From fb54bf78088bf1b195b3693609d2809e3b03ae9e Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Sun, 28 Jul 2019 13:43:01 -0600
Subject: [PATCH 01/20] removed unneeded setting of int_ncid by libhdf5 layer

---
 libhdf5/hdf5create.c | 11 ++++-------
 libhdf5/hdf5open.c   |  2 --
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 66fa0ac230..6ed3f13244 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -290,16 +290,13 @@ NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
     hdf5_set_log_level();
 #endif /* LOGGING */
 
-    /* Check the cmode for validity. */
+    /* Check the cmode for validity. Checking parallel against
+     * NC_DISKLESS already done in NC_create(). */
     if((cmode & ILLEGAL_CREATE_FLAGS) != 0)
-    {res = NC_EINVAL; goto done;}
-
-    /* check parallel against NC_DISKLESS already done in NC_create() */
-
-    nc_file->int_ncid = nc_file->ext_ncid;
+        return NC_EINVAL
 
+    /* Create the netCDF-4/HDF5 file. */
     res = nc4_create_file(path, cmode, initialsz, parameters, nc_file);
 
-done:
     return res;
 }
diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index 1b11855290..009ca03f60 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -887,8 +887,6 @@ NC4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
     hdf5_set_log_level();
 #endif /* LOGGING */
 
-    nc_file->int_ncid = nc_file->ext_ncid;
-
     /* Open the file. */
     return nc4_open_file(path, mode, parameters, nc_file);
 }

From 9d128c35b17dfb76f1f6d35a925c069861a91f0c Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Sun, 28 Jul 2019 13:52:05 -0600
Subject: [PATCH 02/20] comment fix

---
 libhdf5/hdf5create.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 6ed3f13244..8ee88cb8f7 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -27,9 +27,10 @@ extern int NC4_create_image_file(NC_FILE_INFO_T* h5, size_t);
  *
  * @param path The file name of the new file.
  * @param cmode The creation mode flag.
- * @param initialsz The proposed initial file size (advisory)
- * @param parameters extra parameter info (like  MPI communicator)
- * @param nc Pointer to an instance of NC.
+ * @param initialsz The proposed initial file size (advisory, for
+ * in-memory netCDF-4/HDF5 files only).
+ * @param parameters extra parameter info (like MPI communicator).
+ * @param nc Pointer to an already-existing instance of NC.
  *
  * @return ::NC_NOERR No error.
  * @return ::NC_EINVAL Invalid input (check cmode).

From abfec2ee6e207d575172c47400ff6c242e2b0644 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Sun, 28 Jul 2019 15:48:25 -0600
Subject: [PATCH 03/20] adding missing semicolon

---
 libhdf5/hdf5create.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 8ee88cb8f7..9c1c8e4607 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -294,7 +294,7 @@ NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
     /* Check the cmode for validity. Checking parallel against
      * NC_DISKLESS already done in NC_create(). */
     if((cmode & ILLEGAL_CREATE_FLAGS) != 0)
-        return NC_EINVAL
+        return NC_EINVAL;
 
     /* Create the netCDF-4/HDF5 file. */
     res = nc4_create_file(path, cmode, initialsz, parameters, nc_file);

From 6820f41d845cec06df1bd290e92d18fe4b4489c3 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:03:08 -0600
Subject: [PATCH 04/20] turned off broken dap test tst_zero_len_var.sh

---
 ncdap_test/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ncdap_test/Makefile.am b/ncdap_test/Makefile.am
index 44f1d23f96..e4952dc7d0 100644
--- a/ncdap_test/Makefile.am
+++ b/ncdap_test/Makefile.am
@@ -44,7 +44,7 @@ endif
 
 if ENABLE_DAP_REMOTE_TESTS
 if BUILD_UTILITIES
-TESTS += tst_ber.sh tst_remote3.sh tst_formatx.sh testurl.sh tst_fillmismatch.sh tst_zero_len_var.sh
+TESTS += tst_ber.sh tst_remote3.sh tst_formatx.sh testurl.sh tst_fillmismatch.sh #tst_zero_len_var.sh
 endif
 
 TESTS += test_partvar

From f410b31b72a7ea2d4e6824e62e31bde2bf228e4d Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:17:31 -0600
Subject: [PATCH 05/20] whitespace cleanup of hdf5open.c, plus extra
 documentation

---
 libhdf5/hdf5open.c | 112 ++++++++++++++++++++++-----------------------
 1 file changed, 56 insertions(+), 56 deletions(-)

diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index 009ca03f60..c2dd955c36 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -636,28 +636,28 @@ check_for_classic_model(NC_GRP_INFO_T *root_grp, int *is_classic)
 static int
 nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
 {
+    NC_FILE_INFO_T *nc4_info = NULL;
+    NC_HDF5_FILE_INFO_T *h5 = NULL;
     hid_t fapl_id = H5P_DEFAULT;
-    int retval;
     unsigned flags;
-    NC_FILE_INFO_T *nc4_info = NULL;
     int is_classic;
-    NC_HDF5_FILE_INFO_T *h5 = NULL;
-
 #ifdef USE_PARALLEL4
     NC_MPI_INFO* mpiinfo = NULL;
     int comm_duped = 0; /* Whether the MPI Communicator was duplicated */
     int info_duped = 0; /* Whether the MPI Info object was duplicated */
 #endif
+    int retval;
 
     LOG((3, "%s: path %s mode %d", __func__, path, mode));
     assert(path && nc);
 
+    /* Determine the HDF5 open flag to use. */
     flags = (mode & NC_WRITE) ? H5F_ACC_RDWR : H5F_ACC_RDONLY;
 
     /* Add necessary structs to hold netcdf-4 file data. */
     if ((retval = nc4_nc4f_list_add(nc, path, mode)))
         BAIL(retval);
-    nc4_info = NC4_DATA(nc);
+    nc4_info = (NC_FILE_INFO_T *)nc->dispatchdata;
     assert(nc4_info && nc4_info->root_grp);
 
     /* Add struct to hold HDF5-specific file metadata. */
@@ -673,12 +673,12 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
 #ifdef ENABLE_BYTERANGE
     /* See if we want the byte range protocol */
     if(nc->model->iosp == NC_IOSP_HTTP) {
-	h5->http.iosp = 1;
-	/* Kill off any conflicting modes flags */
-	mode &= ~(NC_WRITE|NC_DISKLESS|NC_PERSIST|NC_INMEMORY);
-	parameters = NULL; /* kill off parallel */
+        h5->http.iosp = 1;
+        /* Kill off any conflicting modes flags */
+        mode &= ~(NC_WRITE|NC_DISKLESS|NC_PERSIST|NC_INMEMORY);
+        parameters = NULL; /* kill off parallel */
     } else
-	h5->http.iosp = 0;
+        h5->http.iosp = 0;
 #endif /*ENABLE_BYTERANGE*/
 
     nc4_info->mem.inmemory = ((mode & NC_INMEMORY) == NC_INMEMORY);
@@ -687,7 +687,7 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
 
     /* Does the mode specify that this file is read-only? */
     if ((mode & NC_WRITE) == 0)
-	nc4_info->no_write = NC_TRUE;
+        nc4_info->no_write = NC_TRUE;
 
     if(nc4_info->mem.inmemory && nc4_info->mem.diskless)
         BAIL(NC_EINTERNAL);
@@ -748,76 +748,76 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
 
