/******************************************************************************
 * Purpose:  ASRP/USRP Reader
 * Author:   Frank Warmerdam (warmerdam@pobox.com)
 *
 * Derived from ADRG driver by Even Rouault, even.rouault at spatialys.com.
 *
 ******************************************************************************
 * Copyright (c) 2009-2013, Even Rouault <even dot rouault at spatialys.com>
 * Copyright (c) 2009, Frank Warmerdam
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_string.h"
#include "gdal_pam.h"
#include "gdal_frmts.h"
#include "iso8211.h"
#include "ogr_spatialref.h"

#include <cstdlib>
#include <algorithm>
#include <limits>

// Uncomment to recognize also .gen files in addition to .img files
// #define OPEN_GEN

class SRPDataset final : public GDALPamDataset
{
    friend class SRPRasterBand;

    static CPLString ResetTo01(const char *str);

    VSILFILE *fdIMG;
    int *TILEINDEX;
    int offsetInIMG;
    CPLString osProduct;
    OGRSpatialReference m_oSRS{};
    CPLString osGENFileName;
    CPLString osQALFileName;
    CPLString osIMGFileName;
    int NFC;
    int NFL;
    int ZNA;
    double LSO;
    double PSO;
    double LOD;
    double LAD;
    int ARV;
    int BRV;
    int PCB;
    int PVB;

    char **papszSubDatasets;

    GDALColorTable oCT;

    static char **GetGENListFromTHF(const char *pszFileName);
    static char **GetIMGListFromGEN(const char *pszFileName,
                                    int *pnRecordIndex = nullptr);
    static SRPDataset *OpenDataset(const char *pszGENFileName,
                                   const char *pszIMGFileName,
                                   DDFRecord *record = nullptr);
    static DDFRecord *FindRecordInGENForIMG(DDFModule &module,
                                            const char *pszGENFileName,
                                            const char *pszIMGFileName);

  public:
    SRPDataset();
    ~SRPDataset() override;

    const OGRSpatialReference *GetSpatialRef() const override;
    CPLErr GetGeoTransform(double *padfGeoTransform) override;

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

    char **GetFileList() override;

    bool GetFromRecord(const char *pszFileName, DDFRecord *record);
    void AddSubDataset(const char *pszGENFileName, const char *pszIMGFileName);
    void AddMetadatafromFromTHF(const char *pszFileName);

    static GDALDataset *Open(GDALOpenInfo *);
};

/************************************************************************/
/* ==================================================================== */
/*                            SRPRasterBand                            */
/* ==================================================================== */
/************************************************************************/

class SRPRasterBand final : public GDALPamRasterBand
{
    friend class SRPDataset;

  public:
    SRPRasterBand(SRPDataset *, int);

    CPLErr IReadBlock(int, int, void *) override;

    double GetNoDataValue(int *pbSuccess = nullptr) override;

    GDALColorInterp GetColorInterpretation() override;
    GDALColorTable *GetColorTable() override;
};

/************************************************************************/
/*                           SRPRasterBand()                            */
/************************************************************************/

SRPRasterBand::SRPRasterBand(SRPDataset *poDSIn, int nBandIn)

{
    poDS = poDSIn;
    nBand = nBandIn;

    eDataType = GDT_Byte;

    nBlockXSize = 128;
    nBlockYSize = 128;
}

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

double SRPRasterBand::GetNoDataValue(int *pbSuccess)
{
    if (pbSuccess)
        *pbSuccess = TRUE;

    return 0;
}

/************************************************************************/
/*                       GetColorInterpretation()                       */
/************************************************************************/

GDALColorInterp SRPRasterBand::GetColorInterpretation()

{
    SRPDataset *l_poDS = (SRPDataset *)this->poDS;

    if (l_poDS->oCT.GetColorEntryCount() > 0)
        return GCI_PaletteIndex;
    else
        return GCI_GrayIndex;
}

/************************************************************************/
/*                           GetColorTable()                            */
/************************************************************************/

GDALColorTable *SRPRasterBand::GetColorTable()

{
    SRPDataset *l_poDS = (SRPDataset *)this->poDS;

    if (l_poDS->oCT.GetColorEntryCount() > 0)
        return &(l_poDS->oCT);
    else
        return nullptr;
}

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

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

{
    SRPDataset *l_poDS = (SRPDataset *)this->poDS;
    vsi_l_offset offset;
    int nBlock = nBlockYOff * l_poDS->NFC + nBlockXOff;
    if (nBlockXOff >= l_poDS->NFC || nBlockYOff >= l_poDS->NFL)
    {
        CPLError(CE_Failure, CPLE_AppDefined,
                 "nBlockXOff=%d, NFC=%d, nBlockYOff=%d, NFL=%d", nBlockXOff,
                 l_poDS->NFC, nBlockYOff, l_poDS->NFL);
        return CE_Failure;
    }

    /* -------------------------------------------------------------------- */
    /*      Is this a null block?                                           */
    /* -------------------------------------------------------------------- */
    if (l_poDS->TILEINDEX && l_poDS->TILEINDEX[nBlock] <= 0)
    {
        memset(pImage, 0, 128 * 128);
        return CE_None;
    }

    /* -------------------------------------------------------------------- */
    /*      Compute the offset to the block.                                */
    /* -------------------------------------------------------------------- */
    if (l_poDS->TILEINDEX)
    {
        if (l_poDS->PCB == 0)  // uncompressed
            offset = l_poDS->offsetInIMG +
                     static_cast<vsi_l_offset>(l_poDS->TILEINDEX[nBlock] - 1) *
                         128 * 128;
        else  // compressed
            offset = l_poDS->offsetInIMG +
                     static_cast<vsi_l_offset>(l_poDS->TILEINDEX[nBlock] - 1);
    }
    else
        offset =
            l_poDS->offsetInIMG + static_cast<vsi_l_offset>(nBlock) * 128 * 128;

    /* -------------------------------------------------------------------- */
    /*      Seek to target location.                                        */
    /* -------------------------------------------------------------------- */
    if (VSIFSeekL(l_poDS->fdIMG, offset, SEEK_SET) != 0)
    {
        CPLError(CE_Failure, CPLE_FileIO,
                 "Cannot seek to offset " CPL_FRMT_GUIB, offset);
        return CE_Failure;
    }

    /* -------------------------------------------------------------------- */
    /*      For uncompressed case we read the 128x128 and return with no    */
    /*      further processing.                                             */
    /* -------------------------------------------------------------------- */
    if (l_poDS->PCB == 0)
    {
        if (VSIFReadL(pImage, 1, 128 * 128, l_poDS->fdIMG) != 128 * 128)
        {
            CPLError(CE_Failure, CPLE_FileIO,
                     "Cannot read data at offset " CPL_FRMT_GUIB, offset);
            return CE_Failure;
        }
    }

