diff --git a/src/core/ddsc/CMakeLists.txt b/src/core/ddsc/CMakeLists.txt
index 65c6c34..d5bae0c 100644
--- a/src/core/ddsc/CMakeLists.txt
+++ b/src/core/ddsc/CMakeLists.txt
@@ -30,7 +30,6 @@ PREPEND(srcs_ddsc "${CMAKE_CURRENT_LIST_DIR}/src"
     dds_topic.c
     dds_listener.c
     dds_read.c
-    dds_stream.c
     dds_waitset.c
     dds_readcond.c
     dds_guardcond.c
@@ -70,7 +69,6 @@ PREPEND(hdrs_private_ddsc "${CMAKE_CURRENT_LIST_DIR}/src"
     dds__guardcond.h
     dds__reader.h
     dds__rhc_default.h
-    dds__stream.h
     dds__subscriber.h
     dds__topic.h
     dds__types.h
diff --git a/src/core/ddsc/src/dds__alloc.h b/src/core/ddsc/src/dds__alloc.h
index a8f09db..10eadcf 100644
--- a/src/core/ddsc/src/dds__alloc.h
+++ b/src/core/ddsc/src/dds__alloc.h
@@ -18,8 +18,6 @@
 extern "C" {
 #endif
 
-void dds_sample_free_contents (char * data, const uint32_t * ops);
-
 #if defined (__cplusplus)
 }
 #endif
diff --git a/src/core/ddsc/src/dds__serdata_builtintopic.h b/src/core/ddsc/src/dds__serdata_builtintopic.h
index 60fdec0..52509f2 100644
--- a/src/core/ddsc/src/dds__serdata_builtintopic.h
+++ b/src/core/ddsc/src/dds__serdata_builtintopic.h
@@ -9,9 +9,10 @@
  *
  * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
  */
-#ifndef DDSI_SERDATA_BUILTINTOPIC_H
-#define DDSI_SERDATA_BUILTINTOPIC_H
+#ifndef DDS__SERDATA_BUILTINTOPIC_H
+#define DDS__SERDATA_BUILTINTOPIC_H
 
+#include "dds/dds.h"
 #include "dds/ddsi/ddsi_xqos.h"
 #include "dds/ddsi/ddsi_serdata.h"
 #include "dds/ddsi/ddsi_sertopic.h"
@@ -33,7 +34,6 @@ enum ddsi_sertopic_builtintopic_type {
   DSBT_WRITER
 };
 
-struct ddsi_domaingv;
 struct ddsi_sertopic_builtintopic {
   struct ddsi_sertopic c;
   enum ddsi_sertopic_builtintopic_type type;
diff --git a/src/core/ddsc/src/dds_alloc.c b/src/core/ddsc/src/dds_alloc.c
index 7ff7779..662719d 100644
--- a/src/core/ddsc/src/dds_alloc.c
+++ b/src/core/ddsc/src/dds_alloc.c
@@ -13,21 +13,9 @@
 #include <string.h>
 
 #include "dds__alloc.h"
-#include "dds__stream.h"
 #include "dds/ddsrt/heap.h"
 #include "dds/ddsi/q_config.h"
-
-/*
-#define OP_DEBUG_FREE 1
-*/
-
-#if defined OP_DEBUG_FREE
-static const char * stream_op_type[11] =
-{
-  NULL, "1Byte", "2Byte", "4Byte", "8Byte", "String",
-  "BString", "Sequence", "Array", "Union", "Struct"
-};
-#endif
+#include "dds/ddsi/ddsi_cdrstream.h"
 
 static dds_allocator_t dds_allocator_fns = { ddsrt_malloc, ddsrt_realloc, ddsrt_free };
 
