Jungfraujoch/writer/HDF5Objects.cpp

// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include <cstring>
#include <filesystem>
#include <iostream>

#include <bitshuffle/bshuf_h5filter.h>
#include "HDF5Objects.h"

// HDF Group contributed LZ4 filter, the one DECTRIS Eiger firmware 1.x wrote its images with.
// Read-only here: bshuf_h5filter.h defines 32008 for bitshuffle but nothing defines this one.
#define LZ4_H5FILTER 32004

#include "H5FDpoison_sec2.h"

std::mutex hdf5_mutex;

static void HDF5PoisonCallback(
    const char *filename,
    const char *operation,
    int error_number,
    void *user_data
) {
    std::cerr << "HDF5 Poison callback triggered: filename=" << filename << ", operation=" << operation << ", error_number=" << error_number << std::endl;
}

hid_t HDF5Id::GetID() const {
    return id;
}

HDF5Id::HDF5Id(HDF5Id &&other) noexcept {
    id = other.id;
    other.id = -1;
}

HDF5Id::HDF5Id(const HDF5Id &other) {
    id = other.id;
    if (H5Iis_valid(id)) {
        if (H5Iinc_ref(id) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot increment HDF5 Counter");
    }
}

HDF5DataSpace::HDF5DataSpace(ScalarTag) : HDF5Id() {
    id = H5Screate(H5S_SCALAR);
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create scalar dataspace");

    ndims = 0;
}

HDF5DataSpace::HDF5DataSpace(const std::vector<hsize_t> &dims, const std::vector<hsize_t> &max_dims) : HDF5Id() {
    if (dims.empty())
        throw JFJochException(JFJochExceptionCategory::HDF5, "Dimension vector empty");

    if (max_dims.empty()) {
        if (dims[0] == 0)
            throw JFJochException(JFJochExceptionCategory::HDF5, "Value dimension cannot be 0");

        id = H5Screate_simple(dims.size(), dims.data(), nullptr);
    } else {
        if (max_dims.size() != dims.size())
            throw JFJochException(JFJochExceptionCategory::HDF5, "Discrepancy in size of dims/max_dims");
        id = H5Screate_simple(dims.size(), dims.data(), max_dims.data());
    }
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create dataspace");

    ndims = dims.size();
}

HDF5DataSpace::HDF5DataSpace(const HDF5DataSet &data_set) : HDF5Id() {
    id = H5Dget_space(data_set.GetID());

    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open dataspace");

    int tmp = H5Sget_simple_extent_ndims(id);

    if (tmp < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot check dimensions of dataspace");

    ndims = tmp;
}

std::vector<hsize_t> HDF5DataSpace::GetDimensions() const {
    std::vector<hsize_t> dims(ndims);
    int tmp = H5Sget_simple_extent_dims(id, dims.data(), nullptr);
    if ((tmp < 0) || (tmp != ndims))
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot check dimensions of dataspace");
    return dims;
}

void HDF5DataSpace::SelectHyperslab(const std::vector<hsize_t> &start, const std::vector<hsize_t> &size) {
    if ((start.size() != ndims) || (size.size() != ndims))
        throw JFJochException(JFJochExceptionCategory::HDF5, "Arrays are inconsistent with dataspace dimension number " + std::to_string(ndims));

    if (H5Sselect_hyperslab(id, H5S_SELECT_SET, start.data(), NULL, size.data(), NULL) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot select hyperslab");
}

void HDF5DataSpace::SelectHyperslabWithStride(const std::vector<hsize_t> &start, const std::vector<hsize_t> &size,
                                              const std::vector<hsize_t> &stride) {
    if ((start.size() != ndims) || (stride.size() != ndims) || (size.size() != ndims))
        throw JFJochException(JFJochExceptionCategory::HDF5, "Arrays are inconsistent with dataspace dimension number");

    if (H5Sselect_hyperslab(id, H5S_SELECT_SET, start.data(), stride.data(), size.data(), NULL) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot select hyperslab");
}

HDF5DataSpace::~HDF5DataSpace() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Sclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

uint8_t HDF5DataSpace::GetNumOfDimensions() const {
    return ndims;
}

HDF5DataType::HDF5DataType(CompressedImageMode mode) : HDF5Id() {
    switch (mode) {

        case CompressedImageMode::Int8:
            id = H5Tcopy(H5T_NATIVE_INT8);
            break;
        case CompressedImageMode::Int16:
            id = H5Tcopy(H5T_NATIVE_INT16);
            break;
        case CompressedImageMode::Int32:
            id = H5Tcopy(H5T_NATIVE_INT32);
            break;
        case CompressedImageMode::RGB:
        case CompressedImageMode::Uint8:
            id = H5Tcopy(H5T_NATIVE_UINT8);
            break;
        case CompressedImageMode::Uint16:
            id = H5Tcopy(H5T_NATIVE_UINT16);
            break;
        case CompressedImageMode::Uint32:
            id = H5Tcopy(H5T_NATIVE_UINT32);
            break;
        case CompressedImageMode::Float16:
            id = H5Tcopy(H5T_IEEE_F16LE);
            break;
        case CompressedImageMode::Float32:
            id = H5Tcopy(H5T_IEEE_F32LE);
            break;
        case CompressedImageMode::Float64:
            id = H5Tcopy(H5T_IEEE_F64LE);
            break;
    }
}

HDF5DataType::HDF5DataType(double val) : HDF5Id() {
    id = H5Tcopy(H5T_IEEE_F64LE);
}