    /* -------------------------------------------------------------------- */
    /*      If this is compressed data, we read a goodly chunk of data      */
    /*      and then decode it.                                             */
    /* -------------------------------------------------------------------- */
    else
    {
        const int nBufSize = 128 * 128 * 2;
        GByte *pabyCData = (GByte *)CPLCalloc(nBufSize, 1);

        const int nBytesRead =
            static_cast<int>(VSIFReadL(pabyCData, 1, nBufSize, l_poDS->fdIMG));
        if (nBytesRead == 0)
        {
            CPLError(CE_Failure, CPLE_FileIO,
                     "Cannot read data at offset " CPL_FRMT_GUIB, offset);
            CPLFree(pabyCData);
            return CE_Failure;
        }

        CPLAssert(l_poDS->PVB == 8);
        CPLAssert(l_poDS->PCB == 4 || l_poDS->PCB == 8);

        bool bHalfByteUsed = false;
        for (int iSrc = 0, iPixel = 0; iPixel < 128 * 128;)
        {
            if (iSrc + 2 > nBytesRead)
            {
                CPLFree(pabyCData);
                CPLError(CE_Failure, CPLE_AppDefined,
                         "Out of data decoding image block, only %d available.",
                         iSrc);
                return CE_Failure;
            }

            int nCount = 0;
            int nValue = 0;

            if (l_poDS->PCB == 8)
            {
                nCount = pabyCData[iSrc++];
                nValue = pabyCData[iSrc++];
            }
            else if (l_poDS->PCB == 4)
            {
                if ((iPixel % 128) == 0 && bHalfByteUsed)
                {
                    iSrc++;
                    bHalfByteUsed = false;
                    continue;
                }

                if (bHalfByteUsed)
                {
                    nCount = pabyCData[iSrc++] & 0xf;
                    nValue = pabyCData[iSrc++];
                    bHalfByteUsed = false;
                }
                else
                {
                    nCount = pabyCData[iSrc] >> 4;
                    nValue = ((pabyCData[iSrc] & 0xf) << 4) +
                             (pabyCData[iSrc + 1] >> 4);
                    bHalfByteUsed = true;
                    iSrc++;
                }
            }

            if (iPixel + nCount > 128 * 128)
            {
                CPLFree(pabyCData);
                CPLError(CE_Failure, CPLE_AppDefined,
                         "Too much data decoding image block, likely corrupt.");
                return CE_Failure;
            }

            while (nCount > 0)
            {
                ((GByte *)pImage)[iPixel++] = (GByte)nValue;
                nCount--;
            }
        }

        CPLFree(pabyCData);
    }

    return CE_None;
}

/************************************************************************/
/*                          SRPDataset()                               */
/************************************************************************/

SRPDataset::SRPDataset()
    : fdIMG(nullptr), TILEINDEX(nullptr), offsetInIMG(0), NFC(0), NFL(0),
      ZNA(0), LSO(0.0), PSO(0.0), LOD(0.0), LAD(0.0), ARV(0), BRV(0), PCB(0),
      PVB(0), papszSubDatasets(nullptr)
{
    m_oSRS.SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
}

/************************************************************************/
/*                          ~SRPDataset()                              */
/************************************************************************/

SRPDataset::~SRPDataset()
{
    CSLDestroy(papszSubDatasets);

    if (fdIMG)
    {
        VSIFCloseL(fdIMG);
    }

    if (TILEINDEX)
    {
        delete[] TILEINDEX;
    }
}

/************************************************************************/
/*                          ResetTo01()                                 */
/* Replace the DD in ZZZZZZDD.XXX with 01.                              */
/************************************************************************/

CPLString SRPDataset::ResetTo01(const char *str)
{
    CPLString osResult = str;

    osResult[6] = '0';
    osResult[7] = '1';

    return osResult;
}

/************************************************************************/
/*                        GetSpatialRef()                               */
/************************************************************************/

const OGRSpatialReference *SRPDataset::GetSpatialRef() const
{
    return m_oSRS.IsEmpty() ? nullptr : &m_oSRS;
}

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

CPLErr SRPDataset::GetGeoTransform(double *padfGeoTransform)
{
    if (EQUAL(osProduct, "ASRP"))
    {
        if (ARV == 0)
            return CE_Failure;
        if (ZNA == 9)
        {
            // North Polar Case
            padfGeoTransform[0] = 111319.4907933 * (90.0 - PSO / 3600.0) *
                                  sin(LSO * M_PI / 648000.0);
            padfGeoTransform[1] = 40075016.68558 / ARV;
            padfGeoTransform[2] = 0.0;
            padfGeoTransform[3] = -111319.4907933 * (90.0 - PSO / 3600.0) *
                                  cos(LSO * M_PI / 648000.0);
            padfGeoTransform[4] = 0.0;
            padfGeoTransform[5] = -40075016.68558 / ARV;
        }
        else if (ZNA == 18)
        {
            // South Polar Case
            padfGeoTransform[0] = 111319.4907933 * (90.0 + PSO / 3600.0) *
                                  sin(LSO * M_PI / 648000.0);
            padfGeoTransform[1] = 40075016.68558 / ARV;
            padfGeoTransform[2] = 0.0;
            padfGeoTransform[3] = 111319.4907933 * (90.0 + PSO / 3600.0) *
                                  cos(LSO * M_PI / 648000.0);
            padfGeoTransform[4] = 0.0;
            padfGeoTransform[5] = -40075016.68558 / ARV;
        }
        else
        {
            if (BRV == 0)
                return CE_Failure;
            padfGeoTransform[0] = LSO / 3600.0;
            padfGeoTransform[1] = 360. / ARV;
            padfGeoTransform[2] = 0.0;
            padfGeoTransform[3] = PSO / 3600.0;
            padfGeoTransform[4] = 0.0;
            padfGeoTransform[5] = -360. / BRV;
        }

        return CE_None;
    }
    else if (EQUAL(osProduct, "USRP"))
    {
        padfGeoTransform[0] = LSO;
        padfGeoTransform[1] = LOD;
        padfGeoTransform[2] = 0.0;
        padfGeoTransform[3] = PSO;
        padfGeoTransform[4] = 0.0;
        padfGeoTransform[5] = -LAD;
        return CE_None;
    }

    return CE_Failure;
}

/************************************************************************/
/*                           GetFromRecord()                            */
/************************************************************************/

bool SRPDataset::GetFromRecord(const char *pszFileName, DDFRecord *record)
{
    int bSuccess;

    /* -------------------------------------------------------------------- */
    /*      Read a variety of header fields of interest from the .GEN       */
    /*      file.                                                           */
    /* -------------------------------------------------------------------- */
    const int nSTR = record->GetIntSubfield("GEN", 0, "STR", 0, &bSuccess);
    if (!bSuccess || nSTR != 4)
    {
        CPLDebug("SRP", "Failed to extract STR, or not 4.");
        return false;
    }

    const int SCA = record->GetIntSubfield("GEN", 0, "SCA", 0, &bSuccess);
    CPLDebug("SRP", "SCA=%d", SCA);

