GDALDataset C++ API

class GDALDataset : public GDALMajorObject

A set of associated raster bands, usually from one file.

A dataset encapsulating one or more raster bands.

Details are further discussed in the GDAL Data Model.

Use GDALOpen() or GDALOpenShared() to create a GDALDataset for a named file, or GDALDriver::Create() or GDALDriver::CreateCopy() to create a new dataset.

Subclassed by GDALApplyVSGDataset, GDALColorReliefDataset, GDALDatasetFromArray, GDALGeneric3x3Dataset< T >, GDALOverviewDataset, GDALPamDataset, GDALVectorTranslateWrappedDataset, GNMNetwork, OGRDataSource, PythonPluginDataset

Public Functions

~GDALDataset() override

Destroy an open GDALDataset.

This is the accepted method of closing a GDAL dataset and deallocating all resources associated with it.

Equivalent of the C callable GDALClose(). Except that GDALClose() first decrements the reference count, and then closes only if it has dropped to zero.

For Windows users, it is not recommended to use the delete operator on the dataset object because of known issues when allocating and freeing memory across module boundaries. Calling GDALClose() is then a better option.

int GetRasterXSize()

Fetch raster width in pixels.

Equivalent of the C function GDALGetRasterXSize().

Returns

the width in pixels of raster bands in this GDALDataset.

int GetRasterYSize()

Fetch raster height in pixels.

Equivalent of the C function GDALGetRasterYSize().

Returns

the height in pixels of raster bands in this GDALDataset.

int GetRasterCount()

Fetch the number of raster bands on this dataset.

Same as the C function GDALGetRasterCount().

Returns

the number of raster bands.

GDALRasterBand *GetRasterBand(int)

Fetch a band object for a dataset.

See GetBands() for a C++ iterator version of this method.

Equivalent of the C function GDALGetRasterBand().

Parameters

nBandId – the index number of the band to fetch, from 1 to GetRasterCount().

Returns

the nBandId th band object

Bands GetBands()

Function that returns an iterable object over GDALRasterBand in the dataset.

This is a C++ iterator friendly version of GetRasterBand().

Typical use is:

for( auto&& poBand: poDS->GetBands() )
{
      std::cout << "Band  << poBand->GetDescription() << std::endl;
}

See

GetRasterBand()

Since

GDAL 2.3

virtual void FlushCache(void)

Flush all write cached data to disk.

Any raster (or other GDAL) data written via GDAL calls, but buffered internally will be written to disk.

The default implementation of this method just calls the FlushCache() method on each of the raster bands and the SyncToDisk() method on each of the layers. Conceptionally, calling FlushCache() on a dataset should include any work that might be accomplished by calling SyncToDisk() on layers in that dataset.

Using this method does not prevent use from calling GDALClose() to properly close a dataset and ensure that important data not addressed by FlushCache() is written in the file.

This method is the same as the C function GDALFlushCache().

virtual const OGRSpatialReference *GetSpatialRef() const

Fetch the spatial reference for this dataset.

Same as the C function GDALGetSpatialRef().

When a projection definition is not available, null is returned. If used on a dataset where there are GCPs and not a geotransform, this method returns null. Use GetGCPSpatialRef() instead.

Since

GDAL 3.0

See

https://gdal.org/tutorials/osr_api_tut.html

Returns

a pointer to an internal object. It should not be altered or freed. Its lifetime will be the one of the dataset object, or until the next call to this method.

virtual CPLErr SetSpatialRef(const OGRSpatialReference *poSRS)

Set the spatial reference system for this dataset.

An error may occur because the dataset is not writable, or because the dataset does not support the indicated projection. Many formats do not support writing projections.

This method is the same as the C GDALSetSpatialRef() function.

Since

GDAL 3.0

Parameters

poSRS – spatial reference system object. nullptr can potentially be passed for drivers that support unsetting the SRS.

Returns

CE_Failure if an error occurs, otherwise CE_None.

const char *GetProjectionRef(void) const

Fetch the projection definition string for this dataset.

Same as the C function GDALGetProjectionRef().

The returned string defines the projection coordinate system of the image in OpenGIS WKT format. It should be suitable for use with the OGRSpatialReference class.

When a projection definition is not available an empty (but not NULL) string is returned.

See

https://gdal.org/tutorials/osr_api_tut.html

Note

Startig with GDAL 3.0, this is a compatibility layer around GetSpatialRef()

Returns

a pointer to an internal projection reference string. It should not be altered, freed or expected to last for long.

CPLErr SetProjection(const char *pszProjection)

Set the projection reference string for this dataset.

The string should be in OGC WKT or PROJ.4 format. An error may occur because of incorrectly specified projection strings, because the dataset is not writable, or because the dataset does not support the indicated projection. Many formats do not support writing projections.

This method is the same as the C GDALSetProjection() function.

Note

Startig with GDAL 3.0, this is a compatibility layer around SetSpatialRef()

Parameters

pszProjection – projection reference string.

Returns

CE_Failure if an error occurs, otherwise CE_None.

virtual CPLErr GetGeoTransform(double *padfTransform)

Fetch the affine transformation coefficients.

Fetches the coefficients for transforming between pixel/line (P,L) raster space, and projection coordinates (Xp,Yp) space.

Xp = padfTransform[0] + P*padfTransform[1] + L*padfTransform[2];
Yp = padfTransform[3] + P*padfTransform[4] + L*padfTransform[5];

In a north up image, padfTransform[1] is the pixel width, and padfTransform[5] is the pixel height. The upper left corner of the upper left pixel is at position (padfTransform[0],padfTransform[3]).

The default transform is (0,1,0,0,0,1) and should be returned even when a CE_Failure error is returned, such as for formats that don’t support transformation to projection coordinates.

