Minor improvements to integrated NXmx workflow

broker/OpenAPIConvert.cpp

@@ -795,7 +795,7 @@ org::openapitools::server::model::File_writer_format Convert(FileWriterFormat in
     org::openapitools::server::model::File_writer_format ret;
     switch (input) {
         case FileWriterFormat::DataOnly:
-            ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::NONE);
+            ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXONLYDATA);
             break;
         case FileWriterFormat::NXmxLegacy:
             ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXLEGACY);
@@ -803,6 +803,9 @@ org::openapitools::server::model::File_writer_format Convert(FileWriterFormat in
         case FileWriterFormat::NXmxVDS:
             ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXVDS);
             break;
+        case FileWriterFormat::NXmxIntegrated:
+            ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXINTEGRATED);
+            break;
         case FileWriterFormat::CBF:
             ret.setValue(org::openapitools::server::model::File_writer_format::eFile_writer_format::CBF);
             break;
@@ -820,12 +823,14 @@ org::openapitools::server::model::File_writer_format Convert(FileWriterFormat in
 
 FileWriterFormat Convert(const org::openapitools::server::model::File_writer_format& input) {
     switch (input.getValue()) {
-        case org::openapitools::server::model::File_writer_format::eFile_writer_format::NONE:
+        case org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXONLYDATA:
             return FileWriterFormat::DataOnly;
         case org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXLEGACY:
             return FileWriterFormat::NXmxLegacy;
         case org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXVDS:
             return FileWriterFormat::NXmxVDS;
+        case org::openapitools::server::model::File_writer_format::eFile_writer_format::NXMXINTEGRATED:
+            return FileWriterFormat::NXmxIntegrated;
         case org::openapitools::server::model::File_writer_format::eFile_writer_format::CBF:
             return FileWriterFormat::CBF;
         case org::openapitools::server::model::File_writer_format::eFile_writer_format::TIFF:

broker/gen/model/File_writer_format.cpp

@@ -75,8 +75,8 @@ void to_json(nlohmann::json& j, const File_writer_format& o)
         case File_writer_format::eFile_writer_format::INVALID_VALUE_OPENAPI_GENERATED:
             j = "INVALID_VALUE_OPENAPI_GENERATED";
             break;
-        case File_writer_format::eFile_writer_format::NONE:
-            j = "None";
+        case File_writer_format::eFile_writer_format::NXMXONLYDATA:
+            j = "NXmxOnlyData";
             break;
         case File_writer_format::eFile_writer_format::NXMXLEGACY:
             j = "NXmxLegacy";
@@ -84,6 +84,9 @@ void to_json(nlohmann::json& j, const File_writer_format& o)
         case File_writer_format::eFile_writer_format::NXMXVDS:
             j = "NXmxVDS";
             break;
+        case File_writer_format::eFile_writer_format::NXMXINTEGRATED:
+            j = "NXmxIntegrated";
+            break;
         case File_writer_format::eFile_writer_format::CBF:
             j = "CBF";
             break;
@@ -100,8 +103,8 @@ void from_json(const nlohmann::json& j, File_writer_format& o)
 {
     
     auto s = j.get<std::string>();
-    if (s == "None") {
-     o.setValue(File_writer_format::eFile_writer_format::NONE);
+    if (s == "NXmxOnlyData") {
+     o.setValue(File_writer_format::eFile_writer_format::NXMXONLYDATA);
     } 
     else if (s == "NXmxLegacy") {
      o.setValue(File_writer_format::eFile_writer_format::NXMXLEGACY);
@@ -109,6 +112,9 @@ void from_json(const nlohmann::json& j, File_writer_format& o)
     else if (s == "NXmxVDS") {
      o.setValue(File_writer_format::eFile_writer_format::NXMXVDS);
     } 
+    else if (s == "NXmxIntegrated") {
+     o.setValue(File_writer_format::eFile_writer_format::NXMXINTEGRATED);
+    } 
     else if (s == "CBF") {
      o.setValue(File_writer_format::eFile_writer_format::CBF);
     } 

broker/gen/model/File_writer_format.h

@@ -12,7 +12,7 @@
 /*
  * File_writer_format.h
  *
- * None - no master file written NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling 
+ * NoFileWritten - no files are written at all NXmxOnlyData - only data files are written, no master file NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling NXmxIntegrated - single HDF5 per dataset CBF - CBF format (limited metadata) TIFF - TIFF format (no metadata) 
  */
 
