roipacdataset.cpp

/******************************************************************************
 *
 * Project:  ROI_PAC Raster Reader
 * Purpose:  Implementation of the ROI_PAC raster reader
 * Author:   Matthieu Volat (ISTerre), matthieu.volat@ujf-grenoble.fr
 *
 ******************************************************************************
 * Copyright (c) 2014, Matthieu Volat <matthieu.volat@ujf-grenoble.fr>
 *
 * 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 "gdal_frmts.h"
#include "ogr_spatialref.h"
#include "rawdataset.h"

#include <algorithm>

/************************************************************************/
/* ==================================================================== */
/*                             ROIPACDataset                            */
/* ==================================================================== */
/************************************************************************/

class ROIPACDataset final : public RawDataset
{
    VSILFILE *fpImage;
    VSILFILE *fpRsc;

    char *pszRscFilename;

    double adfGeoTransform[6];
    bool bValidGeoTransform;

    OGRSpatialReference m_oSRS{};

    CPL_DISALLOW_COPY_ASSIGN(ROIPACDataset)

    CPLErr Close() override;

  public:
    ROIPACDataset();
    ~ROIPACDataset() override;

    static GDALDataset *Open(GDALOpenInfo *poOpenInfo);
    static int Identify(GDALOpenInfo *poOpenInfo);
    static GDALDataset *Create(const char *pszFilename, int nXSize, int nYSize,
                               int nBandsIn, GDALDataType eType,
                               char **papszOptions);

    CPLErr FlushCache(bool bAtClosing) override;
    CPLErr GetGeoTransform(double *padfTransform) override;
    CPLErr SetGeoTransform(double *padfTransform) override;

    const OGRSpatialReference *GetSpatialRef() const override
    {
        return m_oSRS.IsEmpty() ? nullptr : &m_oSRS;
    }
    CPLErr SetSpatialRef(const OGRSpatialReference *poSRS) override;

    char **GetFileList() override;
};

/************************************************************************/
/*                           getRscFilename()                           */
/************************************************************************/

static CPLString getRscFilename(GDALOpenInfo *poOpenInfo)
{
    char **papszSiblingFiles = poOpenInfo->GetSiblingFiles();
    if (papszSiblingFiles == nullptr)
    {
        const CPLString osRscFilename =
            CPLFormFilename(nullptr, poOpenInfo->pszFilename, "rsc");
        VSIStatBufL psRscStatBuf;
        if (VSIStatL(osRscFilename, &psRscStatBuf) != 0)
        {
            return "";
        }
        return osRscFilename;
    }

    /* ------------------------------------------------------------ */
    /*      We need to tear apart the filename to form a .rsc       */
    /*      filename.                                               */
    /* ------------------------------------------------------------ */
    const CPLString osPath = CPLGetPath(poOpenInfo->pszFilename);
    const CPLString osName = CPLGetFilename(poOpenInfo->pszFilename);

    int iFile = CSLFindString(papszSiblingFiles,
                              CPLFormFilename(nullptr, osName, "rsc"));
    if (iFile >= 0)
    {
        return CPLFormFilename(osPath, papszSiblingFiles[iFile], nullptr);
    }

    return "";
}

/************************************************************************/
/*                            ROIPACDataset()                           */
/************************************************************************/

ROIPACDataset::ROIPACDataset()
    : fpImage(nullptr), fpRsc(nullptr), pszRscFilename(nullptr),
      bValidGeoTransform(false)
{
    m_oSRS.SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
    adfGeoTransform[0] = 0.0;
    adfGeoTransform[1] = 1.0;
    adfGeoTransform[2] = 0.0;
    adfGeoTransform[3] = 0.0;
    adfGeoTransform[4] = 0.0;
    adfGeoTransform[5] = 1.0;
}

/************************************************************************/
/*                            ~ROIPACDataset()                          */
/************************************************************************/