HDF5DataType::HDF5DataType(float val) : HDF5Id() {
    id = H5Tcopy(H5T_IEEE_F32LE);
}

HDF5DataType::HDF5DataType(bool val) : HDF5Id() {
    id = H5Tcopy(H5T_NATIVE_HBOOL);
}

HDF5DataType::HDF5DataType(uint8_t val) : HDF5DataType(1, false) {}
HDF5DataType::HDF5DataType(int8_t val) : HDF5DataType(1, true) {}

HDF5DataType::HDF5DataType(uint16_t val) : HDF5DataType(2, false) {}
HDF5DataType::HDF5DataType(int16_t val) : HDF5DataType(2, true) {}

HDF5DataType::HDF5DataType(uint32_t val) : HDF5DataType(4, false) {}
HDF5DataType::HDF5DataType(int32_t val) : HDF5DataType(4, true) {}

HDF5DataType::HDF5DataType(uint64_t val) : HDF5DataType(8, false) {}
HDF5DataType::HDF5DataType(int64_t val) : HDF5DataType(8, true) {}

HDF5DataType::HDF5DataType(uint64_t size_in_bytes, bool is_signed) : HDF5Id() {
    switch (size_in_bytes) {
        case 1:
            if (is_signed)
                id = H5Tcopy(H5T_NATIVE_INT8);
            else
                id = H5Tcopy(H5T_NATIVE_UINT8);
            break;
        case 2:
            if (is_signed)
                id = H5Tcopy(H5T_NATIVE_INT16);
            else
                id = H5Tcopy(H5T_NATIVE_UINT16);
            break;
        case 4:
            if (is_signed)
                id = H5Tcopy(H5T_NATIVE_INT32);
            else
                id = H5Tcopy(H5T_NATIVE_UINT32);
            break;
        case 8:
            if (is_signed)
                id = H5Tcopy(H5T_NATIVE_INT64);
            else
                id = H5Tcopy(H5T_NATIVE_UINT64);
            break;
        default:
            throw JFJochException(JFJochExceptionCategory::HDF5, "Type outside of standard types");
    }
}

HDF5DataType::HDF5DataType(const std::string& str) : HDF5Id() {
    id = H5Tcopy(H5T_C_S1);
    H5Tset_size(id, str.length() + 1);
}

HDF5DataType::HDF5DataType(const char * str) : HDF5Id() {
    id = H5Tcopy(H5T_C_S1);
    size_t length = strnlen(str,512);
    H5Tset_size(id, length + 1);
}

HDF5DataType::HDF5DataType(const HDF5DataSet &data_set) :HDF5Id() {
    id = H5Dget_type(data_set.GetID());
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open HDF5 data type");
}

HDF5DataType::~HDF5DataType() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Tclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

size_t HDF5DataType::GetElemSize() const {
    return H5Tget_size(id);
}

bool HDF5DataType::IsSigned() const {
    if (IsFloat())
        return true;
    else if (IsInteger())
        return H5Tget_sign(id) == H5T_SGN_2;
    else
        return false;
}

bool HDF5DataType::IsInteger() const {
    return H5Tget_class(id) == H5T_INTEGER;
}

bool HDF5DataType::IsFloat() const {
    return H5Tget_class(id) == H5T_FLOAT;
}

HDF5Dcpl::HDF5Dcpl() : HDF5Id() {
    id = H5Pcreate(H5P_DATASET_CREATE);
    ndim = 0;
    layout = HDF5DataSetLayout::CONTIGUOUS;
}

HDF5Dcpl::HDF5Dcpl(const HDF5DataSet &data_set) : HDF5Id() {
    id = H5Dget_create_plist(data_set.GetID());

    // Check if chunking is enabled
    H5D_layout_t h5_layout = H5Pget_layout(id);
    if (h5_layout == H5D_VIRTUAL)
        layout = HDF5DataSetLayout::VIRTUAL;
    else if (h5_layout == H5D_CHUNKED) {
        layout = HDF5DataSetLayout::CHUNKED;
        ndim = H5Pget_chunk(id, 0, nullptr);
        if (ndim <= 0) {
            H5Pclose(id);
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Error getting number of chunk dimensions");
        }
    } else
        layout = HDF5DataSetLayout::CONTIGUOUS;
}

HDF5Dcpl::~HDF5Dcpl() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Pclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

void HDF5Dcpl::SetChunking(const std::vector<hsize_t> &dims) {
    layout = HDF5DataSetLayout::CHUNKED;
    if ((dims.empty()) || dims[0] == 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Value dimension cannot be 0");
    ndim = dims.size();
    if (H5Pset_chunk(id, dims.size(), dims.data()) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot set chunking");
}

std::vector<hsize_t> HDF5Dcpl::GetChunking() {
    if (ndim <= 0)
        return {};

    std::vector<hsize_t> ret(ndim);
    if (H5Pget_chunk(id, ndim, ret.data()) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get chunk dimensions");

    return ret;
}

uint8_t HDF5Dcpl::GetNumOfDimensions() const {
    return ndim;
}

void HDF5Dcpl::SetFillValue32(int32_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_INT32, &val);
}

void HDF5Dcpl::SetFillValue16(int16_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_INT16, &val);
}

void HDF5Dcpl::SetFillValue8(int8_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_INT8, &val);
}

void HDF5Dcpl::SetFillValueU32(uint32_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_UINT32, &val);
}

void HDF5Dcpl::SetFillValueU16(uint16_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_UINT16, &val);
}

void HDF5Dcpl::SetFillValueU8(uint8_t val) {
    H5Pset_fill_value(id, H5T_NATIVE_UINT8, &val);
}

void HDF5Dcpl::SetVirtual(const std::string &path, const std::string &dataset, const HDF5DataSpace &src_dataspace, const HDF5DataSpace &dest_dataspace) {
    layout = HDF5DataSetLayout::VIRTUAL;
    std::string filename = ExtractFilename(path);
    if (H5Pset_virtual(id, dest_dataspace.GetID(), filename.c_str(), dataset.c_str(), src_dataspace.GetID()) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot set virtual mapping");
}

