GDAL

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GDALGroup Class Reference

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

`#include <gdal_priv.h>`

Inheritance diagram for GDALGroup:

## Public Member Functions
const std::string & | GetName () const
| Return the name of the group.
const std::string & | GetFullName () const
| Return the full name of the group.
virtual std::vector< std::string > | GetMDArrayNames (CSLConstList papszOptions=nullptr) const
| Return the list of multidimensional array names contained in this group.
virtual std::shared_ptr< GDALMDArray > | OpenMDArray (const std::string &osName, CSLConstList papszOptions=nullptr) const
| Open and return a multidimensional array.
virtual std::vector< std::string > | GetGroupNames (CSLConstList papszOptions=nullptr) const
| Return the list of sub-groups contained in this group.
virtual std::shared_ptr< GDALGroup > | OpenGroup (const std::string &osName, CSLConstList papszOptions=nullptr) const
| Open and return a sub-group.
virtual std::vector< std::string > | GetVectorLayerNames (CSLConstList papszOptions=nullptr) const
| Return the list of layer names contained in this group.
virtual OGRLayer * | OpenVectorLayer (const std::string &osName, CSLConstList papszOptions=nullptr) const
| Open and return a vector layer.
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.
virtual std::shared_ptr< GDALGroup > | CreateGroup (const std::string &osName, CSLConstList papszOptions=nullptr)
| Create a sub-group within a group.
virtual bool | DeleteGroup (const std::string &osName, CSLConstList papszOptions=nullptr)
| Delete a sub-group from a group.
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.
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.
virtual bool | DeleteMDArray (const std::string &osName, CSLConstList papszOptions=nullptr)
| Delete an array from a group.
GUInt64 | GetTotalCopyCost () const
| Return a total "cost" to copy the group.
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.
virtual CSLConstList | GetStructuralInfo () const
| Return structural information on the group.
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.
std::shared_ptr< GDALGroup > | OpenGroupFromFullname (const std::string &osFullName, CSLConstList papszOptions=nullptr) const
| Get a group from its fully qualified name.
std::shared_ptr< GDALDimension > | OpenDimensionFromFullname (const std::string &osFullName) const
| Get a dimension from its fully qualified name.
virtual void | ClearStatistics ()
| Clear statistics.
virtual bool | Rename (const std::string &osNewName)
| Rename the group.
std::shared_ptr< GDALGroup > | SubsetDimensionFromSelection (const std::string &osSelection) const
| Return a virtual group whose one dimension has been subset according to a selection.
virtual std::shared_ptr< GDALAttribute > | GetAttribute (const std::string &osName) const
| Return an attribute by its name.
virtual std::vector< std::shared_ptr< GDALAttribute > > | GetAttributes (CSLConstList papszOptions=nullptr) const
| Return the list of attributes contained in a GDALMDArray or GDALGroup.
virtual std::shared_ptr< GDALAttribute > | CreateAttribute (const std::string &osName, const std::vector< GUInt64 > &anDimensions, const GDALExtendedDataType &oDataType, CSLConstList papszOptions=nullptr)
| Create an attribute within a GDALMDArray or GDALGroup.
virtual bool | DeleteAttribute (const std::string &osName, CSLConstList papszOptions=nullptr)
| Delete an attribute from a GDALMDArray or GDALGroup.

## Protected Member Functions
std::shared_ptr< GDALAttribute > | GetAttributeFromAttributes (const std::string &osName) const
| Possible fallback implementation for GetAttribute() using GetAttributes().

## Detailed Description

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

Hence GDALGroup can describe a hierarchy of objects.

This is based on the HDF5 group concept

Since
  GDAL 3.1

## Member Function Documentation

## ◆ ClearStatistics()

void GDALGroup::ClearStatistics | ( |  | ) |
| virtual

Clear statistics.

Since
  GDAL 3.4

## ◆ CopyFrom()

bool GDALGroup::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`
| ) |  |
| virtual

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

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 strict 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.

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

## ◆ CreateAttribute()

std::shared_ptr< GDALAttribute > GDALIHasAttribute::CreateAttribute | ( | const std::string & | osName,
|  | const std::vector< GUInt64 > & | anDimensions,
|  | const GDALExtendedDataType & | oDataType,
|  | CSLConstList | papszOptions = `nullptr`
| ) |  |
| virtual inherited

Create an attribute within a GDALMDArray or GDALGroup.

