/****************************************************************************
 *
 * Project:  GDAL
 * Purpose:  Implements the Golden Software Surfer 7 Binary Grid Format.
 * Author:   Adam Guernsey, adam@ctech.com
 *           (Based almost entirely on gsbgdataset.cpp by Kevin Locke)
 *           Create functions added by Russell Jurgensen.
 *
 ****************************************************************************
 * Copyright (c) 2007, Adam Guernsey <adam@ctech.com>
 * Copyright (c) 2009-2011, Even Rouault <even dot rouault at spatialys.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <limits>

#include "gdal_frmts.h"
#include "gdal_pam.h"


/************************************************************************/
/* ==================================================================== */
/*                GS7BGDataset                */
/* ==================================================================== */
/************************************************************************/

class GS7BGRasterBand;

constexpr double dfDefaultNoDataValue = 1.701410009187828e+38f;

class GS7BGDataset final: public GDALPamDataset
{
    friend class GS7BGRasterBand;

    double dfNoData_Value;
    static const size_t nHEADER_SIZE;
    size_t nData_Position;

    static CPLErr WriteHeader( VSILFILE *fp, GInt32 nXSize, GInt32 nYSize,
                   double dfMinX, double dfMaxX,
                   double dfMinY, double dfMaxY,
                   double dfMinZ, double dfMaxZ );

    VSILFILE    *fp;

  public:
    GS7BGDataset() :
    /* NOTE:  This is not mentioned in the spec, but Surfer 8 uses this value */
    /* 0x7effffee (Little Endian: eeffff7e) */
        dfNoData_Value(dfDefaultNoDataValue),
        nData_Position(0),
        fp(nullptr) { }
    ~GS7BGDataset();

    static int          Identify( GDALOpenInfo * );
    static GDALDataset *Open( GDALOpenInfo * );
    static GDALDataset *Create( const char * pszFilename,
                    int nXSize, int nYSize, int nBandsIn,
                    GDALDataType eType,
                    char **papszParamList );
    static GDALDataset *CreateCopy( const char *pszFilename,
                    GDALDataset *poSrcDS,
                    int bStrict, char **papszOptions,
                    GDALProgressFunc pfnProgress,
                    void *pProgressData );

    CPLErr GetGeoTransform( double *padfGeoTransform ) override;
    CPLErr SetGeoTransform( double *padfGeoTransform ) override;
};

const size_t GS7BGDataset::nHEADER_SIZE = 100;

constexpr long nHEADER_TAG = 0x42525344;
constexpr long nGRID_TAG = 0x44495247;
constexpr long nDATA_TAG = 0x41544144;
#if 0 /* Unused */
const long  nFAULT_TAG = 0x49544c46;
#endif

/************************************************************************/
/* ==================================================================== */
/*                            GS7BGRasterBand                           */
/* ==================================================================== */
/************************************************************************/

class GS7BGRasterBand final: public GDALPamRasterBand
{
    friend class GS7BGDataset;

    double dfMinX;
    double dfMaxX;
    double dfMinY;
    double dfMaxY;
    double dfMinZ;
    double dfMaxZ;

    double *pafRowMinZ;
    double *pafRowMaxZ;
    int nMinZRow;
    int nMaxZRow;

    CPLErr ScanForMinMaxZ();

  public:

    GS7BGRasterBand( GS7BGDataset *, int );
    ~GS7BGRasterBand();

    CPLErr IReadBlock( int, int, void * ) override;
    CPLErr IWriteBlock( int, int, void * ) override;
    double GetMinimum( int *pbSuccess = nullptr ) override;
    double GetMaximum( int *pbSuccess = nullptr ) override;

    double GetNoDataValue( int *pbSuccess = nullptr ) override;
};

/************************************************************************/
/*                           GS7BGRasterBand()                          */
/************************************************************************/

GS7BGRasterBand::GS7BGRasterBand( GS7BGDataset *poDSIn, int nBandIn ) :
    dfMinX(0.0),
    dfMaxX(0.0),
    dfMinY(0.0),
    dfMaxY(0.0),
    dfMinZ(0.0),
    dfMaxZ(0.0),
    pafRowMinZ(nullptr),
    pafRowMaxZ(nullptr),
    nMinZRow(-1),
    nMaxZRow(-1)

{
    poDS = poDSIn;
    nBand = nBandIn;

    eDataType = GDT_Float64;

    nBlockXSize = poDS->GetRasterXSize();
    nBlockYSize = 1;
}

/************************************************************************/
/*                           ~GSBGRasterBand()                          */
/************************************************************************/

GS7BGRasterBand::~GS7BGRasterBand( )

{
    CPLFree( pafRowMinZ );
    CPLFree( pafRowMaxZ );
}

/************************************************************************/
/*                          ScanForMinMaxZ()                            */
/************************************************************************/

