS);
     pp->bes |= NN_BUILTIN_ENDPOINT_PARTICIPANT_MESSAGE_DATA_WRITER;
   }
 
@@ -1311,17 +1292,18 @@ static void free_wr_rd_match (struct wr_rd_match *m)
 
 static void writer_drop_connection (const struct nn_guid * wr_guid, const struct proxy_reader * prd)
 {
-  struct whc_node *deferred_free_list;
   struct writer *wr;
   if ((wr = ephash_lookup_writer_guid (wr_guid)) != NULL)
   {
+    struct whc_node *deferred_free_list = NULL;
     struct wr_prd_match *m;
     os_mutexLock (&wr->e.lock);
     if ((m = ut_avlLookup (&wr_readers_treedef, &wr->readers, &prd->e.guid)) != NULL)
     {
+      struct whc_state whcst;
       ut_avlDelete (&wr_readers_treedef, &wr->readers, m);
       rebuild_writer_addrset (wr);
-      remove_acked_messages (wr, &deferred_free_list);
+      remove_acked_messages (wr, &whcst, &deferred_free_list);
       wr->num_reliable_readers -= m->is_reliable;
       if (wr->status_cb)
       {
@@ -1333,6 +1315,7 @@ static void writer_drop_connection (const struct nn_guid * wr_guid, const struct
       }
     }
     os_mutexUnlock (&wr->e.lock);
+    wr->whc->ops->free_deferred_free_list (wr->whc, deferred_free_list);
     free_wr_prd_match (m);
   }
 }
@@ -1616,20 +1599,23 @@ static void writer_add_local_connection (struct writer *wr, struct reader *rd)
   ut_avlInsertIPath (&wr_local_readers_treedef, &wr->local_readers, m, &path);
   local_reader_ary_insert (&wr->rdary, rd);
 
-  /* Store available data into the late joining reader when it is reliable. */
+  /* Store available data into the late joining reader when it is reliable (we don't do
-  if ((rd->xqos->reliability.kind > NN_BEST_EFFORT_RELIABILITY_QOS) /* transient reader */ &&
+     historical data for best-effort data over the wire, so also not locally).
-      (!whc_empty(wr->whc))                                         /* data available   */ )
+     FIXME: should limit ourselves to what it is available because of durability history,
+     not writer history */
+  if (rd->xqos->reliability.kind > NN_BEST_EFFORT_RELIABILITY_QOS && rd->xqos->durability.kind > NN_VOLATILE_DURABILITY_QOS)
   {
-    seqno_t seq = -1;
+    struct whc_sample_iter it;
-    struct whc_node *n;
+    struct whc_borrowed_sample sample;
-    while ((n = whc_next_node(wr->whc, seq)) != NULL)
+    wr->whc->ops->sample_iter_init(wr->whc, &it);
+    while (wr->whc->ops->sample_iter_borrow_next(&it, &sample))
     {
       struct proxy_writer_info pwr_info;
-      serdata_t payload = n->serdata;
+      serdata_t payload = sample.serdata;
+      /* FIXME: whc has tk reference in its index nodes, which is what we really should be iterating over anyway, and so we don't really have to look them up anymore */
       struct tkmap_instance *tk = (ddsi_plugin.rhc_plugin.rhc_lookup_fn) (payload);
       make_proxy_writer_info(&pwr_info, &wr->e, wr->xqos);
       (void)(ddsi_plugin.rhc_plugin.rhc_store_fn) (rd->rhc, &pwr_info, payload, tk);
-      seq = n->seq;
     }
   }
 
@@ -1645,7 +1631,6 @@ static void writer_add_local_connection (struct writer *wr, struct reader *rd)
     data.handle = rd->e.iid;
     (wr->status_cb) (wr->status_cb_entity, &data);
   }
-
 }
 
 static void reader_add_connection (struct reader *rd, struct proxy_writer *pwr, nn_count_t *init_count)
@@ -2502,9 +2487,9 @@ seqno_t writer_max_drop_seq (const struct writer *wr)
   return (n->min_seq == MAX_SEQ_NUMBER) ? wr->seq : n->min_seq;
 }
 
-int writer_must_have_hb_scheduled (const struct writer *wr)
+int writer_must_have_hb_scheduled (const struct writer *wr, const struct whc_state *whcst)
 {
-  if (ut_avlIsEmpty (&wr->readers) || whc_empty (wr->whc))
+  if (ut_avlIsEmpty (&wr->readers) || whcst->max_seq < 0)
   {
     /* Can't transmit a valid heartbeat if there is no data; and it
        wouldn't actually be sent anywhere if there are no readers, so
@@ -2528,7 +2513,7 @@ int writer_must_have_hb_scheduled (const struct writer *wr)
        requiring a non-empty whc_seq: if it is transient_local,
        whc_seq usually won't be empty even when all msgs have been
        ack'd. */
-    return writer_max_drop_seq (wr) < whc_max_seq (wr->whc);
+    return writer_max_drop_seq (wr) < whcst->max_seq;
   }
 }
 
@@ -2550,21 +2535,19 @@ void writer_clear_retransmitting (struct writer *wr)
   os_condBroadcast (&wr->throttle_cond);
 }
 
-unsigned remove_acked_messages (struct writer *wr, struct whc_node **deferred_free_list)
+unsigned remove_acked_messages (struct writer *wr, struct whc_state *whcst, struct whc_node **deferred_free_list)
 {
   unsigned n;
-  size_t n_unacked;
   assert (wr->e.guid.entityid.u != NN_ENTITYID_SPDP_BUILTIN_PARTICIPANT_WRITER);
   ASSERT_MUTEX_HELD (&wr->e.lock);
-  n = whc_remove_acked_messages (wr->whc, writer_max_drop_seq (wr), deferred_free_list);
+  n = wr->whc->ops->remove_acked_messages (wr->whc, writer_max_drop_seq (wr), whcst, deferred_free_list);
   /* when transitioning from >= low-water to < low-water, signal
      anyone waiting in throttle_writer() */
-  n_unacked = whc_unacked_bytes (wr->whc);
+  if (wr->throttling && whcst->unacked_bytes <= wr->whc_low)
-  if (wr->throttling && n_unacked <= wr->whc_low)
     os_condBroadcast (&wr->throttle_cond);
-  if (wr->retransmitting && whc_unacked_bytes (wr->whc) == 0)
+  if (wr->retransmitting && whcst->unacked_bytes == 0)
     writer_clear_retransmitting (wr);
-  if (wr->state == WRST_LINGERING && n_unacked == 0)
+  if (wr->state == WRST_LINGERING && whcst->unacked_bytes == 0)
   {
     nn_log (LC_DISCOVERY, "remove_acked_messages: deleting lingering writer %x:%x:%x:%x\n", PGUID (wr->e.guid));
     delete_writer_nolinger_locked (wr);
@@ -2572,26 +2555,8 @@ unsigned remove_acked_messages (struct writer *wr, struct whc_node **deferred_fr
   return n;
 }
 