This method does the same thing as the C GDALGetGeoTransform() function.

Parameters

padfTransform – an existing six double buffer into which the transformation will be placed.

Returns

CE_None on success, or CE_Failure if no transform can be fetched.

virtual CPLErr SetGeoTransform(double *padfTransform)

Set the affine transformation coefficients.

See GetGeoTransform() for details on the meaning of the padfTransform coefficients.

This method does the same thing as the C GDALSetGeoTransform() function.

Parameters

padfTransform – a six double buffer containing the transformation coefficients to be written with the dataset.

Returns

CE_None on success, or CE_Failure if this transform cannot be written.

virtual CPLErr AddBand(GDALDataType eType, char **papszOptions = nullptr)

Add a band to a dataset.

This method will add a new band to the dataset if the underlying format supports this action. Most formats do not.

Note that the new GDALRasterBand is not returned. It may be fetched after successful completion of the method by calling GDALDataset::GetRasterBand(GDALDataset::GetRasterCount()) as the newest band will always be the last band.

Parameters
  • eType – the data type of the pixels in the new band.

  • papszOptions – a list of NAME=VALUE option strings. The supported options are format specific. NULL may be passed by default.

Returns

CE_None on success or CE_Failure on failure.

virtual void *GetInternalHandle(const char *pszHandleName)

Fetch a format specific internally meaningful handle.

This method is the same as the C GDALGetInternalHandle() method.

Parameters

pszHandleName – the handle name desired. The meaningful names will be specific to the file format.

Returns

the desired handle value, or NULL if not recognized/supported.

virtual GDALDriver *GetDriver(void)

Fetch the driver to which this dataset relates.

This method is the same as the C GDALGetDatasetDriver() function.

Returns

the driver on which the dataset was created with GDALOpen() or GDALCreate().

virtual char **GetFileList(void)

Fetch files forming dataset.

Returns a list of files believed to be part of this dataset. If it returns an empty list of files it means there is believed to be no local file system files associated with the dataset (for instance a virtual dataset). The returned file list is owned by the caller and should be deallocated with CSLDestroy().

The returned filenames will normally be relative or absolute paths depending on the path used to originally open the dataset. The strings will be UTF-8 encoded.

This method is the same as the C GDALGetFileList() function.

Returns

NULL or a NULL terminated array of file names.

virtual const char *GetDriverName()

Return driver name.

Returns

driver name.

virtual const OGRSpatialReference *GetGCPSpatialRef() const

Get output spatial reference system for GCPs.

Same as the C function GDALGetGCPSpatialRef().

When a SRS is not available, null is returned. If used on a dataset where there is a geotransform, and not GCPs, this method returns null. Use GetSpatialRef() instead.

Since

GDAL 3.0

Returns

a pointer to an internal object. It should not be altered or freed. Its lifetime will be the one of the dataset object, or until the next call to this method.

virtual int GetGCPCount()

Get number of GCPs.

This method is the same as the C function GDALGetGCPCount().

Returns

number of GCPs for this dataset. Zero if there are none.

virtual const GDAL_GCP *GetGCPs()

Fetch GCPs.

This method is the same as the C function GDALGetGCPs().

Returns

pointer to internal GCP structure list. It should not be modified, and may change on the next GDAL call.

virtual CPLErr SetGCPs(int nGCPCount, const GDAL_GCP *pasGCPList, const OGRSpatialReference *poGCP_SRS)

Assign GCPs.

This method is the same as the C function GDALSetGCPs().

This method assigns the passed set of GCPs to this dataset, as well as setting their coordinate system. Internally copies are made of the coordinate system and list of points, so the caller remains responsible for deallocating these arguments if appropriate.

Most formats do not support setting of GCPs, even formats that can handle GCPs. These formats will return CE_Failure.

Since

GDAL 3.0

Parameters
  • nGCPCount – number of GCPs being assigned.

  • pasGCPList – array of GCP structures being assign (nGCPCount in array).

  • poGCP_SRS – the new coordinate reference system to assign for the GCP output coordinates. This parameter should be null if no output coordinate system is known.

Returns

CE_None on success, CE_Failure on failure (including if action is not supported for this format).

const char *GetGCPProjection()

Get output projection for GCPs.

This method is the same as the C function GDALGetGCPProjection().

The projection string follows the normal rules from GetProjectionRef().

Note

Starting with GDAL 3.0, this is a compatibility layer around GetGCPSpatialRef()

Returns

internal projection string or “” if there are no GCPs. It should not be altered, freed or expected to last for long.

CPLErr SetGCPs(int nGCPCount, const GDAL_GCP *pasGCPList, const char *pszGCPProjection)

Assign GCPs.

This method is the same as the C function GDALSetGCPs().

This method assigns the passed set of GCPs to this dataset, as well as setting their coordinate system. Internally copies are made of the coordinate system and list of points, so the caller remains responsible for deallocating these arguments if appropriate.

Most formats do not support setting of GCPs, even formats that can handle GCPs. These formats will return CE_Failure.

Note

Startig with GDAL 3.0, this is a compatibility layer around SetGCPs(int, const GDAL_GCP*, const char*)

Parameters
  • nGCPCount – number of GCPs being assigned.

  • pasGCPList – array of GCP structures being assign (nGCPCount in array).

  • pszGCPProjection – the new OGC WKT coordinate system to assign for the GCP output coordinates. This parameter should be “” if no output coordinate system is known.

Returns

CE_None on success, CE_Failure on failure (including if action is not supported for this format).

virtual CPLErr AdviseRead(int nXOff, int nYOff, int nXSize, int nYSize, int nBufXSize, int nBufYSize, GDALDataType eDT, int nBandCount, int *panBandList, char **papszOptions)

Advise driver of upcoming read requests.