CPLErr GS7BGRasterBand::ScanForMinMaxZ()

{
    GS7BGDataset* poGDS = reinterpret_cast<GS7BGDataset*>(poDS);
    double *pafRowVals = (double *)VSI_MALLOC2_VERBOSE( nRasterXSize, sizeof(double));

    if( pafRowVals == nullptr )
    {
        return CE_Failure;
    }

    double dfNewMinZ = std::numeric_limits<double>::max();
    double dfNewMaxZ = std::numeric_limits<double>::lowest();
    int nNewMinZRow = 0;
    int nNewMaxZRow = 0;

    /* Since we have to scan, lets calc. statistics too */
    double dfSum = 0.0;
    double dfSum2 = 0.0;
    unsigned long nValuesRead = 0;
    for( int iRow=0; iRow<nRasterYSize; iRow++ )
    {
        CPLErr eErr = IReadBlock( 0, iRow, pafRowVals );
        if( eErr != CE_None )
        {
            VSIFree( pafRowVals );
            return CE_Failure;
        }

        pafRowMinZ[iRow] = std::numeric_limits<float>::max();
        pafRowMaxZ[iRow] = std::numeric_limits<float>::lowest();
        for( int iCol=0; iCol<nRasterXSize; iCol++ )
        {
            if( pafRowVals[iCol] == poGDS->dfNoData_Value )
                continue;

            if( pafRowVals[iCol] < pafRowMinZ[iRow] )
                pafRowMinZ[iRow] = pafRowVals[iCol];

            if( pafRowVals[iCol] > pafRowMinZ[iRow] )
                pafRowMaxZ[iRow] = pafRowVals[iCol];

            dfSum += pafRowVals[iCol];
            dfSum2 += pafRowVals[iCol] * pafRowVals[iCol];
            nValuesRead++;
        }

        if( pafRowMinZ[iRow] < dfNewMinZ )
        {
            dfNewMinZ = pafRowMinZ[iRow];
            nNewMinZRow = iRow;
        }

        if( pafRowMaxZ[iRow] > dfNewMaxZ )
        {
            dfNewMaxZ = pafRowMaxZ[iRow];
            nNewMaxZRow = iRow;
        }
    }

    VSIFree( pafRowVals );

    if( nValuesRead == 0 )
    {
        dfMinZ = 0.0;
        dfMaxZ = 0.0;
        nMinZRow = 0;
        nMaxZRow = 0;
        return CE_None;
    }

    dfMinZ = dfNewMinZ;
    dfMaxZ = dfNewMaxZ;
    nMinZRow = nNewMinZRow;
    nMaxZRow = nNewMaxZRow;

    double dfMean = dfSum / nValuesRead;
    double dfStdDev = sqrt((dfSum2 / nValuesRead) - (dfMean * dfMean));
    SetStatistics( dfMinZ, dfMaxZ, dfMean, dfStdDev );

    return CE_None;
}

/************************************************************************/
/*                             IReadBlock()                             */
/************************************************************************/

CPLErr GS7BGRasterBand::IReadBlock( int nBlockXOff, int nBlockYOff,
        void * pImage )

{
    if( nBlockYOff < 0 || nBlockYOff > nRasterYSize - 1 || nBlockXOff != 0 )
        return CE_Failure;

    GS7BGDataset *poGDS = (GS7BGDataset *) ( poDS );

    if( VSIFSeekL( poGDS->fp,
        ( poGDS->nData_Position +
            sizeof(double) * static_cast<vsi_l_offset>(nRasterXSize) * (nRasterYSize - nBlockYOff - 1) ),
        SEEK_SET ) != 0 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
        "Unable to seek to beginning of grid row.\n" );
        return CE_Failure;
    }

    if( VSIFReadL( pImage, sizeof(double), nBlockXSize,
        poGDS->fp ) != static_cast<unsigned>(nBlockXSize) )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read block from grid file.\n" );
        return CE_Failure;
    }

#ifdef CPL_MSB
    double *pfImage = (double *)pImage;
    for( int iPixel=0; iPixel<nBlockXSize; iPixel++ )
        CPL_LSBPTR64( pfImage + iPixel );
#endif

    return CE_None;
}

/************************************************************************/
/*                            IWriteBlock()                             */
/************************************************************************/

CPLErr GS7BGRasterBand::IWriteBlock( int nBlockXOff, int nBlockYOff,
                    void *pImage )

{
    if( eAccess == GA_ReadOnly )
    {
        CPLError( CE_Failure, CPLE_NoWriteAccess,
          "Unable to write block, dataset opened read only.\n" );
        return CE_Failure;
    }

    if( nBlockYOff < 0 || nBlockYOff > nRasterYSize - 1 || nBlockXOff != 0 )
        return CE_Failure;