@@ -87,287 +75,30 @@ void dds_string_free (char * str)
   dds_free (str);
 }
 
-void dds_sample_free_contents (char *data, const uint32_t * ops)
+static void dds_sample_free_key (void *vsample, const struct dds_topic_descriptor * desc)
 {
-  uint32_t op;
-  uint32_t type;
-  uint32_t num;
-  uint32_t subtype;
-  char * addr;
-
-  while ((op = *ops) != DDS_OP_RTS)
+  char *sample = vsample;
+  for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    switch (DDS_OP_MASK & op)
-    {
-      case DDS_OP_ADR:
-      {
-        type = DDS_OP_TYPE (op);
-#ifdef OP_DEBUG_FREE
-        DDS_TRACE("F-ADR: %s offset %d\n", stream_op_type[type], ops[1]);
-#endif
-        addr = data + ops[1];
-        ops += 2;
-        switch (type)
-        {
-          case DDS_OP_VAL_1BY:
-          case DDS_OP_VAL_2BY:
-          case DDS_OP_VAL_4BY:
-          case DDS_OP_VAL_8BY:
-          {
-            break;
-          }
-          case DDS_OP_VAL_STR:
-          {
-#ifdef OP_DEBUG_FREE
-            DDS_TRACE("F-STR: @ %p %s\n", addr, *((char**) addr));
-#endif
-            dds_free (*((char**) addr));
-            *((char**) addr) = NULL;
-            break;
-          }
-          case DDS_OP_VAL_SEQ:
-          {
-            dds_sequence_t * seq = (dds_sequence_t*) addr;
-            subtype = DDS_OP_SUBTYPE (op);
-            num = (seq->_maximum > seq->_length) ? seq->_maximum : seq->_length;
-
-#ifdef OP_DEBUG_FREE
-            DDS_TRACE("F-SEQ: of %s\n", stream_op_type[subtype]);
-#endif
-            if ((seq->_release && num) || (subtype > DDS_OP_VAL_STR))
-            {
-              switch (subtype)
-              {
-                case DDS_OP_VAL_1BY:
-                case DDS_OP_VAL_2BY:
-                case DDS_OP_VAL_4BY:
-                case DDS_OP_VAL_8BY:
-                {
-                  break;
-                }
-                case DDS_OP_VAL_BST:
-                {
-                  ops++;
-                  break;
-                }
-                case DDS_OP_VAL_STR:
-                {
-                  char ** ptr = (char**) seq->_buffer;
-                  while (num--)
-                  {
-                    dds_free (*ptr++);
-                  }
-                  break;
-                }
-                default:
-                {
-                  const uint32_t elem_size = *ops++;
-                  const uint32_t * jsr_ops = ops + DDS_OP_ADR_JSR (*ops) - 3;
-                  const uint32_t jmp = DDS_OP_ADR_JMP (*ops);
-                  char * ptr = (char*) seq->_buffer;
- 
-                  while (num--)
-                  {
-                    dds_sample_free_contents (ptr, jsr_ops);
-                    ptr += elem_size;
-                  }
-                  ops += jmp ? (jmp - 3) : 1;
-                  break;
-                }
-              }
-            }
-            if (seq->_release)
-            {
-              dds_free (seq->_buffer);
-              seq->_maximum = 0;
-              seq->_length = 0;
-              seq->_buffer = NULL;
-            }
-            break;
-          }
-          case DDS_OP_VAL_ARR:
-          {
-            subtype = DDS_OP_SUBTYPE (op);
-            num = *ops++;
-
-#ifdef OP_DEBUG_FREE
-            DDS_TRACE("F-ARR: of %s size %d\n", stream_op_type[subtype], num);
-#endif
-            switch (subtype)
-            {
-              case DDS_OP_VAL_1BY:
-              case DDS_OP_VAL_2BY:
-              case DDS_OP_VAL_4BY:
-              case DDS_OP_VAL_8BY:
-              {
-                break;
-              }
-              case DDS_OP_VAL_STR:
-              {
-                char ** ptr = (char**) addr;
-                while (num--)
-                {
-                  dds_free (*ptr++);
-                }
-                break;
-              }
-              case DDS_OP_VAL_BST:
-              {
-                ops += 2;
-                break;
-              }
-              default:
-              {
-                const uint32_t * jsr_ops = ops + DDS_OP_ADR_JSR (*ops) - 3;
-                const uint32_t jmp = DDS_OP_ADR_JMP (*ops);
-                const uint32_t elem_size = ops[1];
-
-                while (num--)
-                {
-                  dds_sample_free_contents (addr, jsr_ops);
-                  addr += elem_size;
-                }
-                ops += jmp ? (jmp - 3) : 2;
-                break;
-              }
-            }
-            break;
-          }
-          case DDS_OP_VAL_UNI:
-          {
-            const bool has_default = op & DDS_OP_FLAG_DEF;
-            subtype = DDS_OP_SUBTYPE (op);
-            num = ops[0];
-            const uint32_t * jeq_op = ops + DDS_OP_ADR_JSR (ops[1]) - 2;
-            uint32_t disc = 0;
-
-            assert (subtype <= DDS_OP_VAL_4BY);
-
-#ifdef OP_DEBUG_FREE
-            DDS_TRACE("F-UNI: switch %s cases %d\n", stream_op_type[subtype], num);
-#endif
-            /* Get discriminant */
-
-            switch (subtype)
-            {
-              case DDS_OP_VAL_1BY:
-              {
-                disc = *((uint8_t*) addr);
-                break;
-              }
-              case DDS_OP_VAL_2BY:
-              {
-                disc = *((uint16_t*) addr);
-                break;
-              }
-              case DDS_OP_VAL_4BY:
-              {
-                disc = *((uint32_t*) addr);
-                break;
-              }
-              default: assert (0);
-            }
-
-            /* Free case matching discriminant */
-
-            while (num--)
-            {
-              assert ((DDS_OP_MASK & jeq_op[0]) == DDS_OP_JEQ);
-              if ((jeq_op[1] == disc) || (has_default && (num == 0)))
-              {
-                subtype = DDS_JEQ_TYPE (jeq_op[0]);
-                addr = data + jeq_op[2];
-
-                switch (subtype)
-                {
-                  case DDS_OP_VAL_1BY:
-                  case DDS_OP_VAL_2BY:
-                  case DDS_OP_VAL_4BY:
-                  case DDS_OP_VAL_8BY:
-                  case DDS_OP_VAL_BST:
-                  {
-                    break;
-                  }
-                  case DDS_OP_VAL_STR:
-                  {
-                    dds_free (*((char**) addr));
-                    *((char**) addr) = NULL;
-                    break;
-                  }
-                  default:
-                  {
-                    dds_sample_free_contents (addr, jeq_op + DDS_OP_ADR_JSR (jeq_op[0]));
-                    break;
-                  }
-                }
-                break;
-              }
-              jeq_op += 3;
-            }
-
-            /* Jump to next instruction */
-
-            ops += DDS_OP_ADR_JMP (ops[1]) - 2;
-            break;
-          }
-          case DDS_OP_VAL_BST:
-          {
-            ops++;
-            break;
-          }
-          default: assert (0);
-        }
-        break;
-      }
-      case DDS_OP_JSR: /* Implies nested type */
-      {
-#ifdef OP_DEBUG_FREE
-        DDS_TRACE("F-JSR: %d\n", DDS_OP_JUMP (op));
-#endif
-        dds_sample_free_contents (data, ops + DDS_OP_JUMP (op));
-        ops++;
-        break;
-      }
-      default: assert (0);
-    }
-  }
-#ifdef OP_DEBUG_FREE
-  DDS_TRACE("F-RTS:\n");
-#endif
-}
-
-static void dds_sample_free_key (char * sample, const struct dds_topic_descriptor * desc)
-{
-  uint32_t i;
-  const uint32_t * op;
-
-  for (i = 0; i < desc->m_nkeys; i++)
-  {
-    op = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *op = desc->m_ops + desc->m_keys[i].m_index;
     if (DDS_OP_TYPE (*op) == DDS_OP_VAL_STR)
-    {
-      dds_free (*(char**)(sample + op[1]));
-    }
+      dds_free (*(char **) (sample + op[1]));
   }
 }
 
 void dds_sample_free (void * sample, const struct dds_topic_descriptor * desc, dds_free_op_t op)
 {
+  /* external API, so can't replace the dds_topic_decsriptor type ... */
   assert (desc);
 
   if (sample)
   {
     if (op & DDS_FREE_CONTENTS_BIT)
-    {
-      dds_sample_free_contents ((char*) sample, desc->m_ops);
-    }
+      dds_stream_free_sample (sample, desc->m_ops);
     else if (op & DDS_FREE_KEY_BIT)
-    {
-      dds_sample_free_key ((char*) sample, desc);
-    }
+      dds_sample_free_key (sample, desc);
+
     if (op & DDS_FREE_ALL_BIT)
-    {
       dds_free (sample);
-    }
   }
 }
diff --git a/src/core/ddsc/src/dds_serdata_builtintopic.c b/src/core/ddsc/src/dds_serdata_builtintopic.c
index 4e19675..042d542 100644
--- a/src/core/ddsc/src/dds_serdata_builtintopic.c
+++ b/src/core/ddsc/src/dds_serdata_builtintopic.c
@@ -20,7 +20,6 @@
 #include "dds/ddsi/q_config.h"
 #include "dds/ddsi/q_freelist.h"
 #include "dds/ddsi/ddsi_plist.h"
-#include "dds__stream.h"
 #include "dds__serdata_builtintopic.h"
 #include "dds/ddsi/ddsi_tkmap.h"
 #include "dds/ddsi/q_entity.h"
diff --git a/src/core/ddsc/src/dds_sertopic_builtintopic.c b/src/core/ddsc/src/dds_sertopic_builtintopic.c
index c5ace24..6c9b843 100644
--- a/src/core/ddsc/src/dds_sertopic_builtintopic.c
+++ b/src/core/ddsc/src/dds_sertopic_builtintopic.c
@@ -49,7 +49,7 @@ static bool sertopic_builtin_equal (const struct ddsi_sertopic *acmn, const stru
 static uint32_t sertopic_builtin_hash (const struct ddsi_sertopic *tpcmn)
 {
   const struct ddsi_sertopic_builtintopic *tp = (struct ddsi_sertopic_builtintopic *) tpcmn;
-  return tp->type;
+  return (uint32_t) tp->type;
 }
 
 static void free_pp (void *vsample)
diff --git a/src/core/ddsc/src/dds_topic.c b/src/core/ddsc/src/dds_topic.c
index 13a2f45..93db04a 100644
--- a/src/core/ddsc/src/dds_topic.c
+++ b/src/core/ddsc/src/dds_topic.c
@@ -19,7 +19,6 @@
 #include "dds__topic.h"
 #include "dds__listener.h"
 #include "dds__participant.h"
-#include "dds__stream.h"
 #include "dds__init.h"
 #include "dds__domain.h"
 #include "dds__get_status.h"
@@ -32,6 +31,7 @@
 #include "dds/ddsi/ddsi_iid.h"
 #include "dds/ddsi/ddsi_plist.h"
 #include "dds/ddsi/ddsi_domaingv.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds__serdata_builtintopic.h"
 