ROIPACDataset::~ROIPACDataset()
{
    ROIPACDataset::Close();
}

/************************************************************************/
/*                              Close()                                 */
/************************************************************************/

CPLErr ROIPACDataset::Close()
{
    CPLErr eErr = CE_None;
    if (nOpenFlags != OPEN_FLAGS_CLOSED)
    {
        if (ROIPACDataset::FlushCache(true) != CE_None)
            eErr = CE_Failure;

        if (fpRsc != nullptr && VSIFCloseL(fpRsc) != 0)
        {
            eErr = CE_Failure;
            CPLError(CE_Failure, CPLE_FileIO, "I/O error");
        }
        if (fpImage != nullptr && VSIFCloseL(fpImage) != 0)
        {
            eErr = CE_Failure;
            CPLError(CE_Failure, CPLE_FileIO, "I/O error");
        }
        CPLFree(pszRscFilename);

        if (GDALPamDataset::Close() != CE_None)
            eErr = CE_Failure;
    }
    return eErr;
}

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

GDALDataset *ROIPACDataset::Open(GDALOpenInfo *poOpenInfo)
{
    /* -------------------------------------------------------------------- */
    /*      Confirm that the header is compatible with a ROIPAC dataset.    */
    /* -------------------------------------------------------------------- */
    if (!Identify(poOpenInfo) || poOpenInfo->fpL == nullptr)
    {
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Open the .rsc file                                              */
    /* -------------------------------------------------------------------- */
    CPLString osRscFilename = getRscFilename(poOpenInfo);
    if (osRscFilename.empty())
    {
        return nullptr;
    }
    VSILFILE *fpRsc = nullptr;
    if (poOpenInfo->eAccess == GA_Update)
    {
        fpRsc = VSIFOpenL(osRscFilename, "r+");
    }
    else
    {
        fpRsc = VSIFOpenL(osRscFilename, "r");
    }
    if (fpRsc == nullptr)
    {
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Load the .rsc information.                                      */
    /* -------------------------------------------------------------------- */
    CPLStringList aosRSC;
    while (true)
    {
        const char *pszLine = CPLReadLineL(fpRsc);
        if (pszLine == nullptr)
        {
            break;
        }

        char **papszTokens =
            CSLTokenizeString2(pszLine, " \t",
                               CSLT_STRIPLEADSPACES | CSLT_STRIPENDSPACES |
                                   CSLT_PRESERVEQUOTES | CSLT_PRESERVEESCAPES);
        if (papszTokens == nullptr || papszTokens[0] == nullptr ||
            papszTokens[1] == nullptr)
        {
            CSLDestroy(papszTokens);
            break;
        }
        aosRSC.SetNameValue(papszTokens[0], papszTokens[1]);

        CSLDestroy(papszTokens);
    }

    /* -------------------------------------------------------------------- */
    /*      Fetch required fields.                                          */
    /* -------------------------------------------------------------------- */
    if (aosRSC.FetchNameValue("WIDTH") == nullptr ||
        aosRSC.FetchNameValue("FILE_LENGTH") == nullptr)
    {
        CPL_IGNORE_RET_VAL(VSIFCloseL(fpRsc));
        return nullptr;
    }
    const int nWidth = atoi(aosRSC.FetchNameValue("WIDTH"));
    const int nFileLength = atoi(aosRSC.FetchNameValue("FILE_LENGTH"));

    if (!GDALCheckDatasetDimensions(nWidth, nFileLength))
    {
        CPL_IGNORE_RET_VAL(VSIFCloseL(fpRsc));
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Create a corresponding GDALDataset.                             */
    /* -------------------------------------------------------------------- */
    auto poDS = std::make_unique<ROIPACDataset>();
    poDS->nRasterXSize = nWidth;
    poDS->nRasterYSize = nFileLength;
    poDS->eAccess = poOpenInfo->eAccess;
    poDS->fpRsc = fpRsc;
    poDS->pszRscFilename = CPLStrdup(osRscFilename.c_str());
    std::swap(poDS->fpImage, poOpenInfo->fpL);