-unsigned remove_acked_messages_and_free (struct writer *wr)
+static struct writer * new_writer_guid (const struct nn_guid *guid, const struct nn_guid *group_guid, struct participant *pp, const struct sertopic *topic, const struct nn_xqos *xqos, struct whc *whc, status_cb_t status_cb, void * status_entity)
 {
-  struct whc_node *deferred_free_list;
-  unsigned n = remove_acked_messages (wr, &deferred_free_list);
-  whc_free_deferred_free_list (wr->whc, deferred_free_list);
-  return n;
-}
-
-static struct writer * new_writer_guid
-(
-  const struct nn_guid *guid,
-  const struct nn_guid *group_guid,
-  struct participant *pp,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  status_cb_t status_cb,
-  void * status_entity
-)
-{
-  const size_t sample_overhead = 80; /* INFO_TS + DATA (approximate figure) + inline QoS */
   struct writer *wr;
   nn_mtime_t tnow = now_mt ();
 
@@ -2782,32 +2747,8 @@ static struct writer * new_writer_guid
   }
   wr->lease_duration = T_NEVER; /* FIXME */
 
-  /* Construct WHC -- if aggressive_keep_last1 is set, the WHC will
+  wr->whc = whc;
-     drop all samples for which a later update is available.  This
+  if (wr->xqos->history.kind == NN_KEEP_LAST_HISTORY_QOS && wr->aggressive_keep_last)
-     forces it to maintain a tlidx.  */
-  {
-    unsigned hdepth, tldepth;
-    if (!wr->aggressive_keep_last || wr->xqos->history.kind == NN_KEEP_ALL_HISTORY_QOS)
-      hdepth = 0;
-    else
-      hdepth = (unsigned)wr->xqos->history.depth;
-    if (wr->handle_as_transient_local) {
-      if (wr->xqos->durability_service.history.kind == NN_KEEP_ALL_HISTORY_QOS)
-        tldepth = 0;
-      else
-        tldepth = (unsigned)wr->xqos->durability_service.history.depth;
-    } else if (wr->startup_mode) {
-      tldepth = hdepth;
-    } else {
-      tldepth = 0;
-    }
-    if (hdepth == 0 && tldepth == 0)
-    {
-      /* no index at all - so no need to bother with startup mode */
-      wr->startup_mode = 0;
-    }
-    wr->whc = whc_new (wr->handle_as_transient_local, hdepth, tldepth, sample_overhead);
-    if (hdepth > 0)
   {
     /* hdepth > 0 => "aggressive keep last", and in that case: why
        bother blocking for a slow receiver when the entire point of
@@ -2821,7 +2762,6 @@ static struct writer * new_writer_guid
     wr->whc_high = config.whc_init_highwater_mark.value;
   }
   assert (!is_builtin_entityid(wr->e.guid.entityid, ownvendorid) || (wr->whc_low == wr->whc_high && wr->whc_low == INT32_MAX));
-  }
 
   /* Connection admin */
   ut_avlInit (&wr_readers_treedef, &wr->readers);
@@ -2855,16 +2795,7 @@ static struct writer * new_writer_guid
   return wr;
 }
 
-struct writer * new_writer
+struct writer * new_writer (struct nn_guid *wrguid, const struct nn_guid *group_guid, const struct nn_guid *ppguid, const struct sertopic *topic, const struct nn_xqos *xqos, struct whc * whc, status_cb_t status_cb, void * status_cb_arg)
-(
-  struct nn_guid *wrguid,
-  const struct nn_guid *group_guid,
-  const struct nn_guid *ppguid,
-  const struct sertopic *topic,
-  const struct nn_xqos *xqos,
-  status_cb_t status_cb,
-  void * status_cb_arg
-)
 {
   struct participant *pp;
   struct writer * wr;
@@ -2882,7 +2813,7 @@ struct writer * new_writer
   wrguid->prefix = pp->e.guid.prefix;
   if (pp_allocate_entityid (&wrguid->entityid, entity_kind, pp) < 0)
     return NULL;
-  wr = new_writer_guid (wrguid, group_guid, pp, topic, xqos, status_cb, status_cb_arg);
+  wr = new_writer_guid (wrguid, group_guid, pp, topic, xqos, whc, status_cb, status_cb_arg);
   return wr;
 }
 
@@ -2929,7 +2860,7 @@ static void gc_delete_writer (struct gcreq *gcreq)
     (wr->status_cb) (wr->status_cb_entity, NULL);
   }
 
-  whc_free (wr->whc);
+  wr->whc->ops->free (wr->whc);
 #ifdef DDSI_INCLUDE_SSM
   if (wr->ssm_as)
     unref_addrset (wr->ssm_as);
@@ -3012,6 +2943,7 @@ int delete_writer_nolinger (const struct nn_guid *guid)
 int delete_writer (const struct nn_guid *guid)
 {
   struct writer *wr;
+  struct whc_state whcst;
   if ((wr = ephash_lookup_writer_guid (guid)) == NULL)
   {
     nn_log (LC_DISCOVERY, "delete_writer(guid %x:%x:%x:%x) - unknown guid\n", PGUID (*guid));
@@ -3024,7 +2956,8 @@ int delete_writer (const struct nn_guid *guid)
      be the usual case), do it immediately.  If more data is still
      coming in (which can't really happen at the moment, but might
      again in the future) it'll potentially be discarded.  */
-  if (whc_unacked_bytes (wr->whc) == 0)
+  wr->whc->ops->get_state(wr->whc, &whcst);
+  if (whcst.unacked_bytes == 0)
   {
     nn_log (LC_DISCOVERY, "delete_writer(guid %x:%x:%x:%x) - no unack'ed samples\n", PGUID (*guid));
     delete_writer_nolinger_locked (wr);
@@ -3047,22 +2980,20 @@ int delete_writer (const struct nn_guid *guid)
 
 void writer_exit_startup_mode (struct writer *wr)
 {
+  struct whc_node *deferred_free_list = NULL;
   os_mutexLock (&wr->e.lock);
-  /* startup mode and handle_as_transient_local may not both be set */
+  if (wr->startup_mode)
-  assert (!(wr->startup_mode && wr->handle_as_transient_local));
-  if (!wr->startup_mode)
-    nn_log (LC_DISCOVERY, "  wr %x:%x:%x:%x skipped\n", PGUID (wr->e.guid));
-  else
   {
-    unsigned n;
+    unsigned cnt = 0;
-    assert (wr->e.guid.entityid.u != NN_ENTITYID_SPDP_BUILTIN_PARTICIPANT_WRITER);
+    struct whc_state whcst;
     wr->startup_mode = 0;
-    whc_downgrade_to_volatile (wr->whc);
+    cnt += remove_acked_messages (wr, &whcst, &deferred_free_list);
-    n = remove_acked_messages_and_free (wr);
+    cnt += wr->whc->ops->downgrade_to_volatile (wr->whc, &whcst);
     writer_clear_retransmitting (wr);
-    nn_log (LC_DISCOVERY, "  wr %x:%x:%x:%x dropped %u entr%s\n", PGUID (wr->e.guid), n, n == 1 ? "y" : "ies");
+    nn_log (LC_DISCOVERY, "  %x:%x:%x:%x: dropped %u samples\n", PGUID(wr->e.guid), cnt);
   }
   os_mutexUnlock (&wr->e.lock);
+  wr->whc->ops->free_deferred_free_list (wr->whc, deferred_free_list);
 }
 