HDF5DataSetLayout HDF5Dcpl::GetLayout() const {
    return layout;
}

HDF5Fapl::HDF5Fapl() : HDF5Id() {
    id = H5Pcreate(H5P_FILE_ACCESS);
}

HDF5Fapl::~HDF5Fapl() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Pclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

void HDF5Fapl::SetVersionTo1p10orNewer() {
    H5Pset_libver_bounds(id, H5F_LIBVER_V110, H5F_LIBVER_LATEST);
}

void HDF5Fapl::SetCloseStrong() {
    H5Pset_fclose_degree(id, H5F_CLOSE_STRONG);
}

void HDF5Fapl::SetPoisonSec2() {
    if (H5Pset_fapl_poison_sec2(id) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Cannot enable poisoned sec2 HDF5 VFD");
}

template <typename T>
static HDF5Object& WriteOrCreateScalarAttr(HDF5Object& object, const std::string& name, const T& val) {
    HDF5DataSpace dataspace(HDF5DataSpace::Scalar);
    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(HDF5DataSpace::Scalar);
    HDF5DataType datatype(val);

    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");
    return *this;
}

HDF5Object & HDF5Object::Attr(const std::string &name, int32_t val) {
    return WriteOrCreateScalarAttr(*this, name, val);
}

HDF5Object & HDF5Object::Attr(const std::string &name, uint32_t val) {
    return WriteOrCreateScalarAttr(*this, name, val);
}

HDF5Object & HDF5Object::Attr(const std::string &name, int64_t val) {
    return WriteOrCreateScalarAttr(*this, name, val);
}

HDF5Object & HDF5Object::Attr(const std::string &name, uint64_t val) {
    return WriteOrCreateScalarAttr(*this, name, val);
}

HDF5Object & HDF5Object::Attr(const std::string &name, double val) {
    return WriteOrCreateScalarAttr(*this, name, val);
}

HDF5Object & HDF5Object::Attr(const std::string &name, const std::vector<double> &val) {
    HDF5DataSpace dataspace({val.size()});
    if (val.empty()) throw JFJochException(JFJochExceptionCategory::HDF5, "Empty array cannot be written");
    HDF5DataType datatype(val[0]);

    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.data());
    H5Aclose(attr_id);

    if (ret < 0) throw JFJochException(JFJochExceptionCategory::HDF5, "Atrribute write unsucessful");
    return *this;
}

std::string ReadHDF5String(hid_t type_id, const std::function<herr_t(hid_t, void *)> &read) {
    if (H5Tis_variable_str(type_id) > 0) {
        char *tmp = nullptr;
        if (read(type_id, &tmp) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read variable-length string");
        std::string out = (tmp != nullptr) ? std::string(tmp) : std::string{};
        if (tmp != nullptr)
            H5free_memory(tmp);
        return out;
    }

    const size_t size = H5Tget_size(type_id);
    if (size == 0)
        return "";

    std::string buffer(size, '\0');
    if (read(type_id, buffer.data()) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read string");

    const size_t end = buffer.find('\0');
    if (end != std::string::npos)
        buffer.resize(end);
    return buffer;
}

std::vector<double> HDF5Object::ReadAttrVec(const std::string &name) {
    hid_t attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
    if (attr_id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);

    hid_t space_id = H5Aget_space(attr_id);
    if (space_id < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get dataspace for attribute " + name);
    }

    int ndims = H5Sget_simple_extent_ndims(space_id);
    if (ndims != 1) {
        H5Sclose(space_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute " + name + " is not a vector");
    }

    hsize_t dims[1];
    H5Sget_simple_extent_dims(space_id, dims, NULL);
    std::vector<double> ret(dims[0]);

    if (H5Aread(attr_id, H5T_NATIVE_DOUBLE, ret.data()) < 0) {
        H5Sclose(space_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read attribute " + name);
    }

    H5Sclose(space_id);
    H5Aclose(attr_id);
    return ret;
}

bool HDF5Object::AttrExists(const std::string &name) {
    return H5Aexists(id, name.c_str()) > 0;
}

std::string HDF5Object::ReadAttrStr(const std::string &name) {
    hid_t attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
    if (attr_id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);

    // Get attribute dataspace
    hid_t space_id = H5Aget_space(attr_id);
    if (space_id < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get dataspace for attribute " + name);
    }

    // Check if attribute is scalar
    H5S_class_t space_type = H5Sget_simple_extent_type(space_id);
    if (space_type != H5S_SCALAR) {
        H5Sclose(space_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute " + name + " is not a scalar");
    }
    H5Sclose(space_id);

    // Get attribute type
    hid_t type_id = H5Aget_type(attr_id);
    if (type_id < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get type for attribute " + name);
    }