    /* -------------------------------------------------------------------- */
    /*      Create band information objects.                                */
    /* -------------------------------------------------------------------- */
    GDALDataType eDataType = GDT_Unknown;
    int nBands = 0;
    enum Interleave
    {
        UNKNOWN,
        LINE,
        PIXEL
    } eInterleave = UNKNOWN;
    const char *pszExtension = CPLGetExtension(poOpenInfo->pszFilename);
    if (strcmp(pszExtension, "raw") == 0)
    {
        /* ------------------------------------------------------------ */
        /* TODO: ROI_PAC raw images are what would be GDT_CInt8 typed,  */
        /* but since that type do not exist, we will have to implement  */
        /* a specific case in the RasterBand to convert it to           */
        /* GDT_CInt16 for example                                       */
        /* ------------------------------------------------------------ */
#if 0
        eDataType = GDT_CInt8;
        nBands = 1;
        eInterleave = PIXEL;
#else
        CPLError(CE_Failure, CPLE_NotSupported,
                 "Reading ROI_PAC raw files is not supported yet.");
        return nullptr;
#endif
    }
    else if (strcmp(pszExtension, "int") == 0 ||
             strcmp(pszExtension, "slc") == 0)
    {
        eDataType = GDT_CFloat32;
        nBands = 1;
        eInterleave = PIXEL;
    }
    else if (strcmp(pszExtension, "amp") == 0)
    {
        eDataType = GDT_Float32;
        nBands = 2;
        eInterleave = PIXEL;
    }
    else if (strcmp(pszExtension, "cor") == 0 ||
             strcmp(pszExtension, "hgt") == 0 ||
             strcmp(pszExtension, "unw") == 0 ||
             strcmp(pszExtension, "msk") == 0 ||
             strcmp(pszExtension, "trans") == 0)
    {
        eDataType = GDT_Float32;
        nBands = 2;
        eInterleave = LINE;
    }
    else if (strcmp(pszExtension, "dem") == 0)
    {
        eDataType = GDT_Int16;
        nBands = 1;
        eInterleave = PIXEL;
    }
    else if (strcmp(pszExtension, "flg") == 0)
    {
        eDataType = GDT_Byte;
        nBands = 1;
        eInterleave = PIXEL;
    }
    else
    { /* Eeek */
        return nullptr;
    }

    int nPixelOffset = 0;
    int nLineOffset = 0;
    vsi_l_offset nBandOffset = 0;
    const int nDTSize = GDALGetDataTypeSizeBytes(eDataType);
    bool bIntOverflow = false;
    if (eInterleave == LINE)
    {
        nPixelOffset = nDTSize;
        if (nWidth > INT_MAX / (nPixelOffset * nBands))
            bIntOverflow = true;
        else
        {
            nLineOffset = nPixelOffset * nWidth * nBands;
            nBandOffset = static_cast<vsi_l_offset>(nDTSize) * nWidth;
        }
    }
    else
    { /* PIXEL */
        nPixelOffset = nDTSize * nBands;
        if (nWidth > INT_MAX / nPixelOffset)
            bIntOverflow = true;
        else
        {
            nLineOffset = nPixelOffset * nWidth;
            nBandOffset = nDTSize;

            if (nBands > 1)
            {
                // GDAL 2.0.[0-3] and 2.1.0  had a value of nLineOffset that was
                // equal to the theoretical nLineOffset multiplied by nBands.
                VSIFSeekL(poDS->fpImage, 0, SEEK_END);
                const GUIntBig nWrongFileSize =
                    static_cast<GUIntBig>(nDTSize) * nWidth *
                    (static_cast<GUIntBig>(nFileLength - 1) * nBands * nBands +
                     nBands);
                if (VSIFTellL(poDS->fpImage) == nWrongFileSize)
                {
                    CPLError(
                        CE_Warning, CPLE_AppDefined,
                        "This file has been incorrectly generated by an older "
                        "GDAL version whose line offset computation was "
                        "erroneous.  Taking that into account, "
                        "but the file should be re-encoded ideally.");
                    nLineOffset = nLineOffset * nBands;
                }
            }
        }
    }