 uint64_t writer_instance_id (const struct nn_guid *guid)
@@ -4379,16 +4310,19 @@ static void proxy_reader_set_delete_and_ack_all_messages (struct proxy_reader *p
     os_mutexUnlock (&prd->e.lock);
     if ((wr = ephash_lookup_writer_guid (&wrguid)) != NULL)
     {
+      struct whc_node *deferred_free_list = NULL;
       struct wr_prd_match *m_wr;
       os_mutexLock (&wr->e.lock);
       if ((m_wr = ut_avlLookup (&wr_readers_treedef, &wr->readers, &prd->e.guid)) != NULL)
       {
+        struct whc_state whcst;
         m_wr->seq = MAX_SEQ_NUMBER;
         ut_avlAugmentUpdate (&wr_readers_treedef, m_wr);
-        remove_acked_messages_and_free (wr);
+        (void)remove_acked_messages (wr, &whcst, &deferred_free_list);
         writer_clear_retransmitting (wr);
       }
       os_mutexUnlock (&wr->e.lock);
+      wr->whc->ops->free_deferred_free_list (wr->whc, deferred_free_list);
     }
 
     wrguid = wrguid_next;

src/core/ddsi/src/q_init.c

@@ -38,7 +38,6 @@
 #include "ddsi/q_ephash.h"
 #include "ddsi/q_lease.h"
 #include "ddsi/q_gc.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_entity.h"
 #include "ddsi/q_nwif.h"
 #include "ddsi/q_globals.h"
@@ -59,6 +58,7 @@
 #include "ddsi/ddsi_mcgroup.h"
 
 #include "dds__tkmap.h"
+#include "dds__whc.h"
 
 static void add_peer_addresses (struct addrset *as, const struct config_peer_listelem *list)
 {

src/core/ddsi/src/q_receive.c

@@ -41,7 +41,6 @@
 #include "ddsi/q_ephash.h"
 #include "ddsi/q_lease.h"
 #include "ddsi/q_gc.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_entity.h"
 #include "ddsi/q_xmsg.h"
 #include "ddsi/q_receive.h"
@@ -52,6 +51,7 @@
 #include "ddsi/ddsi_mcgroup.h"
 
 #include "ddsi/sysdeps.h"
+#include "dds__whc.h"
 
 /*
 Notes:
@@ -588,7 +588,7 @@ static int add_Gap (struct nn_xmsg *msg, struct writer *wr, struct proxy_reader
   return 0;
 }
 
-static void force_heartbeat_to_peer (struct writer *wr, struct proxy_reader *prd, int hbansreq)
+static void force_heartbeat_to_peer (struct writer *wr, const struct whc_state *whcst, struct proxy_reader *prd, int hbansreq)
 {
   struct nn_xmsg *m;
 
@@ -603,7 +603,7 @@ static void force_heartbeat_to_peer (struct writer *wr, struct proxy_reader *prd
     return;
   }
 
-  if (whc_empty (wr->whc) && !config.respond_to_rti_init_zero_ack_with_invalid_heartbeat)
+  if (WHCST_ISEMPTY(whcst) && !config.respond_to_rti_init_zero_ack_with_invalid_heartbeat)
   {
     /* If WHC is empty, we send a Gap combined with a Heartbeat.  The
        Gap reuses the latest sequence number (or consumes a new one if
@@ -622,14 +622,14 @@ static void force_heartbeat_to_peer (struct writer *wr, struct proxy_reader *prd
       UPDATE_SEQ_XMIT_LOCKED(wr, 1);
     }
     add_Gap (m, wr, prd, seq, seq+1, 1, &bits);
-    add_Heartbeat (m, wr, hbansreq, prd->e.guid.entityid, 1);
+    add_Heartbeat (m, wr, whcst, hbansreq, prd->e.guid.entityid, 1);
     TRACE (("force_heartbeat_to_peer: %x:%x:%x:%x -> %x:%x:%x:%x - whc empty, queueing gap #%"PRId64" + heartbeat for transmit\n",
             PGUID (wr->e.guid), PGUID (prd->e.guid), seq));
   }
   else
   {
     /* Send a Heartbeat just to this peer */
-    add_Heartbeat (m, wr, hbansreq, prd->e.guid.entityid, 0);
+    add_Heartbeat (m, wr, whcst, hbansreq, prd->e.guid.entityid, 0);
     TRACE (("force_heartbeat_to_peer: %x:%x:%x:%x -> %x:%x:%x:%x - queue for transmit\n",
             PGUID (wr->e.guid), PGUID (prd->e.guid)));
   }
@@ -638,7 +638,7 @@ static void force_heartbeat_to_peer (struct writer *wr, struct proxy_reader *prd
 
 static seqno_t grow_gap_to_next_seq (const struct writer *wr, seqno_t seq)
 {
-  seqno_t next_seq = whc_next_seq (wr->whc, seq - 1);
+  seqno_t next_seq = wr->whc->ops->next_seq (wr->whc, seq - 1);
   seqno_t seq_xmit = READ_SEQ_XMIT(wr);
   if (next_seq == MAX_SEQ_NUMBER) /* no next sample */
     return seq_xmit + 1;
@@ -715,6 +715,7 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
   uint32_t msgs_sent, msgs_lost;
   seqno_t max_seq_in_reply;
   struct whc_node *deferred_free_list = NULL;
+  struct whc_state whcst;
   unsigned i;
   int hb_sent_in_response = 0;
   memset (gapbits, 0, sizeof (gapbits));
@@ -828,19 +829,21 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
       rn->seq = wr->seq;
     }
     ut_avlAugmentUpdate (&wr_readers_treedef, rn);
-    n = remove_acked_messages (wr, &deferred_free_list);
+    n = remove_acked_messages (wr, &whcst, &deferred_free_list);
     TRACE ((" ACK%"PRId64" RM%u", n_ack, n));
   }
+  else
+  {
+    /* There's actually no guarantee that we need this information */
+    wr->whc->ops->get_state(wr->whc, &whcst);
+  }
 