The attribute might not be "physically" created until a value is written into it.

Optionally implemented.

Drivers known to implement it: MEM, netCDF

This is the same as the C function GDALGroupCreateAttribute() or GDALMDArrayCreateAttribute()

Parameters

  osName | Attribute name.
  anDimensions | List of dimension sizes, ordered from the slowest varying dimension first to the fastest varying dimension last. Empty for a scalar attribute (common case)
  oDataType | Attribute data type.
  papszOptions | Driver specific options determining how the attribute. should be created.

Returns
  the new attribute, or nullptr if case of error

## ◆ CreateDimension()

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

Create a dimension within a group.

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

Drivers known to implement it: MEM, netCDF

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

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.

Returns
  the new dimension, or nullptr if case of error

## ◆ CreateGroup()

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

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().

Parameters

  osName | Sub-group name.
  papszOptions | Driver specific options determining how the sub-group should be created.

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

## ◆ CreateMDArray()

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

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.

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.

Returns
  the new array, or nullptr if case of error

## ◆ DeleteAttribute()

bool GDALIHasAttribute::DeleteAttribute | ( | const std::string & | osName,
|  | CSLConstList | papszOptions = `nullptr`
| ) |  |
| virtual inherited

Delete an attribute from a GDALMDArray or GDALGroup.

Optionally implemented.

After this call, if a previously obtained instance of the deleted object is still alive, no method other than for freeing it should be invoked.

Drivers known to implement it: MEM, netCDF

This is the same as the C function GDALGroupDeleteAttribute() or GDALMDArrayDeleteAttribute()

Parameters

  osName | Attribute name.
  papszOptions | Driver specific options determining how the attribute. should be deleted.

Returns
  true in case of success

Since
  GDAL 3.8

## ◆ DeleteGroup()

bool GDALGroup::DeleteGroup | ( | const std::string & | osName,
|  | CSLConstList | papszOptions = `nullptr`
| ) |  |
| virtual

Delete a sub-group from a group.

Optionally implemented.

After this call, if a previously obtained instance of the deleted object is still alive, no method other than for freeing it should be invoked.

Drivers known to implement it: MEM, Zarr

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

Parameters

  osName | Sub-group name.
  papszOptions | Driver specific options determining how the group. should be deleted.

Returns
  true in case of success

Since
  GDAL 3.8

## ◆ DeleteMDArray()

bool GDALGroup::DeleteMDArray | ( | const std::string & | osName,
|  | CSLConstList | papszOptions = `nullptr`
| ) |  |
| virtual

Delete an array from a group.

Optionally implemented.

After this call, if a previously obtained instance of the deleted object is still alive, no method other than for freeing it should be invoked.

Drivers known to implement it: MEM, Zarr

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

Parameters

  osName | Arrayname.
  papszOptions | Driver specific options determining how the array. should be deleted.

Returns
  true in case of success

Since
  GDAL 3.8

## ◆ GetAttribute()

std::shared_ptr< GDALAttribute > GDALIHasAttribute::GetAttribute | ( | const std::string & | osName | ) | const
| virtual inherited

Return an attribute by its name.

If the attribute does not exist, nullptr should be silently returned.

Note
  Driver implementation: this method will fallback to GetAttributeFromAttributes() is not explicitly implemented

Drivers known to implement it for groups and arrays: MEM, netCDF.

This is the same as the C function GDALGroupGetAttribute() or GDALMDArrayGetAttribute().

Parameters

  osName | Attribute name

Returns
  the attribute, or nullptr if it does not exist or an error occurred.

## ◆ GetAttributes()

std::vector< std::shared_ptr< GDALAttribute > > GDALIHasAttribute::GetAttributes | ( | CSLConstList | papszOptions = `nullptr` | ) | const
| virtual inherited

Return the list of attributes contained in a GDALMDArray or GDALGroup.

If the attribute does not exist, nullptr should be silently returned.

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

Drivers known to implement it for groups and arrays: MEM, netCDF.

This is the same as the C function GDALGroupGetAttributes() or GDALMDArrayGetAttributes().

Parameters

  papszOptions | Driver specific options determining how attributes should be retrieved. Pass nullptr for default behavior.

Returns
  the attributes.

## ◆ GetDimensions()

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

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().

Parameters

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

Returns
  the dimensions.

## ◆ GetFullName()

const std::string & GDALGroup::GetFullName | ( |  | ) | const
| inline

Return the full name of the group.

