// ***************************************************************** -*- C++ -*-
/*
 * Copyright (C) 2004-2015 Andreas Huggel <ahuggel@gmx.net>
 *
 * This program is part of the Exiv2 distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, 5th Floor, Boston, MA 02110-1301 USA.
 */
/*
  File:      jpgimage.cpp
  Version:   $Rev$
  Author(s): Andreas Huggel (ahu) <ahuggel@gmx.net>
             Brad Schick (brad) <brad@robotbattle.com>
             Volker Grabsch (vog) <vog@notjusthosting.com>
             Michael Ulbrich (mul) <mul@rentapacs.de>
  History:   15-Jan-05, brad: split out from image.cpp
 */
// *****************************************************************************
#include "rcsid_int.hpp"
EXIV2_RCSID("@(#) $Id$")

// included header files
#include "config.h"

#include "jpgimage.hpp"
#include "tiffimage.hpp"
#include "image_int.hpp"
#include "error.hpp"
#include "futils.hpp"

#ifdef WIN32
#include <windows.h>
#else
#define BYTE   char
#define USHORT uint16_t
#define ULONG  uint32_t
#endif

#include "fff.h"

// + standard includes
#include <cstdio>                               // for EOF
#include <cstring>
#include <cassert>

// *****************************************************************************
// class member definitions

namespace Exiv2 {

    const byte     JpegBase::dht_      = 0xc4;
    const byte     JpegBase::dqt_      = 0xdb;
    const byte     JpegBase::dri_      = 0xdd;
    const byte     JpegBase::sos_      = 0xda;
    const byte     JpegBase::eoi_      = 0xd9;
    const byte     JpegBase::app0_     = 0xe0;
    const byte     JpegBase::app1_     = 0xe1;
    const byte     JpegBase::app2_     = 0xe2;
    const byte     JpegBase::app13_    = 0xed;
    const byte     JpegBase::com_      = 0xfe;

// Start of Frame markers, nondifferential Huffman-coding frames
    const byte     JpegBase::sof0_     = 0xc0;        // start of frame 0, baseline DCT
    const byte     JpegBase::sof1_     = 0xc1;        // start of frame 1, extended sequential DCT, Huffman coding
    const byte     JpegBase::sof2_     = 0xc2;        // start of frame 2, progressive DCT, Huffman coding
    const byte     JpegBase::sof3_     = 0xc3;        // start of frame 3, lossless sequential, Huffman coding

// Start of Frame markers, differential Huffman-coding frames
    const byte     JpegBase::sof5_     = 0xc5;        // start of frame 5, differential sequential DCT, Huffman coding
    const byte     JpegBase::sof6_     = 0xc6;        // start of frame 6, differential progressive DCT, Huffman coding
    const byte     JpegBase::sof7_     = 0xc7;        // start of frame 7, differential lossless, Huffman coding

// Start of Frame markers, nondifferential arithmetic-coding frames
    const byte     JpegBase::sof9_     = 0xc9;        // start of frame 9, extended sequential DCT, arithmetic coding
    const byte     JpegBase::sof10_    = 0xca;        // start of frame 10, progressive DCT, arithmetic coding
    const byte     JpegBase::sof11_    = 0xcb;        // start of frame 11, lossless sequential, arithmetic coding

// Start of Frame markers, differential arithmetic-coding frames
    const byte     JpegBase::sof13_    = 0xcd;        // start of frame 13, differential sequential DCT, arithmetic coding
    const byte     JpegBase::sof14_    = 0xce;        // start of frame 14, progressive DCT, arithmetic coding
    const byte     JpegBase::sof15_    = 0xcf;        // start of frame 15, differential lossless, arithmetic coding

    const char     JpegBase::exifId_[] = "Exif\0\0";
    const char     JpegBase::jfifId_[] = "JFIF\0";
    const char     JpegBase::xmpId_[]  = "http://ns.adobe.com/xap/1.0/\0";

    const char     Photoshop::ps3Id_[] = "Photoshop 3.0\0";
    const char*    Photoshop::irbId_[] = {"8BIM", "AgHg", "DCSR", "PHUT"};
    const char     Photoshop::bimId_[] = "8BIM"; // deprecated
    const uint16_t Photoshop::iptc_    = 0x0404;
    const uint16_t Photoshop::preview_ = 0x040c;

    bool Photoshop::isIrb(const byte* pPsData,
                          long        sizePsData)
    {
        if (sizePsData < 4) return false;
        for (size_t i = 0; i < (sizeof irbId_) / (sizeof *irbId_); i++) {
            assert(strlen(irbId_[i]) == 4);
            if (memcmp(pPsData, irbId_[i], 4) == 0) return true;
        }
        return false;
    }

    bool Photoshop::valid(const byte* pPsData,
                          long        sizePsData)
    {
        const byte *record = 0;
        uint32_t sizeIptc = 0;
        uint32_t sizeHdr = 0;
        const byte* pCur = pPsData;
        const byte* pEnd = pPsData + sizePsData;
        int ret = 0;
        while (pCur < pEnd
               && 0 == (ret = Photoshop::locateIptcIrb(pCur, static_cast<long>(pEnd - pCur),
                                                       &record, &sizeHdr, &sizeIptc))) {
            pCur = record + sizeHdr + sizeIptc + (sizeIptc & 1);
        }
        return ret >= 0;
    }