 DECL_ENTITY_LOCK_UNLOCK (extern inline, dds_topic)
@@ -399,13 +399,19 @@ dds_entity_t dds_create_topic (dds_entity_t participant, const dds_topic_descrip
   ddsi_sertopic_init (&st->c, name, desc->m_typename, &ddsi_sertopic_ops_default, desc->m_nkeys ? &ddsi_serdata_ops_cdr : &ddsi_serdata_ops_cdr_nokey, (desc->m_nkeys == 0));
   st->native_encoding_identifier = (DDSRT_ENDIAN == DDSRT_LITTLE_ENDIAN ? CDR_LE : CDR_BE);
   st->serpool = ppent->m_domain->gv.serpool;
-  st->type = (void*) desc;
-  st->nkeys = desc->m_nkeys;
-  st->keys = desc->m_keys;
+  st->type.m_size = desc->m_size;
+  st->type.m_align = desc->m_align;
+  st->type.m_flagset = desc->m_flagset;
+  st->type.m_nkeys = desc->m_nkeys;
+  st->type.m_keys = ddsrt_malloc (st->type.m_nkeys  * sizeof (*st->type.m_keys));
+  for (uint32_t i = 0; i < st->type.m_nkeys; i++)
+    st->type.m_keys[i] = desc->m_keys[i].m_index;
+  st->type.m_nops = dds_stream_countops (desc->m_ops);
+  st->type.m_ops = ddsrt_memdup (desc->m_ops, st->type.m_nops * sizeof (*st->type.m_ops));
 
   /* Check if topic cannot be optimised (memcpy marshal) */
-  if (!(desc->m_flagset & DDS_TOPIC_NO_OPTIMIZE)) {
-    st->opt_size = dds_stream_check_optimize (desc);
+  if (!(st->type.m_flagset & DDS_TOPIC_NO_OPTIMIZE)) {
+    st->opt_size = dds_stream_check_optimize (&st->type);
     DDS_CTRACE (&ppent->m_domain->gv.logconfig, "Marshalling for type: %s is %soptimised\n", desc->m_typename, st->opt_size ? "" : "not ");
   }
 
diff --git a/src/core/ddsc/src/dds_write.c b/src/core/ddsc/src/dds_write.c
index 3ef2f74..7519548 100644
--- a/src/core/ddsc/src/dds_write.c
+++ b/src/core/ddsc/src/dds_write.c
@@ -18,7 +18,7 @@
 #include "dds/ddsi/q_xmsg.h"
 #include "dds/ddsi/ddsi_rhc.h"
 #include "dds/ddsi/ddsi_serdata.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds/ddsi/q_transmit.h"
 #include "dds/ddsi/ddsi_entity_index.h"
 #include "dds/ddsi/q_config.h"
diff --git a/src/core/ddsc/tests/multi_sertopic.c b/src/core/ddsc/tests/multi_sertopic.c
index 9501b27..1bbdfbf 100644
--- a/src/core/ddsc/tests/multi_sertopic.c
+++ b/src/core/ddsc/tests/multi_sertopic.c
@@ -125,7 +125,6 @@ static const dds_topic_descriptor_t type_uni_desc =
     DDS_OP_ADR | DDS_OP_TYPE_ARR | DDS_OP_SUBTYPE_4BY, 0u, 4,
     DDS_OP_RTS,
     DDS_OP_RTS
-
   },
   .m_meta = "" /* this is on its way out anyway */
 };
diff --git a/src/core/ddsi/CMakeLists.txt b/src/core/ddsi/CMakeLists.txt
index 0fe18ef..87b9c47 100644
--- a/src/core/ddsi/CMakeLists.txt
+++ b/src/core/ddsi/CMakeLists.txt
@@ -33,6 +33,7 @@ PREPEND(srcs_ddsi "${CMAKE_CURRENT_LIST_DIR}/src"
     ddsi_deadline.c
     ddsi_deliver_locally.c
     ddsi_plist.c
+    ddsi_cdrstream.c
     q_addrset.c
     q_bitset_inlines.c
     q_bswap.c
@@ -97,6 +98,7 @@ PREPEND(hdrs_private_ddsi "${CMAKE_CURRENT_LIST_DIR}/include/dds/ddsi"
     ddsi_domaingv.h
     ddsi_plist.h
     ddsi_xqos.h
+    ddsi_cdrstream.h
     q_addrset.h
     q_bitset.h
     q_bswap.h
diff --git a/src/core/ddsc/src/dds__stream.h b/src/core/ddsi/include/dds/ddsi/ddsi_cdrstream.h
similarity index 94%
rename from src/core/ddsc/src/dds__stream.h
rename to src/core/ddsi/include/dds/ddsi/ddsi_cdrstream.h
index 7facf45..56ad225 100644
--- a/src/core/ddsc/src/dds__stream.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_cdrstream.h
@@ -9,8 +9,8 @@
  *
  * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
  */
-#ifndef _DDS_STREAM_H_
-#define _DDS_STREAM_H_
+#ifndef DDSI_CDRSTREAM_H
+#define DDSI_CDRSTREAM_H
 
 #include "dds/ddsi/ddsi_serdata.h"
 #include "dds/ddsi/ddsi_serdata_default.h"
@@ -44,8 +44,10 @@ bool dds_stream_normalize (void * __restrict data, uint32_t size, bool bswap, co
 
 void dds_stream_write_sample (dds_ostream_t * __restrict os, const void * __restrict data, const struct ddsi_sertopic_default * __restrict topic);
 void dds_stream_read_sample (dds_istream_t * __restrict is, void * __restrict data, const struct ddsi_sertopic_default * __restrict topic);
+void dds_stream_free_sample (void *data, const uint32_t * ops);
 
-size_t dds_stream_check_optimize (const dds_topic_descriptor_t * __restrict desc);
+uint32_t dds_stream_countops (const uint32_t * __restrict ops);
+size_t dds_stream_check_optimize (const struct ddsi_sertopic_default_desc * __restrict desc);
 void dds_istream_from_serdata_default (dds_istream_t * __restrict s, const struct ddsi_serdata_default * __restrict d);
 void dds_ostream_from_serdata_default (dds_ostream_t * __restrict s, struct ddsi_serdata_default * __restrict d);
 void dds_ostream_add_to_serdata_default (dds_ostream_t * __restrict s, struct ddsi_serdata_default ** __restrict d);
diff --git a/src/core/ddsi/include/dds/ddsi/ddsi_serdata_default.h b/src/core/ddsi/include/dds/ddsi/ddsi_serdata_default.h
index ae582ff..27a155b 100644
--- a/src/core/ddsi/include/dds/ddsi/ddsi_serdata_default.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_serdata_default.h
@@ -20,7 +20,6 @@
 #include "dds/ddsi/ddsi_sertopic.h"
 
 #include "dds/dds.h"
-#include "dds__topic.h"
 
 #if defined (__cplusplus)
 extern "C" {
@@ -95,41 +94,28 @@ struct ddsi_serdata_default {
 #undef DDSI_SERDATA_DEFAULT_PREPAD
 #undef DDSI_SERDATA_DEFAULT_FIXED_FIELD
 
-struct dds_key_descriptor;
-struct dds_topic_descriptor;
-
 #ifndef DDS_TOPIC_INTERN_FILTER_FN_DEFINED
 #define DDS_TOPIC_INTERN_FILTER_FN_DEFINED
 typedef bool (*dds_topic_intern_filter_fn) (const void * sample, void *ctx);
 #endif
 