    // Check if attribute is a string type
    H5T_class_t type_class = H5Tget_class(type_id);
    if (type_class != H5T_STRING) {
        H5Tclose(type_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute " + name + " is not a string");
    }

    std::string ret;
    try {
        ret = ReadHDF5String(type_id, [&](hid_t type, void *buffer) { return H5Aread(attr_id, type, buffer); });
    } catch (...) {
        H5Tclose(type_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read attribute " + name);
    }

    H5Tclose(type_id);
    H5Aclose(attr_id);
    return ret;
}


double HDF5Object::ReadAttrDouble(const std::string &name) {
    hid_t attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
    if (attr_id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);

    hid_t space_id = H5Aget_space(attr_id);
    if (space_id < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get dataspace for attribute " + name);
    }

    H5S_class_t space_type = H5Sget_simple_extent_type(space_id);
    if (space_type != H5S_SCALAR) {
        H5Sclose(space_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute " + name + " is not a scalar");
    }
    H5Sclose(space_id);

    double value;
    if (H5Aread(attr_id, H5T_NATIVE_DOUBLE, &value) < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read attribute " + name);
    }

    H5Aclose(attr_id);
    return value;
}

int64_t HDF5Object::ReadAttrInt(const std::string &name) {
    hid_t attr_id = H5Aopen(id, name.c_str(), H5P_DEFAULT);
    if (attr_id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open attribute " + name);

    hid_t space_id = H5Aget_space(attr_id);
    if (space_id < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot get dataspace for attribute " + name);
    }

    H5S_class_t space_type = H5Sget_simple_extent_type(space_id);
    if (space_type != H5S_SCALAR) {
        H5Sclose(space_id);
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Attribute " + name + " is not a scalar");
    }
    H5Sclose(space_id);

    int64_t value;
    if (H5Aread(attr_id, H5T_NATIVE_INT64, &value) < 0) {
        H5Aclose(attr_id);
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read attribute " + name);
    }

    H5Aclose(attr_id);
    return value;
}

HDF5Object & HDF5Object::Units(const std::string &val) {
    if (!val.empty()) Attr("units", val);
    return *this;
}

HDF5Object & HDF5Object::NXClass(const std::string &val) {
    if (!val.empty()) Attr("NX_class", val);
    return *this;
}

HDF5Object& HDF5Object::Transformation(const std::string& units, const std::string& depends_on,
                           const std::string& equipment, const std::string& equipment_component,
                           const std::string& transformation_type, const std::vector<double>& vector) {
    if (!units.empty()) Attr("units", units);
    if (!depends_on.empty()) Attr("depends_on", depends_on);
    if (!equipment.empty()) Attr("equipment", equipment);
    if (!equipment_component.empty()) Attr("equipment_component", equipment_component);
    if (!transformation_type.empty()) Attr("transformation_type", transformation_type);
    Attr("vector", vector);
    return *this;
}

HDF5Object& HDF5Object::Transformation(const std::string& units, const std::string& depends_on,
                           const std::string& equipment, const std::string& equipment_component,
                           const std::string& transformation_type, const std::vector<double>& vector,
                           const std::vector<double> &offset, const std::string& offset_units) {
    Transformation(units, depends_on, equipment, equipment_component, transformation_type, vector);
    Attr("offset", offset);
    // An offset is a length, whatever the axis is. Without this attribute a reader falls back to
    // `units`, which on a rotation axis is degrees - NXmx readers then try to convert degrees to
    // millimetres and raise. Harmless while every offset we write is zero, and wrong the moment one
    // is not, so state it always rather than only when a caller remembers to.
    Attr("offset_units", offset_units.empty() ? std::string("m") : offset_units);
    return *this;
}

HDF5Object& HDF5Object::ExternalLink(std::string filename, const std::string &external_dataset, const std::string &local_name) {
    // Linked file is assumed to be in the same directory as current file, so directory information is stripped
    int pos = filename.rfind('/');
    if (pos != std::string::npos) filename = filename.substr(pos+1);

    if (H5Lcreate_external(filename.c_str(),external_dataset.c_str(), GetID(),
                           local_name.c_str(), H5P_DEFAULT, H5P_DEFAULT) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create external link in HDF5 file");
    return *this;
}

HDF5Object & HDF5Object::HardLink(const std::string &source, const std::string &dest) {
    if (H5Lcreate_hard(GetID(), source.c_str(), GetID(), dest.c_str(), H5P_DEFAULT, H5P_DEFAULT) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create link in HDF5 file");
    return *this;
}

std::vector<hsize_t> HDF5Object::GetDimension(const std::string &name) {
    HDF5DataSet dataset(*this, name);
    HDF5DataSpace dscp(dataset);
    return dscp.GetDimensions();
}

std::unique_ptr<HDF5DataSet> HDF5Object::SaveScalar(const std::string &name, const std::string &val) {
    return SaveScalar(name, val.c_str());
}

std::unique_ptr<HDF5DataSet> HDF5Object::SaveScalar(const std::string &name, const char *val) {
    HDF5DataType data_type(val);
    HDF5DataSpace data_space(HDF5DataSpace::Scalar);
    auto dataset = std::make_unique<HDF5DataSet>(*this, name, data_type, data_space);
    dataset->Write(data_type, val);
    return dataset;
}

std::unique_ptr<HDF5DataSet> HDF5Object::SaveVector(const std::string &name, const std::vector<std::string> &val) {
    if (val.empty())
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot write empty vector");

    int pos = 0;
    size_t len = val[0].length();
    for (int i = 1; i < val.size(); i++) { if (val[i].length() > len) {pos = i; len = val[i].length();}}
    HDF5DataType data_type(val[pos]);
    HDF5Dcpl dcpl;
    HDF5DataSpace data_space({val.size()});
    auto dataset = std::make_unique<HDF5DataSet>(*this, name, data_type, data_space, dcpl);

    std::vector<char> buffer((len + 1) * val.size(), '\0');
    for (int i = 0; i < val.size(); i++) strncpy(buffer.data() + i * (len+1), val[i].c_str(), len+1);
    dataset->Write(data_type, buffer.data());
    return dataset;
}