    // Todo: Generalised from JpegBase::locateIptcData without really understanding
    //       the format (in particular the header). So it remains to be confirmed
    //       if this also makes sense for psTag != Photoshop::iptc
    int Photoshop::locateIrb(const byte*     pPsData,
                             long            sizePsData,
                             uint16_t        psTag,
                             const byte**    record,
                             uint32_t *const sizeHdr,
                             uint32_t *const sizeData)
    {
        assert(record);
        assert(sizeHdr);
        assert(sizeData);
        // Used for error checking
        long position = 0;
#ifdef DEBUG
        std::cerr << "Photoshop::locateIrb: ";
#endif
        // Data should follow Photoshop format, if not exit
        while (position <= sizePsData - 12 && isIrb(pPsData + position, 4)) {
            const byte *hrd = pPsData + position;
            position += 4;
            uint16_t type = getUShort(pPsData + position, bigEndian);
            position += 2;
#ifdef DEBUG
            std::cerr << "0x" << std::hex << type << std::dec << " ";
#endif
            // Pascal string is padded to have an even size (including size byte)
            byte psSize = pPsData[position] + 1;
            psSize += (psSize & 1);
            position += psSize;
            if (position + 4 > sizePsData) {
#ifdef DEBUG
                std::cerr << "Warning: "
                          << "Invalid or extended Photoshop IRB\n";
#endif
                return -2;
            }
            uint32_t dataSize = getULong(pPsData + position, bigEndian);
            position += 4;
            if (dataSize > static_cast<uint32_t>(sizePsData - position)) {
#ifdef DEBUG
                std::cerr << "Warning: "
                          << "Invalid Photoshop IRB data size "
                          << dataSize << " or extended Photoshop IRB\n";
#endif
                return -2;
            }
#ifndef DEBUG
            if (   (dataSize & 1)
                && position + dataSize == static_cast<uint32_t>(sizePsData)) {
                std::cerr << "Warning: "
                          << "Photoshop IRB data is not padded to even size\n";
            }
#endif
            if (type == psTag) {
#ifdef DEBUG
                std::cerr << "ok\n";
#endif
                *sizeData = dataSize;
                *sizeHdr = psSize + 10;
                *record = hrd;
                return 0;
            }
            // Data size is also padded to be even
            position += dataSize + (dataSize & 1);
        }
#ifdef DEBUG
        std::cerr << "pPsData doesn't start with '8BIM'\n";
#endif
        if (position < sizePsData) {
#ifdef DEBUG
            std::cerr << "Warning: "
                      << "Invalid or extended Photoshop IRB\n";
#endif
            return -2;
        }
        return 3;
    } // Photoshop::locateIrb

    int Photoshop::locateIptcIrb(const byte*     pPsData,
                                 long            sizePsData,
                                 const byte**    record,
                                 uint32_t *const sizeHdr,
                                 uint32_t *const sizeData)
    {
        return locateIrb(pPsData, sizePsData, iptc_,
                         record, sizeHdr, sizeData);
    }

    int Photoshop::locatePreviewIrb(const byte*     pPsData,
                                    long            sizePsData,
                                    const byte**    record,
                                    uint32_t *const sizeHdr,
                                    uint32_t *const sizeData)
    {
        return locateIrb(pPsData, sizePsData, preview_,
                         record, sizeHdr, sizeData);
    }

    DataBuf Photoshop::setIptcIrb(const byte*     pPsData,
                                  long            sizePsData,
                                  const IptcData& iptcData)
    {
        if (sizePsData > 0) assert(pPsData);
#ifdef DEBUG
        std::cerr << "IRB block at the beginning of Photoshop::setIptcIrb\n";
        if (sizePsData == 0) std::cerr << "  None.\n";
        else hexdump(std::cerr, pPsData, sizePsData);
#endif
        const byte* record    = pPsData;
        uint32_t    sizeIptc  = 0;
        uint32_t    sizeHdr   = 0;
        DataBuf rc;
        // Safe to call with zero psData.size_
        if (0 > Photoshop::locateIptcIrb(pPsData, sizePsData,
                                         &record, &sizeHdr, &sizeIptc)) {
            return rc;
        }
        Blob psBlob;
        const uint32_t sizeFront = static_cast<uint32_t>(record - pPsData);
        // Write data before old record.
        if (sizePsData > 0 && sizeFront > 0) {
            append(psBlob, pPsData, sizeFront);
        }
        // Write new iptc record if we have it
        DataBuf rawIptc = IptcParser::encode(iptcData);
        if (rawIptc.size_ > 0) {
            byte tmpBuf[12];
            std::memcpy(tmpBuf, Photoshop::irbId_[0], 4);
            us2Data(tmpBuf + 4, iptc_, bigEndian);
            tmpBuf[6] = 0;
            tmpBuf[7] = 0;
            ul2Data(tmpBuf + 8, rawIptc.size_, bigEndian);
            append(psBlob, tmpBuf, 12);
            append(psBlob, rawIptc.pData_, rawIptc.size_);
            // Data is padded to be even (but not included in size)
            if (rawIptc.size_ & 1) psBlob.push_back(0x00);
        }
        // Write existing stuff after record,
        // skip the current and all remaining IPTC blocks
        long pos = sizeFront;
        while (0 == Photoshop::locateIptcIrb(pPsData + pos, sizePsData - pos,
                                             &record, &sizeHdr, &sizeIptc)) {
            const long newPos = static_cast<long>(record - pPsData);
            // Copy data up to the IPTC IRB
            if (newPos > pos) {
                append(psBlob, pPsData + pos, newPos - pos);
            }
            // Skip the IPTC IRB
            pos = newPos + sizeHdr + sizeIptc + (sizeIptc & 1);
        }
        if (pos < sizePsData) {
            append(psBlob, pPsData + pos, sizePsData - pos);
        }
        // Data is rounded to be even
        if (psBlob.size() > 0) rc = DataBuf(&psBlob[0], static_cast<long>(psBlob.size()));
#ifdef DEBUG
        std::cerr << "IRB block at the end of Photoshop::setIptcIrb\n";
        if (rc.size_ == 0) std::cerr << "  None.\n";
        else hexdump(std::cerr, rc.pData_, rc.size_);
#endif
        return rc;

