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, GDALGeneric3x3Dataset< T >, GDALOverviewDataset, GDALPamDataset, GDALVectorTranslateWrappedDataset, GNMNetwork, OGRDataSource

Public Functions

~GDALDataset()

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().

Return

the width in pixels of raster bands in this GDALDataset.

int GetRasterYSize()

Fetch raster height in pixels.

Equivalent of the C function GDALGetRasterYSize().

Return

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().

Return

the number of raster bands.

GDALRasterBand *GetRasterBand(int nBandId)

Fetch a band object for a dataset.

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

Equivalent of the C function GDALGetRasterBand().

Return

the nBandId th band object

Parameters

GDALDataset::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

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().

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

Since

GDAL 3.0

Return

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.

See

http://www.gdal.org/osr_tutorial.html

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

Return

CE_Failure if an error occurs, otherwise CE_None.

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

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.

Note

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

Return

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

See

http://www.gdal.org/osr_tutorial.html

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()

Return

CE_Failure if an error occurs, otherwise CE_None.

Parameters
  • pszProjection: projection reference string.

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.

Return

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

Parameters
  • padfTransform: an existing six double buffer into which the transformation will be placed.

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.

Return

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

Parameters
  • padfTransform: a six double buffer containing the transformation coefficients to be written with the dataset.

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.

Return

CE_None on success or CE_Failure on failure.

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.

void *GetInternalHandle(const char *pszHandleName)

Fetch a format specific internally meaningful handle.

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

Return

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

Parameters
  • pszHandleName: the handle name desired. The meaningful names will be specific to the file format.

GDALDriver *GetDriver(void)

Fetch the driver to which this dataset relates.

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

Return

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

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.

Return

NULL or a NULL terminated array of file names.

const char *GetDriverName()

Return driver name.

Return

driver name.

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

Since

GDAL 3.0

Return

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.

int GetGCPCount()

Get number of GCPs.

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

Return

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

const GDAL_GCP *GetGCPs()

Fetch GCPs.

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

Return

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

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

Return

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

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.

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

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

Return

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*)

Return

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

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.

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.

Return

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

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.

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

Return

CE_None on success or CE_Failure on an error.

See

http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

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.

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: http://trac.osgeo.org/gdal/wiki/rfc24_progressive_data_support

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

Return

The GDALAsyncReader object representing the request.

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.

void EndAsyncReader(GDALAsyncReader *poARIO)

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 eRWFlag, int nXOff, int nYOff, int nXSize, int nYSize, void *pData, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nBandCount, int *panBandMap, GSpacing nPixelSpace, GSpacing nLineSpace, GSpacing nBandSpace, 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.

Return

CE_Failure if the access fails, otherwise CE_None.

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 behaviour. 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.

int Reference()

Add one to dataset reference count.

The reference is one after instantiation.

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

Return

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.

Return

the post-decrement reference count.

int ReleaseRef()

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

Return

TRUE if the object has been destroyed.

Since

GDAL 2.2

GDALAccess GetAccess() const

Return access mode.

Return

access mode.

int GetShared() const

Returns shared flag.

Return

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

void MarkAsShared()

Mark this dataset as available for sharing.

void MarkSuppressOnClose()

Set that the dataset must be deleted on close.

char **GetOpenOptions()

Return open options.

Return

open options.

CPLErr BuildOverviews(const char *pszResampling, int nOverviews, int *panOverviewList, int nListBands, int *panBandList, GDALProgressFunc pfnProgress, void *pProgressData)

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.

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 );
Return

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

Parameters
  • pszResampling: one of “AVERAGE”, “AVERAGE_MAGPHASE”, “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.

See

GDALRegenerateOverviews()

void ReportError(CPLErr eErrClass, CPLErrorNum err_no, const char *fmt, ...)

Emits an error related to a dataset.

This function is a wrapper for regular CPLError(). The only difference with CPLError() is that it prepends the error message with the dataset name.

Since

GDAL 1.9.0

Parameters
  • eErrClass: one of CE_Warning, CE_Failure or CE_Fatal.