 #ifndef File_writer_format_H_
@@ -25,7 +25,7 @@ namespace org::openapitools::server::model
 {
 
 /// <summary>
-/// None - no master file written NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling 
+/// NoFileWritten - no files are written at all NXmxOnlyData - only data files are written, no master file NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling NXmxIntegrated - single HDF5 per dataset CBF - CBF format (limited metadata) TIFF - TIFF format (no metadata) 
 /// </summary>
 class  File_writer_format
 {
@@ -38,9 +38,10 @@ public:
     // Avoiding name clashes with user defined
     // enum values
     INVALID_VALUE_OPENAPI_GENERATED = 0,
-    NONE, 
+    NXMXONLYDATA, 
     NXMXLEGACY, 
     NXMXVDS, 
+    NXMXINTEGRATED, 
     CBF, 
     TIFF, 
     NOFILEWRITTEN

broker/jfjoch_api.yaml

@@ -642,17 +642,22 @@ components:
     file_writer_format:
       type: string
       enum:
-        - "None"
+        - "NXmxOnlyData"
         - "NXmxLegacy"
         - "NXmxVDS"
+        - "NXmxIntegrated"
         - "CBF"
         - "TIFF"
         - "NoFileWritten"
       default: "NXmxLegacy"
       description: |
-        None - no master file written
+        NoFileWritten - no files are written at all
+        NXmxOnlyData - only data files are written, no master file
         NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia  
         NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling
+        NXmxIntegrated - single HDF5 per dataset
+        CBF - CBF format (limited metadata)
+        TIFF - TIFF format (no metadata)
     file_writer_settings:
       type: object
       properties:

common/DiffractionExperiment.cpp

@@ -1083,7 +1083,8 @@ DiffractionExperiment &DiffractionExperiment::ImagesPerFile(int64_t input) {
 int64_t DiffractionExperiment::GetImagesPerFile() const {
     auto tmp = dataset.GetImagesPerFile();
 
-    if (tmp == 0)
+    if (tmp == 0
+        || file_writer.GetHDF5MasterFormatVersion() == FileWriterFormat::NXmxIntegrated)
         return GetImageNum();
     else
         return tmp;

common/JFJochMessages.h

@@ -33,7 +33,7 @@ enum class FileWriterFormat : int {
     DataOnly = 0,
     NXmxLegacy = 1,
     NXmxVDS = 2,
-    // TODO: NXmxTR = 3
+    NXmxIntegrated = 3,
     CBF = 4,
     TIFF = 5,
     NoFile = 6

docs/python_client/docs/FileWriterFormat.md

@@ -1,15 +1,17 @@
 # FileWriterFormat
 
-None - no master file written NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling 
+NoFileWritten - no files are written at all NXmxOnlyData - only data files are written, no master file NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia   NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling NXmxIntegrated - single HDF5 per dataset CBF - CBF format (limited metadata) TIFF - TIFF format (no metadata) 
 
 ## Enum
 
-* `NONE` (value: `'None'`)
+* `NXMXONLYDATA` (value: `'NXmxOnlyData'`)
 
 * `NXMXLEGACY` (value: `'NXmxLegacy'`)
 
 * `NXMXVDS` (value: `'NXmxVDS'`)
 
+* `NXMXINTEGRATED` (value: `'NXmxIntegrated'`)
+
 * `CBF` (value: `'CBF'`)
 
 * `TIFF` (value: `'TIFF'`)

frontend/src/components/FileWriterSettings.tsx

@@ -30,8 +30,8 @@ function stringToEnum(value: string): file_writer_format {
         (v) => v === value
     ) as file_writer_format;
 