    ZNA = record->GetIntSubfield("GEN", 0, "ZNA", 0, &bSuccess);
    CPLDebug("SRP", "ZNA=%d", ZNA);

    const double PSP = record->GetFloatSubfield("GEN", 0, "PSP", 0, &bSuccess);
    CPLDebug("SRP", "PSP=%f", PSP);

    ARV = record->GetIntSubfield("GEN", 0, "ARV", 0, &bSuccess);
    CPLDebug("SRP", "ARV=%d", ARV);

    BRV = record->GetIntSubfield("GEN", 0, "BRV", 0, &bSuccess);
    CPLDebug("SRP", "BRV=%d", BRV);

    LSO = record->GetFloatSubfield("GEN", 0, "LSO", 0, &bSuccess);
    CPLDebug("SRP", "LSO=%f", LSO);

    PSO = record->GetFloatSubfield("GEN", 0, "PSO", 0, &bSuccess);
    CPLDebug("SRP", "PSO=%f", PSO);

    LAD = record->GetFloatSubfield("GEN", 0, "LAD", 0);
    LOD = record->GetFloatSubfield("GEN", 0, "LOD", 0);

    NFL = record->GetIntSubfield("SPR", 0, "NFL", 0, &bSuccess);
    CPLDebug("SRP", "NFL=%d", NFL);

    NFC = record->GetIntSubfield("SPR", 0, "NFC", 0, &bSuccess);
    CPLDebug("SRP", "NFC=%d", NFC);

    const auto knIntMax = std::numeric_limits<int>::max();
    if (NFL <= 0 || NFC <= 0 || NFL > knIntMax / 128 || NFC > knIntMax / 128 ||
        NFL > knIntMax / NFC)
    {
        CPLError(CE_Failure, CPLE_AppDefined, "Invalid NFL / NFC values");
        return false;
    }

    const int PNC = record->GetIntSubfield("SPR", 0, "PNC", 0, &bSuccess);
    CPLDebug("SRP", "PNC=%d", PNC);

    const int PNL = record->GetIntSubfield("SPR", 0, "PNL", 0, &bSuccess);
    CPLDebug("SRP", "PNL=%d", PNL);

    if (PNL != 128 || PNC != 128)
    {
        CPLError(CE_Failure, CPLE_AppDefined, "Unsupported PNL or PNC value.");
        return false;
    }

    PCB = record->GetIntSubfield("SPR", 0, "PCB", 0);
    PVB = record->GetIntSubfield("SPR", 0, "PVB", 0);
    if ((PCB != 8 && PCB != 4 && PCB != 0) || PVB != 8)
    {
        CPLError(CE_Failure, CPLE_AppDefined,
                 "PCB(%d) or PVB(%d) value unsupported.", PCB, PVB);
        return false;
    }

    const char *pszBAD =
        record->GetStringSubfield("SPR", 0, "BAD", 0, &bSuccess);
    if (pszBAD == nullptr)
        return false;
    const CPLString osBAD = pszBAD;
    {
        char *c = (char *)strchr(osBAD, ' ');
        if (c)
            *c = 0;
    }
    CPLDebug("SRP", "BAD=%s", osBAD.c_str());

    /* -------------------------------------------------------------------- */
    /*      Read the tile map if available.                                 */
    /* -------------------------------------------------------------------- */
    const char *pszTIF = record->GetStringSubfield("SPR", 0, "TIF", 0);
    const bool TIF = pszTIF != nullptr && EQUAL(pszTIF, "Y");
    CPLDebug("SRP", "TIF=%s", TIF ? "true" : "false");

    if (TIF)
    {
        DDFField *field = record->FindField("TIM");
        if (field == nullptr)
            return false;

        DDFFieldDefn *fieldDefn = field->GetFieldDefn();
        DDFSubfieldDefn *subfieldDefn = fieldDefn->FindSubfieldDefn("TSI");
        if (subfieldDefn == nullptr)
            return false;

        const int nIndexValueWidth = subfieldDefn->GetWidth();

        char offset[30] = {0};
        /* Should be strict comparison, but apparently a few datasets */
        /* have GetDataSize() greater than the required minimum (#3862) */
        if (nIndexValueWidth <= 0 ||
            static_cast<size_t>(nIndexValueWidth) >= sizeof(offset) ||
            nIndexValueWidth > (INT_MAX - 1) / (NFL * NFC) ||
            field->GetDataSize() < nIndexValueWidth * NFL * NFC + 1)
        {
            return false;
        }

        try
        {
            TILEINDEX = new int[NFL * NFC];
        }
        catch (const std::exception &)
        {
            return false;
        }
        const char *ptr = field->GetData();
        offset[nIndexValueWidth] = '\0';

        for (int i = 0; i < NFL * NFC; i++)
        {
            strncpy(offset, ptr, nIndexValueWidth);
            ptr += nIndexValueWidth;
            TILEINDEX[i] = atoi(offset);
            // CPLDebug("SRP", "TSI[%d]=%d", i, TILEINDEX[i]);
        }
    }

    /* -------------------------------------------------------------------- */
    /*      Open the .IMG file.  Try to recover gracefully if the case      */
    /*      of the filename is wrong.                                       */
    /* -------------------------------------------------------------------- */
    const CPLString osDirname = CPLGetDirnameSafe(pszFileName);
    const CPLString osImgName =
        CPLFormCIFilenameSafe(osDirname, osBAD, nullptr);

    fdIMG = VSIFOpenL(osImgName, "rb");
    if (fdIMG == nullptr)
    {
        CPLError(CE_Failure, CPLE_AppDefined, "Cannot find %s",
                 osImgName.c_str());
        return false;
    }

    /* -------------------------------------------------------------------- */
    /*      Establish the offset to the first byte of actual image data     */
    /*      in the IMG file, skipping the ISO8211 header.                   */
    /*                                                                      */
    /*      This code is awfully fragile!                                   */
    /* -------------------------------------------------------------------- */
    char c;
    if (VSIFReadL(&c, 1, 1, fdIMG) != 1)
    {
        return false;
    }
    while (!VSIFEofL(fdIMG))
    {
        if (c == 30)
        {
            char recordName[3] = {};
            if (VSIFReadL(recordName, 1, 3, fdIMG) != 3)
            {
                return false;
            }
            offsetInIMG += 3;
            if (STARTS_WITH(recordName, "IMG"))
            {
                offsetInIMG += 4;
                if (VSIFSeekL(fdIMG, 3, SEEK_CUR) != 0)
                {
                    return false;
                }
                if (VSIFReadL(&c, 1, 1, fdIMG) != 1)
                {
                    return false;
                }
                while (c != 30)
                {
                    offsetInIMG++;
                    if (VSIFReadL(&c, 1, 1, fdIMG) != 1)
                    {
                        return false;
                    }
                }
                offsetInIMG++;
                break;
            }
        }

        offsetInIMG++;
        if (VSIFReadL(&c, 1, 1, fdIMG) != 1)
        {
            return false;
        }
    }

    if (VSIFEofL(fdIMG))
    {
        return false;
    }

    CPLDebug("SRP", "Img offset data = %d", offsetInIMG);