    GS7BGDataset *poGDS = (GS7BGDataset *) ( poDS );

    if( pafRowMinZ == nullptr || pafRowMaxZ == nullptr
        || nMinZRow < 0 || nMaxZRow < 0 )
    {
        pafRowMinZ = (double *)VSI_MALLOC2_VERBOSE( nRasterYSize,sizeof(double) );
        if( pafRowMinZ == nullptr )
        {
            return CE_Failure;
        }

        pafRowMaxZ = (double *)VSI_MALLOC2_VERBOSE( nRasterYSize,sizeof(double) );
        if( pafRowMaxZ == nullptr )
        {
            VSIFree( pafRowMinZ );
            pafRowMinZ = nullptr;
            return CE_Failure;
        }

        CPLErr eErr = ScanForMinMaxZ();
        if( eErr != CE_None )
            return eErr;
    }

    if( VSIFSeekL( poGDS->fp,
           GS7BGDataset::nHEADER_SIZE +
                        sizeof(double) * nRasterXSize * (nRasterYSize - nBlockYOff - 1),
           SEEK_SET ) != 0 )
    {
        CPLError(CE_Failure, CPLE_FileIO,
                 "Unable to seek to beginning of grid row.\n");
        return CE_Failure;
    }

    double *pdfImage = (double *)pImage;
    pafRowMinZ[nBlockYOff] = std::numeric_limits<double>::max();
    pafRowMaxZ[nBlockYOff] = std::numeric_limits<double>::lowest();
    for( int iPixel=0; iPixel < nBlockXSize; iPixel++ )
    {
        if( pdfImage[iPixel] != poGDS->dfNoData_Value )
        {
            if( pdfImage[iPixel] < pafRowMinZ[nBlockYOff] )
                pafRowMinZ[nBlockYOff] = pdfImage[iPixel];

            if( pdfImage[iPixel] > pafRowMaxZ[nBlockYOff] )
                pafRowMaxZ[nBlockYOff] = pdfImage[iPixel];
        }

        CPL_LSBPTR64( pdfImage+iPixel );
    }

    if( VSIFWriteL( pImage, sizeof(double), nBlockXSize,
            poGDS->fp ) != static_cast<unsigned>(nBlockXSize) )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write block to grid file.\n" );
        return CE_Failure;
    }

    /* Update min/max Z values as appropriate */
    bool bHeaderNeedsUpdate = false;
    if( nMinZRow == nBlockYOff && pafRowMinZ[nBlockYOff] > dfMinZ )
    {
        double dfNewMinZ = std::numeric_limits<double>::max();
        for( int iRow=0; iRow<nRasterYSize; iRow++ )
        {
            if( pafRowMinZ[iRow] < dfNewMinZ )
            {
                dfNewMinZ = pafRowMinZ[iRow];
                nMinZRow = iRow;
            }
        }

        if( dfNewMinZ != dfMinZ )
        {
            dfMinZ = dfNewMinZ;
            bHeaderNeedsUpdate = true;
        }
    }

    if( nMaxZRow == nBlockYOff && pafRowMaxZ[nBlockYOff] < dfMaxZ )
    {
        double dfNewMaxZ = std::numeric_limits<double>::lowest();
        for( int iRow=0; iRow<nRasterYSize; iRow++ )
        {
            if( pafRowMaxZ[iRow] > dfNewMaxZ )
            {
                dfNewMaxZ = pafRowMaxZ[iRow];
                nMaxZRow = iRow;
            }
        }

        if( dfNewMaxZ != dfMaxZ )
        {
            dfMaxZ = dfNewMaxZ;
            bHeaderNeedsUpdate = true;
        }
    }

    if( pafRowMinZ[nBlockYOff] < dfMinZ || pafRowMaxZ[nBlockYOff] > dfMaxZ )
    {
        if( pafRowMinZ[nBlockYOff] < dfMinZ )
        {
            dfMinZ = pafRowMinZ[nBlockYOff];
            nMinZRow = nBlockYOff;
        }

        if( pafRowMaxZ[nBlockYOff] > dfMaxZ )
        {
            dfMaxZ = pafRowMaxZ[nBlockYOff];
            nMaxZRow = nBlockYOff;
        }

       bHeaderNeedsUpdate = true;
    }

    if( bHeaderNeedsUpdate && dfMaxZ > dfMinZ )
    {
        CPLErr eErr = poGDS->WriteHeader( poGDS->fp,
                      nRasterXSize, nRasterYSize,
                      dfMinX, dfMaxX,
                      dfMinY, dfMaxY,
                      dfMinZ, dfMaxZ );
        return eErr;
    }

    return CE_None;
}

/************************************************************************/
/*                           GetNoDataValue()                           */
/************************************************************************/