    } // Photoshop::setIptcIrb

    JpegBase::JpegBase(int type, BasicIo::AutoPtr io, bool create,
                       const byte initData[], long dataSize)
        : Image(type, mdExif | mdIptc | mdXmp | mdComment, io)
    {
        if (create) {
            initImage(initData, dataSize);
        }
    }

    int JpegBase::initImage(const byte initData[], long dataSize)
    {
        if (io_->open() != 0) {
            return 4;
        }
        IoCloser closer(*io_);
        if (io_->write(initData, dataSize) != dataSize) {
            return 4;
        }
        return 0;
    }

    int JpegBase::advanceToMarker() const
    {
        int c = -1;
        // Skips potential padding between markers
        while ((c=io_->getb()) != 0xff) {
            if (c == EOF) return -1;
        }

        // Markers can start with any number of 0xff
        while ((c=io_->getb()) == 0xff) {
            if (c == EOF) return -2;
        }
        return c;
    }

    void JpegBase::readMetadata()
    {
        int rc = 0; // Todo: this should be the return value

        if (io_->open() != 0) throw Error(9, io_->path(), strError());
        IoCloser closer(*io_);
        // Ensure that this is the correct image type
        if (!isThisType(*io_, true)) {
            if (io_->error() || io_->eof()) throw Error(14);
            throw Error(15);
        }
        clearMetadata();
        int search = 5;
        const long bufMinSize = 36;
        long bufRead = 0;
        DataBuf buf(bufMinSize);
        Blob psBlob;
        bool foundCompletePsData = false;
        bool foundExifData = false;
        bool foundXmpData = false;
        bool foundIccProfile = false;

        // Read section marker
        int marker = advanceToMarker();
        if (marker < 0) throw Error(15);

        while (marker != sos_ && marker != eoi_ && search > 0) {
            // Read size and signature (ok if this hits EOF)
            std::memset(buf.pData_, 0x0, buf.size_);
            bufRead = io_->read(buf.pData_, bufMinSize);
            if (io_->error()) throw Error(14);
            if (bufRead < 2) throw Error(15);
            uint16_t size = getUShort(buf.pData_, bigEndian);