    if (bIntOverflow)
    {
        CPLError(CE_Failure, CPLE_AppDefined, "Int overflow occurred.");
        return nullptr;
    }

    for (int b = 0; b < nBands; b++)
    {
        auto poBand = RawRasterBand::Create(
            poDS.get(), b + 1, poDS->fpImage, nBandOffset * b, nPixelOffset,
            nLineOffset, eDataType,
            RawRasterBand::ByteOrder::ORDER_LITTLE_ENDIAN,
            RawRasterBand::OwnFP::NO);
        if (!poBand)
            return nullptr;
        poDS->SetBand(b + 1, std::move(poBand));
    }

    /* -------------------------------------------------------------------- */
    /*      Interpret georeferencing, if present.                           */
    /* -------------------------------------------------------------------- */
    if (aosRSC.FetchNameValue("X_FIRST") != nullptr &&
        aosRSC.FetchNameValue("X_STEP") != nullptr &&
        aosRSC.FetchNameValue("Y_FIRST") != nullptr &&
        aosRSC.FetchNameValue("Y_STEP") != nullptr)
    {
        poDS->adfGeoTransform[0] = CPLAtof(aosRSC.FetchNameValue("X_FIRST"));
        poDS->adfGeoTransform[1] = CPLAtof(aosRSC.FetchNameValue("X_STEP"));
        poDS->adfGeoTransform[2] = 0.0;
        poDS->adfGeoTransform[3] = CPLAtof(aosRSC.FetchNameValue("Y_FIRST"));
        poDS->adfGeoTransform[4] = 0.0;
        poDS->adfGeoTransform[5] = CPLAtof(aosRSC.FetchNameValue("Y_STEP"));
        poDS->bValidGeoTransform = true;
    }
    if (aosRSC.FetchNameValue("PROJECTION") != nullptr)
    {
        /* ------------------------------------------------------------ */
        /* In ROI_PAC, images are georeferenced either with lat/long or */
        /* UTM projection. However, using UTM projection is dangerous   */
        /* because there is no North/South field, or use of latitude    */
        /* bands!                                                       */
        /* ------------------------------------------------------------ */
        OGRSpatialReference oSRS;
        if (strcmp(aosRSC.FetchNameValue("PROJECTION"), "LL") == 0)
        {
            if (aosRSC.FetchNameValue("DATUM") != nullptr)
            {
                oSRS.SetWellKnownGeogCS(aosRSC.FetchNameValue("DATUM"));
            }
            else
            {
                oSRS.SetWellKnownGeogCS("WGS84");
            }
        }
        else if (STARTS_WITH(aosRSC.FetchNameValue("PROJECTION"), "UTM"))
        {
            const char *pszZone = aosRSC.FetchNameValue("PROJECTION") + 3;
            oSRS.SetUTM(atoi(pszZone), TRUE); /* FIXME: north/south? */
            if (aosRSC.FetchNameValue("DATUM") != nullptr)
            {
                oSRS.SetWellKnownGeogCS(aosRSC.FetchNameValue("DATUM"));
            }
            else
            {
                oSRS.SetWellKnownGeogCS("NAD27");
            }
        }
        poDS->m_oSRS = std::move(oSRS);
        poDS->m_oSRS.SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
    }
    if (aosRSC.FetchNameValue("Z_OFFSET") != nullptr)
    {
        const double dfOffset =
            strtod(aosRSC.FetchNameValue("Z_OFFSET"), nullptr);
        for (int b = 1; b <= nBands; b++)
        {
            GDALRasterBand *poBand = poDS->GetRasterBand(b);
            poBand->SetOffset(dfOffset);
        }
    }
    if (aosRSC.FetchNameValue("Z_SCALE") != nullptr)
    {
        const double dfScale =
            strtod(aosRSC.FetchNameValue("Z_SCALE"), nullptr);
        for (int b = 1; b <= nBands; b++)
        {
            GDALRasterBand *poBand = poDS->GetRasterBand(b);
            poBand->SetScale(dfScale);
        }
    }