Some GDAL drivers operate more efficiently if they know in advance what set of upcoming read requests will be made. The AdviseRead() method allows an application to notify the driver of the region and bands of interest, and at what resolution the region will be read.

Many drivers just ignore the AdviseRead() call, but it can dramatically accelerate access via some drivers.

Depending on call paths, drivers might receive several calls to AdviseRead() with the same parameters.

Parameters
  • nXOff – The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side.

  • nYOff – The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top.

  • nXSize – The width of the region of the band to be accessed in pixels.

  • nYSize – The height of the region of the band to be accessed in lines.

  • nBufXSize – the width of the buffer image into which the desired region is to be read, or from which it is to be written.

  • nBufYSize – the height of the buffer image into which the desired region is to be read, or from which it is to be written.

  • eBufType – the type of the pixel values in the pData data buffer. The pixel values will automatically be translated to/from the GDALRasterBand data type as needed.

  • nBandCount – the number of bands being read or written.

  • panBandMap – the list of nBandCount band numbers being read/written. Note band numbers are 1 based. This may be NULL to select the first nBandCount bands.

  • papszOptions – a list of name=value strings with special control options. Normally this is NULL.

Returns

CE_Failure if the request is invalid and CE_None if it works or is ignored.

virtual CPLErr CreateMaskBand(int nFlagsIn)

Adds a mask band to the dataset.

The default implementation of the CreateMaskBand() method is implemented based on similar rules to the .ovr handling implemented using the GDALDefaultOverviews object. A TIFF file with the extension .msk will be created with the same basename as the original file, and it will have one band. The mask images will be deflate compressed tiled images with the same block size as the original image if possible. It will have INTERNAL_MASK_FLAGS_xx metadata items set at the dataset level, where xx matches the band number of a band of the main dataset. The value of those items will be the one of the nFlagsIn parameter.

Note that if you got a mask band with a previous call to GetMaskBand(), it might be invalidated by CreateMaskBand(). So you have to call GetMaskBand() again.

Since

GDAL 1.5.0

See

https://gdal.org/development/rfc/rfc15_nodatabitmask.html

See

GDALRasterBand::CreateMaskBand()

Parameters

nFlagsIn – 0 or combination of GMF_PER_DATASET / GMF_ALPHA. GMF_PER_DATASET will be always set, even if not explicitly specified.

Returns

CE_None on success or CE_Failure on an error.

virtual GDALAsyncReader *BeginAsyncReader(int nXOff, int nYOff, int nXSize, int nYSize, void *pBuf, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nBandCount, int *panBandMap, int nPixelSpace, int nLineSpace, int nBandSpace, char **papszOptions)

Sets up an asynchronous data request.

This method establish an asynchronous raster read request for the indicated window on the dataset into the indicated buffer. The parameters for windowing, buffer size, buffer type and buffer organization are similar to those for GDALDataset::RasterIO(); however, this call only launches the request and filling the buffer is accomplished via calls to GetNextUpdatedRegion() on the return GDALAsyncReader session object.

Once all processing for the created session is complete, or if no further refinement of the request is required, the GDALAsyncReader object should be destroyed with the GDALDataset::EndAsyncReader() method.

Note that the data buffer (pData) will potentially continue to be updated as long as the session lives, but it is not deallocated when the session (GDALAsyncReader) is destroyed with EndAsyncReader(). It should be deallocated by the application at that point.

Additional information on asynchronous IO in GDAL may be found at: https://gdal.org/development/rfc/rfc24_progressive_data_support.html

This method is the same as the C GDALBeginAsyncReader() function.

Parameters
  • nXOff – The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side.

  • nYOff – The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top.

  • nXSize – The width of the region of the band to be accessed in pixels.

  • nYSize – The height of the region of the band to be accessed in lines.

  • pBuf – The buffer into which the data should be read. This buffer must contain at least nBufXSize * nBufYSize * nBandCount words of type eBufType. It is organized in left to right,top to bottom pixel order. Spacing is controlled by the nPixelSpace, and nLineSpace parameters.

  • nBufXSize – the width of the buffer image into which the desired region is to be read, or from which it is to be written.

  • nBufYSize – the height of the buffer image into which the desired region is to be read, or from which it is to be written.

  • eBufType – the type of the pixel values in the pData data buffer. The pixel values will automatically be translated to/from the GDALRasterBand data type as needed.

  • nBandCount – the number of bands being read or written.

  • panBandMap – the list of nBandCount band numbers being read/written. Note band numbers are 1 based. This may be NULL to select the first nBandCount bands.

  • nPixelSpace – The byte offset from the start of one pixel value in pData to the start of the next pixel value within a scanline. If defaulted (0) the size of the datatype eBufType is used.

  • nLineSpace – The byte offset from the start of one scanline in pData to the start of the next. If defaulted the size of the datatype eBufType * nBufXSize is used.

  • nBandSpace – the byte offset from the start of one bands data to the start of the next. If defaulted (zero) the value will be nLineSpace * nBufYSize implying band sequential organization of the data buffer.

  • papszOptions – Driver specific control options in a string list or NULL. Consult driver documentation for options supported.

Returns

The GDALAsyncReader object representing the request.

virtual void EndAsyncReader(GDALAsyncReader*)

End asynchronous request.

This method destroys an asynchronous io request and recovers all resources associated with it.

This method is the same as the C function GDALEndAsyncReader().

Parameters

poARIO – pointer to a GDALAsyncReader

CPLErr RasterIO(GDALRWFlag, int, int, int, int, void*, int, int, GDALDataType, int, int*, GSpacing, GSpacing, GSpacing, GDALRasterIOExtraArg *psExtraArg)

Read/write a region of image data from multiple bands.