            if (   !foundExifData
                && marker == app1_ && memcmp(buf.pData_ + 2, exifId_, 6) == 0) {
                if (size < 8) {
                    rc = 1;
                    break;
                }
                // Seek to beginning and read the Exif data
                io_->seek(8 - bufRead, BasicIo::cur);
                DataBuf rawExif(size - 8);
                io_->read(rawExif.pData_, rawExif.size_);
                if (io_->error() || io_->eof()) throw Error(14);
                ByteOrder bo = ExifParser::decode(exifData_, rawExif.pData_, rawExif.size_);
                setByteOrder(bo);
                if (rawExif.size_ > 0 && byteOrder() == invalidByteOrder) {
#ifndef SUPPRESS_WARNINGS
                    EXV_WARNING << "Failed to decode Exif metadata.\n";
#endif
                    exifData_.clear();
                }
                --search;
                foundExifData = true;
            }
            else if (   !foundXmpData
                     && marker == app1_ && memcmp(buf.pData_ + 2, xmpId_, 29) == 0) {
                if (size < 31) {
                    rc = 6;
                    break;
                }
                // Seek to beginning and read the XMP packet
                io_->seek(31 - bufRead, BasicIo::cur);
                DataBuf xmpPacket(size - 31);
                io_->read(xmpPacket.pData_, xmpPacket.size_);
                if (io_->error() || io_->eof()) throw Error(14);
                xmpPacket_.assign(reinterpret_cast<char*>(xmpPacket.pData_), xmpPacket.size_);
                if (xmpPacket_.size() > 0 && XmpParser::decode(xmpData_, xmpPacket_)) {
#ifndef SUPPRESS_WARNINGS
                    EXV_WARNING << "Failed to decode XMP metadata.\n";
#endif
                }
                --search;
                foundXmpData = true;
            }
            else if (   !foundCompletePsData
                     && marker == app13_ && memcmp(buf.pData_ + 2, Photoshop::ps3Id_, 14) == 0) {
                if (size < 16) {
                    rc = 2;
                    break;
                }
                // Read the rest of the APP13 segment
                io_->seek(16 - bufRead, BasicIo::cur);
                DataBuf psData(size - 16);
                io_->read(psData.pData_, psData.size_);
                if (io_->error() || io_->eof()) throw Error(14);
#ifdef DEBUG
                std::cerr << "Found app13 segment, size = " << size << "\n";
                //hexdump(std::cerr, psData.pData_, psData.size_);
#endif
                // Append to psBlob
                append(psBlob, psData.pData_, psData.size_);
                // Check whether psBlob is complete
                if (psBlob.size() > 0 && Photoshop::valid(&psBlob[0], (long) psBlob.size())) {
                    --search;
                    foundCompletePsData = true;
                }
            }
            else if (marker == com_ && comment_.empty())
            {
                if (size < 2) {
                    rc = 3;
                    break;
                }
                // JPEGs can have multiple comments, but for now only read
                // the first one (most jpegs only have one anyway). Comments
                // are simple single byte ISO-8859-1 strings.
                io_->seek(2 - bufRead, BasicIo::cur);
                DataBuf comment(size - 2);
                io_->read(comment.pData_, comment.size_);
                if (io_->error() || io_->eof()) throw Error(14);
                comment_.assign(reinterpret_cast<char*>(comment.pData_), comment.size_);
                while (   comment_.length()
                       && comment_.at(comment_.length()-1) == '\0') {
                    comment_.erase(comment_.length()-1);
                }
                --search;
            }
            else if (   !foundIccProfile && marker == app2_ ) {
                // Seek to beginning and read the iccProfile 
                io_->seek(31 - bufRead, BasicIo::cur);
                DataBuf iccProfile(size);
                io_->read(iccProfile.pData_, iccProfile.size_);
                if (io_->error() || io_->eof()) throw Error(14);
                this->setIccProfile(iccProfile);
                foundXmpData = true;
            }
            else if (   pixelHeight_ == 0
                     && (   marker == sof0_  || marker == sof1_  || marker == sof2_
                         || marker == sof3_  || marker == sof5_  || marker == sof6_
                         || marker == sof7_  || marker == sof9_  || marker == sof10_
                         || marker == sof11_ || marker == sof13_ || marker == sof14_
                         || marker == sof15_)) {
                // We hit a SOFn (start-of-frame) marker
                if (size < 8) {
                    rc = 7;
                    break;
                }
                pixelHeight_ = getUShort(buf.pData_ + 3, bigEndian);
                pixelWidth_ = getUShort(buf.pData_ + 5, bigEndian);
                if (pixelHeight_ != 0) --search;
                // Skip the remainder of the segment
                io_->seek(size-bufRead, BasicIo::cur);
            }
            else {
                if (size < 2) {
                    rc = 4;
                    break;
                }
                // Skip the remainder of the unknown segment
                if (io_->seek(size - bufRead, BasicIo::cur)) throw Error(14);
            }
            // Read the beginning of the next segment
            marker = advanceToMarker();
            if (marker < 0) {
                rc = 5;
                break;
            }
        } // while there are segments to process

        if (psBlob.size() > 0) {
            // Find actual IPTC data within the psBlob
            Blob iptcBlob;
            const byte *record = 0;
            uint32_t sizeIptc = 0;
            uint32_t sizeHdr = 0;
            const byte* pCur = &psBlob[0];
            const byte* pEnd = pCur + psBlob.size();
            while (   pCur < pEnd
                   && 0 == Photoshop::locateIptcIrb(pCur, static_cast<long>(pEnd - pCur),
                                                    &record, &sizeHdr, &sizeIptc)) {
#ifdef DEBUG
                std::cerr << "Found IPTC IRB, size = " << sizeIptc << "\n";
#endif
                if (sizeIptc) {
                    append(iptcBlob, record + sizeHdr, sizeIptc);
                }
                pCur = record + sizeHdr + sizeIptc + (sizeIptc & 1);
            }
            if (   iptcBlob.size() > 0
                && IptcParser::decode(iptcData_,
                                      &iptcBlob[0],
                                      static_cast<uint32_t>(iptcBlob.size()))) {
#ifndef SUPPRESS_WARNINGS
                EXV_WARNING << "Failed to decode IPTC metadata.\n";
#endif
                iptcData_.clear();
            }
        } // psBlob.size() > 0

        if (rc != 0) {
#ifndef SUPPRESS_WARNINGS
            EXV_WARNING << "JPEG format error, rc = " << rc << "\n";
#endif
        }
    } // JpegBase::readMetadata

    bool isBlank(std::string& s)
    {
        for ( std::size_t i = 0 ; i < s.length() ; i++ )
            if ( s[i] != ' ' )
                return false ;
        return true ;
    }

#define REPORT_MARKER if ( (option == kpsBasic||option == kpsRecursive) ) out << Internal::stringFormat("%8ld | %#04x %-5s",io_->tell(), marker,nm[marker].c_str())

    void JpegBase::printStructure(std::ostream& out, PrintStructureOption option,int depth)
    {
        if (io_->open() != 0) throw Error(9, io_->path(), strError());
        // Ensure that this is the correct image type
        if (!isThisType(*io_, false)) {
            if (io_->error() || io_->eof()) throw Error(14);
            throw Error(15);
        }

        bool bPrint = option==kpsBasic || option==kpsRecursive;
        Exiv2::Uint32Vector iptcDataSegs;

        if ( bPrint || option == kpsXMP || option == kpsIccProfile || option == kpsIptcErase ) {