   /* If this reader was marked as "non-responsive" in the past, it's now responding again,
      so update its status */
   if (rn->seq == MAX_SEQ_NUMBER && prd->c.xqos->reliability.kind == NN_RELIABLE_RELIABILITY_QOS)
   {
     seqno_t oldest_seq;
-    if (whc_empty (wr->whc))
+    oldest_seq = WHCST_ISEMPTY(&whcst) ? wr->seq : whcst.max_seq;
-      oldest_seq = wr->seq;
-    else
-      oldest_seq = whc_max_seq (wr->whc);
     rn->has_replied_to_hb = 1; /* was temporarily cleared to ensure heartbeats went out */
     rn->seq = seqbase - 1;
     if (oldest_seq > rn->seq) {
@@ -880,19 +883,19 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
        data in our WHC, we start sending it regardless of whether the
        remote reader asked for it */
     TRACE ((" preemptive-nack"));
-    if (whc_empty (wr->whc))
+    if (WHCST_ISEMPTY(&whcst))
     {
       TRACE ((" whc-empty "));
-      force_heartbeat_to_peer (wr, prd, 0);
+      force_heartbeat_to_peer (wr, &whcst, prd, 0);
       hb_sent_in_response = 1;
     }
     else
     {
       TRACE ((" rebase "));
-      force_heartbeat_to_peer (wr, prd, 0);
+      force_heartbeat_to_peer (wr, &whcst, prd, 0);
       hb_sent_in_response = 1;
       numbits = config.accelerate_rexmit_block_size;
-      seqbase = whc_min_seq (wr->whc);
+      seqbase = whcst.min_seq;
     }
   }
   else if (!rn->assumed_in_sync)
@@ -940,25 +943,25 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
     if (i >= msg->readerSNState.numbits || nn_bitset_isset (numbits, msg->readerSNState.bits, i))
     {
       seqno_t seq = seqbase + i;
-      struct whc_node *whcn;
+      struct whc_borrowed_sample sample;
-      if ((whcn = whc_findseq (wr->whc, seq)) != NULL)
+      if (wr->whc->ops->borrow_sample (wr->whc, seq, &sample))
       {
-        if (!wr->retransmitting && whcn->unacked)
+        if (!wr->retransmitting && sample.unacked)
           writer_set_retransmitting (wr);
 
         if (config.retransmit_merging != REXMIT_MERGE_NEVER && rn->assumed_in_sync)
         {
           /* send retransmit to all receivers, but skip if recently done */
           nn_mtime_t tstamp = now_mt ();
-          if (tstamp.v > whcn->last_rexmit_ts.v + config.retransmit_merging_period)
+          if (tstamp.v > sample.last_rexmit_ts.v + config.retransmit_merging_period)
           {
             TRACE ((" RX%"PRId64, seqbase + i));
-            enqueued = (enqueue_sample_wrlock_held (wr, seq, whcn->plist, whcn->serdata, NULL, 0) >= 0);
+            enqueued = (enqueue_sample_wrlock_held (wr, seq, sample.plist, sample.serdata, NULL, 0) >= 0);
             if (enqueued)
             {
               max_seq_in_reply = seqbase + i;
               msgs_sent++;
-              whcn->last_rexmit_ts = tstamp;
+              sample.last_rexmit_ts = tstamp;
             }
           }
           else
@@ -970,14 +973,16 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
         {
           /* no merging, send directed retransmit */
           TRACE ((" RX%"PRId64"", seqbase + i));
-          enqueued = (enqueue_sample_wrlock_held (wr, seq, whcn->plist, whcn->serdata, prd, 0) >= 0);
+          enqueued = (enqueue_sample_wrlock_held (wr, seq, sample.plist, sample.serdata, prd, 0) >= 0);
           if (enqueued)
           {
             max_seq_in_reply = seqbase + i;
             msgs_sent++;
-            whcn->rexmit_count++;
+            sample.rexmit_count++;
           }
         }
+
+        wr->whc->ops->return_sample(wr->whc, &sample, true);
       }
       else if (gapstart == -1)
       {
@@ -1054,7 +1059,7 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
   if (msgs_sent && max_seq_in_reply < seq_xmit)
   {
     TRACE ((" rexmit#%"PRIu32" maxseq:%"PRId64"<%"PRId64"<=%"PRId64"", msgs_sent, max_seq_in_reply, seq_xmit, wr->seq));
-    force_heartbeat_to_peer (wr, prd, 1);
+    force_heartbeat_to_peer (wr, &whcst, prd, 1);
     hb_sent_in_response = 1;
 
     /* The primary purpose of hbcontrol_note_asyncwrite is to ensure
@@ -1062,16 +1067,16 @@ static int handle_AckNack (struct receiver_state *rst, nn_etime_t tnow, const Ac
        gradually lowering rate.  If we just got a request for a
        retransmit, and there is more to be retransmitted, surely the
        rate should be kept up for now */
-    writer_hbcontrol_note_asyncwrite (wr, now_mt ());
+    writer_hbcontrol_note_asyncwrite (wr, &whcst, now_mt ());
   }
   /* If "final" flag not set, we must respond with a heartbeat. Do it
      now if we haven't done so already */
   if (!(msg->smhdr.flags & ACKNACK_FLAG_FINAL) && !hb_sent_in_response)
-    force_heartbeat_to_peer (wr, prd, 0);
+    force_heartbeat_to_peer (wr, &whcst, prd, 0);
   TRACE ((")"));
  out:
   os_mutexUnlock (&wr->e.lock);
-  whc_free_deferred_free_list (wr->whc, deferred_free_list);
+  wr->whc->ops->free_deferred_free_list (wr->whc, deferred_free_list);
   return 1;
 }
 
@@ -1428,7 +1433,7 @@ static int handle_NackFrag (struct receiver_state *rst, nn_etime_t tnow, const N
   struct proxy_reader *prd;
   struct wr_prd_match *rn;
   struct writer *wr;
-  struct whc_node *whcn;
+  struct whc_borrowed_sample sample;
   nn_guid_t src, dst;
   nn_count_t *countp;
   seqno_t seq = fromSN (msg->writerSN);
@@ -1493,7 +1498,25 @@ static int handle_NackFrag (struct receiver_state *rst, nn_etime_t tnow, const N
 