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

## ◆ GetGroupNames()

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

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

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

Drivers known to implement it: MEM, netCDF.

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

Parameters

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

Returns
  the group names.

## ◆ GetMDArrayNames()

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

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

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

Drivers known to implement it: MEM, netCDF.

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

Parameters

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

Returns
  the array names.

## ◆ GetName()

const std::string & GDALGroup::GetName | ( |  | ) | const
| inline

Return the name of the group.

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

## ◆ GetStructuralInfo()

CSLConstList GDALGroup::GetStructuralInfo | ( |  | ) | const
| virtual

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 GDALGroupGetStructuralInfo().

## ◆ GetTotalCopyCost()

GUInt64 GDALGroup::GetTotalCopyCost | ( |  | ) | const

Return a total "cost" to copy the group.

Used as a parameter for CopFrom()

## ◆ GetVectorLayerNames()

std::vector< std::string > GDALGroup::GetVectorLayerNames | ( | CSLConstList | papszOptions = `nullptr` | ) | const
| virtual

Return the list of layer names contained in this group.

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

Drivers known to implement it: OpenFileGDB, FileGDB

Other drivers will return an empty list. GDALDataset::GetLayerCount() and GDALDataset::GetLayer() should then be used.

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

Parameters

  papszOptions | Driver specific options determining how layers should be retrieved. Pass nullptr for default behavior.

Returns
  the vector layer names.

Since
  GDAL 3.4

## ◆ OpenGroup()

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

Open and return a sub-group.

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

Drivers known to implement it: MEM, netCDF.

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

Parameters

  osName | Sub-group name.
  papszOptions | Driver specific options determining how the sub-group should be opened. Pass nullptr for default behavior.

Returns
  the group, or nullptr.

## ◆ OpenGroupFromFullname()

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

Get a group from its fully qualified name.

Since
  GDAL 3.2

## ◆ OpenMDArray()

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

Open and return a multidimensional array.

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

Drivers known to implement it: MEM, netCDF.

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

Parameters

  osName | Array name.
  papszOptions | Driver specific options determining how the array should be opened. Pass nullptr for default behavior.

Returns
  the array, or nullptr.

## ◆ OpenVectorLayer()

OGRLayer * GDALGroup::OpenVectorLayer | ( | const std::string & | osName,
|  | CSLConstList | papszOptions = `nullptr`
| ) |  | const
| virtual

Open and return a vector layer.

Due to the historical ownership of OGRLayer* by GDALDataset*, the lifetime of the returned OGRLayer* is linked to the one of the owner dataset (contrary to the general design of this class where objects can be used independently of the object that returned them)

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

Drivers known to implement it: MEM, netCDF.

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

Parameters

  osName | Vector layer name.
  papszOptions | Driver specific options determining how the layer should be opened. Pass nullptr for default behavior.

Returns
  the group, or nullptr.

## ◆ Rename()

bool GDALGroup::Rename | ( | const std::string & | osNewName | ) |
| virtual

Rename the group.

This is not implemented by all drivers.

Drivers known to implement it: MEM, netCDF, ZARR.

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

Parameters

  osNewName | New name.

Returns
  true in case of success

Since
  GDAL 3.8

## ◆ ResolveMDArray()

std::shared_ptr< GDALMDArray > GDALGroup::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.

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()

Since
  GDAL 3.2

## ◆ SubsetDimensionFromSelection()

std::shared_ptr< GDALGroup > GDALGroup::SubsetDimensionFromSelection | ( | const std::string & | osSelection | ) | const

Return a virtual group whose one dimension has been subset according to a selection.

The selection criterion is currently restricted to the form "/path/to/array=numeric_value" (no spaces around equal)

This is similar to XArray indexing by name and label on a XArray Dataset using the sel() method. Cf https://docs.xarray.dev/en/latest/user-guide/indexing.html#quick-overview

For example on a EMIT L2A product (https://github.com/nasa/EMIT-Data-Resources/blob/main/python/tutorials/Exploring_EMIT_L2A_Reflectance.ipynb), this can be used to keep only valid bands with SubsetDimensionFromSelection("/sensor_band_parameters/good_wavelengths=1")

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

Parameters

  osSelection | Selection criterion.

Returns
  a virtual group, or nullptr in case of error

Since
  3.8

The documentation for this class was generated from the following files:

- gdal_priv.h
- gdalmultidim.cpp
- gdalmultidim_subsetdimension.cpp