    /* -------------------------------------------------------------------- */
    /*      Set all the other header metadata into the ROI_PAC domain       */
    /* -------------------------------------------------------------------- */
    for (int i = 0; i < aosRSC.size(); ++i)
    {
        char **papszTokens = CSLTokenizeString2(
            aosRSC[i], "=", CSLT_STRIPLEADSPACES | CSLT_STRIPENDSPACES);
        if (CSLCount(papszTokens) < 2 || strcmp(papszTokens[0], "WIDTH") == 0 ||
            strcmp(papszTokens[0], "FILE_LENGTH") == 0 ||
            strcmp(papszTokens[0], "X_FIRST") == 0 ||
            strcmp(papszTokens[0], "X_STEP") == 0 ||
            strcmp(papszTokens[0], "Y_FIRST") == 0 ||
            strcmp(papszTokens[0], "Y_STEP") == 0 ||
            strcmp(papszTokens[0], "PROJECTION") == 0 ||
            strcmp(papszTokens[0], "DATUM") == 0 ||
            strcmp(papszTokens[0], "Z_OFFSET") == 0 ||
            strcmp(papszTokens[0], "Z_SCALE") == 0)
        {
            CSLDestroy(papszTokens);
            continue;
        }
        poDS->SetMetadataItem(papszTokens[0], papszTokens[1], "ROI_PAC");
        CSLDestroy(papszTokens);
    }
    /* -------------------------------------------------------------------- */
    /*      Initialize any PAM information.                                 */
    /* -------------------------------------------------------------------- */
    poDS->SetDescription(poOpenInfo->pszFilename);
    poDS->TryLoadXML();

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

    return poDS.release();
}

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

int ROIPACDataset::Identify(GDALOpenInfo *poOpenInfo)
{
    /* -------------------------------------------------------------------- */
    /*      Check if:                                                       */
    /*      * 1. The data file extension is known                           */
    /* -------------------------------------------------------------------- */
    const char *pszExtension = CPLGetExtension(poOpenInfo->pszFilename);
    if (strcmp(pszExtension, "raw") == 0)
    {
        /* Since gdal do not read natively CInt8, more work is needed
         * to read raw files */
        return false;
    }
    const bool bExtensionIsValid =
        strcmp(pszExtension, "int") == 0 || strcmp(pszExtension, "slc") == 0 ||
        strcmp(pszExtension, "amp") == 0 || strcmp(pszExtension, "cor") == 0 ||
        strcmp(pszExtension, "hgt") == 0 || strcmp(pszExtension, "unw") == 0 ||
        strcmp(pszExtension, "msk") == 0 ||
        strcmp(pszExtension, "trans") == 0 ||
        strcmp(pszExtension, "dem") == 0 || strcmp(pszExtension, "flg") == 0;
    if (!bExtensionIsValid)
    {
        return false;
    }