+/* Reduced version of dds_topic_descriptor_t */
+struct ddsi_sertopic_default_desc {
+  uint32_t m_size;    /* Size of topic type */
+  uint32_t m_align;   /* Alignment of topic type */
+  uint32_t m_flagset; /* Flags */
+  uint32_t m_nkeys;   /* Number of keys (can be 0) */
+  uint32_t *m_keys;   /* Key descriptors (NULL iff m_nkeys 0) */
+  uint32_t m_nops;    /* Number of words in m_ops (which >= number of ops stored in preproc output) */
+  uint32_t *m_ops;    /* Marshalling meta data */
+};
+
 struct ddsi_sertopic_default {
   struct ddsi_sertopic c;
   uint16_t native_encoding_identifier; /* (PL_)?CDR_(LE|BE) */
   struct serdatapool *serpool;
-
-  struct dds_topic_descriptor * type;
-  unsigned nkeys;
-
-  uint32_t flags;
+  struct ddsi_sertopic_default_desc type;
   size_t opt_size;
-  dds_topic_intern_filter_fn filter_fn;
-  void * filter_sample;
-  void * filter_ctx;
-  const struct dds_key_descriptor * keys;
-
-  /*
-    Array of keys, represented as offset in the OpenSplice internal
-    format data blob. Keys must be stored in the order visited by
-    serializer (so that the serializer can simply compare the current
-    offset with the next key offset). Also: keys[nkeys].off =def=
-    ~0u, which won't equal any real offset so that there is no need
-    to test for the end of the array.
-
-    Offsets work 'cos only primitive types, enums and strings are
-    accepted as keys. So there is no ambiguity if a key happens to
-    be inside a nested struct.
-  */
 };
 
 struct ddsi_plist_sample {
diff --git a/src/core/ddsi/include/dds/ddsi/ddsi_sertopic.h b/src/core/ddsi/include/dds/ddsi/ddsi_sertopic.h
index 7713af3..f259c02 100644
--- a/src/core/ddsi/include/dds/ddsi/ddsi_sertopic.h
+++ b/src/core/ddsi/include/dds/ddsi/ddsi_sertopic.h
@@ -32,7 +32,6 @@ struct ddsi_sertopic {
   bool topickind_no_key;
   char *name;
   char *type_name;
-  uint64_t iid;
   struct ddsi_domaingv *gv;
   ddsrt_atomic_uint32_t refc; /* counts refs from entities (topic, reader, writer), not from data */
 };
diff --git a/src/core/ddsc/src/dds_stream.c b/src/core/ddsi/src/ddsi_cdrstream.c
similarity index 85%
rename from src/core/ddsc/src/dds_stream.c
rename to src/core/ddsi/src/ddsi_cdrstream.c
index a6a9218..9fffea9 100644
--- a/src/core/ddsc/src/dds_stream.c
+++ b/src/core/ddsi/src/ddsi_cdrstream.c
@@ -18,7 +18,7 @@
 #include "dds/ddsrt/heap.h"
 #include "dds/ddsi/q_bswap.h"
 #include "dds/ddsi/q_config.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds__alloc.h"
 
 #if DDSRT_ENDIAN == DDSRT_LITTLE_ENDIAN
@@ -210,7 +210,7 @@ static uint32_t get_type_size (enum dds_stream_typecode type)
   return (uint32_t)1 << ((uint32_t) type - 1);
 }
 
-static size_t dds_stream_check_optimize1 (const dds_topic_descriptor_t * __restrict desc)
+static size_t dds_stream_check_optimize1 (const struct ddsi_sertopic_default_desc * __restrict desc)
 {
   const uint32_t *ops = desc->m_ops;
   uint32_t insn;
@@ -251,11 +251,141 @@ static size_t dds_stream_check_optimize1 (const dds_topic_descriptor_t * __restr
   return desc->m_size;
 }
 
-size_t dds_stream_check_optimize (const dds_topic_descriptor_t * __restrict desc)
+size_t dds_stream_check_optimize (const struct ddsi_sertopic_default_desc * __restrict desc)
 {
   return dds_stream_check_optimize1 (desc);
 }
 
+static void dds_stream_countops1 (const uint32_t * __restrict ops, const uint32_t **ops_end);
+
+static const uint32_t *dds_stream_countops_seq (const uint32_t * __restrict ops, uint32_t insn, const uint32_t **ops_end)
+{
+  const enum dds_stream_typecode subtype = DDS_OP_SUBTYPE (insn);
+  switch (subtype)
+  {
+    case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+    case DDS_OP_VAL_STR:
+      ops += 2;
+      break;
+    case DDS_OP_VAL_BST:
+      ops += 3;
+      break;
+    case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU: {
+      const uint32_t jmp = DDS_OP_ADR_JMP (ops[3]);
+      uint32_t const * const jsr_ops = ops + DDS_OP_ADR_JSR (ops[3]);
+      if (ops + 4 > *ops_end)
+        *ops_end = ops + 4;
+      dds_stream_countops1 (jsr_ops, ops_end);
+      ops += (jmp ? jmp : 4); /* FIXME: why would jmp be 0? */
+    }
+  }
+  if (ops > *ops_end)
+    *ops_end = ops;
+  return ops;
+}
+
+static const uint32_t *dds_stream_countops_arr (const uint32_t * __restrict ops, uint32_t insn, const uint32_t **ops_end)
+{
+  const enum dds_stream_typecode subtype = DDS_OP_SUBTYPE (insn);
+  switch (subtype)
+  {
+    case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY:
+    case DDS_OP_VAL_STR:
+      ops += 3;
+      break;
+    case DDS_OP_VAL_BST:
+      ops += 5;
+      break;
+    case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU: {
+      const uint32_t jmp = DDS_OP_ADR_JMP (ops[3]);
+      const uint32_t *jsr_ops = ops + DDS_OP_ADR_JSR (ops[3]);
+      if (ops + 5 > *ops_end)
+        *ops_end = ops + 5;
+      dds_stream_countops1 (jsr_ops, ops_end);
+      ops += (jmp ? jmp : 5);
+      break;
+    }
+  }
+  if (ops > *ops_end)
+    *ops_end = ops;
+  return ops;
+}
+
+static const uint32_t *dds_stream_countops_uni (const uint32_t * __restrict ops, const uint32_t **ops_end)
+{
+  const uint32_t numcases = ops[2];
+  const uint32_t *jeq_op = ops + DDS_OP_ADR_JSR (ops[3]);
+  for (uint32_t i = 0; i < numcases; i++)
+  {
+    const enum dds_stream_typecode valtype = DDS_JEQ_TYPE (jeq_op[0]);
+    switch (valtype)
+    {
+      case DDS_OP_VAL_1BY:
+      case DDS_OP_VAL_2BY:
+      case DDS_OP_VAL_4BY:
+      case DDS_OP_VAL_8BY:
+      case DDS_OP_VAL_STR:
+        break;
+      case DDS_OP_VAL_BST: case DDS_OP_VAL_SEQ: case DDS_OP_VAL_ARR: case DDS_OP_VAL_UNI: case DDS_OP_VAL_STU:
+        dds_stream_countops1 (jeq_op + DDS_OP_ADR_JSR (jeq_op[0]), ops_end);
+        break;
+    }
+    jeq_op += 3;
+  }
+  if (jeq_op > *ops_end)
+    *ops_end = jeq_op;
+  ops += DDS_OP_ADR_JMP (ops[3]);
+  if (ops > *ops_end)
+    *ops_end = ops;
+  return ops;
+}
+
+static void dds_stream_countops1 (const uint32_t * __restrict ops, const uint32_t **ops_end)
+{
+  uint32_t insn;
+  while ((insn = *ops) != DDS_OP_RTS)
+  {
+    switch (DDS_OP (insn))
+    {
+      case DDS_OP_ADR: {
+        switch (DDS_OP_TYPE (insn))
+        {
+          case DDS_OP_VAL_1BY: case DDS_OP_VAL_2BY: case DDS_OP_VAL_4BY: case DDS_OP_VAL_8BY: case DDS_OP_VAL_STR:
+            ops += 2;
+            break;
+          case DDS_OP_VAL_BST:
+            ops += 3;
+            break;
+          case DDS_OP_VAL_SEQ: ops = dds_stream_countops_seq (ops, insn, ops_end); break;
+          case DDS_OP_VAL_ARR: ops = dds_stream_countops_arr (ops, insn, ops_end); break;
+          case DDS_OP_VAL_UNI: ops = dds_stream_countops_uni (ops, ops_end); break;
+          case DDS_OP_VAL_STU: abort (); break;
+        }
+        break;
+      }
+      case DDS_OP_JSR: {
+        dds_stream_countops1 (ops + DDS_OP_JUMP (insn), ops_end);
+        ops++;
+        break;
+      }
+      case DDS_OP_RTS: case DDS_OP_JEQ: {
+        abort ();
+        break;
+      }
+    }
+  }
+  ++ops; /* skip RTS op */
+  if (ops > *ops_end)
+    *ops_end = ops;
+}
+
+uint32_t dds_stream_countops (const uint32_t * __restrict ops)
+{
+  const uint32_t *ops_end = ops;
+  dds_stream_countops1 (ops, &ops_end);
+  return (uint32_t) (ops_end - ops);
+}
+
 static void dds_stream_reuse_string_bound (dds_istream_t * __restrict is, char * __restrict str, const uint32_t bound)
 {
   const uint32_t length = dds_is_get4 (is);
@@ -1039,12 +1169,12 @@ static bool stream_normalize (char * __restrict data, uint32_t * __restrict off,
   return true;
 }
 