double GS7BGRasterBand::GetNoDataValue( int * pbSuccess )
{
    GS7BGDataset* poGDS = reinterpret_cast<GS7BGDataset*>(poDS);
    if( pbSuccess )
        *pbSuccess = TRUE;

    return poGDS->dfNoData_Value;
}

/************************************************************************/
/*                             GetMinimum()                             */
/************************************************************************/

double GS7BGRasterBand::GetMinimum( int *pbSuccess )
{
    if( pbSuccess )
        *pbSuccess = TRUE;

    return dfMinZ;
}

/************************************************************************/
/*                             GetMaximum()                             */
/************************************************************************/

double GS7BGRasterBand::GetMaximum( int *pbSuccess )
{
    if( pbSuccess )
        *pbSuccess = TRUE;

    return dfMaxZ;
}

/************************************************************************/
/* ==================================================================== */
/*                            GS7BGDataset                              */
/* ==================================================================== */
/************************************************************************/

GS7BGDataset::~GS7BGDataset()

{
    FlushCache(true);
    if( fp != nullptr )
        VSIFCloseL( fp );
}

/************************************************************************/
/*                              Identify()                              */
/************************************************************************/

int GS7BGDataset::Identify( GDALOpenInfo * poOpenInfo )

{
    /* Check for signature - for GS7BG the signature is the */
    /* nHEADER_TAG with reverse byte order.                 */
    if( poOpenInfo->nHeaderBytes < 4
        || !STARTS_WITH_CI((const char *) poOpenInfo->pabyHeader, "DSRB") )
    {
        return FALSE;
    }

    return TRUE;
}

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

GDALDataset *GS7BGDataset::Open( GDALOpenInfo * poOpenInfo )

{
    if( !Identify(poOpenInfo) || poOpenInfo->fpL == nullptr )
    {
        return nullptr;
    }

    /* ------------------------------------------------------------------- */
    /*      Create a corresponding GDALDataset.                            */
    /* ------------------------------------------------------------------- */
    GS7BGDataset    *poDS = new GS7BGDataset();
    poDS->eAccess = poOpenInfo->eAccess;
    poDS->fp = poOpenInfo->fpL;
    poOpenInfo->fpL = nullptr;

    /* ------------------------------------------------------------------- */
    /*      Read the header. The Header section must be the first section  */
    /*      in the file.                                                   */
    /* ------------------------------------------------------------------- */
    if( VSIFSeekL( poDS->fp, 0, SEEK_SET ) != 0 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
                "Unable to seek to start of grid file header.\n" );
        return nullptr;
    }

    GInt32 nTag;
    if( VSIFReadL( (void *)&nTag, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO, "Unable to read Tag.\n" );
        return nullptr;
    }

    CPL_LSBPTR32( &nTag );

    if(nTag != nHEADER_TAG)
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO, "Header tag not found.\n" );
        return nullptr;
    }

    GUInt32 nSize;
    if( VSIFReadL( (void *)&nSize, sizeof(GUInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read file section size.\n" );
        return nullptr;
    }

    CPL_LSBPTR32( &nSize );

    GInt32 nVersion;
    if( VSIFReadL( (void *)&nVersion, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read file version.\n" );
        return nullptr;
    }

    CPL_LSBPTR32( &nVersion );

    if(nVersion != 1 && nVersion != 2)
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
                  "Incorrect file version (%d).", nVersion );
        return nullptr;
    }

    // advance until the grid tag is found
    while(nTag != nGRID_TAG)
    {
        if( VSIFReadL( (void *)&nTag, sizeof(GInt32), 1, poDS->fp ) != 1 )
        {
            delete poDS;
            CPLError( CE_Failure, CPLE_FileIO, "Unable to read Tag.\n" );
            return nullptr;
        }

        CPL_LSBPTR32( &nTag );

        if( VSIFReadL( (void *)&nSize, sizeof(GUInt32), 1, poDS->fp ) != 1 )
        {
            delete poDS;
            CPLError( CE_Failure, CPLE_FileIO,
                "Unable to read file section size.\n" );
            return nullptr;
        }

        CPL_LSBPTR32( &nSize );

        if(nTag != nGRID_TAG)
        {
            if( VSIFSeekL( poDS->fp, nSize, SEEK_CUR ) != 0 )
            {
                delete poDS;
                CPLError( CE_Failure, CPLE_FileIO,
                    "Unable to seek to end of file section.\n" );
                return nullptr;
            }
        }
    }

    /* --------------------------------------------------------------------*/
    /*      Read the grid.                                                 */
    /* --------------------------------------------------------------------*/
    /* Parse number of Y axis grid rows */
    GInt32 nRows;
    if( VSIFReadL( (void *)&nRows, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read raster Y size.\n" );
        return nullptr;
    }
    CPL_LSBPTR32( &nRows );
    poDS->nRasterYSize = nRows;