-    // If no match is found, default to file_writer_format.NONE
-    return enumValue || file_writer_format.NONE;
+    // If no match is found, default to file_writer_format.NXMX_ONLY_DATA
+    return enumValue || file_writer_format.NXMX_ONLY_DATA;
 }
 
 
@@ -109,7 +109,8 @@ class FileWriterSettings extends React.Component<MyProps, MyState> {
                     >
                         <MenuItem value={file_writer_format.NXMX_LEGACY}>NXmx HDF5 master file with soft links (DECTRIS file writer compatibility)</MenuItem>
                         <MenuItem value={file_writer_format.NXMX_VDS}>NXmx HDF5 master file with virtual datasets</MenuItem>
-                        <MenuItem value={file_writer_format.NONE}>No NXmx HDF5 master file (only data files)</MenuItem>
+                        <MenuItem value={file_writer_format.NXMX_INTEGRATED}Single HDF5 file with data and metadata</MenuItem>
+                        <MenuItem value={file_writer_format.NXMX_ONLY_DATA}>No NXmx HDF5 master file (only data files)</MenuItem>
                         <MenuItem value={file_writer_format.CBF}>miniCBF (only data files; limited metadata)</MenuItem>
                         <MenuItem value={file_writer_format.TIFF}>TIFF (only data files; no metadata)</MenuItem>
                         <MenuItem value={file_writer_format.NO_FILE_WRITTEN}>No files saved</MenuItem>

frontend/src/openapi/models/file_writer_format.ts

@@ -4,15 +4,20 @@
 /* eslint-disable */
 
 /**
- * None - no master file written
+ * NoFileWritten - no files are written at all
+ * NXmxOnlyData - only data files are written, no master file
  * NXmxLegacy - legacy format with soft links to data files in the master file; necessary for DECTRIS Albula 4.0 and DECTRIS Neggia
  * NXmxVDS - newer format with virtual dataset linking data files in the master file, also includes better metadata handling
+ * NXmxIntegrated - single HDF5 per dataset
+ * CBF - CBF format (limited metadata)
+ * TIFF - TIFF format (no metadata)
  *
  */
 export enum file_writer_format {
-    NONE = 'None',
+    NXMX_ONLY_DATA = 'NXmxOnlyData',
     NXMX_LEGACY = 'NXmxLegacy',
     NXMX_VDS = 'NXmxVDS',
+    NXMX_INTEGRATED = 'NXmxIntegrated',
     CBF = 'CBF',
     TIFF = 'TIFF',
     NO_FILE_WRITTEN = 'NoFileWritten',

tests/HDF5WritingTest.cpp

@@ -13,6 +13,64 @@
 
 using namespace std::literals::chrono_literals;
 
+TEST_CASE("HDF5Group_create_reopen_and_fail", "[HDF5][Unit]") {
+    {
+        HDF5File file("scratch_group_reopen.h5");
+
+        REQUIRE_NOTHROW(HDF5Group(file, "/group1"));
+        REQUIRE(file.Exists("/group1"));
+
+        REQUIRE_NOTHROW(HDF5Group(file, "/group1"));
+        REQUIRE(file.Exists("/group1"));
+
+        REQUIRE_THROWS(HDF5Group(file, "/missing_parent/group2"));
+    }
+
+    remove("scratch_group_reopen.h5");
+    REQUIRE(H5Fget_obj_count(H5F_OBJ_ALL, H5F_OBJ_ALL) == 0);
+}
+
+TEST_CASE("HDF5Attr_string_update", "[HDF5][Unit]") {
+    const std::string first_value = "abc";
+    const std::string second_value = "a much longer attribute value";
+
+    {
+        HDF5File file("scratch_attr_string_update.h5");
+        REQUIRE_NOTHROW(file.Attr("str_attr", first_value));
+        REQUIRE_NOTHROW(file.Attr("str_attr", second_value));
+    }
+
+    {
+        HDF5ReadOnlyFile file("scratch_attr_string_update.h5");
+        REQUIRE(file.ReadAttrStr("str_attr") == second_value);
+    }
+
+    remove("scratch_attr_string_update.h5");
+    REQUIRE(H5Fget_obj_count(H5F_OBJ_ALL, H5F_OBJ_ALL) == 0);
+}
+
+TEST_CASE("HDF5Attr_int64_update", "[HDF5][Unit]") {
+    const int64_t first_value = -1234567890123LL;
+    const int64_t second_value = 9876543210123LL;
+
+    {
+        HDF5File file("scratch_attr_int64_update.h5");
+        REQUIRE_NOTHROW(file.Attr("int_attr", first_value));
+        REQUIRE(file.ReadAttrInt("int_attr") == first_value);
+
+        REQUIRE_NOTHROW(file.Attr("int_attr", second_value));
+        REQUIRE(file.ReadAttrInt("int_attr") == second_value);
+    }
+
+    {
+        HDF5ReadOnlyFile file("scratch_attr_int64_update.h5");
+        REQUIRE(file.ReadAttrInt("int_attr") == second_value);
+    }
+
+    remove("scratch_attr_int64_update.h5");
+    REQUIRE(H5Fget_obj_count(H5F_OBJ_ALL, H5F_OBJ_ALL) == 0);
+}
+
 TEST_CASE("HDF5DataSet_scalar", "[HDF5][Unit]") {
     uint16_t tmp_scalar = 16788;
     {