-static bool stream_normalize_key (void * __restrict data, uint32_t size, bool bswap, const struct dds_topic_descriptor * __restrict desc)
+static bool stream_normalize_key (void * __restrict data, uint32_t size, bool bswap, const struct ddsi_sertopic_default_desc * __restrict desc)
 {
   uint32_t off = 0;
   for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    const uint32_t *op = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *op = desc->m_ops + desc->m_keys[i];
     assert (insn_key_ok_p (*op));
     switch (DDS_OP_TYPE (*op))
     {
@@ -1068,14 +1198,211 @@ bool dds_stream_normalize (void * __restrict data, uint32_t size, bool bswap, co
   if (size > CDR_SIZE_MAX)
     return false;
   if (just_key)
-    return stream_normalize_key (data, size, bswap, topic->type);
+    return stream_normalize_key (data, size, bswap, &topic->type);
   else
   {
     uint32_t off = 0;
-    return stream_normalize (data, &off, size, bswap, topic->type->m_ops);
+    return stream_normalize (data, &off, size, bswap, topic->type.m_ops);
   }
 }
 
+/*******************************************************************************************
+ **
+ **  Freeing samples
+ **
+ *******************************************************************************************/
+
+//#define OP_DEBUG_FREE 1
+void dds_stream_free_sample (void *vdata, const uint32_t * ops)
+{
+#if defined OP_DEBUG_FREE
+  static const char *stream_op_type[11] = {
+    NULL, "1Byte", "2Byte", "4Byte", "8Byte", "String", "BString", "Sequence", "Array", "Union", "Struct"
+  };
+#endif
+  char *data = vdata;
+  uint32_t op;
+  uint32_t type;
+  uint32_t num;
+  uint32_t subtype;
+  char *addr;
+  while ((op = *ops) != DDS_OP_RTS)
+  {
+    switch (DDS_OP_MASK & op)
+    {
+      case DDS_OP_ADR:
+      {
+        type = DDS_OP_TYPE (op);
+#ifdef OP_DEBUG_FREE
+        DDS_TRACE("F-ADR: %s offset %d\n", stream_op_type[type], ops[1]);
+#endif
+        addr = data + ops[1];
+        switch (type)
+        {
+          case DDS_OP_VAL_1BY:
+          case DDS_OP_VAL_2BY:
+          case DDS_OP_VAL_4BY:
+          case DDS_OP_VAL_8BY:
+            ops += 2;
+            break;
+          case DDS_OP_VAL_STR:
+#ifdef OP_DEBUG_FREE
+            DDS_TRACE("F-STR: @ %p %s\n", addr, *((char **) addr));
+#endif
+            ops += 2;
+            dds_free (*((char **) addr));
+            *((char **) addr) = NULL;
+            break;
+          case DDS_OP_VAL_SEQ: {
+            dds_sequence_t * seq = (dds_sequence_t *) addr;
+            ops += 2;
+            subtype = DDS_OP_SUBTYPE (op);
+            num = (seq->_maximum > seq->_length) ? seq->_maximum : seq->_length;
+#ifdef OP_DEBUG_FREE
+            DDS_TRACE("F-SEQ: of %s\n", stream_op_type[subtype]);
+#endif
+            if ((seq->_release && num) || (subtype > DDS_OP_VAL_STR))
+            {
+              switch (subtype)
+              {
+                case DDS_OP_VAL_1BY:
+                case DDS_OP_VAL_2BY:
+                case DDS_OP_VAL_4BY:
+                case DDS_OP_VAL_8BY:
+                  break;
+                case DDS_OP_VAL_BST:
+                  ops++;
+                  break;
+                case DDS_OP_VAL_STR: {
+                  char **ptr = (char **) seq->_buffer;
+                  while (num--)
+                    dds_free (*ptr++);
+                  break;
+                }
+                default: {
+                  const uint32_t elem_size = *ops++;
+                  const uint32_t *jsr_ops = ops + DDS_OP_ADR_JSR (*ops) - 3;
+                  const uint32_t jmp = DDS_OP_ADR_JMP (*ops);
+                  char *ptr = (char *) seq->_buffer;
+                  while (num--)
+                  {
+                    dds_stream_free_sample (ptr, jsr_ops);
+                    ptr += elem_size;
+                  }
+                  ops += jmp ? (jmp - 3) : 1;
+                  break;
+                }
+              }
+            }
+            if (seq->_release)
+            {
+              dds_free (seq->_buffer);
+              seq->_maximum = 0;
+              seq->_length = 0;
+              seq->_buffer = NULL;
+            }
+            break;
+          }
+          case DDS_OP_VAL_ARR: {
+            ops += 2;
+            subtype = DDS_OP_SUBTYPE (op);
+            num = *ops++;
+#ifdef OP_DEBUG_FREE
+            DDS_TRACE("F-ARR: of %s size %d\n", stream_op_type[subtype], num);
+#endif
+            switch (subtype)
+            {
+              case DDS_OP_VAL_1BY:
+              case DDS_OP_VAL_2BY:
+              case DDS_OP_VAL_4BY:
+              case DDS_OP_VAL_8BY:
+                break;
+              case DDS_OP_VAL_STR: {
+                char **ptr = (char **) addr;
+                while (num--)
+                  dds_free (*ptr++);
+                break;
+              }
+              case DDS_OP_VAL_BST:
+                ops += 2;
+                break;
+              default: {
+                const uint32_t *jsr_ops = ops + DDS_OP_ADR_JSR (*ops) - 3;
+                const uint32_t jmp = DDS_OP_ADR_JMP (*ops);
+                const uint32_t elem_size = ops[1];
+                while (num--)
+                {
+                  dds_stream_free_sample (addr, jsr_ops);
+                  addr += elem_size;
+                }
+                ops += jmp ? (jmp - 3) : 2;
+                break;
+              }
+            }
+            break;
+          }
+          case DDS_OP_VAL_UNI: {
+#ifdef OP_DEBUG_FREE
+            DDS_TRACE("F-UNI: switch %s\n", stream_op_type[subtype]);
+#endif
+            /* Get discriminant */
+            uint32_t disc = 0;
+            switch (DDS_OP_SUBTYPE (op))
+            {
+              case DDS_OP_VAL_1BY: disc = *((uint8_t *) addr); break;
+              case DDS_OP_VAL_2BY: disc = *((uint16_t *) addr); break;
+              case DDS_OP_VAL_4BY: disc = *((uint32_t *) addr); break;
+              default: assert (0);
+            }
+            uint32_t const * const jeq_op = find_union_case (ops, disc);
+            ops += DDS_OP_ADR_JMP (ops[3]);
+            if (jeq_op)
+            {
+              subtype = DDS_JEQ_TYPE (jeq_op[0]);
+              addr = data + jeq_op[2];
+              switch (subtype)
+              {
+                case DDS_OP_VAL_1BY:
+                case DDS_OP_VAL_2BY:
+                case DDS_OP_VAL_4BY:
+                case DDS_OP_VAL_8BY:
+                case DDS_OP_VAL_BST:
+                  break;
+                case DDS_OP_VAL_STR:
+                  dds_free (*((char **) addr));
+                  *((char **) addr) = NULL;
+                  break;
+                default:
+                  dds_stream_free_sample (addr, jeq_op + DDS_OP_ADR_JSR (jeq_op[0]));
+                  break;
+              }
+            }
+            break;
+          }
+          case DDS_OP_VAL_BST:
+            ops += 3;
+            break;
+          default:
+            assert (0);
+        }
+        break;
+      }
+      case DDS_OP_JSR: /* Implies nested type */
+#ifdef OP_DEBUG_FREE
+        DDS_TRACE("F-JSR: %d\n", DDS_OP_JUMP (op));
+#endif
+        dds_stream_free_sample (data, ops + DDS_OP_JUMP (op));
+        ops++;
+        break;
+      default:
+        assert (0);
+    }
+  }
+#ifdef OP_DEBUG_FREE
+  DDS_TRACE("F-RTS:\n");
+#endif
+}
+
 /*******************************************************************************************
  **
  **  Read/write of samples and keys -- i.e., DDSI payloads.
@@ -1084,7 +1411,7 @@ bool dds_stream_normalize (void * __restrict data, uint32_t size, bool bswap, co
 