     /* Process  NC_INMEMORY */
     if(nc4_info->mem.inmemory) {
-	NC_memio* memio;
-	/* validate */
-	if(parameters == NULL)
-	    BAIL(NC_EINMEMORY);
-	memio = (NC_memio*)parameters;
-	if(memio->memory == NULL || memio->size == 0)
+        NC_memio* memio;
+        /* validate */
+        if(parameters == NULL)
             BAIL(NC_EINMEMORY);
-	/* initialize h5->mem */
-	nc4_info->mem.memio = *memio;
-	/* Is the incoming memory locked? */
-	nc4_info->mem.locked = (nc4_info->mem.memio.flags & NC_MEMIO_LOCKED) == NC_MEMIO_LOCKED;
-	/* As a safeguard, if not locked and not read-only,
-	   then we must take control of the incoming memory */
-	if(!nc4_info->mem.locked && !nc4_info->no_write) {
+        memio = (NC_memio*)parameters;
+        if(memio->memory == NULL || memio->size == 0)
+            BAIL(NC_EINMEMORY);
+        /* initialize h5->mem */
+        nc4_info->mem.memio = *memio;
+        /* Is the incoming memory locked? */
+        nc4_info->mem.locked = (nc4_info->mem.memio.flags & NC_MEMIO_LOCKED) == NC_MEMIO_LOCKED;
+        /* As a safeguard, if not locked and not read-only,
+           then we must take control of the incoming memory */
+        if(!nc4_info->mem.locked && !nc4_info->no_write) {
             memio->memory = NULL; /* take control */
             memio->size = 0;
-	}
-	retval = NC4_open_image_file(nc4_info);
-	if(retval)
+        }
+        retval = NC4_open_image_file(nc4_info);
+        if(retval)
             BAIL(NC_EHDFERR);
     }
     else
-    if(nc4_info->mem.diskless) {   /* Process  NC_DISKLESS */
-	size_t min_incr = 65536; /* Minimum buffer increment */
-	/* Configure FAPL to use the core file driver */
-	if (H5Pset_fapl_core(fapl_id, min_incr, (nc4_info->mem.persist?1:0)) < 0)
-	BAIL(NC_EHDFERR);
-	/* Open the HDF5 file. */
-	if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
-            BAIL(NC_EHDFERR);
-    }
+        if(nc4_info->mem.diskless) {   /* Process  NC_DISKLESS */
+            size_t min_incr = 65536; /* Minimum buffer increment */
+            /* Configure FAPL to use the core file driver */
+            if (H5Pset_fapl_core(fapl_id, min_incr, (nc4_info->mem.persist?1:0)) < 0)
+                BAIL(NC_EHDFERR);
+            /* Open the HDF5 file. */
+            if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
+                BAIL(NC_EHDFERR);
+        }
 #ifdef ENABLE_BYTERANGE
-    else
-    if(h5->http.iosp) {   /* Arrange to use the byte-range driver */
-	/* Configure FAPL to use the byte-range file driver */
-	if (H5Pset_fapl_http(fapl_id) < 0)
-	    BAIL(NC_EHDFERR);
-	/* Open the HDF5 file. */
-	if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
-	    BAIL(NC_EHDFERR);
-    }
+        else
+            if(h5->http.iosp) {   /* Arrange to use the byte-range driver */
+                /* Configure FAPL to use the byte-range file driver */
+                if (H5Pset_fapl_http(fapl_id) < 0)
+                    BAIL(NC_EHDFERR);
+                /* Open the HDF5 file. */
+                if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
+                    BAIL(NC_EHDFERR);
+            }
 #endif
-    else
-    {
-       /* Open the HDF5 file. */
-       if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
-          BAIL(NC_EHDFERR);
-    }
+            else
+            {
+                /* Open the HDF5 file. */
+                if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
+                    BAIL(NC_EHDFERR);
+            }
 
     /* Now read in all the metadata. Some types and dimscale
      * information may be difficult to resolve here, if, for example, a
      * dataset of user-defined type is encountered before the
      * definition of that type. */
     if ((retval = rec_read_metadata(nc4_info->root_grp)))
-       BAIL(retval);
+        BAIL(retval);
 
     /* Check for classic model attribute. */
     if ((retval = check_for_classic_model(nc4_info->root_grp, &is_classic)))
-       BAIL(retval);
+        BAIL(retval);
     if (is_classic)
-       nc4_info->cmode |= NC_CLASSIC_MODEL;
+        nc4_info->cmode |= NC_CLASSIC_MODEL;
 
     /* Set the provenance info for this file */
     if ((retval = NC4_read_provenance(nc4_info)))
-       BAIL(retval);
+        BAIL(retval);
 
     /* Now figure out which netCDF dims are indicated by the dimscale
      * information. */
     if ((retval = rec_match_dimscales(nc4_info->root_grp)))
-       BAIL(retval);
+        BAIL(retval);
 
 #ifdef LOGGING
     /* This will print out the names, types, lens, etc of the vars and

From e71ff09a0c1510decf2b24da6229fc1b52ea67ff Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:23:58 -0600
Subject: [PATCH 06/20] removed need for NC4_open to have NC passed in

---
 libhdf5/hdf5open.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index c2dd955c36..9e634d76a8 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -638,11 +638,12 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
 {
     NC_FILE_INFO_T *nc4_info = NULL;
     NC_HDF5_FILE_INFO_T *h5 = NULL;
+    NC *nc1;
     hid_t fapl_id = H5P_DEFAULT;
     unsigned flags;
     int is_classic;
 #ifdef USE_PARALLEL4
-    NC_MPI_INFO* mpiinfo = NULL;
+    NC_MPI_INFO *mpiinfo = NULL;
     int comm_duped = 0; /* Whether the MPI Communicator was duplicated */
     int info_duped = 0; /* Whether the MPI Info object was duplicated */
 #endif
@@ -651,6 +652,11 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
     LOG((3, "%s: path %s mode %d", __func__, path, mode));
     assert(path && nc);
 
+    /* Find pointer to NC. */
+    if ((retval = NC_check_id(nc->ext_ncid, &nc1)))
+        return retval;
+    assert(nc1);
+
     /* Determine the HDF5 open flag to use. */
     flags = (mode & NC_WRITE) ? H5F_ACC_RDWR : H5F_ACC_RDONLY;
 

From f80b751585540c60470e36574b3073d221cf9bc9 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:27:53 -0600
Subject: [PATCH 07/20] have pnetcdf look up NC pointer for create

---
 libsrcp/ncpdispatch.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libsrcp/ncpdispatch.c b/libsrcp/ncpdispatch.c
index af0fafff45..6ad285628b 100644
--- a/libsrcp/ncpdispatch.c
+++ b/libsrcp/ncpdispatch.c
@@ -45,10 +45,15 @@ NCP_create(const char *path,
            size_t *chunksizehintp,
            void *mpidata,
            const struct NC_Dispatch *table,
-           NC *nc)
+           NC *nc1)
 {
     int status;
     NCP_INFO *nc5;
+    NC *nc;
+
+    /* Find pointer to NC for this file. */
+    status = NC_check_id(nc1->ext_ncid, &nc);
+    if (status != NC_NOERR) return status;
 
     /* Check the cmode for only valid flags */
     if (cmode & ~LEGAL_CREATE_FLAGS) return NC_EINVAL;

From 5fa67ebe165a9a25c05e2be05a364de1c6eae6e4 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:31:03 -0600
Subject: [PATCH 08/20] removed need of NC pointer in create for pnetcdf
 dispatch layer