   /* Resend the requested fragments if we still have the sample, send
      a Gap if we don't have them anymore. */
-  if ((whcn = whc_findseq (wr->whc, seq)) == NULL)
+  if (wr->whc->ops->borrow_sample (wr->whc, seq, &sample))
+  {
+    const unsigned base = msg->fragmentNumberState.bitmap_base - 1;
+    int enqueued = 1;
+    TRACE ((" scheduling requested frags ...\n"));
+    for (i = 0; i < msg->fragmentNumberState.numbits && enqueued; i++)
+    {
+      if (nn_bitset_isset (msg->fragmentNumberState.numbits, msg->fragmentNumberState.bits, i))
+      {
+        struct nn_xmsg *reply;
+        if (create_fragment_message (wr, seq, sample.plist, sample.serdata, base + i, prd, &reply, 0) < 0)
+          enqueued = 0;
+        else
+          enqueued = qxev_msg_rexmit_wrlock_held (wr->evq, reply, 0);
+      }
+    }
+    wr->whc->ops->return_sample (wr->whc, &sample, false);
+  }
+  else
   {
     static unsigned zero = 0;
     struct nn_xmsg *m;
@@ -1512,30 +1535,15 @@ static int handle_NackFrag (struct receiver_state *rst, nn_etime_t tnow, const N
       qxev_msg (wr->evq, m);
     }
   }
-  else
-  {
-    const unsigned base = msg->fragmentNumberState.bitmap_base - 1;
-    int enqueued = 1;
-    TRACE ((" scheduling requested frags ...\n"));
-    for (i = 0; i < msg->fragmentNumberState.numbits && enqueued; i++)
-    {
-      if (nn_bitset_isset (msg->fragmentNumberState.numbits, msg->fragmentNumberState.bits, i))
-      {
-        struct nn_xmsg *reply;
-        if (create_fragment_message (wr, seq, whcn->plist, whcn->serdata, base + i, prd, &reply, 0) < 0)
-          enqueued = 0;
-        else
-          enqueued = qxev_msg_rexmit_wrlock_held (wr->evq, reply, 0);
-      }
-    }
-  }
   if (seq < READ_SEQ_XMIT(wr))
   {
     /* Not everything was retransmitted yet, so force a heartbeat out
        to give the reader a chance to nack the rest and make sure
        hearbeats will go out at a reasonably high rate for a while */
-    force_heartbeat_to_peer (wr, prd, 1);
+    struct whc_state whcst;
-    writer_hbcontrol_note_asyncwrite (wr, now_mt ());
+    wr->whc->ops->get_state(wr->whc, &whcst);
+    force_heartbeat_to_peer (wr, &whcst, prd, 1);
+    writer_hbcontrol_note_asyncwrite (wr, &whcst, now_mt ());
   }
 
  out:

src/core/ddsi/src/q_transmit.c

@@ -15,7 +15,6 @@
 #include "os/os.h"
 
 #include "util/ut_avl.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_entity.h"
 #include "ddsi/q_addrset.h"
 #include "ddsi/q_xmsg.h"
@@ -36,6 +35,7 @@
 #include "ddsi/ddsi_ser.h"
 
 #include "ddsi/sysdeps.h"
+#include "dds__whc.h"
 
 #if __STDC_VERSION__ >= 199901L
 #define POS_INFINITY_DOUBLE INFINITY
@@ -84,7 +84,7 @@ static void writer_hbcontrol_note_hb (struct writer *wr, nn_mtime_t tnow, int an
   hbc->hbs_since_last_write++;
 }
 
-int64_t writer_hbcontrol_intv (const struct writer *wr, UNUSED_ARG (nn_mtime_t tnow))
+int64_t writer_hbcontrol_intv (const struct writer *wr, const struct whc_state *whcst, UNUSED_ARG (nn_mtime_t tnow))
 {
   struct hbcontrol const * const hbc = &wr->hbcontrol;
   int64_t ret = config.const_hb_intv_sched;
@@ -97,7 +97,7 @@ int64_t writer_hbcontrol_intv (const struct writer *wr, UNUSED_ARG (nn_mtime_t t
       ret *= 2;
   }
 
-  n_unacked = whc_unacked_bytes (wr->whc);
+  n_unacked = whcst->unacked_bytes;
   if (n_unacked >= wr->whc_low + 3 * (wr->whc_high - wr->whc_low) / 4)
     ret /= 2;
   if (n_unacked >= wr->whc_low + (wr->whc_high - wr->whc_low) / 2)
@@ -109,7 +109,7 @@ int64_t writer_hbcontrol_intv (const struct writer *wr, UNUSED_ARG (nn_mtime_t t
   return ret;
 }
 
-void writer_hbcontrol_note_asyncwrite (struct writer *wr, nn_mtime_t tnow)
+void writer_hbcontrol_note_asyncwrite (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow)
 {
   struct hbcontrol * const hbc = &wr->hbcontrol;
   nn_mtime_t tnext;
@@ -131,13 +131,13 @@ void writer_hbcontrol_note_asyncwrite (struct writer *wr, nn_mtime_t tnow)
   }
 }
 
-int writer_hbcontrol_must_send (const struct writer *wr, nn_mtime_t tnow /* monotonic */)
+int writer_hbcontrol_must_send (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow /* monotonic */)
 {
   struct hbcontrol const * const hbc = &wr->hbcontrol;
-  return (tnow.v >= hbc->t_of_last_hb.v + writer_hbcontrol_intv (wr, tnow));
+  return (tnow.v >= hbc->t_of_last_hb.v + writer_hbcontrol_intv (wr, whcst, tnow));
 }
 
-struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, nn_mtime_t tnow, int hbansreq, int issync)
+struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow, int hbansreq, int issync)
 {
   struct nn_xmsg *msg;
   const nn_guid_t *prd_guid;
@@ -200,7 +200,7 @@ struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, nn_mtime_t
 #ifdef DDSI_INCLUDE_NETWORK_PARTITIONS
     nn_xmsg_setencoderid (msg, wr->partition_id);
 #endif
-    add_Heartbeat (msg, wr, hbansreq, to_entityid (NN_ENTITYID_UNKNOWN), issync);
+    add_Heartbeat (msg, wr, whcst, hbansreq, to_entityid (NN_ENTITYID_UNKNOWN), issync);
   }
   else
   {
@@ -221,14 +221,14 @@ struct nn_xmsg *writer_hbcontrol_create_heartbeat (struct writer *wr, nn_mtime_t
 #ifdef DDSI_INCLUDE_NETWORK_PARTITIONS
     nn_xmsg_setencoderid (msg, wr->partition_id);
 #endif
-    add_Heartbeat (msg, wr, hbansreq, prd_guid->entityid, issync);
+    add_Heartbeat (msg, wr, whcst, hbansreq, prd_guid->entityid, issync);
   }
 
   writer_hbcontrol_note_hb (wr, tnow, hbansreq);
   return msg;
 }
 
-static int writer_hbcontrol_ack_required_generic (const struct writer *wr, nn_mtime_t tlast, nn_mtime_t tnow, int piggyback)
+static int writer_hbcontrol_ack_required_generic (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tlast, nn_mtime_t tnow, int piggyback)
 {
   struct hbcontrol const * const hbc = &wr->hbcontrol;
   const int64_t hb_intv_ack = config.const_hb_intv_sched;
@@ -251,7 +251,7 @@ static int writer_hbcontrol_ack_required_generic (const struct writer *wr, nn_mt
       return 2;
   }
 
-  if (whc_unacked_bytes (wr->whc) >= wr->whc_low + (wr->whc_high - wr->whc_low) / 2)
+  if (whcst->unacked_bytes >= wr->whc_low + (wr->whc_high - wr->whc_low) / 2)
   {
     if (tnow.v >= hbc->t_of_last_ackhb.v + config.const_hb_intv_sched_min)
       return 2;
@@ -262,13 +262,13 @@ static int writer_hbcontrol_ack_required_generic (const struct writer *wr, nn_mt
   return 0;
 }
 