    /* Parse number of X axis grid columns */
    GInt32 nCols;
    if( VSIFReadL( (void *)&nCols, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read raster X size.\n" );
        return nullptr;
    }
    CPL_LSBPTR32( &nCols );
    poDS->nRasterXSize = nCols;

    if (!GDALCheckDatasetDimensions(poDS->nRasterXSize, poDS->nRasterYSize))
    {
        delete poDS;
        return nullptr;
    }

    /* --------------------------------------------------------------------*/
    /*      Create band information objects.                               */
    /* --------------------------------------------------------------------*/
    GS7BGRasterBand *poBand = new GS7BGRasterBand( poDS, 1 );
    poDS->SetBand( 1, poBand );

    // find the min X Value of the grid
    double dfTemp;
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read minimum X value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMinX = dfTemp;

    // find the min Y value of the grid
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read minimum X value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMinY = dfTemp;

    // find the spacing between adjacent nodes in the X direction
    // (between columns)
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read spacing in X value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMaxX = poBand->dfMinX + (dfTemp * (nCols - 1));

    // find the spacing between adjacent nodes in the Y direction
    // (between rows)
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read spacing in Y value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMaxY = poBand->dfMinY + (dfTemp * (nRows - 1));

    // set the z min
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read Z min value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMinZ = dfTemp;

    // set the z max
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read Z max value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poBand->dfMaxZ = dfTemp;

    // read and ignore the rotation value
    //(This is not used in the current version).
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to read rotation value.\n" );
        return nullptr;
    }

    // read and set the cell blank value
    if( VSIFReadL( (void *)&dfTemp, sizeof(double), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to Blank value.\n" );
        return nullptr;
    }
    CPL_LSBPTR64( &dfTemp );
    poDS->dfNoData_Value = dfTemp;

    /* --------------------------------------------------------------------*/
    /*      Set the current offset of the grid data.                       */
    /* --------------------------------------------------------------------*/
    if( VSIFReadL( (void *)&nTag, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO, "Unable to read Tag.\n" );
        return nullptr;
    }

    CPL_LSBPTR32( &nTag );
    if(nTag != nDATA_TAG)
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO, "Data tag not found.\n" );
        return nullptr;
    }

    if( VSIFReadL( (void *)&nSize, sizeof(GInt32), 1, poDS->fp ) != 1 )
    {
        delete poDS;
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to data section size.\n" );
        return nullptr;
    }

    poDS->nData_Position = (size_t) VSIFTellL(poDS->fp);

    /* --------------------------------------------------------------------*/
    /*      Initialize any PAM information.                                */
    /* --------------------------------------------------------------------*/
    poDS->SetDescription( poOpenInfo->pszFilename );
    poDS->TryLoadXML();

/* -------------------------------------------------------------------- */
/*      Check for external overviews.                                   */
/* -------------------------------------------------------------------- */
    poDS->oOvManager.Initialize( poDS, poOpenInfo->pszFilename, poOpenInfo->GetSiblingFiles() );

    return poDS;
}

/************************************************************************/
/*                          GetGeoTransform()                           */
/************************************************************************/

CPLErr GS7BGDataset::GetGeoTransform( double *padfGeoTransform )
{
    if( padfGeoTransform == nullptr )
        return CE_Failure;

    GS7BGRasterBand *poGRB = (GS7BGRasterBand *)GetRasterBand( 1 );

    if( poGRB == nullptr )
    {
        padfGeoTransform[0] = 0;
        padfGeoTransform[1] = 1;
        padfGeoTransform[2] = 0;
        padfGeoTransform[3] = 0;
        padfGeoTransform[4] = 0;
        padfGeoTransform[5] = 1;
        return CE_Failure;
    }

    /* check if we have a PAM GeoTransform stored */
    CPLPushErrorHandler( CPLQuietErrorHandler );
    CPLErr eErr = GDALPamDataset::GetGeoTransform( padfGeoTransform );
    CPLPopErrorHandler();

    if( eErr == CE_None )
        return CE_None;

    if( nRasterXSize == 1 || nRasterYSize == 1 )
        return CE_Failure;

    /* calculate pixel size first */
    padfGeoTransform[1] = (poGRB->dfMaxX - poGRB->dfMinX)/(nRasterXSize - 1);
    padfGeoTransform[5] = (poGRB->dfMinY - poGRB->dfMaxY)/(nRasterYSize - 1);

    /* then calculate image origin */
    padfGeoTransform[0] = poGRB->dfMinX - padfGeoTransform[1] / 2;
    padfGeoTransform[3] = poGRB->dfMaxY - padfGeoTransform[5] / 2;

    /* tilt/rotation does not supported by the GS grids */
    padfGeoTransform[4] = 0.0;
    padfGeoTransform[2] = 0.0;

    return CE_None;
}

/************************************************************************/
/*                          SetGeoTransform()                           */
/************************************************************************/