---
 libsrcp/ncpdispatch.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libsrcp/ncpdispatch.c b/libsrcp/ncpdispatch.c
index 6ad285628b..f586c34810 100644
--- a/libsrcp/ncpdispatch.c
+++ b/libsrcp/ncpdispatch.c
@@ -87,10 +87,15 @@ NCP_open(const char *path,
          size_t *chunksizehintp,
          void *mpidata,
          const struct NC_Dispatch *table,
-         NC *nc)
+         NC *nc1)
 {
     int status;
     NCP_INFO *nc5;
+    NC *nc;
+
+    /* Find pointer to NC for this file. */
+    status = NC_check_id(nc1->ext_ncid, &nc);
+    if (status != NC_NOERR) return status;
 
     /* Check the omode for only valid flags */
     if (omode & ~LEGAL_OPEN_FLAGS) return NC_EINVAL;

From ef9b459977603b2584e4211566c447ce55708cad Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 11:40:36 -0600
Subject: [PATCH 09/20] now libhdf4 layer also looks up the NC on open

---
 libhdf4/hdf4file.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index d78f59176f..578264d3a0 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -601,6 +601,7 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
 {
     NC_FILE_INFO_T *h5;
     NC_HDF4_FILE_INFO_T *hdf4_file;
+    NC *nc1;
     int32 num_datasets, num_gatts;
     int32 sdid;
     int v, a;
@@ -611,6 +612,10 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
 
     LOG((1, "%s: path %s mode %d params %x", __func__, path, mode, parameters));
 
+    /* Find pointer to NC. */
+    if ((retval = NC_check_id(nc_file->ext_ncid, &nc1)))
+        return retval;
+
     /* Check the mode for validity */
     if (mode & ILLEGAL_OPEN_FLAGS)
         return NC_EINVAL;
@@ -624,9 +629,9 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
         return NC_EHDFERR;
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    if ((retval = nc4_nc4f_list_add(nc_file, path, mode)))
+    if ((retval = nc4_nc4f_list_add(nc1, path, mode)))
         return retval;
-    h5 = (NC_FILE_INFO_T *)nc_file->dispatchdata;
+    h5 = (NC_FILE_INFO_T *)nc1->dispatchdata;
     assert(h5 && h5->root_grp);
     h5->no_write = NC_TRUE;
     h5->root_grp->atts_read = 1;

From 659939d3976c166fd57b1c4ff082ca233b48c53e Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 12:46:12 -0600
Subject: [PATCH 10/20] turned off tst_zero_len_var.sh in cmake build

---
 libdap2/ncd2dispatch.c    | 7 ++++++-
 libdap4/d4file.c          | 7 ++++++-
 ncdap_test/CMakeLists.txt | 2 +-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/libdap2/ncd2dispatch.c b/libdap2/ncd2dispatch.c
index 0b2d81d233..592af90e61 100644
--- a/libdap2/ncd2dispatch.c
+++ b/libdap2/ncd2dispatch.c
@@ -271,14 +271,19 @@ NCD2_get_vars(int ncid, int varid,
 /* See ncd2dispatch.c for other version */
 int
 NCD2_open(const char* path, int mode, int basepe, size_t *chunksizehintp,
-          void* mpidata, const NC_Dispatch* dispatch, NC* drno)
+          void* mpidata, const NC_Dispatch* dispatch, NC* drno1)
 {
     NCerror ncstat = NC_NOERR;
     OCerror ocstat = OC_NOERR;
     NCDAPCOMMON* dapcomm = NULL;
+    NC* drno;
     const char* value;
     int nc3id = -1;
 
+    /* Find pointer to NC struct for this file. */
+    ncstat = NC_check_id(drno1->ext_ncid,&drno);
+    if(ncstat != NC_NOERR) {goto done;}
+
     if(path == NULL)
 	{ncstat = NC_EDAPURL; goto done;}
     if(dispatch == NULL)
diff --git a/libdap4/d4file.c b/libdap4/d4file.c
index 401550d9a8..853cc0b436 100644
--- a/libdap4/d4file.c
+++ b/libdap4/d4file.c
@@ -38,18 +38,23 @@ static const char* checkseps = "+,:;";
 int
 NCD4_open(const char * path, int mode,
           int basepe, size_t *chunksizehintp,
-          void *mpidata, const NC_Dispatch *dispatch, NC *nc)
+          void *mpidata, const NC_Dispatch *dispatch, NC *nc1)
 {
     int ret = NC_NOERR;
     NCD4INFO* d4info = NULL;
     const char* value;
     NCD4meta* meta;
+    NC* nc;
 
     if(path == NULL)
 	return THROW(NC_EDAPURL);
 
     assert(dispatch != NULL);
 
+    /* Find pointer to NC struct for this file. */
+    ret = NC_check_id(nc1->ext_ncid,&nc);
+    if(ret != NC_NOERR) {goto done;}
+
     /* Setup our NC and NCDAPCOMMON state*/
 
     d4info = (NCD4INFO*)calloc(1,sizeof(NCD4INFO));
diff --git a/ncdap_test/CMakeLists.txt b/ncdap_test/CMakeLists.txt
index f9b1706f75..34606826f4 100644
--- a/ncdap_test/CMakeLists.txt
+++ b/ncdap_test/CMakeLists.txt
@@ -39,7 +39,7 @@ IF(ENABLE_TESTS)
     IF(BUILD_UTILITIES)
       add_sh_test(ncdap tst_ber)
       add_sh_test(ncdap tst_remote3)
-      add_sh_test(ncdap tst_zero_len_var)
+#      add_sh_test(ncdap tst_zero_len_var)
 # not yet      add_sh_test(ncdap tst_hyrax)
       add_sh_test(ncdap tst_fillmismatch)
       IF(ENABLE_DAP_LONG_TESTS)

From 64f983ee14f037454ad79ad5a5fa16ae6b52cc9a Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 12:58:17 -0600
Subject: [PATCH 11/20] now looking up NC in the libsrc dispatch layer
 open/create

---
 libsrc/nc3internal.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/libsrc/nc3internal.c b/libsrc/nc3internal.c
index b52a6e3623..28b7e20bde 100644
--- a/libsrc/nc3internal.c
+++ b/libsrc/nc3internal.c
@@ -1039,13 +1039,18 @@ int NC3_new_nc(NC3_INFO** ncpp)
 int
 NC3_create(const char *path, int ioflags, size_t initialsz, int basepe,
            size_t *chunksizehintp, void *parameters,
-           const NC_Dispatch *dispatch, NC *nc)
+           const NC_Dispatch *dispatch, NC *nc1)
 {
 	int status = NC_NOERR;
 	void *xp = NULL;
 	int sizeof_off_t = 0;
+        NC *nc;
 	NC3_INFO* nc3 = NULL;
 
+        /* Find NC struct for this file. */
+        if ((status = NC_check_id(nc1->ext_ncid, &nc)))
+            return status;
+
 	/* Create our specific NC3_INFO instance */
 	nc3 = new_NC3INFO(chunksizehintp);
 
@@ -1171,10 +1176,15 @@ nc_set_default_format(int format, int *old_formatp)
 
 int
 NC3_open(const char *path, int ioflags, int basepe, size_t *chunksizehintp,
-         void *parameters, const NC_Dispatch *dispatch, NC *nc)
+         void *parameters, const NC_Dispatch *dispatch, NC *nc1)
 {
 	int status;
 	NC3_INFO* nc3 = NULL;
+        NC *nc;
+
+        /* Find NC struct for this file. */
+        if ((status = NC_check_id(nc1->ext_ncid, &nc)))
+            return status;
 
 	/* Create our specific NC3_INFO instance */
 	nc3 = new_NC3INFO(chunksizehintp);

From 170c5b09016d66a9f5fb795f80e1dfd0bdbf39ad Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 14:30:20 -0600
Subject: [PATCH 12/20] removed NC from open in dispatch table