HDF5Group::HDF5Group(const HDF5Object& parent, const std::string &name) : HDF5Group(parent, name.c_str()) {
}

HDF5Group::HDF5Group(const HDF5Object& parent, const char *name) : HDF5Object() {
    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() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Gclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

HDF5File::HDF5File(const std::string& filename, bool v1_10) : HDF5Object() {
    HDF5Fapl fapl;

    H5FD_poison_sec2_init();
    H5FD_poison_sec2_set_callback(HDF5PoisonCallback, nullptr);
    if (v1_10)
        fapl.SetVersionTo1p10orNewer();
    fapl.SetCloseStrong();
    fapl.SetPoisonSec2();

    id = H5Fcreate(filename.c_str(), H5F_ACC_TRUNC, H5P_DEFAULT, fapl.GetID());
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open/create data HDF5 file " + filename);
}

void HDF5File::Close() {
    if (id < 0)
        return;

    // Invalidate first; if anything below fails we must NOT leave a live id
    // behind for the destructor or later code to touch.
    const hid_t local_id = id;
    id = -1;

    H5FD_poison_sec2_begin_fail_pass();

    herr_t close_err = 0;
    H5E_BEGIN_TRY {
        close_err = H5Fclose(local_id);
    } H5E_END_TRY;

    H5FD_poison_sec2_end_fail_pass();

    const char *filename = nullptr;
    const char *operation = nullptr;
    int error_number = 0;
    const int poison_error = H5FD_poison_sec2_get_last_error(
        &filename,
        &operation,
        &error_number
    );

    if (close_err < 0 || poison_error > 0)
        throw JFJochException(
            JFJochExceptionCategory::HDF5,
            "Failed to close HDF5 file, operation=" +
            std::string(operation != nullptr ? operation : "") +
            ", filename=" +
            std::string(filename != nullptr ? filename : "") +
            ", errno=" +
            std::to_string(error_number)
        );
}

HDF5File::~HDF5File() {
    if (id >= 0) {
        const hid_t tmp = id;
        id = -1;
        H5FD_poison_sec2_begin_fail_pass();
        H5E_BEGIN_TRY {
            H5Fclose(tmp);
        } H5E_END_TRY;
        H5FD_poison_sec2_end_fail_pass();
    }
}

void HDF5File::Delete(const std::string& path) {
    H5Ldelete(id, path.c_str(), H5P_DEFAULT);
}

HDF5ReadOnlyFile::HDF5ReadOnlyFile(const std::string &filename) {
    id = H5Fopen(filename.c_str(), H5F_ACC_RDONLY, H5P_DEFAULT);
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open/create data HDF5 file" + filename);
}

HDF5ReadOnlyFile::~HDF5ReadOnlyFile() {
    if (id >= 0) {
        H5E_BEGIN_TRY {H5Fclose(id); } H5E_END_TRY;
        id = -1;
    }
}

HDF5DataSet::HDF5DataSet(const HDF5Object &parent, const std::string &name, const HDF5DataType &data_type,
        const HDF5DataSpace &data_space, const HDF5Dcpl &dcpl) : dataset_name(name) {

    ndim = data_space.GetNumOfDimensions();
    if ((dcpl.GetNumOfDimensions() != 0) && (dcpl.GetNumOfDimensions() != data_space.GetNumOfDimensions()))
        throw JFJochException(JFJochExceptionCategory::HDF5, "Inconsistent dimension settings");

    id = H5Dcreate2(parent.GetID(), name.c_str(), data_type.GetID(), data_space.GetID(), H5P_DEFAULT, dcpl.GetID(), H5P_DEFAULT);
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create HDF5 dataset: " + name);
}

HDF5DataSet::HDF5DataSet(const HDF5Object &parent, const std::string &name, const HDF5DataType &data_type,
                         const HDF5DataSpace &data_space) : dataset_name(name) {

    ndim = data_space.GetNumOfDimensions();

    id = H5Dcreate2(parent.GetID(), name.c_str(), data_type.GetID(), data_space.GetID(), H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot create HDF5 dataset " + name);
}

HDF5DataSet::HDF5DataSet(const HDF5Object &parent, const std::string &name) : ndim(0), dataset_name(name) {
    id = H5Dopen2(parent.GetID(), name.c_str(), H5P_DEFAULT);

    if (id < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open HDF5 dataset " + name);

    ndim = HDF5DataSpace(*this).GetNumOfDimensions();
}

void HDF5DataSet::SetExtent(const std::vector<hsize_t> &dims) {
    if (dims.size() != ndim)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Mismatch in dataset dimensions " + std::to_string(ndim));
    herr_t ret = H5Dset_extent(id, dims.data());
    if (ret < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Error in H5Dset_extent");
}

HDF5DataSet& HDF5DataSet::Write(const HDF5DataType &data_type, const void *val) {
    if (H5Dwrite(id, data_type.GetID(), H5S_ALL, H5S_ALL, H5P_DEFAULT, val) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot write to HDF5 file");
    return *this;
}