CPLErr GS7BGDataset::SetGeoTransform( double *padfGeoTransform )
{
    if( eAccess == GA_ReadOnly )
    {
        CPLError( CE_Failure, CPLE_NoWriteAccess,
              "Unable to set GeoTransform, dataset opened read only.\n" );
        return CE_Failure;
    }

    GS7BGRasterBand *poGRB = cpl::down_cast<GS7BGRasterBand *>(GetRasterBand( 1 ));

    if( padfGeoTransform == nullptr)
        return CE_Failure;

    /* non-zero transform 2 or 4 or negative 1 or 5 not supported natively */
    /*if( padfGeoTransform[2] != 0.0 || padfGeoTransform[4] != 0.0
    || padfGeoTransform[1] < 0.0 || padfGeoTransform[5] < 0.0 )
    eErr = GDALPamDataset::SetGeoTransform( padfGeoTransform );

    if( eErr != CE_None )
    return eErr;*/

    double dfMinX = padfGeoTransform[0] + padfGeoTransform[1] / 2;
    double dfMaxX = padfGeoTransform[1] * (nRasterXSize - 0.5) + padfGeoTransform[0];
    double dfMinY = padfGeoTransform[5] * (nRasterYSize - 0.5) + padfGeoTransform[3];
    double dfMaxY = padfGeoTransform[3] + padfGeoTransform[5] / 2;

    CPLErr eErr = WriteHeader( fp, poGRB->nRasterXSize, poGRB->nRasterYSize,
            dfMinX, dfMaxX, dfMinY, dfMaxY,
            poGRB->dfMinZ, poGRB->dfMaxZ );

    if( eErr == CE_None )
    {
        poGRB->dfMinX = dfMinX;
        poGRB->dfMaxX = dfMaxX;
        poGRB->dfMinY = dfMinY;
        poGRB->dfMaxY = dfMaxY;
    }

    return eErr;
}

/************************************************************************/
/*                             WriteHeader()                            */
/************************************************************************/

CPLErr GS7BGDataset::WriteHeader( VSILFILE *fp, GInt32 nXSize, GInt32 nYSize,
                 double dfMinX, double dfMaxX,
                 double dfMinY, double dfMaxY,
                 double dfMinZ, double dfMaxZ )

{
    if( VSIFSeekL( fp, 0, SEEK_SET ) != 0 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to seek to start of grid file.\n" );
        return CE_Failure;
    }

    GInt32 nTemp = CPL_LSBWORD32(nHEADER_TAG);
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write header tag to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(sizeof(GInt32)); // Size of version section.
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write size to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(1); // Version
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write size to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(nGRID_TAG); // Mark start of grid
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write size to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(72); // Grid info size (the remainder of the header)
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write size to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(nYSize);
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write Y size to grid file.\n" );
        return CE_Failure;
    }

    nTemp = CPL_LSBWORD32(nXSize);
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write X size to grid file.\n" );
        return CE_Failure;
    }

    double dfTemp = dfMinX;
    CPL_LSBPTR64(&dfTemp);
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write minimum X value to grid file.\n" );
        return CE_Failure;
    }

    dfTemp = dfMinY;
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write minimum Y value to grid file.\n" );
        return CE_Failure;
    }

    // Write node spacing in x direction
    dfTemp = (dfMaxX - dfMinX) / (nXSize - 1);
    CPL_LSBPTR64(&dfTemp);
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write spacing in X value.\n" );
        return CE_Failure;
    }

    // Write node spacing in y direction
    dfTemp = (dfMaxY - dfMinY) / (nYSize -1);
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write spacing in Y value.\n" );
        return CE_Failure;
    }

    dfTemp = dfMinZ;
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write minimum Z value to grid file.\n" );
        return CE_Failure;
    }

    dfTemp = dfMaxZ;
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write maximum Z value to grid file.\n" );
        return CE_Failure;
    }

    dfTemp = 0;  // Rotation value is zero
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write rotation value to grid file.\n" );
        return CE_Failure;
    }

    dfTemp = dfDefaultNoDataValue;
    CPL_LSBPTR64( &dfTemp );
    if( VSIFWriteL( (void *)&dfTemp, sizeof(double), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
          "Unable to write cell blank value to grid file.\n" );
        return CE_Failure;
    }

    // Only supports 1 band so go ahead and write band info here
    nTemp = CPL_LSBWORD32(nDATA_TAG); // Mark start of data
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to data tag to grid file.\n" );
        return CE_Failure;
    }

    int nSize = nXSize * nYSize * (int)sizeof(double);
    nTemp = CPL_LSBWORD32(nSize); // Mark size of data
    if( VSIFWriteL( (void *)&nTemp, sizeof(GInt32), 1, fp ) != 1 )
    {
        CPLError( CE_Failure, CPLE_FileIO,
            "Unable to write data size to grid file.\n" );
        return CE_Failure;
    }

    return CE_None;
}

/************************************************************************/
/*                               Create()                               */
/************************************************************************/