This method allows reading a region of one or more GDALRasterBands from this dataset into a buffer, or writing data from a buffer into a region of the GDALRasterBands. It automatically takes care of data type translation if the data type (eBufType) of the buffer is different than that of the GDALRasterBand. The method also takes care of image decimation / replication if the buffer size (nBufXSize x nBufYSize) is different than the size of the region being accessed (nXSize x nYSize).

The nPixelSpace, nLineSpace and nBandSpace parameters allow reading into or writing from various organization of buffers.

For highest performance full resolution data access, read and write on “block boundaries” as returned by GetBlockSize(), or use the ReadBlock() and WriteBlock() methods.

This method is the same as the C GDALDatasetRasterIO() or GDALDatasetRasterIOEx() functions.

Parameters
  • eRWFlag – Either GF_Read to read a region of data, or GF_Write to write a region of data.

  • nXOff – The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side.

  • nYOff – The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top.

  • nXSize – The width of the region of the band to be accessed in pixels.

  • nYSize – The height of the region of the band to be accessed in lines.

  • pData – The buffer into which the data should be read, or from which it should be written. This buffer must contain at least nBufXSize * nBufYSize * nBandCount words of type eBufType. It is organized in left to right,top to bottom pixel order. Spacing is controlled by the nPixelSpace, and nLineSpace parameters.

  • nBufXSize – the width of the buffer image into which the desired region is to be read, or from which it is to be written.

  • nBufYSize – the height of the buffer image into which the desired region is to be read, or from which it is to be written.

  • eBufType – the type of the pixel values in the pData data buffer. The pixel values will automatically be translated to/from the GDALRasterBand data type as needed.

  • nBandCount – the number of bands being read or written.

  • panBandMap – the list of nBandCount band numbers being read/written. Note band numbers are 1 based. This may be NULL to select the first nBandCount bands.

  • nPixelSpace – The byte offset from the start of one pixel value in pData to the start of the next pixel value within a scanline. If defaulted (0) the size of the datatype eBufType is used.

  • nLineSpace – The byte offset from the start of one scanline in pData to the start of the next. If defaulted (0) the size of the datatype eBufType * nBufXSize is used.

  • nBandSpace – the byte offset from the start of one bands data to the start of the next. If defaulted (0) the value will be nLineSpace * nBufYSize implying band sequential organization of the data buffer.

  • psExtraArg – (new in GDAL 2.0) pointer to a GDALRasterIOExtraArg structure with additional arguments to specify resampling and progress callback, or NULL for default behavior. The GDAL_RASTERIO_RESAMPLING configuration option can also be defined to override the default resampling to one of BILINEAR, CUBIC, CUBICSPLINE, LANCZOS, AVERAGE or MODE.

Returns

CE_Failure if the access fails, otherwise CE_None.

int Reference()

Add one to dataset reference count.

The reference is one after instantiation.

This method is the same as the C GDALReferenceDataset() function.

Returns

the post-increment reference count.

int Dereference()

Subtract one from dataset reference count.

The reference is one after instantiation. Generally when the reference count has dropped to zero the dataset may be safely deleted (closed).

This method is the same as the C GDALDereferenceDataset() function.

Returns

the post-decrement reference count.

int ReleaseRef()

Drop a reference to this object, and destroy if no longer referenced.

Since

GDAL 2.2

Returns

TRUE if the object has been destroyed.

inline GDALAccess GetAccess() const

Return access mode.

Returns

access mode.

int GetShared() const

Returns shared flag.

Returns

TRUE if the GDALDataset is available for sharing, or FALSE if not.

void MarkAsShared()

Mark this dataset as available for sharing.

inline void MarkSuppressOnClose()

Set that the dataset must be deleted on close.

inline char **GetOpenOptions()

Return open options.

Returns

open options.

CPLErr BuildOverviews(const char*, int, int*, int, int*, GDALProgressFunc, void*)

Build raster overview(s)

If the operation is unsupported for the indicated dataset, then CE_Failure is returned, and CPLGetLastErrorNo() will return CPLE_NotSupported.

Depending on the actual file format, all overviews level can be also deleted by specifying nOverviews == 0. This works at least for external overviews (.ovr), TIFF internal overviews, etc.

Starting with GDAL 3.2, the GDAL_NUM_THREADS configuration option can be set to “ALL_CPUS” or a integer value to specify the number of threads to use for overview computation.

This method is the same as the C function GDALBuildOverviews().

For example, to build overview level 2, 4 and 8 on all bands the following call could be made:

int       anOverviewList[3] = { 2, 4, 8 };

poDataset->BuildOverviews( "NEAREST", 3, anOverviewList, 0, nullptr,
                           GDALDummyProgress, nullptr );

See

GDALRegenerateOverviews()

Parameters
  • pszResampling – one of “AVERAGE”, “AVERAGE_MAGPHASE”, “RMS”, “BILINEAR”, “CUBIC”, “CUBICSPLINE”, “GAUSS”, “LANCZOS”, “MODE”, “NEAREST”, or “NONE” controlling the downsampling method applied.

  • nOverviews – number of overviews to build, or 0 to clean overviews.

  • panOverviewList – the list of overview decimation factors to build, or NULL if nOverviews == 0.

  • nListBands – number of bands to build overviews for in panBandList. Build for all bands if this is 0.

  • panBandList – list of band numbers.

  • pfnProgress – a function to call to report progress, or NULL.

  • pProgressData – application data to pass to the progress function.

Returns

CE_None on success or CE_Failure if the operation doesn’t work.

virtual char **GetMetadata(const char *pszDomain = "") override

Fetch metadata.

The returned string list is owned by the object, and may change at any time. It is formatted as a “Name=value” list with the last pointer value being NULL. Use the CPL StringList functions such as CSLFetchNameValue() to manipulate it.