    /* -------------------------------------------------------------------- */
    /*      * 2. there is a .rsc file                                      */
    /* -------------------------------------------------------------------- */
    CPLString osRscFilename = getRscFilename(poOpenInfo);
    if (osRscFilename.empty())
    {
        return false;
    }

    return true;
}

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

GDALDataset *ROIPACDataset::Create(const char *pszFilename, int nXSize,
                                   int nYSize, int nBandsIn, GDALDataType eType,
                                   char ** /* papszOptions */)
{
    /* -------------------------------------------------------------------- */
    /*      Verify input options.                                           */
    /* -------------------------------------------------------------------- */
    const char *pszExtension = CPLGetExtension(pszFilename);
    if (strcmp(pszExtension, "int") == 0 || strcmp(pszExtension, "slc") == 0)
    {
        if (nBandsIn != 1 || eType != GDT_CFloat32)
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Attempt to create ROI_PAC %s dataset with an illegal "
                     "number of bands (%d) and/or data type (%s).",
                     pszExtension, nBandsIn, GDALGetDataTypeName(eType));
            return nullptr;
        }
    }
    else if (strcmp(pszExtension, "amp") == 0)
    {
        if (nBandsIn != 2 || eType != GDT_Float32)
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Attempt to create ROI_PAC %s dataset with an illegal "
                     "number of bands (%d) and/or data type (%s).",
                     pszExtension, nBandsIn, GDALGetDataTypeName(eType));
            return nullptr;
        }
    }
    else if (strcmp(pszExtension, "cor") == 0 ||
             strcmp(pszExtension, "hgt") == 0 ||
             strcmp(pszExtension, "unw") == 0 ||
             strcmp(pszExtension, "msk") == 0 ||
             strcmp(pszExtension, "trans") == 0)
    {
        if (nBandsIn != 2 || eType != GDT_Float32)
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Attempt to create ROI_PAC %s dataset with an illegal "
                     "number of bands (%d) and/or data type (%s).",
                     pszExtension, nBandsIn, GDALGetDataTypeName(eType));
            return nullptr;
        }
    }
    else if (strcmp(pszExtension, "dem") == 0)
    {
        if (nBandsIn != 1 || eType != GDT_Int16)
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Attempt to create ROI_PAC %s dataset with an illegal "
                     "number of bands (%d) and/or data type (%s).",
                     pszExtension, nBandsIn, GDALGetDataTypeName(eType));
            return nullptr;
        }
    }
    else if (strcmp(pszExtension, "flg") == 0)
    {
        if (nBandsIn != 1 || eType != GDT_Byte)
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Attempt to create ROI_PAC %s dataset with an illegal "
                     "number of bands (%d) and/or data type (%s).",
                     pszExtension, nBandsIn, GDALGetDataTypeName(eType));
            return nullptr;
        }
    }
    else
    { /* Eeek */
        CPLError(CE_Failure, CPLE_AppDefined,
                 "Attempt to create ROI_PAC dataset with an unknown type (%s)",
                 pszExtension);
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Try to create the file.                                         */
    /* -------------------------------------------------------------------- */
    VSILFILE *fp = VSIFOpenL(pszFilename, "wb");
    if (fp == nullptr)
    {
        CPLError(CE_Failure, CPLE_OpenFailed,
                 "Attempt to create file `%s' failed.", pszFilename);
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Just write out a couple of bytes to establish the binary        */
    /*      file, and then close it.                                        */
    /* -------------------------------------------------------------------- */
    CPL_IGNORE_RET_VAL(VSIFWriteL("\0\0", 2, 1, fp));
    CPL_IGNORE_RET_VAL(VSIFCloseL(fp));

    /* -------------------------------------------------------------------- */
    /*      Open the RSC file.                                              */
    /* -------------------------------------------------------------------- */
    const char *pszRSCFilename = CPLFormFilename(nullptr, pszFilename, "rsc");
    fp = VSIFOpenL(pszRSCFilename, "wt");
    if (fp == nullptr)
    {
        CPLError(CE_Failure, CPLE_OpenFailed,
                 "Attempt to create file `%s' failed.", pszRSCFilename);
        return nullptr;
    }