            // nmonic for markers
            std::string nm[256] ;
            nm[0xd8]="SOI"  ;
            nm[0xd9]="EOI"  ;
            nm[0xda]="SOS"  ;
            nm[0xdb]="DQT"  ;
            nm[0xdd]="DRI"  ;
            nm[0xfe]="COM"  ;

            // 0xe0 .. 0xef are APPn
            // 0xc0 .. 0xcf are SOFn (except 4)
            nm[0xc4]="DHT"  ;
            for ( int i = 0 ; i <= 15 ; i++ ) {
                char MN[10];
                sprintf(MN,"APP%d",i);
                nm[0xe0+i] = MN;
                if ( i != 4 ) {
                    sprintf(MN,"SOF%d",i);
                    nm[0xc0+i] = MN;
                }
            }

            // Container for the signature
            bool        bExtXMP    = false;
            long        bufRead    =  0;
            const long  bufMinSize = 36;
            DataBuf     buf(bufMinSize);

            // Read section marker
            int marker = advanceToMarker();
            if (marker < 0) throw Error(15);

            bool    done = false;
            bool    first= true;
            while (!done) {
                // print marker bytes
                if ( first && bPrint ) {
                    out << "STRUCTURE OF JPEG FILE: " << io_->path() << std::endl;
                    out << " address | marker     | length  | data" << std::endl ;
                    REPORT_MARKER;
                }
                first    = false;
                bool bLF = bPrint;

                // Read size and signature
                std::memset(buf.pData_, 0x0, buf.size_);
                bufRead = io_->read(buf.pData_, bufMinSize);
                if (io_->error()) throw Error(14);
                if (bufRead < 2) throw Error(15);
                uint16_t size = 0;

                // not all markers have size field.
                if( ( marker >= sof0_ && marker <= sof15_)
                ||  ( marker >= app0_ && marker <= (app0_ | 0x0F))
                ||    marker == dht_
                ||    marker == dqt_
                ||    marker == dri_
                ||    marker == com_
                ||    marker == sos_
                ){
                    size = getUShort(buf.pData_, bigEndian);
                }
                if ( bPrint ) out << Internal::stringFormat(" | %7d ", size);

                // only print the signature for appn
                if (marker >= app0_ && marker <= (app0_ | 0x0F)) {
                    // http://www.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/XMPSpecificationPart3.pdf p75
                    const char* signature = (const char*) buf.pData_+2;

					// 728 rmills@rmillsmbp:~/gnu/exiv2/ttt $ exiv2 -pS test/data/exiv2-bug922.jpg
					// STRUCTURE OF JPEG FILE: test/data/exiv2-bug922.jpg
					// address | marker     | length  | data
					//       2 | 0xd8 SOI   |       0
					//       4 | 0xe1 APP1  |     911 | Exif..MM.*.......%.........#....
					//     917 | 0xe1 APP1  |     870 | http://ns.adobe.com/xap/1.0/.<x:
					//    1789 | 0xe1 APP1  |   65460 | http://ns.adobe.com/xmp/extensio
                    if ( option == kpsXMP && std::string(signature).find("http://ns.adobe.com/x")== 0 ) {
                        // extract XMP
                        if ( size > 0 ) {
                            io_->seek(-bufRead , BasicIo::cur);
                            byte* xmp  = new byte[size+1];
                            io_->read(xmp,size);
                            int start = 0 ;

                            // http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/XMPSpecificationPart3.pdf
                            // if we find HasExtendedXMP, set the flag and ignore this block
                            // the first extended block is a copy of the Standard block.
                            // a robust implementation allows extended blocks to be out of sequence
                            // we could implement out of sequence with a dictionary of sequence/offset
                            // and dumping the XMP in a post read operation similar to kpsIptcErase
                            // for the moment, dumping 'on the fly' is working fine
                            if ( ! bExtXMP ) {
                                while (xmp[start]) start++; start++;
                                if ( ::strstr((char*)xmp+start,"HasExtendedXMP") ) {
                                    start  = size ; // ignore this packet, we'll get on the next time around
                                    bExtXMP = true;
                                }
                            } else {
                                start = 2+35+32+4+4; // Adobe Spec, p19
                            }
                            xmp[size]=0;

                            out << xmp + start;
                            delete [] xmp;
                            bufRead = size;
                        }
                    } else if ( option == kpsIccProfile && std::strcmp(signature,"ICC_PROFILE") == 0 ) {
                        // extract ICCProfile
                        if ( size > 0 ) {
                            io_->seek(-bufRead , BasicIo::cur);
                            byte* icc  = new byte[size];
                            io_->read(icc,size);
                            std::size_t start=16;
                            out.write( ((const char*)icc)+start,size-start);
                            bufRead = size;
                            delete [] icc;
                        }
                    } else if ( option == kpsIptcErase && std::strcmp(signature,"Photoshop 3.0") == 0 ) {
                        // delete IPTC data segment from JPEG
                        if ( size > 0 ) {
                            io_->seek(-bufRead , BasicIo::cur);
                            iptcDataSegs.push_back(io_->tell());
                            iptcDataSegs.push_back(size);
                        }
                    } else if ( bPrint ) {
                        out << "| " << Internal::binaryToString(buf,size>32?32:size,size>0?2:0);
                    }