Note that relatively few formats return any metadata at this time.

This method does the same thing as the C function GDALGetMetadata().

Parameters

pszDomain – the domain of interest. Use “” or NULL for the default domain.

Returns

NULL or a string list.

virtual CPLErr SetMetadata(char **papszMetadata, const char *pszDomain) override

Set metadata.

CAUTION: depending on the format, older values of the updated information might still be found in the file in a “ghost” state, even if no longer accessible through the GDAL API. This is for example the case of the GTiff format (this is not a exhaustive list)

The C function GDALSetMetadata() does the same thing as this method.

Parameters
  • papszMetadata – the metadata in name=value string list format to apply.

  • pszDomain – the domain of interest. Use “” or NULL for the default domain.

Returns

CE_None on success, CE_Failure on failure and CE_Warning if the metadata has been accepted, but is likely not maintained persistently by the underlying object between sessions.

virtual CPLErr SetMetadataItem(const char *pszName, const char *pszValue, const char *pszDomain) override

Set single metadata item.

CAUTION: depending on the format, older values of the updated information might still be found in the file in a “ghost” state, even if no longer accessible through the GDAL API. This is for example the case of the GTiff format (this is not a exhaustive list)

The C function GDALSetMetadataItem() does the same thing as this method.

Parameters
  • pszName – the key for the metadata item to fetch.

  • pszValue – the value to assign to the key.

  • pszDomain – the domain to set within, use NULL for the default domain.

Returns

CE_None on success, or an error code on failure.

virtual char **GetMetadataDomainList() override

Fetch list of metadata domains.

The returned string list is the list of (non-empty) metadata domains.

This method does the same thing as the C function GDALGetMetadataDomainList().

Since

GDAL 1.11

Returns

NULL or a string list. Must be freed with CSLDestroy()

virtual void ClearStatistics()

Clear statistics.

Only implemented for now in PAM supported datasets

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

Since

GDAL 3.2

virtual int GetLayerCount()

Get the number of layers in this dataset.

This method is the same as the C function GDALDatasetGetLayerCount(), and the deprecated OGR_DS_GetLayerCount().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Returns

layer count.

virtual OGRLayer *GetLayer(int iLayer)

Fetch a layer by index.

The returned layer remains owned by the GDALDataset and should not be deleted by the application.

See GetLayers() for a C++ iterator version of this method.

This method is the same as the C function GDALDatasetGetLayer() and the deprecated OGR_DS_GetLayer().

In GDAL 1.X, this method used to be in the OGRDataSource class.

See

GetLayers()

Parameters

iLayer – a layer number between 0 and GetLayerCount()-1.

Returns

the layer, or NULL if iLayer is out of range or an error occurs.

Layers GetLayers()

Function that returns an iterable object over layers in the dataset.

This is a C++ iterator friendly version of GetLayer().

Typical use is:

for( auto&& poLayer: poDS->GetLayers() )
{
      std::cout << "Layer  << poLayer->GetName() << std::endl;
}

See

GetLayer()

Since

GDAL 2.3

virtual OGRLayer *GetLayerByName(const char*)

Fetch a layer by name.

The returned layer remains owned by the GDALDataset and should not be deleted by the application.

This method is the same as the C function GDALDatasetGetLayerByName() and the deprecated OGR_DS_GetLayerByName().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

pszName – the layer name of the layer to fetch.

Returns

the layer, or NULL if Layer is not found or an error occurs.

virtual OGRErr DeleteLayer(int iLayer)

Delete the indicated layer from the datasource.

If this method is supported the ODsCDeleteLayer capability will test TRUE on the GDALDataset.

This method is the same as the C function GDALDatasetDeleteLayer() and the deprecated OGR_DS_DeleteLayer().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

iLayer – the index of the layer to delete.

Returns

OGRERR_NONE on success, or OGRERR_UNSUPPORTED_OPERATION if deleting layers is not supported for this datasource.

virtual void ResetReading()

Reset feature reading to start on the first feature.

This affects GetNextFeature().

Depending on drivers, this may also have the side effect of calling OGRLayer::ResetReading() on the layers of this dataset.

This method is the same as the C function GDALDatasetResetReading().

Since

GDAL 2.2

virtual OGRFeature *GetNextFeature(OGRLayer **ppoBelongingLayer, double *pdfProgressPct, GDALProgressFunc pfnProgress, void *pProgressData)

Fetch the next available feature from this dataset.

This method is intended for the few drivers where OGRLayer::GetNextFeature() is not efficient, but in general OGRLayer::GetNextFeature() is a more natural API.

See GetFeatures() for a C++ iterator version of this method.

The returned feature becomes the responsibility of the caller to delete with OGRFeature::DestroyFeature().

Depending on the driver, this method may return features from layers in a non sequential way. This is what may happen when the ODsCRandomLayerRead capability is declared (for example for the OSM and GMLAS drivers). When datasets declare this capability, it is strongly advised to use GDALDataset::GetNextFeature() instead of OGRLayer::GetNextFeature(), as the later might have a slow, incomplete or stub implementation.

The default implementation, used by most drivers, will however iterate over each layer, and then over each feature within this layer.

This method takes into account spatial and attribute filters set on layers that will be iterated upon.

The ResetReading() method can be used to start at the beginning again.

Depending on drivers, this may also have the side effect of calling OGRLayer::GetNextFeature() on the layers of this dataset.

This method is the same as the C function GDALDatasetGetNextFeature().

Since

GDAL 2.2

See

GetFeatures()

Parameters
  • ppoBelongingLayer – a pointer to a OGRLayer* variable to receive the layer to which the object belongs to, or NULL. It is possible that the output of *ppoBelongingLayer to be NULL despite the feature not being NULL.