    /* -------------------------------------------------------------------- */
    /*      Establish the SRP Dataset.                                     */
    /* -------------------------------------------------------------------- */
    nRasterXSize = NFC * 128;
    nRasterYSize = NFL * 128;

    char szValue[32] = {};
    snprintf(szValue, sizeof(szValue), "%d", SCA);
    SetMetadataItem("SRP_SCA", szValue);

    // PSP Pixel Spacing, Microns at capture stage {000.0 - 100.0}
    snprintf(szValue, sizeof(szValue), "%3.1f", PSP);
    SetMetadataItem("SRP_PSP", szValue);

    nBands = 1;
    for (int i = 0; i < nBands; i++)
        SetBand(i + 1, new SRPRasterBand(this, i + 1));

    /* -------------------------------------------------------------------- */
    /*      Try to collect a color map from the .QAL file.                  */
    /* -------------------------------------------------------------------- */
    const CPLString osBasename = CPLGetBasenameSafe(pszFileName);
    osQALFileName = CPLFormCIFilenameSafe(osDirname, osBasename, "QAL");

    DDFModule oQALModule;

    if (oQALModule.Open(osQALFileName, TRUE))
    {
        while ((record = oQALModule.ReadRecord()) != nullptr)
        {
            if (record->FindField("COL") != nullptr)
            {
                const int nColorCount =
                    std::min(256, record->FindField("COL")->GetRepeatCount());

                for (int iColor = 0; iColor < nColorCount; iColor++)
                {
                    const int nCCD = record->GetIntSubfield("COL", 0, "CCD",
                                                            iColor, &bSuccess);
                    if (!bSuccess || nCCD < 0 || nCCD > 255)
                        break;

                    int nNSR = record->GetIntSubfield("COL", 0, "NSR", iColor);
                    int nNSG = record->GetIntSubfield("COL", 0, "NSG", iColor);
                    int nNSB = record->GetIntSubfield("COL", 0, "NSB", iColor);

                    GDALColorEntry sEntry = {static_cast<short>(nNSR),
                                             static_cast<short>(nNSG),
                                             static_cast<short>(nNSB), 255};

                    oCT.SetColorEntry(nCCD, &sEntry);
                }
            }

            if (record->FindField("QUV") != nullptr)
            {
                // TODO: Translate to English or state why this should not be in
                // English.
                // Date de production du produit : QAL.QUV.DAT1
                // Numero d'edition  du produit : QAL.QUV.EDN

                const int EDN =
                    record->GetIntSubfield("QUV", 0, "EDN", 0, &bSuccess);
                if (bSuccess)
                {
                    CPLDebug("SRP", "EDN=%d", EDN);
                    snprintf(szValue, sizeof(szValue), "%d", EDN);
                    SetMetadataItem("SRP_EDN", szValue);
                }

                const char *pszCDV07 =
                    record->GetStringSubfield("QUV", 0, "CDV07", 0);
                if (pszCDV07 != nullptr)
                    SetMetadataItem("SRP_CREATIONDATE", pszCDV07);
                else
                { /*USRP1.2*/
                    const char *pszDAT =
                        record->GetStringSubfield("QUV", 0, "DAT1", 0);
                    if (pszDAT != nullptr && strlen(pszDAT) >= 12)
                    {
                        char dat[9];
                        strncpy(dat, pszDAT + 4, 8);
                        dat[8] = '\0';
                        CPLDebug("SRP", "Record DAT %s", dat);
                        SetMetadataItem("SRP_CREATIONDATE", dat);
                    }
                }

                const char *pszCDV24 =
                    record->GetStringSubfield("QUV", 0, "CDV24", 0);
                if (pszCDV24 != nullptr)
                {
                    SetMetadataItem("SRP_REVISIONDATE", pszCDV24);
                }
                else
                { /*USRP1.2*/
                    const char *pszDAT =
                        record->GetStringSubfield("QUV", 0, "DAT2", 0);
                    if (pszDAT != nullptr && strlen(pszDAT) >= 12)
                    {
                        char dat[9];
                        strncpy(dat, pszDAT + 4, 8);
                        dat[8] = '\0';
                        CPLDebug("SRP", "Record DAT %s", dat);
                        SetMetadataItem("SRP_REVISIONDATE", dat);
                    }
                }

                const char *pszQSS =
                    record->GetStringSubfield("QSR", 0, "QSS", 0);
                if (pszQSS != nullptr)
                    SetMetadataItem("SRP_CLASSIFICATION", pszQSS);
            }
        }
    }
    else
    {
        osQALFileName = "";
        CPLError(CE_Warning, CPLE_AppDefined,
                 "Unable to find .QAL file, no color table applied.");
    }

    /* -------------------------------------------------------------------- */
    /*      Derive the coordinate system.                                   */
    /* -------------------------------------------------------------------- */
    if (EQUAL(osProduct, "ASRP"))
    {
        m_oSRS.importFromWkt(SRS_WKT_WGS84_LAT_LONG);

        if (ZNA == 9)
        {
            m_oSRS.importFromWkt(
                "PROJCS[\"ARC_System_Zone_09\",GEOGCS[\"GCS_Sphere\","
                "DATUM[\"D_Sphere\",SPHEROID[\"Sphere\",6378137.0,0.0]],"
                "PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433]],"
                "PROJECTION[\"Azimuthal_Equidistant\"],"
                "PARAMETER[\"latitude_of_center\",90],"
                "PARAMETER[\"longitude_of_center\",0],"
                "PARAMETER[\"false_easting\",0],"
                "PARAMETER[\"false_northing\",0],"
                "UNIT[\"metre\",1]]");
        }

        if (ZNA == 18)
        {
            m_oSRS.importFromWkt(
                "PROJCS[\"ARC_System_Zone_18\",GEOGCS[\"GCS_Sphere\","
                "DATUM[\"D_Sphere\",SPHEROID[\"Sphere\",6378137.0,0.0]],"
                "PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433]],"
                "PROJECTION[\"Azimuthal_Equidistant\"],"
                "PARAMETER[\"latitude_of_center\",-90],"
                "PARAMETER[\"longitude_of_center\",0],"
                "PARAMETER[\"false_easting\",0],"
                "PARAMETER[\"false_northing\",0],"
                "UNIT[\"metre\",1]]");
        }
    }
    else
    {
        if (ZNA >= -60 && ZNA <= 60 && ZNA != 0)
        {
            m_oSRS.SetUTM(std::abs(ZNA), ZNA > 0);
            m_oSRS.SetWellKnownGeogCS("WGS84");
        }
        else if (ZNA == 61)
        {
            m_oSRS.importFromEPSG(32661);  // WGS84 UPS North
        }
        else if (ZNA == -61)
        {
            m_oSRS.importFromEPSG(32761);  // WGS84 UPS South
        }
    }

    snprintf(szValue, sizeof(szValue), "%d", ZNA);
    SetMetadataItem("SRP_ZNA", szValue);

    return true;
}

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

char **SRPDataset::GetFileList()