GDALDataset *GS7BGDataset::Create( const char * pszFilename,
                                   int nXSize,
                                   int nYSize,
                                   int nBandsIn,
                                   GDALDataType eType,
                                   CPL_UNUSED char **papszParamList )

{
    if( nXSize <= 0 || nYSize <= 0 )
    {
        CPLError( CE_Failure, CPLE_IllegalArg,
              "Unable to create grid, both X and Y size must be "
              "non-negative.\n" );

        return nullptr;
    }

    if( eType != GDT_Byte && eType != GDT_Float32 && eType != GDT_UInt16
        && eType != GDT_Int16 && eType != GDT_Float64)
    {
        CPLError( CE_Failure, CPLE_AppDefined,
              "GS7BG Grid only supports Byte, Int16, "
              "Uint16, Float32, and Float64 datatypes.  Unable to create with "
              "type %s.\n", GDALGetDataTypeName( eType ) );

        return nullptr;
    }

    if (nBandsIn > 1)
    {
        CPLError( CE_Failure, CPLE_NotSupported,
            "Unable to create copy, "
            "format only supports one raster band.\n" );
        return nullptr;
    }

    VSILFILE *fp = VSIFOpenL( pszFilename, "w+b" );

    if( fp == nullptr )
    {
        CPLError( CE_Failure, CPLE_OpenFailed,
                  "Attempt to create file '%s' failed.\n",
                  pszFilename );
        return nullptr;
    }

    CPLErr eErr = WriteHeader( fp, nXSize, nYSize,
                   0.0, nXSize, 0.0, nYSize, 0.0, 0.0 );
    if( eErr != CE_None )
    {
        VSIFCloseL( fp );
        return nullptr;
    }

    double dfVal = dfDefaultNoDataValue;
    CPL_LSBPTR64( &dfVal );
    for( int iRow = 0; iRow < nYSize; iRow++ )
    {
        for( int iCol=0; iCol<nXSize; iCol++ )
        {
            if( VSIFWriteL( (void *)&dfVal, sizeof(double), 1, fp ) != 1 )
            {
                VSIFCloseL( fp );
                CPLError( CE_Failure, CPLE_FileIO,
                      "Unable to write grid cell.  Disk full?\n" );
                return nullptr;
            }
        }
    }

    VSIFCloseL( fp );

    return (GDALDataset *)GDALOpen( pszFilename, GA_Update );
}

/************************************************************************/
/*                             CreateCopy()                             */
/************************************************************************/

GDALDataset *GS7BGDataset::CreateCopy( const char *pszFilename,
                                       GDALDataset *poSrcDS,
                                       int bStrict,
                                       CPL_UNUSED char **papszOptions,
                                       GDALProgressFunc pfnProgress,
                                       void *pProgressData )
{
    if( pfnProgress == nullptr )
        pfnProgress = GDALDummyProgress;

    int nBands = poSrcDS->GetRasterCount();
    if (nBands == 0)
    {
        CPLError( CE_Failure, CPLE_NotSupported,
                  "Driver does not support source dataset with zero band.\n");
        return nullptr;
    }
    else if (nBands > 1)
    {
        if( bStrict )
        {
            CPLError( CE_Failure, CPLE_NotSupported,
                "Unable to create copy, "
                "format only supports one raster band.\n" );
            return nullptr;
        }
        else
            CPLError( CE_Warning, CPLE_NotSupported,
                "Format only supports one "
                "raster band, first band will be copied.\n" );
    }

    GDALRasterBand *poSrcBand = poSrcDS->GetRasterBand( 1 );

    if( !pfnProgress( 0.0, nullptr, pProgressData ) )
    {
        CPLError( CE_Failure, CPLE_UserInterrupt, "User terminated\n" );
        return nullptr;
    }

    VSILFILE    *fp = VSIFOpenL( pszFilename, "w+b" );

    if( fp == nullptr )
    {
        CPLError( CE_Failure, CPLE_OpenFailed,
                  "Attempt to create file '%s' failed.\n",
                  pszFilename );
        return nullptr;
    }