  • pdfProgressPct – a pointer to a double variable to receive the percentage progress (in [0,1] range), or NULL. On return, the pointed value might be negative if determining the progress is not possible.

  • pfnProgress – a progress callback to report progress (for GetNextFeature() calls that might have a long duration) and offer cancellation possibility, or NULL.

  • pProgressData – user data provided to pfnProgress, or NULL

Returns

a feature, or NULL if no more features are available.

Features GetFeatures()

Function that return an iterable object over features in the dataset layer.

This is a C++ iterator friendly version of GetNextFeature().

Using this iterator for standard range-based loops is safe, but due to implementation limitations, you shouldn’t try to access (dereference) more than one iterator step at a time, since the FeatureLayerPair reference which is returned is reused.

Typical use is:

for( auto&& oFeatureLayerPair: poDS->GetFeatures() )
{
      std::cout << "Feature of layer " <<
              oFeatureLayerPair.layer->GetName() << std::endl;
      oFeatureLayerPair.feature->DumpReadable();
}

See

GetNextFeature()

Since

GDAL 2.3

virtual int TestCapability(const char*)

Test if capability is available.

One of the following dataset capability names can be passed into this method, and a TRUE or FALSE value will be returned indicating whether or not the capability is available for this object.

  • ODsCCreateLayer: True if this datasource can create new layers.

  • ODsCDeleteLayer: True if this datasource can delete existing layers.

  • ODsCCreateGeomFieldAfterCreateLayer: True if the layers of this datasource support CreateGeomField() just after layer creation.

  • ODsCCurveGeometries: True if this datasource supports curve geometries.

  • ODsCTransactions: True if this datasource supports (efficient) transactions.

  • ODsCEmulatedTransactions: True if this datasource supports transactions through emulation.

  • ODsCRandomLayerRead: True if this datasource has a dedicated GetNextFeature() implementation, potentially returning features from layers in a non sequential way.

  • ODsCRandomLayerWrite: True if this datasource supports calling CreateFeature() on layers in a non sequential way.

The #define macro forms of the capability names should be used in preference to the strings themselves to avoid misspelling.

This method is the same as the C function GDALDatasetTestCapability() and the deprecated OGR_DS_TestCapability().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

pszCap – the capability to test.

Returns

TRUE if capability available otherwise FALSE.

virtual const OGRFieldDomain *GetFieldDomain(const std::string &name) const

Get a field domain from its name.

Since

GDAL 3.3

Returns

the field domain, or nullptr if not found.

virtual bool AddFieldDomain(std::unique_ptr<OGRFieldDomain> &&domain, std::string &failureReason)

Add a field domain to the dataset.

Only a few drivers will support this operation, and some of them might only support it only for some types of field domains. At the time of writing (GDAL 3.3), only the Memory and GeoPackage drivers support this operation. A dataset having at least some support for this operation should report the ODsCAddFieldDomain dataset capability.

Anticipated failures will not be emitted through the CPLError() infrastructure, but will be reported in the failureReason output parameter.

Since

GDAL 3.3

Parameters
  • domain – The domain definition.

  • failureReason – Output parameter. Will contain an error message if an error occurs.

Returns

true in case of success.

virtual OGRLayer *CreateLayer(const char *pszName, OGRSpatialReference *poSpatialRef = nullptr, OGRwkbGeometryType eGType = wkbUnknown, char **papszOptions = nullptr)

This method attempts to create a new layer on the dataset with the indicated name, coordinate system, geometry type.

The papszOptions argument can be used to control driver specific creation options. These options are normally documented in the format specific documentation.

In GDAL 2.0, drivers should extend the ICreateLayer() method and not CreateLayer(). CreateLayer() adds validation of layer creation options, before delegating the actual work to ICreateLayer().

This method is the same as the C function GDALDatasetCreateLayer() and the deprecated OGR_DS_CreateLayer().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Example:

#include "gdal.h"
#include "cpl_string.h"

...

        OGRLayer *poLayer;
        char     **papszOptions;

        if( !poDS->TestCapability( ODsCCreateLayer ) )
        {
        ...
        }

        papszOptions = CSLSetNameValue( papszOptions, "DIM", "2" );
        poLayer = poDS->CreateLayer( "NewLayer", nullptr, wkbUnknown,
                                     papszOptions );
        CSLDestroy( papszOptions );

        if( poLayer == NULL )
        {
            ...
        }

Parameters
  • pszName – the name for the new layer. This should ideally not match any existing layer on the datasource.

  • poSpatialRef – the coordinate system to use for the new layer, or NULL if no coordinate system is available. The driver might only increase the reference counter of the object to take ownership, and not make a full copy, so do not use OSRDestroySpatialReference(), but OSRRelease() instead when you are done with the object.

  • eGType – the geometry type for the layer. Use wkbUnknown if there are no constraints on the types geometry to be written.

  • papszOptions – a StringList of name=value options. Options are driver specific.

Returns

NULL is returned on failure, or a new OGRLayer handle on success.

virtual OGRLayer *CopyLayer(OGRLayer *poSrcLayer, const char *pszNewName, char **papszOptions = nullptr)

Duplicate an existing layer.

This method creates a new layer, duplicate the field definitions of the source layer and then duplicate each features of the source layer. The papszOptions argument can be used to control driver specific creation options. These options are normally documented in the format specific documentation. The source layer may come from another dataset.

This method is the same as the C function GDALDatasetCopyLayer() and the deprecated OGR_DS_CopyLayer().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters
  • poSrcLayer – source layer.

  • pszNewName – the name of the layer to create.

  • papszOptions – a StringList of name=value options. Options are driver specific. There is a common option to set output layer spatial reference: DST_SRSWKT. The option should be in WKT format.