    /* -------------------------------------------------------------------- */
    /*      Write out the header.                                           */
    /* -------------------------------------------------------------------- */
    CPL_IGNORE_RET_VAL(VSIFPrintfL(fp, "%-40s %d\n", "WIDTH", nXSize));
    CPL_IGNORE_RET_VAL(VSIFPrintfL(fp, "%-40s %d\n", "FILE_LENGTH", nYSize));
    CPL_IGNORE_RET_VAL(VSIFCloseL(fp));

    return GDALDataset::FromHandle(GDALOpen(pszFilename, GA_Update));
}

/************************************************************************/
/*                             FlushCache()                             */
/************************************************************************/

CPLErr ROIPACDataset::FlushCache(bool bAtClosing)
{
    CPLErr eErr = RawDataset::FlushCache(bAtClosing);

    GDALRasterBand *band = (GetRasterCount() > 0) ? GetRasterBand(1) : nullptr;

    if (eAccess == GA_ReadOnly || band == nullptr)
        return eErr;

    // If opening an existing file in Update mode (i.e. "r+") we need to make
    // sure any existing content is cleared, otherwise the file may contain
    // trailing content from the previous write.
    bool bOK = VSIFTruncateL(fpRsc, 0) == 0;

    bOK &= VSIFSeekL(fpRsc, 0, SEEK_SET) == 0;
    /* -------------------------------------------------------------------- */
    /*      Rewrite out the header.                                         */
    /* -------------------------------------------------------------------- */
    /* -------------------------------------------------------------------- */
    /*      Raster dimensions.                                              */
    /* -------------------------------------------------------------------- */
    bOK &= VSIFPrintfL(fpRsc, "%-40s %d\n", "WIDTH", nRasterXSize) > 0;
    bOK &= VSIFPrintfL(fpRsc, "%-40s %d\n", "FILE_LENGTH", nRasterYSize) > 0;

    /* -------------------------------------------------------------------- */
    /*      Georeferencing.                                                 */
    /* -------------------------------------------------------------------- */
    if (!m_oSRS.IsEmpty())
    {
        int bNorth = FALSE;
        int iUTMZone = m_oSRS.GetUTMZone(&bNorth);
        if (iUTMZone != 0)
        {
            bOK &= VSIFPrintfL(fpRsc, "%-40s %s%d\n", "PROJECTION", "UTM",
                               iUTMZone) > 0;
        }
        else if (m_oSRS.IsGeographic())
        {
            bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", "PROJECTION", "LL") > 0;
        }
        else
        {
            CPLError(CE_Warning, CPLE_AppDefined,
                     "ROI_PAC format only support Latitude/Longitude and "
                     "UTM projections, discarding projection.");
        }

        if (m_oSRS.GetAttrValue("DATUM") != nullptr)
        {
            if (strcmp(m_oSRS.GetAttrValue("DATUM"), "WGS_1984") == 0)
            {
                bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", "DATUM", "WGS84") > 0;
            }
            else
            {
                CPLError(CE_Warning, CPLE_AppDefined,
                         "Datum \"%s\" probably not supported in the "
                         "ROI_PAC format, saving it anyway",
                         m_oSRS.GetAttrValue("DATUM"));
                bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", "DATUM",
                                   m_oSRS.GetAttrValue("DATUM")) > 0;
            }
        }
        if (m_oSRS.GetAttrValue("UNIT") != nullptr)
        {
            bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", "X_UNIT",
                               m_oSRS.GetAttrValue("UNIT")) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", "Y_UNIT",
                               m_oSRS.GetAttrValue("UNIT")) > 0;
        }
    }
    if (bValidGeoTransform)
    {
        if (adfGeoTransform[2] != 0 || adfGeoTransform[4] != 0)
        {
            CPLError(CE_Warning, CPLE_AppDefined,
                     "ROI_PAC format do not support geotransform with "
                     "rotation, discarding info.");
        }
        else
        {
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "X_FIRST",
                               adfGeoTransform[0]) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "X_STEP",
                               adfGeoTransform[1]) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "Y_FIRST",
                               adfGeoTransform[3]) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "Y_STEP",
                               adfGeoTransform[5]) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "Z_OFFSET",
                               band->GetOffset(nullptr)) > 0;
            bOK &= VSIFPrintfL(fpRsc, "%-40s %.16g\n", "Z_SCALE",
                               band->GetScale(nullptr)) > 0;
        }
    }

