# GDALGroup C++ API

class `GDALGroup` : public GDALIHasAttribute

  Class modeling a named container of GDALAttribute, GDALMDArray or other GDALGroup.

  Hence GDALGroup can describe a hierarchy of objects.

  This is based on the HDF5 group concept

  Since

    GDAL 3.1

  Public Functions

  inline const std::string &`GetName`() const

    Return the name of the group.

    This is the same as the C function GDALGroupGetName().

  inline const std::string &`GetFullName`() const

    Return the full name of the group.

    This is the same as the C function GDALGroupGetFullName().

  virtual std::vector<std::string> `GetMDArrayNames`(CSLConstList papszOptions = nullptr) const

    Return the list of multidimensional array names contained in this group.

    Drivers known to implement it: MEM, netCDF.

    Note

      Driver implementation: optionally implemented. If implemented, OpenMDArray() should also be implemented.

    This is the same as the C function GDALGroupGetMDArrayNames().

    Return

      the array names.

    Parameters

      - `papszOptions`: Driver specific options determining how arrays should be retrieved. Pass nullptr for default behavior.

  virtual std::shared_ptr<GDALMDArray> `OpenMDArray`(const std::string &osName, CSLConstList papszOptions = nullptr) const

    Open and return a multidimensional array.

    Drivers known to implement it: MEM, netCDF.

    Note

      Driver implementation: optionally implemented. If implemented, GetMDArrayNames() should also be implemented.

    This is the same as the C function GDALGroupOpenMDArray().

    Return

      the array, or nullptr.

    Parameters

      - `osName`: Array name.

      - `papszOptions`: Driver specific options determining how the array should be opened. Pass nullptr for default behavior.

  virtual std::vector<std::string> `GetGroupNames`(CSLConstList papszOptions = nullptr) const

    Return the list of sub-groups contained in this group.

    Drivers known to implement it: MEM, netCDF.

    Note

      Driver implementation: optionally implemented. If implemented, OpenGroup() should also be implemented.

    This is the same as the C function GDALGroupGetGroupNames().

    Return

      the group names.

    Parameters

      - `papszOptions`: Driver specific options determining how groups should be retrieved. Pass nullptr for default behavior.

  virtual std::shared_ptr<GDALGroup> `OpenGroup`(const std::string &osName, CSLConstList papszOptions = nullptr) const

    Open and return a sub-group.

    Drivers known to implement it: MEM, netCDF.

    Note

      Driver implementation: optionally implemented. If implemented, GetGroupNames() should also be implemented.

    This is the same as the C function GDALGroupOpenGroup().

    Return

      the group, or nullptr.

    Parameters

      - `osName`: Sub-group name.

      - `papszOptions`: Driver specific options determining how the sub-group should be opened. Pass nullptr for default behavior.

  virtual std::vector<std::shared_ptr<GDALDimension>> `GetDimensions`(CSLConstList papszOptions = nullptr) const

    Return the list of dimensions contained in this group and used by its arrays.

    This is for dimensions that can potentially be used by several arrays. Not all drivers might implement this. To retrieve the dimensions used by a specific array, use GDALMDArray::GetDimensions().

    Drivers known to implement it: MEM, netCDF

    This is the same as the C function GDALGroupGetDimensions().

    Return

      the dimensions.

    Parameters

      - `papszOptions`: Driver specific options determining how groups should be retrieved. Pass nullptr for default behavior.

  virtual std::shared_ptr<GDALGroup> `CreateGroup`(const std::string &osName, CSLConstList papszOptions = nullptr)

    Create a sub-group within a group.

    Optionally implemented by drivers.

    Drivers known to implement it: MEM, netCDF

    This is the same as the C function GDALGroupCreateGroup().

    Return

      the new sub-group, or nullptr in case of error.

    Parameters

      - `osName`: Sub-group name.

      - `papszOptions`: Driver specific options determining how the sub-group should be created.

  virtual std::shared_ptr<GDALDimension> `CreateDimension`(const std::string &osName, const std::string &osType, const std::string &osDirection, GUInt64 nSize, CSLConstList papszOptions = nullptr)

    Create a dimension within a group.

    Drivers known to implement it: MEM, netCDF

    Note

      Driver implementation: drivers supporting CreateDimension() should implement this method, but do not have necessarily to implement GDALGroup::GetDimensions().

    This is the same as the C function GDALGroupCreateDimension().

    Return

      the new dimension, or nullptr if case of error

    Parameters

      - `osName`: Dimension name.

      - `osType`: Dimension type (might be empty, and ignored by drivers)

      - `osDirection`: Dimension direction (might be empty, and ignored by drivers)

      - `nSize`: Number of values indexed by this dimension. Should be > 0.

      - `papszOptions`: Driver specific options determining how the dimension should be created.

  virtual std::shared_ptr<GDALMDArray> `CreateMDArray`(const std::string &osName, const std::vector<std::shared_ptr<GDALDimension>> &aoDimensions, const GDALExtendedDataType &oDataType, CSLConstList papszOptions = nullptr)

    Create a multidimensional array within a group.