{
    char **papszFileList = GDALPamDataset::GetFileList();
    if (!osGENFileName.empty() && !osIMGFileName.empty())
    {
        CPLString osMainFilename = GetDescription();
        VSIStatBufL sStat;

        const bool bMainFileReal = VSIStatL(osMainFilename, &sStat) == 0;
        if (bMainFileReal)
        {
            CPLString osShortMainFilename = CPLGetFilename(osMainFilename);
            CPLString osShortGENFileName = CPLGetFilename(osGENFileName);
            if (!EQUAL(osShortMainFilename.c_str(), osShortGENFileName.c_str()))
                papszFileList =
                    CSLAddString(papszFileList, osGENFileName.c_str());
        }
        else
        {
            papszFileList = CSLAddString(papszFileList, osGENFileName.c_str());
        }

        papszFileList = CSLAddString(papszFileList, osIMGFileName.c_str());

        if (!osQALFileName.empty())
            papszFileList = CSLAddString(papszFileList, osQALFileName);
    }
    return papszFileList;
}

/************************************************************************/
/*                           AddSubDataset()                            */
/************************************************************************/

void SRPDataset::AddSubDataset(const char *pszGENFileName,
                               const char *pszIMGFileName)
{
    const int nCount = CSLCount(papszSubDatasets) / 2;

    CPLString osSubDatasetName = "SRP:";
    osSubDatasetName += pszGENFileName;
    osSubDatasetName += ",";
    osSubDatasetName += pszIMGFileName;

    char szName[80];
    snprintf(szName, sizeof(szName), "SUBDATASET_%d_NAME", nCount + 1);
    papszSubDatasets =
        CSLSetNameValue(papszSubDatasets, szName, osSubDatasetName);

    snprintf(szName, sizeof(szName), "SUBDATASET_%d_DESC", nCount + 1);
    papszSubDatasets =
        CSLSetNameValue(papszSubDatasets, szName, osSubDatasetName);
}

/************************************************************************/
/*                            GetMetadata()                             */
/************************************************************************/

char **SRPDataset::GetMetadata(const char *pszDomain)

{
    if (pszDomain != nullptr && EQUAL(pszDomain, "SUBDATASETS"))
        return papszSubDatasets;

    return GDALPamDataset::GetMetadata(pszDomain);
}

/************************************************************************/
/*                      FindRecordInGENForIMG()                         */
/************************************************************************/

DDFRecord *SRPDataset::FindRecordInGENForIMG(DDFModule &module,
                                             const char *pszGENFileName,
                                             const char *pszIMGFileName)
{
    /* Finds the GEN file corresponding to the IMG file */
    if (!module.Open(pszGENFileName, TRUE))
        return nullptr;

    CPLString osShortIMGFilename = CPLGetFilename(pszIMGFileName);

    DDFField *field = nullptr;
    DDFFieldDefn *fieldDefn = nullptr;

    // Now finds the record.
    while (true)
    {
        CPLPushErrorHandler(CPLQuietErrorHandler);
        DDFRecord *record = module.ReadRecord();
        CPLPopErrorHandler();
        CPLErrorReset();
        if (record == nullptr)
            return nullptr;

        if (record->GetFieldCount() >= 5)
        {
            field = record->GetField(0);
            fieldDefn = field->GetFieldDefn();
            if (!(strcmp(fieldDefn->GetName(), "001") == 0 &&
                  fieldDefn->GetSubfieldCount() == 2))
            {
                continue;
            }

            const char *RTY = record->GetStringSubfield("001", 0, "RTY", 0);
            if (RTY == nullptr)
                continue;
            /* Ignore overviews */
            if (strcmp(RTY, "OVV") == 0)
                continue;

            if (strcmp(RTY, "GIN") != 0)
                continue;

            field = record->GetField(3);
            fieldDefn = field->GetFieldDefn();

            if (!(strcmp(fieldDefn->GetName(), "SPR") == 0 &&
                  fieldDefn->GetSubfieldCount() == 15))
            {
                continue;
            }

            const char *pszBAD = record->GetStringSubfield("SPR", 0, "BAD", 0);
            if (pszBAD == nullptr || strlen(pszBAD) != 12)
                continue;
            const CPLString osBAD = pszBAD;
            {
                char *c = (char *)strchr(osBAD.c_str(), ' ');
                if (c)
                    *c = 0;
            }

            if (EQUAL(osShortIMGFilename.c_str(), osBAD.c_str()))
            {
                return record;
            }
        }
    }
}

/************************************************************************/
/*                           OpenDataset()                              */
/************************************************************************/

SRPDataset *SRPDataset::OpenDataset(const char *pszGENFileName,
                                    const char *pszIMGFileName,
                                    DDFRecord *record)
{
    DDFModule module;  // Don't move this line as it holds ownership of record.

    if (record == nullptr)
    {
        record = FindRecordInGENForIMG(module, pszGENFileName, pszIMGFileName);
        if (record == nullptr)
            return nullptr;
    }

    DDFField *field = record->GetField(1);
    if (field == nullptr)
        return nullptr;
    DDFFieldDefn *fieldDefn = field->GetFieldDefn();

    if (!(strcmp(fieldDefn->GetName(), "DSI") == 0 &&
          fieldDefn->GetSubfieldCount() == 2))
    {
        return nullptr;
    }

    const char *pszPRT = record->GetStringSubfield("DSI", 0, "PRT", 0);
    if (pszPRT == nullptr)
        return nullptr;

    CPLString osPRT = pszPRT;
    osPRT.resize(4);
    CPLDebug("SRP", "osPRT=%s", osPRT.c_str());
    if (!EQUAL(osPRT, "ASRP") && !EQUAL(osPRT, "USRP"))
        return nullptr;

    const char *pszNAM = record->GetStringSubfield("DSI", 0, "NAM", 0);
    if (pszNAM == nullptr)
        return nullptr;

    const CPLString osNAM = pszNAM;
    CPLDebug("SRP", "osNAM=%s", osNAM.c_str());
    if (strlen(pszNAM) != 8)
    {
        CPLDebug("SRP", "Name Size=%d", (int)strlen(pszNAM));
    }