Returns

a handle to the layer, or NULL if an error occurs.

virtual OGRStyleTable *GetStyleTable()

Returns dataset style table.

This method is the same as the C function GDALDatasetGetStyleTable() and the deprecated OGR_DS_GetStyleTable().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Returns

pointer to a style table which should not be modified or freed by the caller.

virtual void SetStyleTableDirectly(OGRStyleTable *poStyleTable)

Set dataset style table.

This method operate exactly as SetStyleTable() except that it assumes ownership of the passed table.

This method is the same as the C function GDALDatasetSetStyleTableDirectly() and the deprecated OGR_DS_SetStyleTableDirectly().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

poStyleTable – pointer to style table to set

virtual void SetStyleTable(OGRStyleTable *poStyleTable)

Set dataset style table.

This method operate exactly as SetStyleTableDirectly() except that it does not assume ownership of the passed table.

This method is the same as the C function GDALDatasetSetStyleTable() and the deprecated OGR_DS_SetStyleTable().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

poStyleTable – pointer to style table to set

virtual OGRLayer *ExecuteSQL(const char *pszStatement, OGRGeometry *poSpatialFilter, const char *pszDialect)

Execute an SQL statement against the data store.

The result of an SQL query is either NULL for statements that are in error, or that have no results set, or an OGRLayer pointer representing a results set from the query. Note that this OGRLayer is in addition to the layers in the data store and must be destroyed with ReleaseResultSet() before the dataset is closed (destroyed).

This method is the same as the C function GDALDatasetExecuteSQL() and the deprecated OGR_DS_ExecuteSQL().

For more information on the SQL dialect supported internally by OGR review the OGR SQL document. Some drivers (i.e. Oracle and PostGIS) pass the SQL directly through to the underlying RDBMS.

Starting with OGR 1.10, the SQLITE dialect can also be used.

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters
  • pszStatement – the SQL statement to execute.

  • poSpatialFilter – geometry which represents a spatial filter. Can be NULL.

  • pszDialect – allows control of the statement dialect. If set to NULL, the OGR SQL engine will be used, except for RDBMS drivers that will use their dedicated SQL engine, unless OGRSQL is explicitly passed as the dialect. Starting with OGR 1.10, the SQLITE dialect can also be used.

Returns

an OGRLayer containing the results of the query. Deallocate with ReleaseResultSet().

virtual void ReleaseResultSet(OGRLayer *poResultsSet)

Release results of ExecuteSQL().

This method should only be used to deallocate OGRLayers resulting from an ExecuteSQL() call on the same GDALDataset. Failure to deallocate a results set before destroying the GDALDataset may cause errors.

This method is the same as the C function GDALDatasetReleaseResultSet() and the deprecated OGR_DS_ReleaseResultSet().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Parameters

poResultsSet – the result of a previous ExecuteSQL() call.

virtual OGRErr AbortSQL()

Abort any SQL statement running in the data store.

This function can be safely called from any thread (pending that the dataset object is still alive). Driver implementations will make sure that it can be called in a thread-safe way.

This might not be implemented by all drivers. At time of writing, only SQLite, GPKG and PG drivers implement it

This method is the same as the C method GDALDatasetAbortSQL()

Since

GDAL 3.2.0

int GetRefCount() const

Fetch reference count.

This method is the same as the C function OGR_DS_GetRefCount().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Returns

the current reference count for the datasource object itself.

int GetSummaryRefCount() const

Fetch reference count of datasource and all owned layers.

This method is the same as the C function OGR_DS_GetSummaryRefCount().

In GDAL 1.X, this method used to be in the OGRDataSource class.

Deprecated:

Returns

the current summary reference count for the datasource and its layers.

OGRErr Release()

Drop a reference to this dataset, and if the reference count drops to one close (destroy) the dataset.

This method is the same as the C function OGRReleaseDataSource().

Deprecated:

. In GDAL 2, use GDALClose() instead

Returns

OGRERR_NONE on success or an error code.

virtual OGRErr StartTransaction(int bForce = FALSE)

For datasources which support transactions, StartTransaction creates a `transaction.

If starting the transaction fails, will return OGRERR_FAILURE. Datasources which do not support transactions will always return OGRERR_UNSUPPORTED_OPERATION.

Nested transactions are not supported.

All changes done after the start of the transaction are definitely applied in the datasource if CommitTransaction() is called. They may be canceled by calling RollbackTransaction() instead.

At the time of writing, transactions only apply on vector layers.

Datasets that support transactions will advertise the ODsCTransactions capability. Use of transactions at dataset level is generally preferred to transactions at layer level, whose scope is rarely limited to the layer from which it was started.

In case StartTransaction() fails, neither CommitTransaction() or RollbackTransaction() should be called.

If an error occurs after a successful StartTransaction(), the whole transaction may or may not be implicitly canceled, depending on drivers. (e.g. the PG driver will cancel it, SQLite/GPKG not). In any case, in the event of an error, an explicit call to RollbackTransaction() should be done to keep things balanced.

By default, when bForce is set to FALSE, only “efficient” transactions will be attempted. Some drivers may offer an emulation of transactions, but sometimes with significant overhead, in which case the user must explicitly allow for such an emulation by setting bForce to TRUE. Drivers that offer emulated transactions should advertise the ODsCEmulatedTransactions capability (and not ODsCTransactions).

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

Since

GDAL 2.0

Parameters

bForce – can be set to TRUE if an emulation, possibly slow, of a transaction mechanism is acceptable.

Returns

OGRERR_NONE on success.

virtual OGRErr CommitTransaction()

For datasources which support transactions, CommitTransaction commits a transaction.

If no transaction is active, or the commit fails, will return OGRERR_FAILURE. Datasources which do not support transactions will always return OGRERR_UNSUPPORTED_OPERATION.