    It is recommended that the GDALDimension objects passed in aoDimensions belong to this group, either by retrieving them with GetDimensions() or creating a new one with CreateDimension().

    Optionally implemented.

    Drivers known to implement it: MEM, netCDF

    This is the same as the C function GDALGroupCreateMDArray().

    Note

      Driver implementation: drivers should take into account the possibility that GDALDimension object passed in aoDimensions might belong to a different group / dataset / driver and act accordingly.

    Return

      the new array, or nullptr if case of error

    Parameters

      - `osName`: Array name.

      - `aoDimensions`: List of dimensions, ordered from the slowest varying dimension first to the fastest varying dimension last. Might be empty for a scalar array (if supported by driver)

      - `oDataType`: Array data type.

      - `papszOptions`: Driver specific options determining how the array should be created.

  GUInt64 `GetTotalCopyCost`() const

    Return a total “cost” to copy the group.

    Used as a parameter for CopFrom()

  virtual bool `CopyFrom`(const std::shared_ptr<GDALGroup> &poDstRootGroup, GDALDataset *poSrcDS, const std::shared_ptr<GDALGroup> &poSrcGroup, bool bStrict, GUInt64 &nCurCost, const GUInt64 nTotalCost, GDALProgressFunc pfnProgress, void *pProgressData, CSLConstList papszOptions = nullptr)

    Copy the content of a group into a new (generally empty) group.

    Return

      true in case of success (or partial success if bStrict == false).

    Parameters

      - `poDstRootGroup`: Destination root group. Must NOT be nullptr.

      - `poSrcDS`: Source dataset. Might be nullptr (but for correct behavior of some output drivers this is not recommended)

      - `poSrcGroup`: Source group. Must NOT be nullptr.

      - `bStrict`: Whether to enable stict mode. In strict mode, any error will stop the copy. In relaxed mode, the copy will be attempted to be pursued.

      - `nCurCost`: Should be provided as a variable initially set to 0.

      - `nTotalCost`: Total cost from GetTotalCopyCost().

      - `pfnProgress`: Progress callback, or nullptr.

      - `pProgressData`: Progress user data, or nulptr.

      - `papszOptions`: Creation options. Currently, only array creation options are supported. They must be prefixed with “ARRAY:” . The scope may be further restricted to arrays of a certain dimension by adding “IF(DIM={ndims}):” after “ARRAY:”. For example, “ARRAY:IF(DIM=2):BLOCKSIZE=256,256” will restrict BLOCKSIZE=256,256 to arrays of dimension 2. Restriction to arrays of a given name is done with adding “IF(NAME={name}):” after “ARRAY:”. {name} can also be a full qualified name. A non-driver specific ARRAY option, “AUTOSCALE=YES” can be used to ask (non indexing) variables of type Float32 or Float64 to be scaled to UInt16 with scale and offset values being computed from the minimum and maximum of the source array. The integer data type used can be set with AUTOSCALE_DATA_TYPE=Byte/UInt16/Int16/UInt32/Int32.

  virtual CSLConstList `GetStructuralInfo`() const

    Return structural information on the group.

    This may be the compression, etc..

    The return value should not be freed and is valid until GDALGroup is released or this function called again.

    This is the same as the C function GDALGroupGetStruturalInfo().

  std::shared_ptr<GDALMDArray> `OpenMDArrayFromFullname`(const std::string &osFullName, CSLConstList papszOptions = nullptr) const

    Get an array from its fully qualified name.

  std::shared_ptr<GDALMDArray> `ResolveMDArray`(const std::string &osName, const std::string &osStartingPath, CSLConstList papszOptions = nullptr) const

    Locate an array in a group and its subgroups by name.

    If osName is a fully qualified name, then OpenMDArrayFromFullname() is first used Otherwise the search will start from the group identified by osStartingPath, and an array whose name is osName will be looked for in this group (if osStartingPath is empty or “/”, then the current group is used). If there is no match, then a recursive descendent search will be made in its subgroups. If there is no match in the subgroups, then the parent (if existing) of the group pointed by osStartingPath will be used as the new starting point for the search.

    Since

      GDAL 3.2

    Parameters

      - `osName`: name, qualified or not

      - `osStartingPath`: fully qualified name of the (sub-)group from which the search should be started. If this is a non-empty string, the group on which this method is called should nominally be the root group (otherwise the path will be interpreted as from the current group)

      - `papszOptions`: options to pass to OpenMDArray()

  std::shared_ptr<GDALGroup> `OpenGroupFromFullname`(const std::string &osFullName, CSLConstList papszOptions = nullptr) const

    Get a group from its fully qualified name.

    Since

      GDAL 3.2

  std::shared_ptr<GDALDimension> `OpenDimensionFromFullname`(const std::string &osFullName) const

    Get a dimension from its fully qualified name.