  • err_no: the error number (CPLE_*) from cpl_error.h.

  • fmt: a printf() style format string. Any additional arguments will be treated as arguments to fill in this format in a manner similar to printf().

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

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().

Return

NULL or a string list.

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

SetMetadata(char **papszMetadata, const char *pszDomain)

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.

Return

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.

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

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

const char *GetMetadataItem(const char *pszName, const char *pszDomain)

Fetch single metadata item.

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

Return

NULL on failure to find the key, or a pointer to an internal copy of the value string on success.

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

  • pszDomain: the domain to fetch for, use NULL for the default domain.

SetMetadataItem(const char *pszName, const char *pszValue, const char *pszDomain)

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.

Return

CE_None on success, or an error code on failure.

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.

char **GetMetadataDomainList()

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().

Return

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

Since

GDAL 1.11

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.

Return

layer count.

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.

Return

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

See

GetLayers()

Parameters

GDALDataset::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

OGRLayer *GetLayerByName(const char *pszName)

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.

Return

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

Parameters
  • pszName: the layer name of the layer to fetch.

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.

Return

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

Parameters
  • iLayer: the index of the layer to delete.

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

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().

Return

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

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

GDALDataset::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

int TestCapability(const char *pszCap)

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.

Return

TRUE if capability available otherwise FALSE.

Parameters
  • pszCap: the capability to test.

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 )
        {
            ...
        }

Return

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

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.

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.

Return

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

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.

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.

Return

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

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

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

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.

Return

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

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.

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

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.

Return

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.

Return

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().

Return

OGRERR_NONE on success or an error code.

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().

Return

OGRERR_NONE on success.

Since

GDAL 2.0

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

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().

Return

OGRERR_NONE on success.

Since

GDAL 2.0

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().

Return

OGRERR_NONE on success.

Since

GDAL 2.0

Public Static Functions

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.

Return

a pointer to an array of dataset handles.

Parameters
  • pnCount: integer into which to place the count of dataset pointers being returned.

static GDALDatasetH ToHandle(GDALDataset *poDS)

Convert a GDALDataset* to a GDALDatasetH.

Since

GDAL 2.3

static GDALDataset *FromHandle(GDALDatasetH hDS)

Convert a GDALDatasetH to a GDALDataset*.

Since

GDAL 2.3

static 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 GDALDataset::Bands::Iterator begin() const

Return beginning of band iterator.

Since

GDAL 2.3

const GDALDataset::Bands::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.

Return

raster band count.

Since

GDAL 2.3

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.

Warning

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

Return

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

Since

GDAL 2.3

Parameters
  • iBand: a band index between 0 and size()-1.

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.

Warning

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

Return

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

Since

GDAL 2.3

Parameters
  • iBand: a band index between 0 and size()-1.

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 GDALDataset::Features::Iterator begin() const

Return beginning of feature iterator.

Since

GDAL 2.3

const GDALDataset::Features::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

GDALDataset::Layers::Iterator begin() const

Return beginning of layer iterator.

Since

GDAL 2.3

GDALDataset::Layers::Iterator end() const

Return end of layer iterator.

Since

GDAL 2.3

size_t size() const

Get the number of layers in this dataset.

Return

layer count.

Since

GDAL 2.3

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.

Return

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

Since

GDAL 2.3

Parameters
  • iLayer: a layer number between 0 and size()-1.

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.

Return

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

Since

GDAL 2.3

Parameters
  • iLayer: a layer number between 0 and size()-1.

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.

Return

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

Since

GDAL 2.3

Parameters
  • pszLayerName: layer name

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)

Move constructor.

~Iterator()

Destructor.

GDALDataset::Layers::Iterator &operator=(const Iterator &oOther)

Assignment operator.

GDALDataset::Layers::Iterator &operator=(Iterator &&oOther)

Move assignment operator.

OGRLayer *operator*() const

Dereference operator.

GDALDataset::Layers::Iterator &operator++()

Pre-increment operator.

GDALDataset::Layers::Iterator operator++(int)

Post-increment operator.

bool operator!=(const Iterator &it) const

Difference comparison operator.