Depending on drivers, this may or may not abort layer sequential readings that are active.

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

Since

GDAL 2.0

Returns

OGRERR_NONE on success.

virtual OGRErr RollbackTransaction()

For datasources which support transactions, RollbackTransaction will roll back a datasource to its state before the start of the current transaction.

If no transaction is active, or the rollback fails, will return OGRERR_FAILURE. Datasources which do not support transactions will always return OGRERR_UNSUPPORTED_OPERATION.

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

Since

GDAL 2.0

Returns

OGRERR_NONE on success.

virtual std::shared_ptr<GDALGroup> GetRootGroup() const

Return the root GDALGroup of this dataset.

Only valid for multidimensional datasets.

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

Since

GDAL 3.1

Public Static Functions

static GDALDataset **GetOpenDatasets(int *pnDatasetCount)

Fetch all open GDAL dataset handles.

This method is the same as the C function GDALGetOpenDatasets().

NOTE: This method is not thread safe. The returned list may change at any time and it should not be freed.

Parameters

pnCount – integer into which to place the count of dataset pointers being returned.

Returns

a pointer to an array of dataset handles.

static inline GDALDatasetH ToHandle(GDALDataset *poDS)

Convert a GDALDataset* to a GDALDatasetH.

Since

GDAL 2.3

static inline GDALDataset *FromHandle(GDALDatasetH hDS)

Convert a GDALDatasetH to a GDALDataset*.

Since

GDAL 2.3

static inline GDALDataset *Open(const char *pszFilename, unsigned int nOpenFlags = 0, const char *const *papszAllowedDrivers = nullptr, const char *const *papszOpenOptions = nullptr, const char *const *papszSiblingFiles = nullptr)

See

GDALOpenEx().

Since

GDAL 2.3

class Bands

Class returned by GetBands() that act as a container for raster bands.

Public Functions

const Iterator begin() const

Return beginning of band iterator.

Since

GDAL 2.3

const Iterator end() const

Return end of band iterator.

Since

GDAL 2.3

size_t size() const

Get the number of raster bands in this dataset.

Since

GDAL 2.3

Returns

raster band count.

GDALRasterBand *operator[](int iBand)

Fetch a raster band by index.

The returned band remains owned by the GDALDataset and should not be deleted by the application.

Since

GDAL 2.3

Warning

Contrary to GDALDataset::GetRasterBand(), the indexing here is consistent with the conventions of C/C++, i.e. starting at 0.

Parameters

iBand – a band index between 0 and size()-1.

Returns

the band, or nullptr if iBand is out of range or an error occurs.

GDALRasterBand *operator[](size_t iBand)

Fetch a raster band by index.

The returned band remains owned by the GDALDataset and should not be deleted by the application.

Since

GDAL 2.3

Warning

Contrary to GDALDataset::GetRasterBand(), the indexing here is consistent with the conventions of C/C++, i.e. starting at 0.

Parameters

iBand – a band index between 0 and size()-1.

Returns

the band, or nullptr if iBand is out of range or an error occurs.

struct FeatureLayerPair

Object returned by GetFeatures() iterators.

Public Members

OGRFeatureUniquePtr feature = {}

Unique pointer to a OGRFeature.

OGRLayer *layer = nullptr

Layer to which the feature belongs to.

class Features

Class returned by GetFeatures() that act as a container for vector features.

Public Functions

const Iterator begin() const

Return beginning of feature iterator.

Since

GDAL 2.3

const Iterator end() const

Return end of feature iterator.

Since

GDAL 2.3

class Layers

Class returned by GetLayers() that acts as a range of layers.

Since

GDAL 2.3

Public Functions

Iterator begin() const

Return beginning of layer iterator.

Since

GDAL 2.3

Iterator end() const

Return end of layer iterator.

Since

GDAL 2.3

size_t size() const

Get the number of layers in this dataset.

Since

GDAL 2.3

Returns

layer count.

OGRLayer *operator[](int iLayer)

Fetch a layer by index.

The returned layer remains owned by the GDALDataset and should not be deleted by the application.

Since

GDAL 2.3

Parameters

iLayer – a layer number between 0 and size()-1.

Returns

the layer, or nullptr if iLayer is out of range or an error occurs.

OGRLayer *operator[](size_t iLayer)

Fetch a layer by index.

The returned layer remains owned by the GDALDataset and should not be deleted by the application.

Since

GDAL 2.3

Parameters

iLayer – a layer number between 0 and size()-1.

Returns

the layer, or nullptr if iLayer is out of range or an error occurs.

OGRLayer *operator[](const char *pszLayername)

Fetch a layer by name.

The returned layer remains owned by the GDALDataset and should not be deleted by the application.

Since

GDAL 2.3

Parameters

pszLayerName – layer name

Returns

the layer, or nullptr if pszLayerName does not match with a layer

class Iterator

Layer iterator.

Since

GDAL 2.3

Public Types

using value_type = OGRLayer*

value_type

using reference = OGRLayer*

reference

using difference_type = void

difference_type

using pointer = void

pointer

using iterator_category = std::input_iterator_tag

iterator_category

Public Functions

Iterator()

Default constructor.

Iterator(GDALDataset *poDS, bool bStart)

Constructor.

Iterator(const Iterator &oOther)

Copy constructor.

Iterator(Iterator &&oOther) noexcept

Move constructor.

~Iterator()

Destructor.

Iterator &operator=(const Iterator &oOther)

Assignment operator.

Iterator &operator=(Iterator &&oOther) noexcept

Move assignment operator.

OGRLayer *operator*() const

Dereference operator.

Iterator &operator++()

Pre-increment operator.

Iterator operator++(int)

Post-increment operator.

bool operator!=(const Iterator &it) const

Difference comparison operator.

struct Private
class Private