HDF5DataSet& HDF5DataSet::Flush() {
    if (H5Dflush(id) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Error flushing HDF5 dataset");
    return *this;
}

HDF5DataSet& HDF5DataSet::WriteDirectChunk(const void *data, hsize_t data_size, const std::vector<hsize_t> &offset) {
    if (offset.size() != ndim)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Inconsistent dimension settings");
    if (H5Dwrite_chunk(id, H5P_DEFAULT, 0, offset.data(), data_size, data) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Error writing dataset to HDF5 file");
    return *this;
}

std::string HDF5DataSet::ReadString() const {
    HDF5DataSpace file_space(*this);
    // A rank-1 dataset holding exactly one string is the same thing as a scalar, and facilities
    // write it both ways - JUNGFRAU masters from an early beamline deployment store
    // sensor_material and description as shape (1,). Refusing those loses the whole file over a
    // difference that carries no information.
    if (file_space.GetNumOfDimensions() != 0) {
        const auto dims = file_space.GetDimensions();
        hsize_t elements = 1;
        for (const auto d : dims)
            elements *= d;
        if (elements != 1)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Dataset tries to read string (scalar) from vector dataset");
    }

    HDF5DataType file_data_type(*this);
    try {
        return ReadHDF5String(file_data_type.GetID(), [&](hid_t type, void *buffer) {
            return H5Dread(id, type, H5S_ALL, H5S_ALL, H5P_DEFAULT, buffer);
        });
    } catch (const JFJochException &) {
        throw JFJochException(JFJochExceptionCategory::HDF5, dataset_name + ": read unsuccessful");
    }
}

void HDF5DataSet::Close() {
    if (id < 0)
        return;

    const hid_t local_id = id;
    id = -1;

    herr_t err = 0;
    H5E_BEGIN_TRY {
        err = H5Dclose(local_id);
    } H5E_END_TRY;

    if (err < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot close HDF5 dataset");
}

HDF5DataSet::~HDF5DataSet() {
    if (id >= 0) {
        H5E_BEGIN_TRY {
            H5Dclose(id);
        } H5E_END_TRY;
        id = -1;
    }
}

void RegisterHDF5Filter() {
    if (H5Zregister(bshuf_H5Filter) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot register Bitshuffle filter");
}

void HDF5Dcpl::SetCompression(CompressionAlgorithm c, size_t block_size) {
    constexpr uint32_t cd_nelmts = 2;
    unsigned int params[cd_nelmts];
    switch (c) {
        case CompressionAlgorithm::BSHUF_LZ4:
            params[0] = block_size;
            params[1] = BSHUF_H5_COMPRESS_LZ4;
            if (H5Pset_filter(id, (H5Z_filter_t)BSHUF_H5FILTER, H5Z_FLAG_MANDATORY, cd_nelmts, params) < 0)
                throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot set bshuf/lz4 filter");
            break;
        case CompressionAlgorithm::BSHUF_ZSTD:
        case CompressionAlgorithm::BSHUF_ZSTD_RLE:
        case CompressionAlgorithm::BSHUF_ZSTD_RLE_HUFF:
#ifdef USE_ZSTD
            params[0] = block_size;
            params[1] = BSHUF_H5_COMPRESS_ZSTD;
            if (H5Pset_filter(id, (H5Z_filter_t)BSHUF_H5FILTER, H5Z_FLAG_MANDATORY, cd_nelmts, params) < 0)
                throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot set bshuf/zstd filter");
            break;
#else
            throw SLSException(SLSExceptionCategory::Compression, "ZSTD support not available");
#endif
        case CompressionAlgorithm::NO_COMPRESSION:
            break;
        default:
            throw JFJochException(JFJochExceptionCategory::HDF5, "SetCompression: algorithm not supported");
    }

}

CompressionAlgorithm HDF5Dcpl::GetCompression() {
    int num_filters = H5Pget_nfilters(id);
    if (num_filters > 1)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Only single filter supported");
    if (num_filters == 0)
        return CompressionAlgorithm::NO_COMPRESSION;

    uint32_t cd_values[8];
    size_t cd_nelemts = std::size(cd_values);
    memset(cd_values, 0, sizeof(cd_values));

    const auto filter = H5Pget_filter2(id, 0, nullptr, &cd_nelemts, cd_values, 0, nullptr, nullptr);

    // Plain LZ4, no bit shuffle. DECTRIS Eiger firmware 1.x wrote images this way, and those files
    // are still deposited; read-only, we never write it. Same block framing as bitshuffle - a 64-bit
    // total size, a 32-bit block size, then 32-bit-prefixed blocks - which is why only the unshuffle
    // step differs downstream.
    if (filter == LZ4_H5FILTER)
        return CompressionAlgorithm::LZ4_NO_SHUFFLE;

    if (filter != BSHUF_H5FILTER)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Unsupported HDF5 compression filter " + std::to_string(filter)
                              + " (supported: bitshuffle " + std::to_string(BSHUF_H5FILTER)
                              + ", LZ4 " + std::to_string(LZ4_H5FILTER) + ")");

    if (cd_values[4] == BSHUF_H5_COMPRESS_LZ4)
        return CompressionAlgorithm::BSHUF_LZ4;
    if (cd_values[4] == BSHUF_H5_COMPRESS_ZSTD)
        return CompressionAlgorithm::BSHUF_ZSTD;
    throw JFJochException(JFJochExceptionCategory::HDF5,"Weird value of parameter " + std::to_string(cd_values[4]));
}