    /* -------------------------------------------------------------------- */
    /*      Metadata stored in the ROI_PAC domain.                          */
    /* -------------------------------------------------------------------- */
    char **papszROIPACMetadata = GetMetadata("ROI_PAC");
    for (int i = 0; i < CSLCount(papszROIPACMetadata); i++)
    {
        /* Get the tokens from the metadata item */
        char **papszTokens =
            CSLTokenizeString2(papszROIPACMetadata[i], "=",
                               CSLT_STRIPLEADSPACES | CSLT_STRIPENDSPACES);
        if (CSLCount(papszTokens) != 2)
        {
            CPLDebug("ROI_PAC",
                     "Line of header file could not be split at = "
                     "into two elements: %s",
                     papszROIPACMetadata[i]);
            CSLDestroy(papszTokens);
            continue;
        }

        /* Don't write it out if it is one of the bits of metadata that is
         * written out elsewhere in this routine */
        if (strcmp(papszTokens[0], "WIDTH") == 0 ||
            strcmp(papszTokens[0], "FILE_LENGTH") == 0)
        {
            CSLDestroy(papszTokens);
            continue;
        }
        bOK &= VSIFPrintfL(fpRsc, "%-40s %s\n", papszTokens[0],
                           papszTokens[1]) > 0;
        CSLDestroy(papszTokens);
    }
    if (!bOK)
        eErr = CE_Failure;
    return eErr;
}

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

CPLErr ROIPACDataset::GetGeoTransform(double *padfTransform)
{
    memcpy(padfTransform, adfGeoTransform, sizeof(adfGeoTransform));
    return bValidGeoTransform ? CE_None : CE_Failure;
}

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

CPLErr ROIPACDataset::SetGeoTransform(double *padfTransform)
{
    memcpy(adfGeoTransform, padfTransform, sizeof(adfGeoTransform));
    bValidGeoTransform = true;
    return CE_None;
}

/************************************************************************/
/*                           SetSpatialRef()                            */
/************************************************************************/

CPLErr ROIPACDataset::SetSpatialRef(const OGRSpatialReference *poSRS)

{
    if (poSRS)
        m_oSRS = *poSRS;
    else
        m_oSRS.Clear();
    return CE_None;
}

/************************************************************************/
/*                            GetFileList()                             */
/************************************************************************/

char **ROIPACDataset::GetFileList()
{
    // Main data file, etc.
    char **papszFileList = RawDataset::GetFileList();

    // RSC file.
    papszFileList = CSLAddString(papszFileList, pszRscFilename);

    return papszFileList;
}

/************************************************************************/
/*                        GDALRegister_ROIPAC()                         */
/************************************************************************/

void GDALRegister_ROIPAC()
{
    if (GDALGetDriverByName("ROI_PAC") != nullptr)
        return;

    GDALDriver *poDriver = new GDALDriver();

    poDriver->SetDescription("ROI_PAC");
    poDriver->SetMetadataItem(GDAL_DMD_LONGNAME, "ROI_PAC raster");
    poDriver->SetMetadataItem(GDAL_DMD_HELPTOPIC,
                              "drivers/raster/roi_pac.html");
    poDriver->SetMetadataItem(GDAL_DCAP_RASTER, "YES");
    poDriver->SetMetadataItem(GDAL_DCAP_VIRTUALIO, "YES");

    poDriver->pfnOpen = ROIPACDataset::Open;
    poDriver->pfnIdentify = ROIPACDataset::Identify;
    poDriver->pfnCreate = ROIPACDataset::Create;

    GetGDALDriverManager()->RegisterDriver(poDriver);
}