    SRPDataset *poDS = new SRPDataset();

    poDS->osProduct = osPRT;
    poDS->osGENFileName = pszGENFileName;
    poDS->osIMGFileName = pszIMGFileName;

    poDS->SetMetadataItem("SRP_NAM", osNAM);
    poDS->SetMetadataItem("SRP_PRODUCT", osPRT);

    if (!poDS->GetFromRecord(pszGENFileName, record))
    {
        delete poDS;
        return nullptr;
    }

    return poDS;
}

/************************************************************************/
/*                          GetGENListFromTHF()                         */
/************************************************************************/

char **SRPDataset::GetGENListFromTHF(const char *pszFileName)
{
    DDFModule module;
    DDFRecord *record = nullptr;
    DDFField *field = nullptr;
    DDFFieldDefn *fieldDefn = nullptr;
    int nFilenames = 0;

    char **papszFileNames = nullptr;
    if (!module.Open(pszFileName, TRUE))
        return papszFileNames;

    CPLString osDirName(CPLGetDirnameSafe(pszFileName));

    while (true)
    {
        CPLPushErrorHandler(CPLQuietErrorHandler);
        record = module.ReadRecord();
        CPLPopErrorHandler();
        CPLErrorReset();
        if (record == nullptr)
            break;
        if (record->GetFieldCount() > 2)
        {
            field = record->GetField(0);
            fieldDefn = field->GetFieldDefn();
            if (!(strcmp(fieldDefn->GetName(), "001") == 0 &&
                  fieldDefn->GetSubfieldCount() == 2))
            {
                continue;
            }

            const char *RTY = record->GetStringSubfield("001", 0, "RTY", 0);
            if (RTY == nullptr)
            {
                continue;
            }

            if (strcmp(RTY, "THF") == 0)
            {
                field = record->GetField(1);
                fieldDefn = field->GetFieldDefn();
                if (!(strcmp(fieldDefn->GetName(), "VDR") == 0 &&
                      fieldDefn->GetSubfieldCount() == 8))
                {
                    continue;
                }

                int iFDRFieldInstance = 0;
                for (int i = 2; i < record->GetFieldCount(); i++)
                {
                    field = record->GetField(i);
                    fieldDefn = field->GetFieldDefn();

                    if (!(strcmp(fieldDefn->GetName(), "FDR") == 0 &&
                          fieldDefn->GetSubfieldCount() == 7))
                    {
                        CPLDebug("SRP", "Record FDR  %d",
                                 fieldDefn->GetSubfieldCount());
                        continue;
                    }

                    const char *pszNAM = record->GetStringSubfield(
                        "FDR", iFDRFieldInstance++, "NAM", 0);
                    if (pszNAM == nullptr)
                        continue;

                    CPLString osName = CPLString(pszNAM);

                    /* Define a subdirectory from Dataset but with only 6
                     * characters */
                    CPLString osDirDataset = pszNAM;
                    osDirDataset.resize(6);
                    CPLString osDatasetDir = CPLFormFilenameSafe(
                        osDirName.c_str(), osDirDataset.c_str(), nullptr);

                    CPLString osGENFileName = "";

                    int bFound = 0;

                    {
                        char **papszDirContent =
                            VSIReadDir(osDatasetDir.c_str());
                        char **ptrDir = papszDirContent;
                        if (ptrDir)
                        {
                            while (*ptrDir)
                            {
                                if (EQUAL(CPLGetExtensionSafe(*ptrDir).c_str(),
                                          "GEN"))
                                {
                                    bFound = 1;
                                    osGENFileName = CPLFormFilenameSafe(
                                        osDatasetDir.c_str(), *ptrDir, nullptr);
                                    CPLDebug("SRP",
                                             "Building GEN full file name : %s",
                                             osGENFileName.c_str());
                                    break;
                                }
                                ptrDir++;
                            }
                            CSLDestroy(papszDirContent);
                        }
                    }

                    /* If not found in sub directory then search in the same
                     * directory of the THF file */
                    if (bFound == 0)
                    {
                        char **papszDirContent = VSIReadDir(osDirName.c_str());
                        char **ptrDir = papszDirContent;
                        if (ptrDir)
                        {
                            while (*ptrDir)
                            {
                                if (EQUAL(CPLGetExtensionSafe(*ptrDir).c_str(),
                                          "GEN") &&
                                    EQUALN(CPLGetBasenameSafe(*ptrDir).c_str(),
                                           osName, 6))
                                {
                                    bFound = 1;
                                    osGENFileName = CPLFormFilenameSafe(
                                        osDirName.c_str(), *ptrDir, nullptr);
                                    CPLDebug("SRP",
                                             "Building GEN full file name : %s",
                                             osGENFileName.c_str());
                                    break;
                                }
                                ptrDir++;
                            }
                            CSLDestroy(papszDirContent);
                        }
                    }

                    if (bFound == 1)
                    {
                        papszFileNames = (char **)CPLRealloc(
                            papszFileNames, sizeof(char *) * (nFilenames + 2));
                        papszFileNames[nFilenames] =
                            CPLStrdup(osGENFileName.c_str());
                        papszFileNames[nFilenames + 1] = nullptr;
                        nFilenames++;
                    }
                }
            }
        }
    }
    return papszFileNames;
}

/************************************************************************/
/*                          AddMetadatafromFromTHF()                         */
/************************************************************************/

void SRPDataset::AddMetadatafromFromTHF(const char *pszFileName)
{
    DDFModule module;
    DDFRecord *record = nullptr;
    DDFField *field = nullptr;
    DDFFieldDefn *fieldDefn = nullptr;

    int bSuccess = 0;
    if (!module.Open(pszFileName, TRUE))
        return;

    while (true)
    {
        CPLPushErrorHandler(CPLQuietErrorHandler);
        record = module.ReadRecord();
        CPLPopErrorHandler();
        CPLErrorReset();
        if (record == nullptr || record->GetFieldCount() <= 2)
            break;

        field = record->GetField(0);
        fieldDefn = field->GetFieldDefn();
        if (!(strcmp(fieldDefn->GetName(), "001") == 0) ||
            fieldDefn->GetSubfieldCount() != 2)
            break;

        const char *RTY = record->GetStringSubfield("001", 0, "RTY", 0);
        if (RTY != nullptr && strcmp(RTY, "THF") == 0)
        {
            field = record->GetField(1);
            fieldDefn = field->GetFieldDefn();
            if ((strcmp(fieldDefn->GetName(), "VDR") == 0 &&
                 fieldDefn->GetSubfieldCount() == 8))
            {

                const char *pszVOO =
                    record->GetStringSubfield("VDR", 0, "VOO", 0);
                if (pszVOO != nullptr)
                {
                    CPLDebug("SRP", "Record VOO %s", pszVOO);
                    SetMetadataItem("SRP_VOO", pszVOO);
                }

                int EDN = record->GetIntSubfield("VDR", 0, "EDN", 0, &bSuccess);
                if (bSuccess)
                {
                    CPLDebug("SRP", "Record EDN %d", EDN);
                    char szValue[5];
                    snprintf(szValue, sizeof(szValue), "%d", EDN);
                    SetMetadataItem("SRP_EDN", szValue);
                }