                    // for MPF: http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/MPF.html
                    // for FLIR: http://owl.phy.queensu.ca/~phil/exiftool/TagNames/FLIR.html
                    bool bFlir = option == kpsRecursive && marker == (app0_+1) && std::strcmp(signature,"FLIR")==0;
                    bool bExif = option == kpsRecursive && marker == (app0_+1) && std::strcmp(signature,"Exif")==0;
                    bool bMPF  = option == kpsRecursive && marker == (app0_+2) && std::strcmp(signature,"MPF")==0;
                    bool bPS   = option == kpsRecursive                        && std::strcmp(signature,"Photoshop 3.0")==0;
                    if( bFlir || bExif || bMPF || bPS ) {
                        // extract Exif data block which is tiff formatted
                        if ( size > 0 ) {
                            out << std::endl;

                            // allocate storage and current file position
                            byte*    exif      = new byte[size];
                            uint32_t restore   = io_->tell();

                            // copy the data to memory
                            io_->seek(-bufRead , BasicIo::cur);
                            io_->read(exif,size);
                            uint32_t start     = std::strcmp(signature,"Exif")==0 ? 8 : 6;
                            uint32_t max       = (uint32_t) size -1;

                            // is this an fff block?
                            if ( bFlir ) {
                                start = 0 ;
                                bFlir = false;
                                while ( start < max ) {
                                    if ( std::strcmp((const char*)(exif+start),"FFF")==0 ) {
                                        bFlir = true ;
                                        break;
                                    }
                                    start++;
                                }
                            }

                            // there is a header in FLIR, followed by a tiff block
                            // Hunt down the tiff using brute force
                            if ( bFlir ) {
                                // FLIRFILEHEAD* pFFF = (FLIRFILEHEAD*) (exif+start) ;
                                while ( start < max ) {
                                    if ( exif[start] == 'I' && exif[start+1] == 'I' ) break;
                                    if ( exif[start] == 'M' && exif[start+1] == 'M' ) break;
                                    start++;
                                }
                                if ( start < max ) std::cout << "  FFF start = " << start << std::endl ;
                                // << " index = " << pFFF->dwIndexOff << std::endl;
                            }

                            if ( bPS ) {
                                IptcData::printStructure(out,exif,size,depth);
                            } else {
	                            // create a copy on write memio object with the data, then print the structure
    	                        BasicIo::AutoPtr p = BasicIo::AutoPtr(new MemIo(exif+start,size-start));
        	                    if ( start < max ) TiffImage::printTiffStructure(*p,out,option,depth);
        	                }

                            // restore and clean up
                            io_->seek(restore,Exiv2::BasicIo::beg);
                            delete [] exif;
                            bLF    = false;

                        }
                    }
                }

                // Skip the segment if the size is known
                if (io_->seek(size - bufRead, BasicIo::cur)) throw Error(14);

                if ( bLF ) out << std::endl;

                if (marker == sos_)
                    // sos_ is immediately followed by entropy-coded data & eoi_
                    done = true;
                else {
                    // Read the beginning of the next segment
                    marker = advanceToMarker();
                    REPORT_MARKER;
                    if ( marker == eoi_ ) {
                        if ( option == kpsBasic ) out << std::endl;
                        done = true;
                    }
                }
            }
        }
        if ( option == kpsIptcErase ) {
        	std::cout << "iptc data blocks: " << (iptcDataSegs.size() ? "FOUND" : "none") << std::endl;
        	uint32_t toggle = 0 ;
        	for ( Uint32Vector_i it = iptcDataSegs.begin(); it != iptcDataSegs.end() ; it++ ) {
        		std::cout << *it ;
        		if ( toggle++ % 2 ) std::cout << std::endl; else std::cout << ' ' ;
        	}
        }
    }

    void JpegBase::writeMetadata()
    {
        if (io_->open() != 0) {
            throw Error(9, io_->path(), strError());
        }
        IoCloser closer(*io_);
        BasicIo::AutoPtr tempIo(io_->temporary()); // may throw
        assert (tempIo.get() != 0);

        doWriteMetadata(*tempIo); // may throw
        io_->close();
        io_->transfer(*tempIo); // may throw
    } // JpegBase::writeMetadata

    void JpegBase::doWriteMetadata(BasicIo& outIo)
    {
        if (!io_->isopen()) throw Error(20);
        if (!outIo.isopen()) throw Error(21);

        // Ensure that this is the correct image type
        if (!isThisType(*io_, true)) {
            if (io_->error() || io_->eof()) throw Error(20);
            throw Error(22);
        }

        const long bufMinSize = 36;
        long bufRead = 0;
        DataBuf buf(bufMinSize);
        const long seek = io_->tell();
        int count = 0;
        int search = 0;
        int insertPos = 0;
        int comPos = 0;
        int skipApp1Exif = -1;
        int skipApp1Xmp = -1;
        int skipApp2IccProfile = -1;
        bool foundCompletePsData = false;
        std::vector<int> skipApp13Ps3;
        int skipCom = -1;
        Blob psBlob;
        DataBuf rawExif;

        // Write image header
        if (writeHeader(outIo)) throw Error(21);

        // Read section marker
        int marker = advanceToMarker();
        if (marker < 0) throw Error(22);