writer/HDF5NXmx.cpp

@@ -695,7 +695,7 @@ void NXmx::Finalize(const EndMessage &end) {
 
     if (start_message.file_format == FileWriterFormat::NXmxVDS)
         LinkToData_VDS(start_message, end);
-    else
+    else if (start_message.file_format == FileWriterFormat::NXmxLegacy)
         LinkToData(start_message, end);
 
     if (end.rotation_lattice)
@@ -731,3 +731,7 @@ void NXmx::UserData(const StartMessage &start) {
         }
     }
 }
+
+HDF5File *NXmx::GetFile() {
+    return hdf5_file.get();
+}

writer/HDF5NXmx.h

@@ -58,6 +58,8 @@ public:
     NXmx& operator=(const NXmx &other) = delete;
     void Finalize(const EndMessage &end);
     void WriteCalibration(const CompressedImage &image);
+
+    HDF5File *GetFile();
 };
 
 #endif //JUNGFRAUJOCH_HDF5NXMX_H

writer/HDF5Objects.cpp

@@ -315,76 +315,119 @@ void HDF5Fapl::SetVersionTo1p10orNewer() {
     H5Pset_libver_bounds(id, H5F_LIBVER_V110, H5F_LIBVER_LATEST);
 }
 
+template <typename T>
+static HDF5Object& WriteOrCreateScalarAttr(HDF5Object& object, const std::string& name, const T& val) {
+    HDF5DataSpace dataspace;
+    HDF5DataType datatype(val);
+
+    hid_t attr_id = -1;
+
+    if (H5Aexists(object.GetID(), name.c_str()) > 0) {
+        attr_id = H5Aopen(object.GetID(), name.c_str(), H5P_DEFAULT);
+        if (attr_id < 0)
+            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);
+
+        hid_t existing_type = H5Aget_type(attr_id);
+        if (existing_type < 0) {
+            H5Aclose(attr_id);
+            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get attribute type " + name);
+        }
+
+        const bool recreate =
+                (H5Tget_class(existing_type) != H5Tget_class(datatype.GetID())) ||
+                (H5Tget_size(existing_type) != H5Tget_size(datatype.GetID()));
+
+        H5Tclose(existing_type);
+        H5Aclose(attr_id);
+
+        if (recreate) {
+            if (H5Adelete(object.GetID(), name.c_str()) < 0)
+                throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot delete attribute " + name);
+
+            attr_id = H5Acreate2(object.GetID(), name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
+        } else {
+            attr_id = H5Aopen(object.GetID(), name.c_str(), H5P_DEFAULT);
+        }
+    } else {
+        attr_id = H5Acreate2(object.GetID(), name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
+    }
+
+    if (attr_id < 0)
+        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create/open attribute " + name);
+
+    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
+    H5Aclose(attr_id);
+
+    if (ret < 0)
+        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute write unsuccessful");
+    return object;
+}
+
 HDF5Object & HDF5Object::Attr(const std::string &name, const std::string &val) {
     HDF5DataSpace dataspace;
     HDF5DataType datatype(val);
 