                const char *pszCDV07 =
                    record->GetStringSubfield("VDR", 0, "CDV07", 0);
                if (pszCDV07 != nullptr)
                {
                    CPLDebug("SRP", "Record pszCDV07 %s", pszCDV07);
                    SetMetadataItem("SRP_CREATIONDATE", pszCDV07);
                }
                else
                { /*USRP1.2*/
                    const char *pszDAT =
                        record->GetStringSubfield("VDR", 0, "DAT", 0);
                    if (pszDAT != nullptr)
                    {
                        char dat[9];
                        strncpy(dat, pszDAT + 4, 8);
                        dat[8] = '\0';
                        CPLDebug("SRP", "Record DAT %s", dat);
                        SetMetadataItem("SRP_CREATIONDATE", dat);
                    }
                }
            }
        } /* End of THF part */

        if (RTY != nullptr && strcmp(RTY, "LCF") == 0)
        {
            field = record->GetField(1);
            fieldDefn = field->GetFieldDefn();
            if ((strcmp(fieldDefn->GetName(), "QSR") == 0 &&
                 fieldDefn->GetSubfieldCount() == 4))
            {

                const char *pszQSS =
                    record->GetStringSubfield("QSR", 0, "QSS", 0);
                if (pszQSS != nullptr)
                {
                    CPLDebug("SRP", "Record Classification %s", pszQSS);
                    SetMetadataItem("SRP_CLASSIFICATION", pszQSS);
                }
            }

            field = record->GetField(2);
            fieldDefn = field->GetFieldDefn();
            if ((strcmp(fieldDefn->GetName(), "QUV") == 0 &&
                 fieldDefn->GetSubfieldCount() == 6))
            {
                const char *pszSRC2 =
                    record->GetStringSubfield("QUV", 0, "SRC1", 0);
                if (pszSRC2 != nullptr)
                {
                    SetMetadataItem("SRP_PRODUCTVERSION", pszSRC2);
                }
                else
                {
                    const char *pszSRC =
                        record->GetStringSubfield("QUV", 0, "SRC", 0);
                    if (pszSRC != nullptr)
                    {
                        SetMetadataItem("SRP_PRODUCTVERSION", pszSRC);
                    }
                }
            }
        } /* End of LCF part */
    }
}

/************************************************************************/
/*                          GetIMGListFromGEN()                         */
/************************************************************************/

char **SRPDataset::GetIMGListFromGEN(const char *pszFileName,
                                     int *pnRecordIndex)
{
    DDFRecord *record = nullptr;
    DDFField *field = nullptr;
    DDFFieldDefn *fieldDefn = nullptr;
    int nFilenames = 0;
    char **papszFileNames = nullptr;
    int nRecordIndex = -1;

    if (pnRecordIndex)
        *pnRecordIndex = -1;

    DDFModule module;
    if (!module.Open(pszFileName, TRUE))
        return nullptr;

    while (true)
    {
        nRecordIndex++;

        CPLPushErrorHandler(CPLQuietErrorHandler);
        record = module.ReadRecord();
        CPLPopErrorHandler();
        CPLErrorReset();
        if (record == nullptr)
            break;

        if (record->GetFieldCount() >= 5)
        {
            field = record->GetField(0);
            fieldDefn = field->GetFieldDefn();
            if (!(strcmp(fieldDefn->GetName(), "001") == 0 &&
                  fieldDefn->GetSubfieldCount() == 2))
            {
                continue;
            }

            const char *RTY = record->GetStringSubfield("001", 0, "RTY", 0);
            if (RTY == nullptr)
                continue;
            /* Ignore overviews */
            if (strcmp(RTY, "OVV") == 0)
                continue;

            if (strcmp(RTY, "GIN") != 0)
                continue;

            /* make sure that the GEN file is part of a SRP dataset, not an ADRG
             * dataset, by checking that the GEN field does not contain a NOW
             * subfield */
            const char *NWO = record->GetStringSubfield("GEN", 0, "NWO", 0);
            if (NWO)
            {
                CSLDestroy(papszFileNames);
                return nullptr;
            }

            field = record->GetField(3);
            if (field == nullptr)
                continue;
            fieldDefn = field->GetFieldDefn();

            if (!(strcmp(fieldDefn->GetName(), "SPR") == 0 &&
                  fieldDefn->GetSubfieldCount() == 15))
            {
                continue;
            }

            const char *pszBAD = record->GetStringSubfield("SPR", 0, "BAD", 0);
            if (pszBAD == nullptr || strlen(pszBAD) != 12)
                continue;
            CPLString osBAD = pszBAD;
            {
                char *c = (char *)strchr(osBAD.c_str(), ' ');
                if (c)
                    *c = 0;
            }
            CPLDebug("SRP", "BAD=%s", osBAD.c_str());

            /* Build full IMG file name from BAD value */
            const CPLString osGENDir(CPLGetDirnameSafe(pszFileName));

            const CPLString osFileName =
                CPLFormFilenameSafe(osGENDir.c_str(), osBAD.c_str(), nullptr);
            VSIStatBufL sStatBuf;
            if (VSIStatL(osFileName, &sStatBuf) == 0)
            {
                osBAD = osFileName;
                CPLDebug("SRP", "Building IMG full file name : %s",
                         osBAD.c_str());
            }
            else
            {
                char **papszDirContent = nullptr;
                if (strcmp(osGENDir.c_str(), "/vsimem") == 0)
                {
                    CPLString osTmp = osGENDir + "/";
                    papszDirContent = VSIReadDir(osTmp);
                }
                else
                    papszDirContent = VSIReadDir(osGENDir);
                char **ptrDir = papszDirContent;
                while (ptrDir && *ptrDir)
                {
                    if (EQUAL(*ptrDir, osBAD.c_str()))
                    {
                        osBAD = CPLFormFilenameSafe(osGENDir.c_str(), *ptrDir,
                                                    nullptr);
                        CPLDebug("SRP", "Building IMG full file name : %s",
                                 osBAD.c_str());
                        break;
                    }
                    ptrDir++;
                }
                CSLDestroy(papszDirContent);
            }

            if (nFilenames == 0 && pnRecordIndex)
                *pnRecordIndex = nRecordIndex;

            papszFileNames = (char **)CPLRealloc(
                papszFileNames, sizeof(char *) * (nFilenames + 2));
            papszFileNames[nFilenames] = CPLStrdup(osBAD.c_str());
            papszFileNames[nFilenames + 1] = nullptr;
            nFilenames++;
        }
    }

    return papszFileNames;
}

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

GDALDataset *SRPDataset::Open(GDALOpenInfo *poOpenInfo)
{
    int nRecordIndex = -1;
    CPLString osGENFileName;
    CPLString osIMGFileName;
    int bFromSubdataset = FALSE;
    int bTHFWithSingleGEN = FALSE;