 void dds_stream_read_sample (dds_istream_t * __restrict is, void * __restrict data, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const struct dds_topic_descriptor *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   if (topic->opt_size)
     dds_is_get_bytes (is, data, desc->m_size, 1);
   else
@@ -1097,7 +1424,7 @@ void dds_stream_read_sample (dds_istream_t * __restrict is, void * __restrict da
          make any preallocated buffers go to waste, but it does allow reusing the message
          from read-to-read, at the somewhat reasonable price of a slower deserialization
          and not being able to use preallocated sequences in topics containing unions. */
-      dds_sample_free_contents (data, desc->m_ops);
+      dds_stream_free_sample (data, desc->m_ops);
       memset (data, 0, desc->m_size);
     }
     dds_stream_read (is, data, desc->m_ops);
@@ -1106,7 +1433,7 @@ void dds_stream_read_sample (dds_istream_t * __restrict is, void * __restrict da
 
 void dds_stream_write_sample (dds_ostream_t * __restrict os, const void * __restrict data, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const struct dds_topic_descriptor *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   if (topic->opt_size && desc->m_align && (os->m_index % desc->m_align) == 0)
     dds_os_put_bytes (os, data, desc->m_size);
   else
@@ -1115,10 +1442,10 @@ void dds_stream_write_sample (dds_ostream_t * __restrict os, const void * __rest
 
 void dds_stream_read_key (dds_istream_t * __restrict is, char * __restrict sample, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    const uint32_t *op = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *op = desc->m_ops + desc->m_keys[i];
     char *dst = sample + op[1];
     assert (insn_key_ok_p (*op));
     switch (DDS_OP_TYPE (*op))
@@ -1141,10 +1468,10 @@ void dds_stream_read_key (dds_istream_t * __restrict is, char * __restrict sampl
 
 void dds_stream_write_key (dds_ostream_t * __restrict os, const char * __restrict sample, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const struct dds_topic_descriptor *desc = (const struct dds_topic_descriptor *) topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    const uint32_t *insnp = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *insnp = desc->m_ops + desc->m_keys[i];
     const void *src = sample + insnp[1];
     assert (insn_key_ok_p (*insnp));
     switch (DDS_OP_TYPE (*insnp))
@@ -1201,10 +1528,10 @@ static void dds_stream_swap_insitu (void * __restrict vbuf, uint32_t size, uint3
 
 void dds_stream_write_keyBE (dds_ostreamBE_t * __restrict os, const char * __restrict sample, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const struct dds_topic_descriptor *desc = (const struct dds_topic_descriptor *) topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    const uint32_t *insnp = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *insnp = desc->m_ops + desc->m_keys[i];
     const void *src = sample + insnp[1];
     assert (insn_key_ok_p (*insnp));
     switch (DDS_OP_TYPE (*insnp))
@@ -1362,10 +1689,10 @@ static void dds_stream_extract_keyBE_from_key_prim_op (dds_istream_t * __restric
 
 static void dds_stream_extract_keyBE_from_key (dds_istream_t * __restrict is, dds_ostreamBE_t * __restrict os, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   for (uint32_t i = 0; i < desc->m_nkeys; i++)
   {
-    uint32_t const * const op = desc->m_ops + desc->m_keys[i].m_index;
+    uint32_t const * const op = desc->m_ops + desc->m_keys[i];
     dds_stream_extract_keyBE_from_key_prim_op (is, os, op);
   }
 }
@@ -1565,21 +1892,21 @@ static void dds_stream_extract_keyBE_from_data1 (dds_istream_t * __restrict is,
 
 void dds_stream_extract_key_from_data (dds_istream_t * __restrict is, dds_ostream_t * __restrict os, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   uint32_t keys_remaining = desc->m_nkeys;
   dds_stream_extract_key_from_data1 (is, os, desc->m_ops, &keys_remaining);
 }
 
 void dds_stream_extract_keyBE_from_data (dds_istream_t * __restrict is, dds_ostreamBE_t * __restrict os, const struct ddsi_sertopic_default * __restrict topic)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   uint32_t keys_remaining = desc->m_nkeys;
   dds_stream_extract_keyBE_from_data1 (is, os, desc->m_ops, &keys_remaining);
 }
 
 void dds_stream_extract_keyhash (dds_istream_t * __restrict is, dds_keyhash_t * __restrict kh, const struct ddsi_sertopic_default * __restrict topic, const bool just_key)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   kh->m_set = 1;
   if (desc->m_nkeys == 0)
     kh->m_iskey = 1;
@@ -1869,17 +2196,17 @@ static bool dds_stream_print_sample1 (char * __restrict *buf, size_t * __restric
 
 size_t dds_stream_print_sample (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t bufsize)
 {
-  (void) dds_stream_print_sample1 (&buf, &bufsize, is, topic->type->m_ops, true);
+  (void) dds_stream_print_sample1 (&buf, &bufsize, is, topic->type.m_ops, true);
   return bufsize;
 }
 