        // First find segments of interest. Normally app0 is first and we want
        // to insert after it. But if app0 comes after com, app1 and app13 then
        // don't bother.
        while (marker != sos_ && marker != eoi_ && search < 5) {
            // Read size and signature (ok if this hits EOF)
            bufRead = io_->read(buf.pData_, bufMinSize);
            if (io_->error()) throw Error(20);
            uint16_t size = getUShort(buf.pData_, bigEndian);

            if (marker == app0_) {
                if (size < 2) throw Error(22);
                insertPos = count + 1;
                if (io_->seek(size-bufRead, BasicIo::cur)) throw Error(22);
            }
            else if (   skipApp1Exif == -1
                     && marker == app1_ && memcmp(buf.pData_ + 2, exifId_, 6) == 0) {
                if (size < 8) throw Error(22);
                skipApp1Exif = count;
                ++search;
                // Seek to beginning and read the current Exif data
                io_->seek(8 - bufRead, BasicIo::cur);
                rawExif.alloc(size - 8);
                io_->read(rawExif.pData_, rawExif.size_);
                if (io_->error() || io_->eof()) throw Error(22);
            }
            else if (   skipApp1Xmp == -1
                     && marker == app1_ && memcmp(buf.pData_ + 2, xmpId_, 29) == 0) {
                if (size < 31) throw Error(22);
                skipApp1Xmp = count;
                ++search;
                if (io_->seek(size-bufRead, BasicIo::cur)) throw Error(22);
            }
            else if (   skipApp2IccProfile == -1 && marker == app2_) {
                if (size < 31) throw Error(22);
                skipApp2IccProfile = count;
                ++search;
                if (io_->seek(size-bufRead, BasicIo::cur)) throw Error(22);
            }
            else if (   !foundCompletePsData
                     && marker == app13_ && memcmp(buf.pData_ + 2, Photoshop::ps3Id_, 14) == 0) {
#ifdef DEBUG
                std::cerr << "Found APP13 Photoshop PS3 segment\n";
#endif
                if (size < 16) throw Error(22);
                skipApp13Ps3.push_back(count);
                io_->seek(16 - bufRead, BasicIo::cur);
                // Load PS data now to allow reinsertion at any point
                DataBuf psData(size - 16);
                io_->read(psData.pData_, size - 16);
                if (io_->error() || io_->eof()) throw Error(20);
                // Append to psBlob
                append(psBlob, psData.pData_, psData.size_);
                // Check whether psBlob is complete
                if (psBlob.size() > 0 && Photoshop::valid(&psBlob[0],(long) psBlob.size())) {
                    foundCompletePsData = true;
                }
            }
            else if (marker == com_ && skipCom == -1) {
                if (size < 2) throw Error(22);
                // Jpegs can have multiple comments, but for now only handle
                // the first one (most jpegs only have one anyway).
                skipCom = count;
                ++search;
                if (io_->seek(size-bufRead, BasicIo::cur)) throw Error(22);
            }
            else {
                if (size < 2) throw Error(22);
                if (io_->seek(size-bufRead, BasicIo::cur)) throw Error(22);
            }
            // As in jpeg-6b/wrjpgcom.c:
            // We will insert the new comment marker just before SOFn.
            // This (a) causes the new comment to appear after, rather than before,
            // existing comments; and (b) ensures that comments come after any JFIF
            // or JFXX markers, as required by the JFIF specification.
            if (   comPos == 0
                && (   marker == sof0_
                    || marker == sof1_
                    || marker == sof2_
                    || marker == sof3_
                    || marker == sof5_
                    || marker == sof6_
                    || marker == sof7_
                    || marker == sof9_
                    || marker == sof10_
                    || marker == sof11_
                    || marker == sof13_
                    || marker == sof14_
                    || marker == sof15_)) {
                comPos = count;
                ++search;
            }
            marker = advanceToMarker();
            if (marker < 0) throw Error(22);
            ++count;
        }

        if (!foundCompletePsData && psBlob.size() > 0) throw Error(22);
        search += (int) skipApp13Ps3.size();

        if (comPos == 0) {
            if (marker == eoi_) comPos = count;
            else comPos = insertPos;
            ++search;
        }
        if (exifData_.count() > 0) ++search;
        if (writeXmpFromPacket() == false && xmpData_.count() > 0) ++search;
        if (writeXmpFromPacket() == true && xmpPacket_.size() > 0) ++search;
        if (foundCompletePsData || iptcData_.count() > 0) ++search;
        if (!comment_.empty()) ++search;

        io_->seek(seek, BasicIo::beg);
        count = 0;
        marker = advanceToMarker();
        if (marker < 0) throw Error(22);

        // To simplify this a bit, new segments are inserts at either the start
        // or right after app0. This is standard in most jpegs, but has the
        // potential to change segment ordering (which is allowed).
        // Segments are erased if there is no assigned metadata.
        while (marker != sos_ && search > 0) {
            // Read size and signature (ok if this hits EOF)
            bufRead = io_->read(buf.pData_, bufMinSize);
            if (io_->error()) throw Error(20);
            // Careful, this can be a meaningless number for empty
            // images with only an eoi_ marker
            uint16_t size = getUShort(buf.pData_, bigEndian);

            if (insertPos == count) {
                byte tmpBuf[64];
                // Write Exif data first so that - if there is no app0 - we
                // create "Exif images" according to the Exif standard.
                if (exifData_.count() > 0) {
                    Blob blob;
                    ByteOrder bo = byteOrder();
                    if (bo == invalidByteOrder) {
                        bo = littleEndian;
                        setByteOrder(bo);
                    }
                    WriteMethod wm = ExifParser::encode(blob,
                                                        rawExif.pData_,
                                                        rawExif.size_,
                                                        bo,
                                                        exifData_);
                    const byte* pExifData = rawExif.pData_;
                    uint32_t exifSize = rawExif.size_;
                    if (wm == wmIntrusive) {
                        pExifData = blob.size() > 0 ? &blob[0] : 0;
                        exifSize = static_cast<uint32_t>(blob.size());
                    }
                    if (exifSize > 0) {
                        // Write APP1 marker, size of APP1 field, Exif id and Exif data
                        tmpBuf[0] = 0xff;
                        tmpBuf[1] = app1_;