std::string ExtractFilename(const std::string& str) {
    std::filesystem::path path(str);
    // if (std::filesystem::is_regular_file(path))
    return path.filename().string();
}

bool HDF5Object::GetBool(const std::string &name) const {
    HDF5DataSet dataset(*this, name);
    return dataset.ReadScalar<bool>();
}

std::optional<bool> HDF5Object::GetOptBool(const std::string &name) const {
    if (Exists(name))
        return GetBool(name);
    return std::nullopt;
}

float HDF5Object::GetFloat(const std::string &name) const {
    HDF5DataSet dataset(*this, name);
    return dataset.ReadScalar<float>();
}

int64_t HDF5Object::GetInt(const std::string &name) const {
    HDF5DataSet dataset(*this, name);
    return dataset.ReadScalar<int64_t>();
}

std::optional<float> HDF5Object::GetOptFloat(const std::string &name) const {
    if (Exists(name))
        return GetFloat(name);
    return std::nullopt;
}

std::optional<int64_t> HDF5Object::GetOptInt(const std::string &name) const {
    if (Exists(name))
        return GetInt(name);
    return std::nullopt;
}

std::string HDF5Object::GetString(const std::string &name, const std::string &def) const {
    if (Exists(name)) {
        HDF5DataSet dataset(*this, name);
        return dataset.ReadString();
    }
    return def;
}

bool HDF5Object::Exists(const std::string &name) const {
    H5E_BEGIN_TRY {
        // The LINK has to be there and the object it names has to be reachable. Those are two
        // different questions for an external link, and every DECTRIS Eiger master asks the second
        // one: it links saturation_value, pixel_mask, bit_depth_readout and serial_number into a
        // companion <prefix>_meta.h5 that is routinely not kept when a dataset is archived or
        // deposited. H5Lexists then says yes - the link is written in the master - and the read that
        // follows throws, which turns every optional-field guard in the reader into a hard failure
        // and refuses the whole file over a value it was prepared to do without.
        if (H5Lexists(GetID(), name.c_str(), H5P_DEFAULT) <= 0)
            return false;
        return H5Oexists_by_name(GetID(), name.c_str(), H5P_DEFAULT) > 0;
    } H5E_END_TRY;
    return false;
}

bool HDF5Object::IsDataSet(const std::string &name) const {
    hid_t dataset_id;
    H5E_BEGIN_TRY {
        dataset_id = H5Dopen(GetID(), name.c_str(), H5P_DEFAULT);
    } H5E_END_TRY;
    if (dataset_id < 0)
        return false;
    H5Dclose(dataset_id);
    return true;
}

herr_t func(hid_t group, const char *name, const H5L_info2_t *info, void *op_data) {
    auto ret = reinterpret_cast<std::vector<std::string> *>(op_data);
    ret->emplace_back(name);
    return 0;
}

std::vector<std::string> HDF5Object::FindLeafs(const std::string &name) const {
    hid_t gid = H5Gopen(id, name.c_str(), H5P_DEFAULT);
    if (gid < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot open HDF5 group " + name);
    std::vector<std::string> ret;
    hsize_t idx = 0;
    H5Literate(gid, H5_INDEX_NAME, H5_ITER_INC, &idx, func, &ret);

    H5Gclose(gid);
    return ret;
}

bool HDF5Object::IsExternalLink(const std::string& name) const {
    H5L_info2_t link_info;

    // Get information about the link
    if (H5Lget_info(id, name.c_str(), &link_info, H5P_DEFAULT) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Failed to retrieve information about the link");

    return (link_info.type == H5L_TYPE_EXTERNAL);
}

std::pair<std::string, std::string> HDF5Object::GetLinkedTarget(const std::string& name) const {
    H5L_info2_t link_info;

    // Get information about the link
    if (H5Lget_info(id, name.c_str(), &link_info, H5P_DEFAULT) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Failed to retrieve information about the link");

    if (link_info.type != H5L_TYPE_EXTERNAL)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "This is not an external link");

    std::vector<char> link_target(link_info.u.val_size + 2, '\0');
    if (H5Lget_val(id,
                   name.c_str(),
                   link_target.data(),
                   link_info.u.val_size + 1, H5P_DEFAULT) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Failed to get link location");

    const char *target_file_name = nullptr;            // To store unpacked file name
    const char *target_object_path = nullptr;          // To store unpacked object path

    // Unpack the external link's value
    if (H5Lunpack_elink_val(link_target.data(),
                            link_info.u.val_size,
                            nullptr,
                            &target_file_name,
                            &target_object_path) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Failed to get link location");

    return {target_file_name, target_object_path};
}

std::string HDF5Object::GetLinkedFileName(const std::string& name) const {
    return GetLinkedTarget(name).first;
}


namespace {
    std::vector<hsize_t> GetDataspaceDimensions(hid_t dataspace_id) {
        const int ndims = H5Sget_simple_extent_ndims(dataspace_id);
        if (ndims < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read dataspace dimensions");

        std::vector<hsize_t> dims(ndims);
        if (ndims > 0 && H5Sget_simple_extent_dims(dataspace_id, dims.data(), nullptr) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5, "Cannot read dataspace dimensions");

        return dims;
    }

    void GetRegularSelection(hid_t dataspace_id,
                             std::vector<hsize_t> &start,
                             std::vector<hsize_t> &stride,
                             std::vector<hsize_t> &count,
                             std::vector<hsize_t> &block) {
        const auto dims = GetDataspaceDimensions(dataspace_id);