-int writer_hbcontrol_ack_required (const struct writer *wr, nn_mtime_t tnow)
+int writer_hbcontrol_ack_required (const struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow)
 {
   struct hbcontrol const * const hbc = &wr->hbcontrol;
-  return writer_hbcontrol_ack_required_generic (wr, hbc->t_of_last_write, tnow, 0);
+  return writer_hbcontrol_ack_required_generic (wr, whcst, hbc->t_of_last_write, tnow, 0);
 }
 
-struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, nn_mtime_t tnow, unsigned packetid, int *hbansreq)
+struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, const struct whc_state *whcst, nn_mtime_t tnow, unsigned packetid, int *hbansreq)
 {
   struct hbcontrol * const hbc = &wr->hbcontrol;
   unsigned last_packetid;
@@ -284,20 +284,20 @@ struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, nn_mtime_t tnow,
   /* Update statistics, intervals, scheduling of heartbeat event,
      &c. -- there's no real difference between async and sync so we
      reuse the async version. */
-  writer_hbcontrol_note_asyncwrite (wr, tnow);
+  writer_hbcontrol_note_asyncwrite (wr, whcst, tnow);
 
-  *hbansreq = writer_hbcontrol_ack_required_generic (wr, tlast, tnow, 1);
+  *hbansreq = writer_hbcontrol_ack_required_generic (wr, whcst, tlast, tnow, 1);
   if (*hbansreq >= 2) {
     /* So we force a heartbeat in - but we also rely on our caller to
        send the packet out */
-    msg = writer_hbcontrol_create_heartbeat (wr, tnow, *hbansreq, 1);
+    msg = writer_hbcontrol_create_heartbeat (wr, whcst, tnow, *hbansreq, 1);
   } else if (last_packetid != packetid) {
     /* If we crossed a packet boundary since the previous write,
        piggyback a heartbeat, with *hbansreq determining whether or
        not an ACK is needed.  We don't force the packet out either:
        this is just to ensure a regular flow of ACKs for cleaning up
        the WHC & for allowing readers to NACK missing samples. */
-    msg = writer_hbcontrol_create_heartbeat (wr, tnow, *hbansreq, 1);
+    msg = writer_hbcontrol_create_heartbeat (wr, whcst, tnow, *hbansreq, 1);
   } else {
     *hbansreq = 0;
     msg = NULL;
@@ -311,13 +311,13 @@ struct nn_xmsg *writer_hbcontrol_piggyback (struct writer *wr, nn_mtime_t tnow,
             (hbc->tsched.v == T_NEVER) ? POS_INFINITY_DOUBLE : (double) (hbc->tsched.v - tnow.v) / 1e9,
             ut_avlIsEmpty (&wr->readers) ? -1 : root_rdmatch (wr)->min_seq,
             ut_avlIsEmpty (&wr->readers) || root_rdmatch (wr)->all_have_replied_to_hb ? "" : "!",
-            whc_empty (wr->whc) ? -1 : whc_max_seq (wr->whc), READ_SEQ_XMIT(wr)));
+            whcst->max_seq, READ_SEQ_XMIT(wr)));
   }
 
   return msg;
 }
 
-void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, int hbansreq, nn_entityid_t dst, int issync)
+void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, const struct whc_state *whcst, int hbansreq, nn_entityid_t dst, int issync)
 {
   struct nn_xmsg_marker sm_marker;
   Heartbeat_t * hb;
@@ -343,7 +343,7 @@ void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, int hbansreq, nn_ent
 
   hb->readerId = nn_hton_entityid (dst);
   hb->writerId = nn_hton_entityid (wr->e.guid.entityid);
-  if (whc_empty (wr->whc))
+  if (WHCST_ISEMPTY(whcst))
   {
     /* Really don't have data.  Fake one at the current wr->seq.
        We're not really allowed to generate heartbeats when the WHC is
@@ -360,7 +360,7 @@ void add_Heartbeat (struct nn_xmsg *msg, struct writer *wr, int hbansreq, nn_ent
   else
   {
     seqno_t seq_xmit;
-    min = whc_min_seq (wr->whc);
+    min = whcst->min_seq;
     max = wr->seq;
     seq_xmit = READ_SEQ_XMIT(wr);
     assert (min <= max);
@@ -669,7 +669,7 @@ static int must_skip_frag (const char *frags_to_skip, unsigned frag)
 }
 #endif
 
-static void transmit_sample_lgmsg_unlocked (struct nn_xpack *xp, struct writer *wr, seqno_t seq, const struct nn_plist *plist, serdata_t serdata, struct proxy_reader *prd, int isnew, unsigned nfrags)
+static void transmit_sample_lgmsg_unlocked (struct nn_xpack *xp, struct writer *wr, const struct whc_state *whcst, seqno_t seq, const struct nn_plist *plist, serdata_t serdata, struct proxy_reader *prd, int isnew, unsigned nfrags)
 {
   unsigned i;
 #if 0
@@ -714,8 +714,7 @@ static void transmit_sample_lgmsg_unlocked (struct nn_xpack *xp, struct writer *
     struct nn_xmsg *msg = NULL;
     int hbansreq;
     os_mutexLock (&wr->e.lock);
-    msg = writer_hbcontrol_piggyback
+    msg = writer_hbcontrol_piggyback (wr, whcst, ddsi_serdata_twrite (serdata), nn_xpack_packetid (xp), &hbansreq);
-      (wr, ddsi_serdata_twrite (serdata), nn_xpack_packetid (xp), &hbansreq);
     os_mutexUnlock (&wr->e.lock);
     if (msg)
     {
@@ -726,7 +725,7 @@ static void transmit_sample_lgmsg_unlocked (struct nn_xpack *xp, struct writer *
   }
 }
 
-static void transmit_sample_unlocks_wr (struct nn_xpack *xp, struct writer *wr, seqno_t seq, const struct nn_plist *plist, serdata_t serdata, struct proxy_reader *prd, int isnew)
+static void transmit_sample_unlocks_wr (struct nn_xpack *xp, struct writer *wr, const struct whc_state *whcst, seqno_t seq, const struct nn_plist *plist, serdata_t serdata, struct proxy_reader *prd, int isnew)
 {
   /* on entry: &wr->e.lock held; on exit: lock no longer held */
   struct nn_xmsg *fmsg;
@@ -739,7 +738,7 @@ static void transmit_sample_unlocks_wr (struct nn_xpack *xp, struct writer *wr,
     unsigned nfrags;
     os_mutexUnlock (&wr->e.lock);
     nfrags = (sz + config.fragment_size - 1) / config.fragment_size;
-    transmit_sample_lgmsg_unlocked (xp, wr, seq, plist, serdata, prd, isnew, nfrags);
+    transmit_sample_lgmsg_unlocked (xp, wr, whcst, seq, plist, serdata, prd, isnew, nfrags);
     return;
   }
   else if (create_fragment_message_simple (wr, seq, serdata, &fmsg) < 0)
@@ -754,7 +753,7 @@ static void transmit_sample_unlocks_wr (struct nn_xpack *xp, struct writer *wr,
 