 size_t dds_stream_print_key (dds_istream_t * __restrict is, const struct ddsi_sertopic_default * __restrict topic, char * __restrict buf, size_t bufsize)
 {
-  const dds_topic_descriptor_t *desc = topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   bool cont = prtf (&buf, &bufsize, ":k:{");
   for (uint32_t i = 0; cont && i < desc->m_nkeys; i++)
   {
-    const uint32_t *op = desc->m_ops + desc->m_keys[i].m_index;
+    const uint32_t *op = desc->m_ops + desc->m_keys[i];
     assert (insn_key_ok_p (*op));
     switch (DDS_OP_TYPE (*op))
     {
diff --git a/src/core/ddsi/src/ddsi_serdata_default.c b/src/core/ddsi/src/ddsi_serdata_default.c
index a5502ac..2889ba6 100644
--- a/src/core/ddsi/src/ddsi_serdata_default.c
+++ b/src/core/ddsi/src/ddsi_serdata_default.c
@@ -22,7 +22,7 @@
 #include "dds/ddsi/q_config.h"
 #include "dds/ddsi/q_freelist.h"
 #include "dds/ddsi/ddsi_tkmap.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds/ddsi/q_radmin.h"
 #include "dds/ddsi/ddsi_domaingv.h"
 #include "dds/ddsi/ddsi_serdata_default.h"
@@ -349,7 +349,7 @@ static struct ddsi_serdata *ddsi_serdata_from_keyhash_cdr (const struct ddsi_ser
 {
   /* FIXME: not quite sure this is correct, though a check against a specially hacked OpenSplice suggests it is */
   const struct ddsi_sertopic_default *tp = (const struct ddsi_sertopic_default *)tpcmn;
-  if (!(tp->type->m_flagset & DDS_TOPIC_FIXED_KEY))
+  if (!(tp->type.m_flagset & DDS_TOPIC_FIXED_KEY))
   {
     /* keyhash is MD5 of a key value, so impossible to turn into a key value */
     return NULL;
@@ -386,7 +386,7 @@ static struct ddsi_serdata *ddsi_serdata_from_keyhash_cdr_nokey (const struct dd
 
 static void gen_keyhash_from_sample (const struct ddsi_sertopic_default *topic, dds_keyhash_t *kh, const char *sample)
 {
-  const struct dds_topic_descriptor *desc = (const struct dds_topic_descriptor *) topic->type;
+  const struct ddsi_sertopic_default_desc *desc = &topic->type;
   kh->m_set = 1;
   if (desc->m_nkeys == 0)
     kh->m_iskey = 1;
diff --git a/src/core/ddsi/src/ddsi_sertopic.c b/src/core/ddsi/src/ddsi_sertopic.c
index 278bd7e..8776ede 100644
--- a/src/core/ddsi/src/ddsi_sertopic.c
+++ b/src/core/ddsi/src/ddsi_sertopic.c
@@ -39,6 +39,8 @@ bool ddsi_sertopic_equal (const struct ddsi_sertopic *a, const struct ddsi_serto
     return false;
   if (a->serdata_ops != b->serdata_ops)
     return false;
+  if (a->topickind_no_key != b->topickind_no_key)
+    return false;
   return a->ops->equal (a, b);
 }
 
@@ -47,6 +49,7 @@ uint32_t ddsi_sertopic_hash (const struct ddsi_sertopic *a)
   uint32_t h;
   h = ddsrt_mh3 (a->name, strlen (a->name), a->serdata_basehash);
   h = ddsrt_mh3 (a->type_name, strlen (a->type_name), h);
+  h ^= a->serdata_basehash ^ (uint32_t) a->topickind_no_key;
   return h ^ a->ops->hash (a);
 }
 
@@ -63,10 +66,7 @@ struct ddsi_sertopic *ddsi_sertopic_lookup_locked (struct ddsi_domaingv *gv, con
   struct ddsi_sertopic *sertopic = ddsrt_hh_lookup (gv->sertopics, sertopic_template);
 #ifndef NDEBUG
   if (sertopic != NULL)
-  {
     assert (sertopic->gv != NULL);
-    assert (sertopic->iid != 0);
-  }
 #endif
   return ddsi_sertopic_ref (sertopic);
 }
@@ -74,12 +74,10 @@ struct ddsi_sertopic *ddsi_sertopic_lookup_locked (struct ddsi_domaingv *gv, con
 void ddsi_sertopic_register_locked (struct ddsi_domaingv *gv, struct ddsi_sertopic *sertopic)
 {
   assert (sertopic->gv == NULL);
-  assert (sertopic->iid == 0);
   assert (ddsrt_atomic_ld32 (&sertopic->refc) == 1);
 
   (void) ddsi_sertopic_ref (sertopic);
   sertopic->gv = gv;
-  sertopic->iid = ddsi_iid_gen ();
   int x = ddsrt_hh_add (gv->sertopics, sertopic);
   assert (x);
   (void) x;
@@ -98,7 +96,6 @@ void ddsi_sertopic_unref (struct ddsi_sertopic *sertopic)
         (void) ddsrt_hh_remove (sertopic->gv->sertopics, sertopic);
         ddsrt_mutex_unlock (&sertopic->gv->sertopics_lock);
         sertopic->gv = NULL;
-        sertopic->iid = 0;
       }
 
       ddsi_sertopic_free (sertopic);
@@ -116,7 +113,6 @@ void ddsi_sertopic_init (struct ddsi_sertopic *tp, const char *name, const char
   tp->serdata_basehash = ddsi_sertopic_compute_serdata_basehash (tp->serdata_ops);
   tp->topickind_no_key = topickind_no_key;
   /* set later, on registration */
-  tp->iid = 0;
   tp->gv = NULL;
 }
 
diff --git a/src/core/ddsi/src/ddsi_sertopic_default.c b/src/core/ddsi/src/ddsi_sertopic_default.c
index 0da5c5c..a10cb96 100644
--- a/src/core/ddsi/src/ddsi_sertopic_default.c
+++ b/src/core/ddsi/src/ddsi_sertopic_default.c
@@ -20,6 +20,7 @@
 #include "dds/ddsi/q_bswap.h"
 #include "dds/ddsi/q_config.h"
 #include "dds/ddsi/q_freelist.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds/ddsi/ddsi_sertopic.h"
 #include "dds/ddsi/ddsi_serdata_default.h"
 
@@ -27,37 +28,58 @@ static bool sertopic_default_equal (const struct ddsi_sertopic *acmn, const stru
 {
   const struct ddsi_sertopic_default *a = (struct ddsi_sertopic_default *) acmn;
   const struct ddsi_sertopic_default *b = (struct ddsi_sertopic_default *) bcmn;
-  return a->type == b->type;
+  if (a->native_encoding_identifier != b->native_encoding_identifier)
+    return false;
+  if (a->type.m_size != b->type.m_size)
+    return false;
+  if (a->type.m_align != b->type.m_align)
+    return false;
+  if (a->type.m_flagset != b->type.m_flagset)
+    return false;
+  if (a->type.m_nkeys != b->type.m_nkeys)
+    return false;
+  if (memcmp (a->type.m_keys, b->type.m_keys, a->type.m_nkeys * sizeof (*a->type.m_keys)) != 0)
+    return false;
+  if (a->type.m_nops != b->type.m_nops)
+    return false;
+  if (memcmp (a->type.m_ops, b->type.m_ops, a->type.m_nops * sizeof (*a->type.m_ops)) != 0)
+    return false;
+  assert (a->opt_size == b->opt_size);
+  return true;
 }
 
 static uint32_t sertopic_default_hash (const struct ddsi_sertopic *tpcmn)
 {
   const struct ddsi_sertopic_default *tp = (struct ddsi_sertopic_default *) tpcmn;
-  if (tp->type == NULL)
-    return 0;
-  else
-  {
-    return ddsrt_mh3 (tp->type->m_keys, tp->type->m_nkeys * sizeof (*tp->type->m_keys),
-                      ddsrt_mh3 (tp->type->m_ops, tp->type->m_nops * sizeof (*tp->type->m_ops), 0));
-  }
+  uint32_t h = 0;
+  h = ddsrt_mh3 (&tp->native_encoding_identifier, sizeof (tp->native_encoding_identifier), 0);
+  h = ddsrt_mh3 (&tp->type.m_size, sizeof (tp->type.m_size), h);
+  h = ddsrt_mh3 (&tp->type.m_align, sizeof (tp->type.m_align), h);
+  h = ddsrt_mh3 (&tp->type.m_flagset, sizeof (tp->type.m_flagset), h);
+  h = ddsrt_mh3 (tp->type.m_keys, tp->type.m_nkeys * sizeof (*tp->type.m_keys), h);
+  h = ddsrt_mh3 (tp->type.m_ops, tp->type.m_nops * sizeof (*tp->type.m_ops), h);
+  return h;
 }
 