---
 include/hdf4dispatch.h    |  2 +-
 include/nc3dispatch.h     |  2 +-
 include/nc4dispatch.h     |  4 ++--
 include/netcdf_dispatch.h |  6 +++---
 libdap2/ncd2dispatch.c    |  8 ++++----
 libdap2/ncd2dispatch.h    |  2 +-
 libdap4/d4file.c          |  4 ++--
 libdap4/ncd4dispatch.c    |  2 +-
 libdap4/ncd4dispatch.h    |  2 +-
 libdispatch/dfile.c       |  6 +++---
 libdispatch/dreadonly.c   |  4 ++--
 libhdf4/hdf4file.c        |  6 +++---
 libhdf5/hdf5create.c      | 15 +++++++++++----
 libhdf5/hdf5open.c        | 19 +++++++++----------
 libsrc/nc3internal.c      |  8 ++++----
 libsrcp/ncpdispatch.c     |  8 ++++----
 nc_test4/tst_udf.c        |  2 +-
 17 files changed, 53 insertions(+), 47 deletions(-)

diff --git a/include/hdf4dispatch.h b/include/hdf4dispatch.h
index 36b9766935..c8dcffee71 100644
--- a/include/hdf4dispatch.h
+++ b/include/hdf4dispatch.h
@@ -40,7 +40,7 @@ extern "C" {
 
     extern int
     NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
-                 void *parameters, const NC_Dispatch *, NC *);
+                 void *parameters, const NC_Dispatch *, int);
 
     extern int
     NC_HDF4_abort(int ncid);
diff --git a/include/nc3dispatch.h b/include/nc3dispatch.h
index bab7318319..e9b9ad5825 100644
--- a/include/nc3dispatch.h
+++ b/include/nc3dispatch.h
@@ -53,7 +53,7 @@ extern "C" {
     extern int
     NC3_create(const char *path, int cmode,
                size_t initialsz, int basepe, size_t *chunksizehintp,
-               void* mpidata, const struct NC_Dispatch*, NC* ncp);
+               void* mpidata, const struct NC_Dispatch*, int ncid);
 
 /* WARNING: this signature differs from external nc_open API*/
     extern int
diff --git a/include/nc4dispatch.h b/include/nc4dispatch.h
index 75bc3f9893..65f9518398 100644
--- a/include/nc4dispatch.h
+++ b/include/nc4dispatch.h
@@ -23,12 +23,12 @@ extern "C" {
     EXTERNL int
     NC4_create(const char *path, int cmode,
                size_t initialsz, int basepe, size_t *chunksizehintp,
-               void* parameters, const NC_Dispatch*, NC*);
+               void* parameters, const NC_Dispatch*, int);
 
     EXTERNL int
     NC4_open(const char *path, int mode,
              int basepe, size_t *chunksizehintp,
-             void* parameters, const NC_Dispatch*, NC*);
+             void* parameters, const NC_Dispatch*, int);
 
     EXTERNL int
     NC4_redef(int ncid);
diff --git a/include/netcdf_dispatch.h b/include/netcdf_dispatch.h
index fedb072d94..63040d2d0b 100644
--- a/include/netcdf_dispatch.h
+++ b/include/netcdf_dispatch.h
@@ -25,9 +25,9 @@ struct NC_Dispatch
 
     int (*create)(const char *path, int cmode, size_t initialsz,
                   int basepe, size_t *chunksizehintp, void *parameters,
-                  const struct NC_Dispatch *table, NC *ncp);
+                  const struct NC_Dispatch *table, int ncid);
     int (*open)(const char *path, int mode, int basepe, size_t *chunksizehintp,
-                void *parameters, const struct NC_Dispatch *table, NC *ncp);
+                void *parameters, const struct NC_Dispatch *table, int ncid);
 
     int (*redef)(int);
     int (*_enddef)(int,size_t,size_t,size_t,size_t);
@@ -140,7 +140,7 @@ struct NC_Dispatch
 
 EXTERNL int NC_RO_create(const char *path, int cmode, size_t initialsz, int basepe,
                  size_t *chunksizehintp, void* parameters,
-                 const NC_Dispatch*, NC*);
+                 const NC_Dispatch*, int);
 EXTERNL int NC_RO_redef(int ncid);
 EXTERNL int NC_RO__enddef(int ncid, size_t h_minfree, size_t v_align, size_t v_minfree,
                   size_t r_align);
diff --git a/libdap2/ncd2dispatch.c b/libdap2/ncd2dispatch.c
index 592af90e61..1299f91431 100644
--- a/libdap2/ncd2dispatch.c
+++ b/libdap2/ncd2dispatch.c
@@ -63,7 +63,7 @@ static NCerror applyclientparams(NCDAPCOMMON*);
 static int
 NCD2_create(const char *path, int cmode,
            size_t initialsz, int basepe, size_t *chunksizehintp,
-           void* mpidata, const struct NC_Dispatch*,NC* ncp);
+           void* mpidata, const struct NC_Dispatch*,int);
 
 static int NCD2_redef(int ncid);
 static int NCD2__enddef(int ncid, size_t h_minfree, size_t v_align, size_t v_minfree, size_t r_align);
@@ -227,7 +227,7 @@ NCD2_abort(int ncid)
 static int
 NCD2_create(const char *path, int cmode,
            size_t initialsz, int basepe, size_t *chunksizehintp,
-           void* mpidata, const NC_Dispatch* dispatch, NC* ncp)
+           void* mpidata, const NC_Dispatch* dispatch, int ncid)
 {
    return NC_EPERM;
 }
@@ -271,7 +271,7 @@ NCD2_get_vars(int ncid, int varid,
 /* See ncd2dispatch.c for other version */
 int
 NCD2_open(const char* path, int mode, int basepe, size_t *chunksizehintp,
-          void* mpidata, const NC_Dispatch* dispatch, NC* drno1)
+          void* mpidata, const NC_Dispatch* dispatch, int ncid)
 {
     NCerror ncstat = NC_NOERR;
     OCerror ocstat = OC_NOERR;
@@ -281,7 +281,7 @@ NCD2_open(const char* path, int mode, int basepe, size_t *chunksizehintp,
     int nc3id = -1;
 
     /* Find pointer to NC struct for this file. */
-    ncstat = NC_check_id(drno1->ext_ncid,&drno);
+    ncstat = NC_check_id(ncid,&drno);
     if(ncstat != NC_NOERR) {goto done;}
 
     if(path == NULL)
diff --git a/libdap2/ncd2dispatch.h b/libdap2/ncd2dispatch.h
index 902fd9df30..d0947ab091 100644
--- a/libdap2/ncd2dispatch.h
+++ b/libdap2/ncd2dispatch.h
@@ -46,7 +46,7 @@ extern "C" {
 extern int
 NCD2_open(const char *path, int mode,
        int basepe, size_t *chunksizehintp,
-       void* mpidata, const struct NC_Dispatch* dispatch, NC* ncp);
+       void* mpidata, const struct NC_Dispatch* dispatch, int ncid);
 
 extern int
 NCD2_close(int ncid,void*);
diff --git a/libdap4/d4file.c b/libdap4/d4file.c
index 853cc0b436..3d68761c14 100644
--- a/libdap4/d4file.c
+++ b/libdap4/d4file.c
@@ -38,7 +38,7 @@ static const char* checkseps = "+,:;";
 int
 NCD4_open(const char * path, int mode,
           int basepe, size_t *chunksizehintp,
-          void *mpidata, const NC_Dispatch *dispatch, NC *nc1)
+          void *mpidata, const NC_Dispatch *dispatch, int ncid)
 {
     int ret = NC_NOERR;
     NCD4INFO* d4info = NULL;
@@ -52,7 +52,7 @@ NCD4_open(const char * path, int mode,
     assert(dispatch != NULL);
 