        const H5S_sel_type selection_type = H5Sget_select_type(dataspace_id);
        if (selection_type == H5S_SEL_ALL) {
            start.clear();
            stride.clear();
            count.clear();
            block.clear();
            return;
        }

        start.assign(dims.size(), 0);
        stride.assign(dims.size(), 1);
        count.assign(dims.size(), 1);
        block = dims;

        if (selection_type != H5S_SEL_HYPERSLABS)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Only regular hyperslab VDS selections are supported");

        if (H5Sis_regular_hyperslab(dataspace_id) <= 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Only regular hyperslab VDS selections are supported");

        if (H5Sget_regular_hyperslab(dataspace_id,
                                     start.data(),
                                     stride.data(),
                                     count.data(),
                                     block.data()) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot decode VDS hyperslab selection");
    }

    bool ContainsInRegularHyperslab(hsize_t value,
                                    hsize_t start,
                                    hsize_t stride,
                                    hsize_t count,
                                    hsize_t block) {
        for (hsize_t i = 0; i < count; i++) {
            const hsize_t block_start = start + i * stride;
            if ((value >= block_start) && (value < block_start + block))
                return true;
        }
        return false;
    }

    hsize_t IndexInRegularHyperslab(hsize_t value,
                                    hsize_t start,
                                    hsize_t stride,
                                    hsize_t count,
                                    hsize_t block) {
        for (hsize_t i = 0; i < count; i++) {
            const hsize_t block_start = start + i * stride;
            if ((value >= block_start) && (value < block_start + block))
                return i * block + (value - block_start);
        }

        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Image is not part of VDS hyperslab");
    }

    hsize_t ValueFromRegularHyperslabIndex(hsize_t index,
                                           hsize_t start,
                                           hsize_t stride,
                                           hsize_t count,
                                           hsize_t block) {
        if (index >= count * block)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Source image is outside of VDS source hyperslab");

        const hsize_t block_number = index / block;
        const hsize_t in_block = index % block;
        return start + block_number * stride + in_block;
    }
}

bool HDF5VirtualDatasetMapping::ContainsVirtualImage(hsize_t image_number) const {
    if (virtual_start.empty() || virtual_stride.empty() || virtual_count.empty() || virtual_block.empty())
        return false;

    return ContainsInRegularHyperslab(image_number,
                                      virtual_start[0],
                                      virtual_stride[0],
                                      virtual_count[0],
                                      virtual_block[0]);
}

hsize_t HDF5VirtualDatasetMapping::SourceImage(hsize_t image_number) const {
    if (!ContainsVirtualImage(image_number))
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Image is outside of VDS mapping");

    const hsize_t source_index = IndexInRegularHyperslab(image_number,
                                                        virtual_start[0],
                                                        virtual_stride[0],
                                                        virtual_count[0],
                                                        virtual_block[0]);

    if (source_start.empty() || source_stride.empty() || source_count.empty() || source_block.empty())
        return source_index;

    return ValueFromRegularHyperslabIndex(source_index,
                                          source_start[0],
                                          source_stride[0],
                                          source_count[0],
                                          source_block[0]);
}


std::vector<HDF5VirtualDatasetMapping> HDF5Dcpl::GetVirtualMappings() const {
    size_t mapping_count = 0;

    if (H5Pget_virtual_count(id, &mapping_count) < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Cannot get number of VDS mappings");
    if (mapping_count < 0)
        throw JFJochException(JFJochExceptionCategory::HDF5,
                              "Cannot get number of VDS mappings");

    std::vector<HDF5VirtualDatasetMapping> ret;
    ret.reserve(static_cast<size_t>(mapping_count));

    for (size_t i = 0; i < static_cast<size_t>(mapping_count); i++) {
        HDF5VirtualDatasetMapping mapping;

        const ssize_t filename_size = H5Pget_virtual_filename(id, i, nullptr, 0);
        if (filename_size < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS source filename size");

        std::vector<char> filename(filename_size + 1, '\0');
        if (H5Pget_virtual_filename(id, i, filename.data(), filename.size()) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS source filename");
        mapping.filename = filename.data();

        const ssize_t dataset_size = H5Pget_virtual_dsetname(id, i, nullptr, 0);
        if (dataset_size < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS source dataset size");

        std::vector<char> dataset(dataset_size + 1, '\0');
        if (H5Pget_virtual_dsetname(id, i, dataset.data(), dataset.size()) < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS source dataset");
        mapping.dataset = dataset.data();

        const hid_t virtual_space = H5Pget_virtual_vspace(id, i);
        if (virtual_space < 0)
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS virtual dataspace");

        const hid_t source_space = H5Pget_virtual_srcspace(id, i);
        if (source_space < 0) {
            H5Sclose(virtual_space);
            throw JFJochException(JFJochExceptionCategory::HDF5,
                                  "Cannot get VDS source dataspace");
        }

        try {
            GetRegularSelection(virtual_space,
                                mapping.virtual_start,
                                mapping.virtual_stride,
                                mapping.virtual_count,
                                mapping.virtual_block);

            GetRegularSelection(source_space,
                                mapping.source_start,
                                mapping.source_stride,
                                mapping.source_count,
                                mapping.source_block);
        } catch (...) {
            H5Sclose(source_space);
            H5Sclose(virtual_space);
            throw;
        }

        H5Sclose(source_space);
        H5Sclose(virtual_space);

        ret.emplace_back(std::move(mapping));
    }

    return ret;
}