     /* Note: wr->heartbeat_xevent != NULL <=> wr is reliable */
     if (wr->heartbeat_xevent)
-      hmsg = writer_hbcontrol_piggyback (wr, ddsi_serdata_twrite (serdata), nn_xpack_packetid (xp), &hbansreq);
+      hmsg = writer_hbcontrol_piggyback (wr, whcst, ddsi_serdata_twrite (serdata), nn_xpack_packetid (xp), &hbansreq);
     else
       hmsg = NULL;
 
@@ -855,7 +854,7 @@ static int insert_sample_in_whc (struct writer *wr, seqno_t seq, struct nn_plist
 
   if (!do_insert)
     res = 0;
-  else if ((insres = whc_insert (wr->whc, writer_max_drop_seq (wr), seq, plist, serdata, tk)) < 0)
+  else if ((insres = wr->whc->ops->insert (wr->whc, writer_max_drop_seq (wr), seq, plist, serdata, tk)) < 0)
     res = insres;
   else
     res = 1;
@@ -863,16 +862,18 @@ static int insert_sample_in_whc (struct writer *wr, seqno_t seq, struct nn_plist
 #ifndef NDEBUG
   if (wr->e.guid.entityid.u == NN_ENTITYID_SPDP_BUILTIN_PARTICIPANT_WRITER)
   {
-    if (whc_findmax (wr->whc) == NULL)
+    struct whc_state whcst;
+    wr->whc->ops->get_state(wr->whc, &whcst);
+    if (WHCST_ISEMPTY(&whcst))
       assert (wr->c.pp->builtins_deleted);
   }
 #endif
   return res;
 }
 
-static int writer_may_continue (const struct writer *wr)
+static int writer_may_continue (const struct writer *wr, const struct whc_state *whcst)
 {
-  return (whc_unacked_bytes (wr->whc) <= wr->whc_low && !wr->retransmitting) || (wr->state != WRST_OPERATIONAL);
+  return (whcst->unacked_bytes <= wr->whc_low && !wr->retransmitting) || (wr->state != WRST_OPERATIONAL);
 }
 
 
@@ -915,7 +916,8 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
   os_result result = os_resultSuccess;
   nn_mtime_t tnow = now_mt ();
   const nn_mtime_t abstimeout = add_duration_to_mtime (tnow, nn_from_ddsi_duration (wr->xqos->reliability.max_blocking_time));
-  size_t n_unacked = whc_unacked_bytes (wr->whc);
+  struct whc_state whcst;
+  wr->whc->ops->get_state(wr->whc, &whcst);
 
   {
     nn_vendorid_t ownvendorid = MY_VENDOR_ID;
@@ -925,7 +927,7 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
     assert (!is_builtin_entityid(wr->e.guid.entityid, ownvendorid));
   }
 
-  nn_log (LC_THROTTLE, "writer %x:%x:%x:%x waiting for whc to shrink below low-water mark (whc %"PRIuSIZE" low=%u high=%u)\n", PGUID (wr->e.guid), n_unacked, wr->whc_low, wr->whc_high);
+  nn_log (LC_THROTTLE, "writer %x:%x:%x:%x waiting for whc to shrink below low-water mark (whc %"PRIuSIZE" low=%u high=%u)\n", PGUID (wr->e.guid), whcst.unacked_bytes, wr->whc_low, wr->whc_high);
   wr->throttling = 1;
   wr->throttle_count++;
 
@@ -934,7 +936,7 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
      things the wrong way round ... */
   if (xp)
   {
-    struct nn_xmsg *hbmsg = writer_hbcontrol_create_heartbeat (wr, tnow, 1, 1);
+    struct nn_xmsg *hbmsg = writer_hbcontrol_create_heartbeat (wr, &whcst, tnow, 1, 1);
     os_mutexUnlock (&wr->e.lock);
     if (hbmsg)
     {
@@ -944,7 +946,7 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
     os_mutexLock (&wr->e.lock);
   }
 
-  while (gv.rtps_keepgoing && !writer_may_continue (wr))
+  while (gv.rtps_keepgoing && !writer_may_continue (wr, &whcst))
   {
     int64_t reltimeout;
     tnow = now_mt ();
@@ -958,6 +960,7 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
       thread_state_asleep (lookup_thread_state());
       result = os_condTimedWait (&wr->throttle_cond, &wr->e.lock, &timeout);
       thread_state_awake (lookup_thread_state());
+      wr->whc->ops->get_state(wr->whc, &whcst);
     }
     if (result == os_resultTimeout)
     {
@@ -972,8 +975,7 @@ static os_result throttle_writer (struct nn_xpack *xp, struct writer *wr)
     os_condBroadcast (&wr->throttle_cond);
   }
 
-  n_unacked = whc_unacked_bytes (wr->whc);
+  nn_log (LC_THROTTLE, "writer %x:%x:%x:%x done waiting for whc to shrink below low-water mark (whc %"PRIuSIZE" low=%u high=%u)\n", PGUID (wr->e.guid), whcst.unacked_bytes, wr->whc_low, wr->whc_high);
-  nn_log (LC_THROTTLE, "writer %x:%x:%x:%x done waiting for whc to shrink below low-water mark (whc %"PRIuSIZE" low=%u high=%u)\n", PGUID (wr->e.guid), n_unacked, wr->whc_low, wr->whc_high);
   return result;
 }
 
@@ -1028,8 +1030,9 @@ static int write_sample_eot (struct nn_xpack *xp, struct writer *wr, struct nn_p
 
   /* If WHC overfull, block. */
   {
-    size_t unacked_bytes = whc_unacked_bytes (wr->whc);
+    struct whc_state whcst;
-    if (unacked_bytes > wr->whc_high)
+    wr->whc->ops->get_state(wr->whc, &whcst);
+    if (whcst.unacked_bytes > wr->whc_high)
     {
       os_result ores;
       assert(gc_allowed); /* also see beginning of the function */
@@ -1038,7 +1041,7 @@ static int write_sample_eot (struct nn_xpack *xp, struct writer *wr, struct nn_p
       else
       {
         maybe_grow_whc (wr);
-        if (unacked_bytes <= wr->whc_high)
+        if (whcst.unacked_bytes <= wr->whc_high)
           ores = os_resultSuccess;
         else
           ores = throttle_writer (xp, wr);
@@ -1081,6 +1084,10 @@ static int write_sample_eot (struct nn_xpack *xp, struct writer *wr, struct nn_p
   }
   else
   {
+    struct whc_state whcst;
+    if (wr->heartbeat_xevent)
+      wr->whc->ops->get_state(wr->whc, &whcst);
+
     /* Note the subtlety of enqueueing with the lock held but
        transmitting without holding the lock. Still working on
        cleaning that up. */
@@ -1098,14 +1105,14 @@ static int write_sample_eot (struct nn_xpack *xp, struct writer *wr, struct nn_p
         plist_copy = &plist_stk;
         nn_plist_copy (plist_copy, plist);
       }
-      transmit_sample_unlocks_wr (xp, wr, seq, plist_copy, serdata, NULL, 1);
+      transmit_sample_unlocks_wr (xp, wr, &whcst, seq, plist_copy, serdata, NULL, 1);
       if (plist_copy)
         nn_plist_fini (plist_copy);
     }
     else
     {
       if (wr->heartbeat_xevent)
-        writer_hbcontrol_note_asyncwrite (wr, tnow);
+        writer_hbcontrol_note_asyncwrite (wr, &whcst, tnow);
       enqueue_sample_wrlock_held (wr, seq, plist, serdata, NULL, 1);
       os_mutexUnlock (&wr->e.lock);
     }