     /* Find pointer to NC struct for this file. */
-    ret = NC_check_id(nc1->ext_ncid,&nc);
+    ret = NC_check_id(ncid,&nc);
     if(ret != NC_NOERR) {goto done;}
 
     /* Setup our NC and NCDAPCOMMON state*/
diff --git a/libdap4/ncd4dispatch.c b/libdap4/ncd4dispatch.c
index e6f9405d57..a91b68934f 100644
--- a/libdap4/ncd4dispatch.c
+++ b/libdap4/ncd4dispatch.c
@@ -85,7 +85,7 @@ NCD4_sync(int ncid)
 static int
 NCD4_create(const char *path, int cmode,
            size_t initialsz, int basepe, size_t *chunksizehintp,
-           void* mpidata, const NC_Dispatch *dispatch, NC *ncp)
+           void* mpidata, const NC_Dispatch *dispatch, int ncid)
 {
    return THROW(NC_EPERM);
 }
diff --git a/libdap4/ncd4dispatch.h b/libdap4/ncd4dispatch.h
index 8513a75e27..d3aadbbcab 100644
--- a/libdap4/ncd4dispatch.h
+++ b/libdap4/ncd4dispatch.h
@@ -17,7 +17,7 @@ extern "C" {
 extern int
 NCD4_open(const char *path, int mode,
          int basepe, size_t *chunksizehintp,
-         void *mpidata, const struct NC_Dispatch *dispatch, NC *ncp);
+         void *mpidata, const struct NC_Dispatch *dispatch, int ncid);
 
 extern int
 NCD4_close(int ncid,void*);
diff --git a/libdispatch/dfile.c b/libdispatch/dfile.c
index 0d4eecaf97..f74c2dd242 100644
--- a/libdispatch/dfile.c
+++ b/libdispatch/dfile.c
@@ -1901,7 +1901,7 @@ NC_create(const char *path0, int cmode, size_t initialsz,
 
     /* Assume create will fill in remaining ncp fields */
     if ((stat = dispatcher->create(ncp->path, cmode, initialsz, basepe, chunksizehintp,
-				  parameters, dispatcher, ncp))) {
+				  parameters, dispatcher, ncp->ext_ncid))) {
 	del_from_NCList(ncp); /* oh well */
 	free_NC(ncp);
     } else {
@@ -2090,12 +2090,12 @@ NC_open(const char *path0, int omode, int basepe, size_t *chunksizehintp,
     /* Create the NC* instance and insert its dispatcher */
     if((stat = new_NC(dispatcher,path,omode,&model,&ncp))) goto done;
 
-    /* Add to list of known open files */
+    /* Add to list of known open files. This assignes an ext_ncid. */
     add_to_NCList(ncp);
 
     /* Assume open will fill in remaining ncp fields */
     stat = dispatcher->open(ncp->path, omode, basepe, chunksizehintp,
-			    parameters, dispatcher, ncp);
+			    parameters, dispatcher, ncp->ext_ncid);
     if(stat == NC_NOERR) {
 	if(ncidp) *ncidp = ncp->ext_ncid;
     } else {
diff --git a/libdispatch/dreadonly.c b/libdispatch/dreadonly.c
index 6cf9e48bee..f8c03ffb5e 100644
--- a/libdispatch/dreadonly.c
+++ b/libdispatch/dreadonly.c
@@ -245,7 +245,7 @@ NC_RO_sync(int ncid)
  * @param use_parallel Ignored.
  * @param parameters Ignored.
  * @param dispatch Ignored.
- * @param nc_file Ignored.
+ * @param ncid Ignored.
  *
  * @return ::NC_EPERM Cannot create files.
  * @author Ed Hartnett
@@ -253,7 +253,7 @@ NC_RO_sync(int ncid)
 int
 NC_RO_create(const char* path, int cmode, size_t initialsz, int basepe,
              size_t *chunksizehintp, void *parameters,
-             const NC_Dispatch *dispatch, NC *nc_file)
+             const NC_Dispatch *dispatch, int ncid)
 {
    return NC_EPERM;
 }
diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index 578264d3a0..6b6f1ab363 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -597,7 +597,7 @@ hdf4_read_var(NC_FILE_INFO_T *h5, int v)
  */
 int
 NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
-             void *parameters, const NC_Dispatch *dispatch, NC *nc_file)
+             void *parameters, const NC_Dispatch *dispatch, int ncid)
 {
     NC_FILE_INFO_T *h5;
     NC_HDF4_FILE_INFO_T *hdf4_file;
@@ -608,12 +608,12 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
     int retval;
 
     /* Check inputs. */
-    assert(nc_file && path);
+    assert(path);
 
     LOG((1, "%s: path %s mode %d params %x", __func__, path, mode, parameters));
 
     /* Find pointer to NC. */
-    if ((retval = NC_check_id(nc_file->ext_ncid, &nc1)))
+    if ((retval = NC_check_id(ncid, &nc1)))
         return retval;
 
     /* Check the mode for validity */
diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 9c1c8e4607..54c17d8e0a 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -262,7 +262,8 @@ nc4_create_file(const char *path, int cmode, size_t initialsz,
  * @param parameters pointer to struct holding extra data (e.g. for
  * parallel I/O) layer. Ignored if NULL.
  * @param dispatch Pointer to the dispatch table for this file.
- * @param nc_file Pointer to an instance of NC.
+ * @param ncid The ncid that has been assigned by the dispatch layer
+ * (aka ext_ncid).
  *
  * @return ::NC_NOERR No error.
  * @return ::NC_EINVAL Invalid input (check cmode).
@@ -272,11 +273,12 @@ nc4_create_file(const char *path, int cmode, size_t initialsz,
 int
 NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
            size_t *chunksizehintp, void *parameters,
-           const NC_Dispatch *dispatch, NC *nc_file)
+           const NC_Dispatch *dispatch, int ncid)
 {
+    NC *nc_file;
     int res;
 
-    assert(nc_file && path);
+    assert(path);
 
     LOG((1, "%s: path %s cmode 0x%x parameters %p",
          __func__, path, cmode, parameters));
@@ -293,9 +295,14 @@ NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
 
     /* Check the cmode for validity. Checking parallel against
      * NC_DISKLESS already done in NC_create(). */
-    if((cmode & ILLEGAL_CREATE_FLAGS) != 0)
+    if (cmode & ILLEGAL_CREATE_FLAGS)
         return NC_EINVAL;
 
+    /* Find pointer to NC. */
+    if ((res = NC_check_id(ncid, &nc_file)))
+        return res;
+    assert(nc_file);
+
     /* Create the netCDF-4/HDF5 file. */
     res = nc4_create_file(path, cmode, initialsz, parameters, nc_file);
 
diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index 9e634d76a8..06d97a65b4 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -622,7 +622,7 @@ check_for_classic_model(NC_GRP_INFO_T *root_grp, int *is_classic)
  * @param path The file name of the new file.
  * @param mode The open mode flag.
  * @param parameters File parameters.
- * @param nc Pointer to NC file info.
+ * @param ncid The ncid that has been assigned to this file.
  *
  * @return ::NC_NOERR No error.
  * @return ::NC_ENOMEM Out of memory.
@@ -634,11 +634,11 @@ check_for_classic_model(NC_GRP_INFO_T *root_grp, int *is_classic)
  * @author Ed Hartnett, Dennis Heimbigner
  */
 static int
-nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
+nc4_open_file(const char *path, int mode, void* parameters, int ncid)
 {
     NC_FILE_INFO_T *nc4_info = NULL;
     NC_HDF5_FILE_INFO_T *h5 = NULL;
-    NC *nc1;
+    NC *nc;
     hid_t fapl_id = H5P_DEFAULT;
     unsigned flags;
     int is_classic;
@@ -650,12 +650,12 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
     int retval;
 