-static void sertopic_default_free (struct ddsi_sertopic *tp)
+static void sertopic_default_free (struct ddsi_sertopic *tpcmn)
 {
-  ddsi_sertopic_fini (tp);
+  struct ddsi_sertopic_default *tp = (struct ddsi_sertopic_default *) tpcmn;
+  ddsrt_free (tp->type.m_keys);
+  ddsrt_free (tp->type.m_ops);
+  ddsi_sertopic_fini (&tp->c);
   ddsrt_free (tp);
 }
 
 static void sertopic_default_zero_samples (const struct ddsi_sertopic *sertopic_common, void *sample, size_t count)
 {
   const struct ddsi_sertopic_default *tp = (const struct ddsi_sertopic_default *)sertopic_common;
-  memset (sample, 0, tp->type->m_size * count);
+  memset (sample, 0, tp->type.m_size * count);
 }
 
 static void sertopic_default_realloc_samples (void **ptrs, const struct ddsi_sertopic *sertopic_common, void *old, size_t oldcount, size_t count)
 {
   const struct ddsi_sertopic_default *tp = (const struct ddsi_sertopic_default *)sertopic_common;
-  const size_t size = tp->type->m_size;
+  const size_t size = tp->type.m_size;
   char *new = (oldcount == count) ? old : dds_realloc (old, size * count);
   if (new && count > oldcount)
     memset (new + size * oldcount, 0, size * (count - oldcount));
@@ -73,7 +95,7 @@ static void sertopic_default_free_samples (const struct ddsi_sertopic *sertopic_
   if (count > 0)
   {
     const struct ddsi_sertopic_default *tp = (const struct ddsi_sertopic_default *)sertopic_common;
-    const struct dds_topic_descriptor *type = tp->type;
+    const struct ddsi_sertopic_default_desc *type = &tp->type;
     const size_t size = type->m_size;
 #ifndef NDEBUG
     for (size_t i = 0, off = 0; i < count; i++, off += size)
@@ -84,7 +106,7 @@ static void sertopic_default_free_samples (const struct ddsi_sertopic *sertopic_
       char *ptr = ptrs[0];
       for (size_t i = 0; i < count; i++)
       {
-        dds_sample_free (ptr, type, DDS_FREE_CONTENTS);
+        dds_stream_free_sample (ptr, type->m_ops);
         ptr += size;
       }
     }
diff --git a/src/core/ddsi/src/ddsi_tkmap.c b/src/core/ddsi/src/ddsi_tkmap.c
index 7f281cd..9b6324b 100644
--- a/src/core/ddsi/src/ddsi_tkmap.c
+++ b/src/core/ddsi/src/ddsi_tkmap.c
@@ -22,9 +22,9 @@
 #include "dds/ddsi/q_config.h"
 #include "dds/ddsi/ddsi_iid.h"
 #include "dds/ddsi/ddsi_tkmap.h"
-#include "dds/ddsrt/hopscotch.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds/ddsi/ddsi_serdata.h"
+#include "dds/ddsrt/hopscotch.h"
 
 #define REFC_DELETE 0x80000000
 #define REFC_MASK   0x0fffffff
diff --git a/src/core/ddsi/src/q_init.c b/src/core/ddsi/src/q_init.c
index af5e849..3d48219 100644
--- a/src/core/ddsi/src/q_init.c
+++ b/src/core/ddsi/src/q_init.c
@@ -782,7 +782,6 @@ static struct ddsi_sertopic *make_special_topic (const char *name, struct serdat
   ddsi_sertopic_init (&st->c, name, name, &ddsi_sertopic_ops_default, ops, false);
   st->native_encoding_identifier = enc_id;
   st->serpool = serpool;
-  st->nkeys = 1;
   return (struct ddsi_sertopic *) st;
 }
 
diff --git a/src/core/ddsi/src/q_receive.c b/src/core/ddsi/src/q_receive.c
index c01e730..7f0bf28 100644
--- a/src/core/ddsi/src/q_receive.c
+++ b/src/core/ddsi/src/q_receive.c
@@ -22,7 +22,7 @@
 #include "dds/ddsrt/static_assert.h"
 
 #include "dds/ddsrt/avl.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 #include "dds/ddsi/q_protocol.h"
 #include "dds/ddsi/q_rtps.h"
 #include "dds/ddsi/q_misc.h"
diff --git a/src/core/xtests/cdrtest/CMakeLists.txt b/src/core/xtests/cdrtest/CMakeLists.txt
index 1535a9c..2021e0b 100644
--- a/src/core/xtests/cdrtest/CMakeLists.txt
+++ b/src/core/xtests/cdrtest/CMakeLists.txt
@@ -11,6 +11,8 @@
 #
 cmake_minimum_required(VERSION 3.5)
 
+find_package(CycloneDDS COMPONENTS idlc)
+
 add_compile_options("-I${PROJECT_SOURCE_DIR}/src/ddsrt/include")
 add_compile_options("-I${PROJECT_SOURCE_DIR}/src/core/ddsc/include")
 add_compile_options("-I${PROJECT_SOURCE_DIR}/src/core/ddsc/src")
diff --git a/src/core/xtests/cdrtest/cdrtest.pl b/src/core/xtests/cdrtest/cdrtest.pl
index e850927..f42a7c2 100644
--- a/src/core/xtests/cdrtest/cdrtest.pl
+++ b/src/core/xtests/cdrtest/cdrtest.pl
@@ -54,7 +54,7 @@ print CYC <<EOF;
 #include "dds/ddsrt/random.h"
 #include "dds/ddsrt/sockets.h"
 #include "dds/ddsi/ddsi_serdata_default.h"
-#include "dds__stream.h"
+#include "dds/ddsi/ddsi_cdrstream.h"
 
 #include "c_base.h"
 #include "sd_cdr.h"
@@ -116,7 +116,15 @@ EOF
   ;
   print CYC gencmp ($t);
   print CYC <<EOF;
-  ddd.type = (struct dds_topic_descriptor *) &$t->[1]_desc;
+  ddd.type = (struct ddsi_sertopic_default_desc) {
+    .m_size = $t->[1]_desc.m_size,
+    .m_align = $t->[1]_desc.m_align,
+    .m_flagset = $t->[1]_desc.m_flagset,
+    .m_nkeys = 0,
+    .m_keys = NULL,
+    .m_nops = dds_stream_countops ($t->[1]_desc.m_ops),
+    .m_ops = (uint32_t *) $t->[1]_desc.m_ops
+  };
   for (uint32_t i = 0; i < 1000; i++) {
     for (size_t j = 0; j < sizeof (garbage); j++)
       garbage[j] = (unsigned char) ddsrt_random ();