    if (STARTS_WITH_CI(poOpenInfo->pszFilename, "SRP:"))
    {
        char **papszTokens =
            CSLTokenizeString2(poOpenInfo->pszFilename + 4, ",", 0);
        if (CSLCount(papszTokens) == 2)
        {
            osGENFileName = papszTokens[0];
            osIMGFileName = papszTokens[1];
            bFromSubdataset = TRUE;
        }
        CSLDestroy(papszTokens);
    }
    else
    {
        if (poOpenInfo->nHeaderBytes < 500)
            return nullptr;
        CPLString osFileName(poOpenInfo->pszFilename);

        if (EQUAL(CPLGetExtensionSafe(osFileName.c_str()).c_str(), "THF"))
        {

            CPLDebug("SRP", "Read THF");

            char **papszFileNames = GetGENListFromTHF(osFileName.c_str());
            if (papszFileNames == nullptr)
                return nullptr;
            if (papszFileNames[1] == nullptr &&
                CPLTestBool(CPLGetConfigOption(
                    "SRP_SINGLE_GEN_IN_THF_AS_DATASET", "TRUE")))
            {
                osFileName = papszFileNames[0];
                CSLDestroy(papszFileNames);
                bTHFWithSingleGEN = TRUE;
            }
            else
            {
                char **ptr = papszFileNames;
                SRPDataset *poDS = new SRPDataset();
                poDS->AddMetadatafromFromTHF(osFileName.c_str());
                while (*ptr)
                {
                    char **papszIMGFileNames = GetIMGListFromGEN(*ptr);
                    char **papszIMGIter = papszIMGFileNames;
                    while (papszIMGIter && *papszIMGIter)
                    {
                        poDS->AddSubDataset(*ptr, *papszIMGIter);
                        papszIMGIter++;
                    }
                    CSLDestroy(papszIMGFileNames);

                    ptr++;
                }
                CSLDestroy(papszFileNames);
                return poDS;
            }
        }

        if (bTHFWithSingleGEN
#ifdef OPEN_GEN
            || EQUAL(CPLGetExtensionSafe(osFileName.c_str()).c_str(), "GEN")
#endif
        )
        {
            osGENFileName = osFileName;

            char **papszFileNames =
                GetIMGListFromGEN(osFileName.c_str(), &nRecordIndex);
            if (papszFileNames == nullptr)
                return nullptr;
            if (papszFileNames[1] == nullptr)
            {
                osIMGFileName = papszFileNames[0];
                CSLDestroy(papszFileNames);
            }
            else
            {
                char **ptr = papszFileNames;
                SRPDataset *poDS = new SRPDataset();
                while (*ptr)
                {
                    poDS->AddSubDataset(osFileName.c_str(), *ptr);
                    ptr++;
                }
                CSLDestroy(papszFileNames);
                return poDS;
            }
        }

        if (EQUAL(CPLGetExtensionSafe(osFileName.c_str()).c_str(), "IMG"))
        {

            osIMGFileName = osFileName;

            constexpr int nLeaderSize = 24;

            int i = 0;  // Used after for.
            for (; i < nLeaderSize; i++)
            {
                if (poOpenInfo->pabyHeader[i] < 32 ||
                    poOpenInfo->pabyHeader[i] > 126)
                    return nullptr;
            }

            if (poOpenInfo->pabyHeader[5] != '1' &&
                poOpenInfo->pabyHeader[5] != '2' &&
                poOpenInfo->pabyHeader[5] != '3')
                return nullptr;

            if (poOpenInfo->pabyHeader[6] != 'L')
                return nullptr;
            if (poOpenInfo->pabyHeader[8] != '1' &&
                poOpenInfo->pabyHeader[8] != ' ')
                return nullptr;

            // --------------------------------------------------------------------
            //      Find and open the .GEN file.
            // --------------------------------------------------------------------
            VSIStatBufL sStatBuf;

            CPLString basename = CPLGetBasenameSafe(osFileName);
            if (basename.size() != 8)
            {
                CPLDebug("SRP", "Invalid basename file");
                return nullptr;
            }

            nRecordIndex = static_cast<int>(CPLScanLong(basename + 6, 2));

            CPLString path = CPLGetDirnameSafe(osFileName);
            CPLString basename01 = ResetTo01(basename);
            osFileName = CPLFormFilenameSafe(path, basename01, ".IMG");

            osFileName = CPLResetExtensionSafe(osFileName, "GEN");
            if (VSIStatL(osFileName, &sStatBuf) != 0)
            {
                osFileName = CPLResetExtensionSafe(osFileName, "gen");
                if (VSIStatL(osFileName, &sStatBuf) != 0)
                    return nullptr;
            }

            osGENFileName = std::move(osFileName);
        }
    }

    if (!osGENFileName.empty() && !osIMGFileName.empty())
    {

        if (poOpenInfo->eAccess == GA_Update)
        {
            ReportUpdateNotSupportedByDriver("SRP");
            return nullptr;
        }

        DDFModule module;
        DDFRecord *record = nullptr;
        if (nRecordIndex >= 0 && module.Open(osGENFileName.c_str(), TRUE))
        {
            for (int i = 0; i < nRecordIndex; i++)
            {
                CPLPushErrorHandler(CPLQuietErrorHandler);
                record = module.ReadRecord();
                CPLPopErrorHandler();
                CPLErrorReset();
                if (record == nullptr)
                    break;
            }
        }
        SRPDataset *poDS =
            OpenDataset(osGENFileName.c_str(), osIMGFileName.c_str(), record);

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

            /* ---------------------------------------------------------- */
            /*      Check for external overviews.                         */
            /* ---------------------------------------------------------- */
            if (bFromSubdataset)
                poDS->oOvManager.Initialize(poDS, osIMGFileName.c_str());
            else
                poDS->oOvManager.Initialize(poDS, poOpenInfo->pszFilename);

            return poDS;
        }
    }

    return nullptr;
}

/************************************************************************/
/*                         GDALRegister_SRP()                          */
/************************************************************************/

void GDALRegister_SRP()

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

    GDALDriver *poDriver = new GDALDriver();

    poDriver->SetDescription("SRP");
    poDriver->SetMetadataItem(GDAL_DCAP_RASTER, "YES");
    poDriver->SetMetadataItem(GDAL_DMD_LONGNAME,
                              "Standard Raster Product (ASRP/USRP)");
    poDriver->SetMetadataItem(GDAL_DMD_HELPTOPIC, "drivers/raster/srp.html");
    poDriver->SetMetadataItem(GDAL_DMD_EXTENSION, "img");
    poDriver->SetMetadataItem(GDAL_DMD_SUBDATASETS, "YES");
    poDriver->SetMetadataItem(GDAL_DCAP_VIRTUALIO, "YES");

    poDriver->pfnOpen = SRPDataset::Open;

    GetGDALDriverManager()->RegisterDriver(poDriver);
}