     LOG((3, "%s: path %s mode %d", __func__, path, mode));
-    assert(path && nc);
+    assert(path);
 
     /* Find pointer to NC. */
-    if ((retval = NC_check_id(nc->ext_ncid, &nc1)))
+    if ((retval = NC_check_id(ncid, &nc)))
         return retval;
-    assert(nc1);
+    assert(nc && nc->model->impl == NC_FORMATX_NC4);
 
     /* Determine the HDF5 open flag to use. */
     flags = (mode & NC_WRITE) ? H5F_ACC_RDWR : H5F_ACC_RDONLY;
@@ -868,10 +868,9 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
  */
 int
 NC4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
-         void *parameters, const NC_Dispatch *dispatch, NC *nc_file)
+         void *parameters, const NC_Dispatch *dispatch, int ncid)
 {
-    assert(nc_file && path && dispatch && nc_file &&
-           nc_file->model->impl == NC_FORMATX_NC4);
+    assert(path && dispatch);
 
     LOG((1, "%s: path %s mode %d params %x",
          __func__, path, mode, parameters));
@@ -894,7 +893,7 @@ NC4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
 #endif /* LOGGING */
 
     /* Open the file. */
-    return nc4_open_file(path, mode, parameters, nc_file);
+    return nc4_open_file(path, mode, parameters, ncid);
 }
 
 /**
diff --git a/libsrc/nc3internal.c b/libsrc/nc3internal.c
index 28b7e20bde..dc0bdc5e67 100644
--- a/libsrc/nc3internal.c
+++ b/libsrc/nc3internal.c
@@ -1039,7 +1039,7 @@ int NC3_new_nc(NC3_INFO** ncpp)
 int
 NC3_create(const char *path, int ioflags, size_t initialsz, int basepe,
            size_t *chunksizehintp, void *parameters,
-           const NC_Dispatch *dispatch, NC *nc1)
+           const NC_Dispatch *dispatch, int ncid)
 {
 	int status = NC_NOERR;
 	void *xp = NULL;
@@ -1048,7 +1048,7 @@ NC3_create(const char *path, int ioflags, size_t initialsz, int basepe,
 	NC3_INFO* nc3 = NULL;
 
         /* Find NC struct for this file. */
-        if ((status = NC_check_id(nc1->ext_ncid, &nc)))
+        if ((status = NC_check_id(ncid, &nc)))
             return status;
 
 	/* Create our specific NC3_INFO instance */
@@ -1176,14 +1176,14 @@ nc_set_default_format(int format, int *old_formatp)
 
 int
 NC3_open(const char *path, int ioflags, int basepe, size_t *chunksizehintp,
-         void *parameters, const NC_Dispatch *dispatch, NC *nc1)
+         void *parameters, const NC_Dispatch *dispatch, int ncid)
 {
 	int status;
 	NC3_INFO* nc3 = NULL;
         NC *nc;
 
         /* Find NC struct for this file. */
-        if ((status = NC_check_id(nc1->ext_ncid, &nc)))
+        if ((status = NC_check_id(ncid, &nc)))
             return status;
 
 	/* Create our specific NC3_INFO instance */
diff --git a/libsrcp/ncpdispatch.c b/libsrcp/ncpdispatch.c
index f586c34810..1fde2c4784 100644
--- a/libsrcp/ncpdispatch.c
+++ b/libsrcp/ncpdispatch.c
@@ -45,14 +45,14 @@ NCP_create(const char *path,
            size_t *chunksizehintp,
            void *mpidata,
            const struct NC_Dispatch *table,
-           NC *nc1)
+           int ncid)
 {
     int status;
     NCP_INFO *nc5;
     NC *nc;
 
     /* Find pointer to NC for this file. */
-    status = NC_check_id(nc1->ext_ncid, &nc);
+    status = NC_check_id(ncid, &nc);
     if (status != NC_NOERR) return status;
 
     /* Check the cmode for only valid flags */
@@ -87,14 +87,14 @@ NCP_open(const char *path,
          size_t *chunksizehintp,
          void *mpidata,
          const struct NC_Dispatch *table,
-         NC *nc1)
+         int ncid)
 {
     int status;
     NCP_INFO *nc5;
     NC *nc;
 
     /* Find pointer to NC for this file. */
-    status = NC_check_id(nc1->ext_ncid, &nc);
+    status = NC_check_id(ncid, &nc);
     if (status != NC_NOERR) return status;
 
     /* Check the omode for only valid flags */
diff --git a/nc_test4/tst_udf.c b/nc_test4/tst_udf.c
index 64fefb0308..534d3be42d 100644
--- a/nc_test4/tst_udf.c
+++ b/nc_test4/tst_udf.c
@@ -26,7 +26,7 @@ NC4_show_metadata(int ncid)
 
 int
 tst_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
-             void *parameters, const NC_Dispatch *dispatch, NC *nc_file)
+             void *parameters, const NC_Dispatch *dispatch, int ncid)
 {
    return NC_NOERR;
 }

From 49dcb48c25f3b2b2d2b3a196f68c9ecf6005747e Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 14:39:45 -0600
Subject: [PATCH 13/20] clean up

---
 libhdf4/hdf4file.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index 6b6f1ab363..36b54cd167 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -601,7 +601,7 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
 {
     NC_FILE_INFO_T *h5;
     NC_HDF4_FILE_INFO_T *hdf4_file;
-    NC *nc1;
+    NC *nc;
     int32 num_datasets, num_gatts;
     int32 sdid;
     int v, a;
@@ -613,7 +613,7 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
     LOG((1, "%s: path %s mode %d params %x", __func__, path, mode, parameters));
 
     /* Find pointer to NC. */
-    if ((retval = NC_check_id(ncid, &nc1)))
+    if ((retval = NC_check_id(ncid, &nc)))
         return retval;
 
     /* Check the mode for validity */
@@ -629,9 +629,9 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
         return NC_EHDFERR;
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    if ((retval = nc4_nc4f_list_add(nc1, path, mode)))
+    if ((retval = nc4_nc4f_list_add(nc, path, mode)))
         return retval;
-    h5 = (NC_FILE_INFO_T *)nc1->dispatchdata;
+    h5 = (NC_FILE_INFO_T *)nc->dispatchdata;
     assert(h5 && h5->root_grp);
     h5->no_write = NC_TRUE;
     h5->root_grp->atts_read = 1;

From cb3101c59c4db79d50e93543b29c277526b97856 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 16:13:32 -0600
Subject: [PATCH 14/20] clean up

---
 libhdf5/hdf5open.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index 06d97a65b4..20356b6b93 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -776,6 +776,7 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
             BAIL(NC_EHDFERR);
     }
     else
+    {
         if(nc4_info->mem.diskless) {   /* Process  NC_DISKLESS */
             size_t min_incr = 65536; /* Minimum buffer increment */
             /* Configure FAPL to use the core file driver */
@@ -787,6 +788,7 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
         }
 #ifdef ENABLE_BYTERANGE
         else
+        {
             if(h5->http.iosp) {   /* Arrange to use the byte-range driver */
                 /* Configure FAPL to use the byte-range file driver */
                 if (H5Pset_fapl_http(fapl_id) < 0)
@@ -802,6 +804,8 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
                 if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
                     BAIL(NC_EHDFERR);
             }
+        }
+    }
 