src/core/ddsi/src/q_xevent.c

@@ -21,7 +21,6 @@
 #include "ddsi/q_log.h"
 #include "ddsi/q_addrset.h"
 #include "ddsi/q_xmsg.h"
-#include "ddsi/q_whc.h"
 #include "ddsi/q_xevent.h"
 #include "ddsi/q_thread.h"
 #include "ddsi/q_config.h"
@@ -39,6 +38,7 @@
 #include "ddsi/q_xmsg.h"
 #include "q__osplser.h"
 #include "ddsi/ddsi_ser.h"
+#include "dds__whc.h"
 
 #include "ddsi/sysdeps.h"
 
@@ -596,6 +596,7 @@ static void handle_xevk_heartbeat (struct nn_xpack *xp, struct xevent *ev, nn_mt
   struct writer *wr;
   nn_mtime_t t_next;
   int hbansreq = 0;
+  struct whc_state whcst;
 
   if ((wr = ephash_lookup_writer_guid (&ev->u.heartbeat.wr_guid)) == NULL)
   {
@@ -606,23 +607,24 @@ static void handle_xevk_heartbeat (struct nn_xpack *xp, struct xevent *ev, nn_mt
 
   assert (wr->reliable);
   os_mutexLock (&wr->e.lock);
-  if (!writer_must_have_hb_scheduled (wr))
+  wr->whc->ops->get_state(wr->whc, &whcst);
+  if (!writer_must_have_hb_scheduled (wr, &whcst))
   {
     hbansreq = 1; /* just for trace */
     msg = NULL; /* Need not send it now, and no need to schedule it for the future */
     t_next.v = T_NEVER;
   }
-  else if (!writer_hbcontrol_must_send (wr, tnow))
+  else if (!writer_hbcontrol_must_send (wr, &whcst, tnow))
   {
     hbansreq = 1; /* just for trace */
     msg = NULL;
-    t_next.v = tnow.v + writer_hbcontrol_intv (wr, tnow);
+    t_next.v = tnow.v + writer_hbcontrol_intv (wr, &whcst, tnow);
   }
   else
   {
-    hbansreq = writer_hbcontrol_ack_required (wr, tnow);
+    hbansreq = writer_hbcontrol_ack_required (wr, &whcst, tnow);
-    msg = writer_hbcontrol_create_heartbeat (wr, tnow, hbansreq, 0);
+    msg = writer_hbcontrol_create_heartbeat (wr, &whcst, tnow, hbansreq, 0);
-    t_next.v = tnow.v + writer_hbcontrol_intv (wr, tnow);
+    t_next.v = tnow.v + writer_hbcontrol_intv (wr, &whcst, tnow);
   }
 
   TRACE (("heartbeat(wr %x:%x:%x:%x%s) %s, resched in %g s (min-ack %"PRId64"%s, avail-seq %"PRId64", xmit %"PRId64")\n",
@@ -632,7 +634,7 @@ static void handle_xevk_heartbeat (struct nn_xpack *xp, struct xevent *ev, nn_mt
           (t_next.v == T_NEVER) ? POS_INFINITY_DOUBLE : (double)(t_next.v - tnow.v) / 1e9,
           ut_avlIsEmpty (&wr->readers) ? (seqno_t) -1 : ((struct wr_prd_match *) ut_avlRootNonEmpty (&wr_readers_treedef, &wr->readers))->min_seq,
           ut_avlIsEmpty (&wr->readers) || ((struct wr_prd_match *) ut_avlRootNonEmpty (&wr_readers_treedef, &wr->readers))->all_have_replied_to_hb ? "" : "!",
-          whc_empty (wr->whc) ? (seqno_t) -1 : whc_max_seq (wr->whc), READ_SEQ_XMIT(wr)));
+          whcst.max_seq, READ_SEQ_XMIT(wr)));
   resched_xevent_if_earlier (ev, t_next);
   wr->hbcontrol.tsched = t_next;
   os_mutexUnlock (&wr->e.lock);
@@ -963,10 +965,13 @@ static void handle_xevk_spdp (UNUSED_ARG (struct nn_xpack *xp), struct xevent *e
   struct participant *pp;
   struct proxy_reader *prd;
   struct writer *spdp_wr;
-  struct whc_node *whcn;
+  struct whc_borrowed_sample sample;
   serstate_t st;
   serdata_t sd;
   nn_guid_t kh;
+#ifndef NDEBUG
+  bool sample_found;
+#endif
 
   if ((pp = ephash_lookup_participant_guid (&ev->u.spdp.pp_guid)) == NULL)
   {
@@ -1011,21 +1016,31 @@ static void handle_xevk_spdp (UNUSED_ARG (struct nn_xpack *xp), struct xevent *e
   sd = ddsi_serstate_fix (st);
 
   os_mutexLock (&spdp_wr->e.lock);
-  if ((whcn = whc_findkey (spdp_wr->whc, sd)) != NULL)
+  if (spdp_wr->whc->ops->borrow_sample_key (spdp_wr->whc, sd, &sample))
   {
     /* Claiming it is new rather than a retransmit so that the rexmit
        limiting won't kick in.  It is best-effort and therefore the
        updating of the last transmitted sequence number won't take
        place anyway.  Nor is it necessary to fiddle with heartbeat
        control stuff. */
-    enqueue_sample_wrlock_held (spdp_wr, whcn->seq, whcn->plist, whcn->serdata, prd, 1);
+    enqueue_sample_wrlock_held (spdp_wr, sample.seq, sample.plist, sample.serdata, prd, 1);
+    spdp_wr->whc->ops->return_sample(spdp_wr->whc, &sample, false);
+#ifndef NDEBUG
+    sample_found = true;
+#endif
   }
+#ifndef NDEBUG
+  else
+  {
+    sample_found = false;
+  }
+#endif
   os_mutexUnlock (&spdp_wr->e.lock);
 
   ddsi_serdata_unref (sd);
 
 #ifndef NDEBUG
-  if (whcn == NULL)
+  if (!sample_found)
   {
     /* If undirected, it is pp->spdp_xevent, and that one must never
        run into an empty WHC unless it is already marked for deletion.