    GInt32  nXSize = poSrcBand->GetXSize();
    GInt32  nYSize = poSrcBand->GetYSize();
    double  adfGeoTransform[6];

    poSrcDS->GetGeoTransform( adfGeoTransform );

    double dfMinX = adfGeoTransform[0] + adfGeoTransform[1] / 2;
    double dfMaxX = adfGeoTransform[1] * (nXSize - 0.5) + adfGeoTransform[0];
    double dfMinY = adfGeoTransform[5] * (nYSize - 0.5) + adfGeoTransform[3];
    double dfMaxY = adfGeoTransform[3] + adfGeoTransform[5] / 2;
    CPLErr eErr = WriteHeader( fp, nXSize, nYSize,
                   dfMinX, dfMaxX, dfMinY, dfMaxY, 0.0, 0.0 );

    if( eErr != CE_None )
    {
        VSIFCloseL( fp );
        return nullptr;
    }

/* -------------------------------------------------------------------- */
/*      Copy band data.                                                 */
/* -------------------------------------------------------------------- */
    double *pfData = (double *)VSI_MALLOC2_VERBOSE( nXSize, sizeof( double ) );
    if( pfData == nullptr )
    {
        VSIFCloseL( fp );
        return nullptr;
    }

    int bSrcHasNDValue;
    double dfSrcNoDataValue = poSrcBand->GetNoDataValue( &bSrcHasNDValue );
    double dfMinZ = std::numeric_limits<double>::max();
    double dfMaxZ = std::numeric_limits<double>::lowest();
    for( GInt32 iRow = nYSize - 1; iRow >= 0; iRow-- )
    {
        eErr = poSrcBand->RasterIO( GF_Read, 0, iRow,
                    nXSize, 1, pfData,
                    nXSize, 1, GDT_Float64, 0, 0, nullptr );

        if( eErr != CE_None )
        {
            VSIFCloseL( fp );
            VSIFree( pfData );
            return nullptr;
        }

        for( int iCol=0; iCol<nXSize; iCol++ )
        {
            if( bSrcHasNDValue && pfData[iCol] == dfSrcNoDataValue )
            {
                pfData[iCol] = dfDefaultNoDataValue;
            }
            else
            {
                if( pfData[iCol] > dfMaxZ )
                    dfMaxZ = pfData[iCol];

                if( pfData[iCol] < dfMinZ )
                    dfMinZ = pfData[iCol];
            }

            CPL_LSBPTR64( pfData+iCol );
        }

        if( VSIFWriteL( (void *)pfData, sizeof( double ), nXSize,
                fp ) != static_cast<unsigned>(nXSize) )
        {
            VSIFCloseL( fp );
            VSIFree( pfData );
            CPLError( CE_Failure, CPLE_FileIO,
                "Unable to write grid row. Disk full?\n" );
            return nullptr;
        }

        if( !pfnProgress( static_cast<double>(nYSize - iRow)/nYSize,
                nullptr, pProgressData ) )
        {
            VSIFCloseL( fp );
            VSIFree( pfData );
            CPLError( CE_Failure, CPLE_UserInterrupt, "User terminated" );
            return nullptr;
        }
    }

    VSIFree( pfData );

    /* write out the min and max values */
    eErr = WriteHeader( fp, nXSize, nYSize,
            dfMinX, dfMaxX, dfMinY, dfMaxY, dfMinZ, dfMaxZ );

    if( eErr != CE_None )
    {
        VSIFCloseL( fp );
        return nullptr;
    }

    VSIFCloseL( fp );

    GDALPamDataset *poDS = (GDALPamDataset *)GDALOpen( pszFilename,
                                                GA_Update );
    if (poDS)
    {
        poDS->CloneInfo( poSrcDS, GCIF_PAM_DEFAULT );
    }

    return poDS;
}

/************************************************************************/
/*                          GDALRegister_GS7BG()                        */
/************************************************************************/
void GDALRegister_GS7BG()

{
    if( GDALGetDriverByName( "GS7BG" ) != nullptr )
        return;

    GDALDriver *poDriver = new GDALDriver();

    poDriver->SetDescription( "GS7BG" );
    poDriver->SetMetadataItem( GDAL_DCAP_RASTER, "YES" );
    poDriver->SetMetadataItem( GDAL_DMD_LONGNAME,
                               "Golden Software 7 Binary Grid (.grd)" );
    poDriver->SetMetadataItem( GDAL_DMD_HELPTOPIC, "drivers/raster/gs7bg.html" );
    poDriver->SetMetadataItem( GDAL_DMD_EXTENSION, "grd" );
    poDriver->SetMetadataItem( GDAL_DMD_CREATIONDATATYPES,
                               "Byte Int16 UInt16 Float32 Float64" );
    poDriver->SetMetadataItem( GDAL_DCAP_VIRTUALIO, "YES" );

    poDriver->pfnIdentify = GS7BGDataset::Identify;
    poDriver->pfnOpen = GS7BGDataset::Open;
    poDriver->pfnCreate = GS7BGDataset::Create;
    poDriver->pfnCreateCopy = GS7BGDataset::CreateCopy;

    GetGDALDriverManager()->RegisterDriver( poDriver );
}