     /* Now read in all the metadata. Some types and dimscale
      * information may be difficult to resolve here, if, for example, a

From fc1d9baf43aa1fa91a263b23ac579e686c22b4d3 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Thu, 1 Aug 2019 18:24:11 -0600
Subject: [PATCH 15/20] fixed spacing

---
 libhdf5/hdf5open.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index 20356b6b93..06d97a65b4 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -776,7 +776,6 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
             BAIL(NC_EHDFERR);
     }
     else
-    {
         if(nc4_info->mem.diskless) {   /* Process  NC_DISKLESS */
             size_t min_incr = 65536; /* Minimum buffer increment */
             /* Configure FAPL to use the core file driver */
@@ -788,7 +787,6 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
         }
 #ifdef ENABLE_BYTERANGE
         else
-        {
             if(h5->http.iosp) {   /* Arrange to use the byte-range driver */
                 /* Configure FAPL to use the byte-range file driver */
                 if (H5Pset_fapl_http(fapl_id) < 0)
@@ -804,8 +802,6 @@ nc4_open_file(const char *path, int mode, void* parameters, int ncid)
                 if ((h5->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
                     BAIL(NC_EHDFERR);
             }
-        }
-    }
 
     /* Now read in all the metadata. Some types and dimscale
      * information may be difficult to resolve here, if, for example, a

From ad086e23d6f1ae8564269f6f8d90b50bc3264158 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Fri, 2 Aug 2019 04:41:36 -0600
Subject: [PATCH 16/20] turned dap test back on

---
 ncdap_test/CMakeLists.txt | 2 +-
 ncdap_test/Makefile.am    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ncdap_test/CMakeLists.txt b/ncdap_test/CMakeLists.txt
index 34606826f4..f9b1706f75 100644
--- a/ncdap_test/CMakeLists.txt
+++ b/ncdap_test/CMakeLists.txt
@@ -39,7 +39,7 @@ IF(ENABLE_TESTS)
     IF(BUILD_UTILITIES)
       add_sh_test(ncdap tst_ber)
       add_sh_test(ncdap tst_remote3)
-#      add_sh_test(ncdap tst_zero_len_var)
+      add_sh_test(ncdap tst_zero_len_var)
 # not yet      add_sh_test(ncdap tst_hyrax)
       add_sh_test(ncdap tst_fillmismatch)
       IF(ENABLE_DAP_LONG_TESTS)
diff --git a/ncdap_test/Makefile.am b/ncdap_test/Makefile.am
index e4952dc7d0..44f1d23f96 100644
--- a/ncdap_test/Makefile.am
+++ b/ncdap_test/Makefile.am
@@ -44,7 +44,7 @@ endif
 
 if ENABLE_DAP_REMOTE_TESTS
 if BUILD_UTILITIES
-TESTS += tst_ber.sh tst_remote3.sh tst_formatx.sh testurl.sh tst_fillmismatch.sh #tst_zero_len_var.sh
+TESTS += tst_ber.sh tst_remote3.sh tst_formatx.sh testurl.sh tst_fillmismatch.sh tst_zero_len_var.sh
 endif
 
 TESTS += test_partvar

From 181f260a20c6893513f02628814a3394783b5258 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Fri, 2 Aug 2019 09:14:35 -0600
Subject: [PATCH 17/20] adding, and starting to use nc4_file_list_add()

---
 include/nc4internal.h |  2 ++
 libhdf4/hdf4file.c    |  6 ++++--
 libsrc4/nc4internal.c | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/include/nc4internal.h b/include/nc4internal.h
index e0c076aa9c..51a6f4218b 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -334,6 +334,8 @@ int nc4_get_typeclass(const NC_FILE_INFO_T *h5, nc_type xtype,
 int nc4_type_free(NC_TYPE_INFO_T *type);
 
 /* These list functions add and delete vars, atts. */
+int nc4_file_list_add(int ncid, const char *path, int mode,
+                      void **dispatchdata);
 int nc4_nc4f_list_add(NC *nc, const char *path, int mode);
 int nc4_nc4f_list_del(NC_FILE_INFO_T *h5);
 int nc4_var_list_add(NC_GRP_INFO_T* grp, const char* name, int ndims,
diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index 36b54cd167..af0a8d7725 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -629,9 +629,11 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
         return NC_EHDFERR;
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    if ((retval = nc4_nc4f_list_add(nc, path, mode)))
+    /* if ((retval = nc4_nc4f_list_add(nc, path, mode))) */
+    /*     return retval; */
+    /* h5 = (NC_FILE_INFO_T *)nc->dispatchdata; */
+    if ((retval = nc4_file_list_add(ncid, path, mode, &h5)))
         return retval;
-    h5 = (NC_FILE_INFO_T *)nc->dispatchdata;
     assert(h5 && h5->root_grp);
     h5->no_write = NC_TRUE;
     h5->root_grp->atts_read = 1;
diff --git a/libsrc4/nc4internal.c b/libsrc4/nc4internal.c
index c57a8b1b42..d3864db574 100644
--- a/libsrc4/nc4internal.c
+++ b/libsrc4/nc4internal.c
@@ -82,6 +82,40 @@ nc4_check_name(const char *name, char *norm_name)
     return NC_NOERR;
 }
 
+/**
+ * @internal Add a file to the list of libsrc4 open files. This is
+ * used by dispatch layers that wish to use the libsrc4 metadata
+ * model, but don't know about struct NC. This is the same as
+ * nc4_nc4f_list_add(), except it takes an ncid instead of an NC *.
+ *
+ * @param ncid The ncid of the file (aka ext_ncid).
+ * @param path The file name of the new file.
+ * @param mode The mode flag.
+ *
+ * @return ::NC_NOERR No error.
+ * @return ::NC_EBADID No NC struct with this ext_ncid.
+ * @return ::NC_ENOMEM Out of memory.
+ * @author Ed Hartnett
+ */
+int
+nc4_file_list_add(int ncid, const char *path, int mode, void **dispatchdata)
+{
+    NC *nc;
+    int ret;
+
+    /* Find NC pointer for this file. */
+    if ((ret = NC_check_id(ncid, &nc)))
+        return ret;
+
+    /* Add necessary structs to hold netcdf-4 file data. */
+    if ((ret = nc4_nc4f_list_add(nc, path, mode)))
+        return ret;
+
+    *dispatchdata = nc->dispatchdata;
+
+    return NC_NOERR;
+}
+
 /**
  * @internal Given an NC pointer, add the necessary stuff for a
  * netcdf-4 file.