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
+    hid_t attr_id = -1;
+
+    if (H5Aexists(id, name.c_str()) > 0) {
+        attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
+        if (attr_id < 0)
+            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);
+
+        hid_t existing_type = H5Aget_type(attr_id);
+        if (existing_type < 0) {
+            H5Aclose(attr_id);
+            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get attribute type " + name);
+        }
+
+        const bool recreate =
+                (H5Tget_class(existing_type) != H5T_STRING) ||
+                (H5Tget_size(existing_type) < val.length() + 1);
+
+        H5Tclose(existing_type);
+        H5Aclose(attr_id);
+
+        if (recreate) {
+            if (H5Adelete(id, name.c_str()) < 0)
+                throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot delete attribute " + name);
+
+            attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
+        } else {
+            attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
+        }
+    } else {
+        attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
+    }
+
+    if (attr_id < 0)
+        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create/open attribute " + name);
+
     herr_t ret = H5Awrite(attr_id, datatype.GetID(), val.c_str());
     H5Aclose(attr_id);
 
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute write unsuccessful");
+    if (ret < 0)
+        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute write unsuccessful");
     return *this;
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, int32_t val) {
-    HDF5DataSpace dataspace;
-    HDF5DataType datatype(val);
-
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
-    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
-    H5Aclose(attr_id);
-
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
-    return *this;
+    return WriteOrCreateScalarAttr(*this, name, val);
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, uint32_t val) {
-    HDF5DataSpace dataspace;
-    HDF5DataType datatype(val);
-
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
-    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
-    H5Aclose(attr_id);
-
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
-    return *this;
+    return WriteOrCreateScalarAttr(*this, name, val);
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, int64_t val) {
-    HDF5DataSpace dataspace;
-    HDF5DataType datatype(val);
-
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
-    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
-    H5Aclose(attr_id);
-
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
-    return *this;
+    return WriteOrCreateScalarAttr(*this, name, val);
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, uint64_t val) {
-    HDF5DataSpace dataspace;
-    HDF5DataType datatype(val);
-
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
-    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
-    H5Aclose(attr_id);
-
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
-    return *this;
+    return WriteOrCreateScalarAttr(*this, name, val);
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, double val) {
-    HDF5DataSpace dataspace;
-    HDF5DataType datatype(val);
-
-    hid_t attr_id = H5Acreate2(id, name.c_str(), datatype.GetID(), dataspace.GetID(), H5P_DEFAULT, H5P_DEFAULT);
-    herr_t ret = H5Awrite(attr_id, datatype.GetID(), &val);
-    H5Aclose(attr_id);
-
-    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
-    return *this;
+    return WriteOrCreateScalarAttr(*this, name, val);
 }
 
 HDF5Object & HDF5Object::Attr(const std::string &name, const std::vector<double> &val) {
@@ -632,14 +675,19 @@ HDF5Group::HDF5Group(const HDF5Object& parent, const std::string &name) : HDF5Gr
 }
 
 HDF5Group::HDF5Group(const HDF5Object& parent, const char *name) : HDF5Object() {
-    id = H5Gcreate(parent.GetID(), name, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+    if (H5Lexists(parent.GetID(), name, H5P_DEFAULT) > 0)
+        id = H5Gopen(parent.GetID(), name, H5P_DEFAULT);
+    else
+        id = H5Gcreate(parent.GetID(), name, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+
+    if (id < 0)
+        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open/create HDF5 group " + std::string(name));
 }
 
 HDF5Group::~HDF5Group() {
     H5Gclose(id);
 }
 
-
 HDF5File::HDF5File(const std::string& filename, bool v1_10) : HDF5Object() {
     HDF5Fapl fapl;