Do subset write through H5Tpack + H5Tconvert

src/rest_vol.h

@@ -451,22 +451,6 @@ typedef enum {
     H5T_SUBSET_CAP            /* Must be the last value */
 } RV_subset_t;
 
-/* Information about members of a compound type for subsetting */
-typedef struct RV_compound_info_t {
-    RV_subset_t subset_info; /* Subset relationship between src and dst */
-
-    int    nmembers;       /* Number of offset/length pairs in the subset */
-    int    nalloc;         /* Number of offset/length pairs allocated */
-    size_t full_type_size; /* Size of compound type with all fields */
-
-    size_t *src_offsets; /* Offsets of fields within source datatype */
-    size_t *lengths;     /* Lengths of members (in both datatypes) */
-
-    size_t subset_buf_size;
-    void  *subset_buf;
-    void  *subset_ptr; /* Pointer for writing into the subset buffer */
-} RV_compound_info_t;
-
 /*
  * A struct which is used to return a link's name or the size of
  * a link's name when calling H5Lget_name_by_idx.
@@ -600,6 +584,10 @@ typedef struct dataset_write_info {
     char       *base64_encoded_values;
     curl_off_t  write_len;
     upload_info uinfo;
+
+    /* If writing using compound subsetting, this is a packed version of the
+     *  compound type containing only the selected members */
+    hid_t dense_cmpd_subset_dtype_id;
 } dataset_write_info;
 
 typedef struct dataset_read_info {
@@ -631,9 +619,6 @@ typedef struct dataset_transfer_info {
     void *tconv_buf;
     void *bkg_buf;
 
-    /* Fields for writing to subsets of compound types */
-    RV_compound_info_t compound_info;
-
     transfer_type_t transfer_type;
 
     union {
@@ -795,11 +780,10 @@ herr_t RV_convert_datatype_to_JSON(hid_t type_id, char **type_body, size_t *type
 herr_t RV_JSON_escape_string(const char *in, char *out, size_t *out_size);
 
 /* Determine if a read from file to mem dtype is a compound subset read */
-herr_t RV_get_compound_subset_info(hid_t src_type_id, hid_t dst_type_id, RV_subset_t *subset_info);
+herr_t RV_get_cmpd_subset_type(hid_t src_type_id, hid_t dst_type_id, RV_subset_t *subset_info);
 
 /* Helper to get information about members in dst that are included in src compound */
-herr_t RV_get_compound_subset_members(hid_t src_type_id, hid_t dst_type_id,
-                                      RV_compound_info_t *compound_info);
+herr_t RV_get_cmpd_subset_nmembers(hid_t src_type_id, hid_t dst_type_id, size_t *num_cmpd_members);
 
 #define SERVER_VERSION_MATCHES_OR_EXCEEDS(version, major_needed, minor_needed, patch_needed)                 \
     (version.major > major_needed) || (version.major == major_needed && version.minor > minor_needed) ||     \