From 7ce322a6f1ef5db38bb89d3d2351769f148376d0 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Fri, 2 Aug 2019 09:29:18 -0600
Subject: [PATCH 18/20] now have libhdf5 use nc4_file_list_add()

---
 libhdf4/hdf4file.c    |  5 +----
 libhdf5/hdf5create.c  | 19 ++++++-------------
 libsrc4/nc4internal.c | 21 ++++++++++++++++-----
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index af0a8d7725..2cc120ac13 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -629,10 +629,7 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
         return NC_EHDFERR;
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    /* if ((retval = nc4_nc4f_list_add(nc, path, mode))) */
-    /*     return retval; */
-    /* h5 = (NC_FILE_INFO_T *)nc->dispatchdata; */
-    if ((retval = nc4_file_list_add(ncid, path, mode, &h5)))
+    if ((retval = nc4_file_list_add(ncid, path, mode, (void **)&h5)))
         return retval;
     assert(h5 && h5->root_grp);
     h5->no_write = NC_TRUE;
diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 54c17d8e0a..507b424c13 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -30,7 +30,7 @@ extern int NC4_create_image_file(NC_FILE_INFO_T* h5, size_t);
  * @param initialsz The proposed initial file size (advisory, for
  * in-memory netCDF-4/HDF5 files only).
  * @param parameters extra parameter info (like MPI communicator).
- * @param nc Pointer to an already-existing instance of NC.
+ * @param ncid The already-assigned ncid for this file (aka ext_ncid).
  *
  * @return ::NC_NOERR No error.
  * @return ::NC_EINVAL Invalid input (check cmode).
@@ -41,13 +41,13 @@ extern int NC4_create_image_file(NC_FILE_INFO_T* h5, size_t);
  */
 static int
 nc4_create_file(const char *path, int cmode, size_t initialsz,
-                void* parameters, NC *nc)
+                void* parameters, int ncid)
 {
     hid_t fcpl_id, fapl_id = -1;
     unsigned flags;
     FILE *fp;
     int retval = NC_NOERR;
-    NC_FILE_INFO_T* nc4_info = NULL;
+    NC_FILE_INFO_T *nc4_info;
     NC_HDF5_FILE_INFO_T *hdf5_info;
     NC_HDF5_GRP_INFO_T *hdf5_grp;
 
@@ -59,13 +59,12 @@ nc4_create_file(const char *path, int cmode, size_t initialsz,
     int info_duped = 0; /* Whether the MPI Info object was duplicated */
 #endif /* !USE_PARALLEL4 */
 
-    assert(nc && path);
+    assert(path);
     LOG((3, "%s: path %s mode 0x%x", __func__, path, cmode));
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    if ((retval = nc4_nc4f_list_add(nc, path, (NC_WRITE | cmode))))
+    if ((retval = nc4_file_list_add(ncid, path, NC_WRITE | cmode, (void **)&nc4_info)))
         BAIL(retval);
-    nc4_info = NC4_DATA(nc);
     assert(nc4_info && nc4_info->root_grp);
     nc4_info->root_grp->atts_read = 1;
 
@@ -275,7 +274,6 @@ NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
            size_t *chunksizehintp, void *parameters,
            const NC_Dispatch *dispatch, int ncid)
 {
-    NC *nc_file;
     int res;
 
     assert(path);
@@ -298,13 +296,8 @@ NC4_create(const char* path, int cmode, size_t initialsz, int basepe,
     if (cmode & ILLEGAL_CREATE_FLAGS)
         return NC_EINVAL;
 
-    /* Find pointer to NC. */
-    if ((res = NC_check_id(ncid, &nc_file)))
-        return res;
-    assert(nc_file);
-
     /* Create the netCDF-4/HDF5 file. */
-    res = nc4_create_file(path, cmode, initialsz, parameters, nc_file);
+    res = nc4_create_file(path, cmode, initialsz, parameters, ncid);
 
     return res;
 }
diff --git a/libsrc4/nc4internal.c b/libsrc4/nc4internal.c
index d3864db574..461419c83c 100644
--- a/libsrc4/nc4internal.c
+++ b/libsrc4/nc4internal.c
@@ -86,11 +86,16 @@ nc4_check_name(const char *name, char *norm_name)
  * @internal Add a file to the list of libsrc4 open files. This is
  * used by dispatch layers that wish to use the libsrc4 metadata
  * model, but don't know about struct NC. This is the same as
- * nc4_nc4f_list_add(), except it takes an ncid instead of an NC *.
+ * nc4_nc4f_list_add(), except it takes an ncid instead of an NC *,
+ * and also passes back the dispatchdata pointer.
  *
  * @param ncid The ncid of the file (aka ext_ncid).
  * @param path The file name of the new file.
  * @param mode The mode flag.
+ * @param dispatchdata Void * that gets pointer to dispatch data,
+ * which is the NC_FILE_INFO_T struct allocated for this file and its
+ * metadata. Ignored if NULL. (This is passed as a void to allow
+ * external user-defined formats to use this function.)
  *
  * @return ::NC_NOERR No error.
  * @return ::NC_EBADID No NC struct with this ext_ncid.
@@ -107,18 +112,24 @@ nc4_file_list_add(int ncid, const char *path, int mode, void **dispatchdata)
     if ((ret = NC_check_id(ncid, &nc)))
         return ret;
 
-    /* Add necessary structs to hold netcdf-4 file data. */
+    /* Add necessary structs to hold netcdf-4 file data. This is where
+     * the NC_FILE_INFO_T struct is allocated for the file. */
     if ((ret = nc4_nc4f_list_add(nc, path, mode)))
         return ret;
 
-    *dispatchdata = nc->dispatchdata;
+    /* If the user wants a pointer to the NC_FILE_INFO_T, then provide
+     * it. */
+    if (dispatchdata)
+        *dispatchdata = nc->dispatchdata;
 
     return NC_NOERR;
 }
 
 /**
  * @internal Given an NC pointer, add the necessary stuff for a
- * netcdf-4 file.
+ * netcdf-4 file. This allocates the NC_FILE_INFO_T struct for the
+ * file, which is used by libhdf5 and libhdf4 (and perhaps other
+ * future dispatch layers) to hold the metadata for the file.
  *
  * @param nc Pointer to file's NC struct.
  * @param path The file name of the new file.
@@ -137,7 +148,7 @@ nc4_nc4f_list_add(NC *nc, const char *path, int mode)
     assert(nc && !NC4_DATA(nc) && path);
 
     /* We need to malloc and initialize the substructure
-       NC_HDF_FILE_INFO_T. */
+       NC_FILE_INFO_T. */
     if (!(h5 = calloc(1, sizeof(NC_FILE_INFO_T))))
         return NC_ENOMEM;
     nc->dispatchdata = h5;

From 3c9a25b688678079d6acd091bc01b48971befc86 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Sat, 3 Aug 2019 09:04:58 -0600
Subject: [PATCH 19/20] whitespace cleanup

---
 libhdf5/hdf5create.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libhdf5/hdf5create.c b/libhdf5/hdf5create.c
index 507b424c13..39b3f3a614 100644
--- a/libhdf5/hdf5create.c
+++ b/libhdf5/hdf5create.c
@@ -63,7 +63,8 @@ nc4_create_file(const char *path, int cmode, size_t initialsz,
     LOG((3, "%s: path %s mode 0x%x", __func__, path, cmode));
 
     /* Add necessary structs to hold netcdf-4 file data. */
-    if ((retval = nc4_file_list_add(ncid, path, NC_WRITE | cmode, (void **)&nc4_info)))
+    if ((retval = nc4_file_list_add(ncid, path, NC_WRITE | cmode,
+                                    (void **)&nc4_info)))
         BAIL(retval);
     assert(nc4_info && nc4_info->root_grp);
     nc4_info->root_grp->atts_read = 1;

From d1ddc9281876be4e5ae39cf32005a3eb006d0205 Mon Sep 17 00:00:00 2001
From: edwardhartnett <edwardjameshartnett@gmail.com>
Date: Sat, 3 Aug 2019 12:25:46 -0600
Subject: [PATCH 20/20] fixed prototype

---
 include/nc3dispatch.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/nc3dispatch.h b/include/nc3dispatch.h
index e9b9ad5825..998ee4314d 100644
--- a/include/nc3dispatch.h
+++ b/include/nc3dispatch.h
@@ -59,7 +59,7 @@ extern "C" {
     extern int
     NC3_open(const char *path, int mode,
              int basepe, size_t *chunksizehintp,
-             void* mpidata, const NC_Dispatch*, NC* ncp);
+             void* mpidata, const NC_Dispatch*, int ncid);
 
     extern int
     NC3_new_nc(NC**);