                        if (exifSize + 8 > 0xffff) throw Error(37, "Exif");
                        us2Data(tmpBuf + 2, static_cast<uint16_t>(exifSize + 8), bigEndian);
                        std::memcpy(tmpBuf + 4, exifId_, 6);
                        if (outIo.write(tmpBuf, 10) != 10) throw Error(21);

                        // Write new Exif data buffer
                        if (   outIo.write(pExifData, exifSize)
                            != static_cast<long>(exifSize)) throw Error(21);
                        if (outIo.error()) throw Error(21);
                        --search;
                    }
                }
                if (writeXmpFromPacket() == false) {
                    if (XmpParser::encode(xmpPacket_, xmpData_, XmpParser::useCompactFormat | XmpParser::omitAllFormatting) > 1) {
#ifndef SUPPRESS_WARNINGS
                        EXV_ERROR << "Failed to encode XMP metadata.\n";
#endif
                    }
                }
                if (xmpPacket_.size() > 0) {
                    // Write APP1 marker, size of APP1 field, XMP id and XMP packet
                    tmpBuf[0] = 0xff;
                    tmpBuf[1] = app1_;

                    if (xmpPacket_.size() + 31 > 0xffff) throw Error(37, "XMP");
                    us2Data(tmpBuf + 2, static_cast<uint16_t>(xmpPacket_.size() + 31), bigEndian);
                    std::memcpy(tmpBuf + 4, xmpId_, 29);
                    if (outIo.write(tmpBuf, 33) != 33) throw Error(21);

                    // Write new XMP packet
                    if (   outIo.write(reinterpret_cast<const byte*>(xmpPacket_.data()), static_cast<long>(xmpPacket_.size()))
                        != static_cast<long>(xmpPacket_.size())) throw Error(21);
                    if (outIo.error()) throw Error(21);
                    --search;
                }
                if (iccProfile_.size_ > 0) {
                    // Write APP2 marker, size of APP2 field, and IccProfile
                    tmpBuf[0] = 0xff;
                    tmpBuf[1] = app2_;

                    if (iccProfile_.size_ > 0xffff) throw Error(37, "IccProfile");
                    us2Data(tmpBuf + 2, static_cast<uint16_t>(iccProfile_.size_), bigEndian);
                    if (outIo.write(tmpBuf, 4) != 4) throw Error(21);

                    // Write new iccProfile 
                    if ( outIo.write(iccProfile_.pData_,iccProfile_.size_) != static_cast<long>(iccProfile_.size_) ) throw Error(21);
                    if ( outIo.error() ) throw Error(21);
                    --search;
                }
                if (foundCompletePsData || iptcData_.count() > 0) {
                    // Set the new IPTC IRB, keeps existing IRBs but removes the
                    // IPTC block if there is no new IPTC data to write
                    DataBuf newPsData = Photoshop::setIptcIrb(psBlob.size() > 0 ? &psBlob[0] : 0,
                                                              (long) psBlob.size(),
                                                              iptcData_);
                    const long maxChunkSize = 0xffff - 16;
                    const byte* chunkStart = newPsData.pData_;
                    const byte* chunkEnd = chunkStart + newPsData.size_;
                    while (chunkStart < chunkEnd) {
                        // Determine size of next chunk
                        long chunkSize = static_cast<long>(chunkEnd - chunkStart);
                        if (chunkSize > maxChunkSize) {
                            chunkSize = maxChunkSize;
                            // Don't break at a valid IRB boundary
                            const long writtenSize = static_cast<long>(chunkStart - newPsData.pData_);
                            if (Photoshop::valid(newPsData.pData_, writtenSize + chunkSize)) {
                                // Since an IRB has minimum size 12,
                                // (chunkSize - 8) can't be also a IRB boundary
                                chunkSize -= 8;
                            }
                        }

                        // Write APP13 marker, chunk size, and ps3Id
                        tmpBuf[0] = 0xff;
                        tmpBuf[1] = app13_;
                        us2Data(tmpBuf + 2, static_cast<uint16_t>(chunkSize + 16), bigEndian);
                        std::memcpy(tmpBuf + 4, Photoshop::ps3Id_, 14);
                        if (outIo.write(tmpBuf, 18) != 18) throw Error(21);
                        if (outIo.error()) throw Error(21);

                        // Write next chunk of the Photoshop IRB data buffer
                        if (outIo.write(chunkStart, chunkSize) != chunkSize) throw Error(21);
                        if (outIo.error()) throw Error(21);

                        chunkStart += chunkSize;
                    }
                    --search;
                }
            }
            if (comPos == count) {
                if (!comment_.empty()) {
                    byte tmpBuf[4];
                    // Write COM marker, size of comment, and string
                    tmpBuf[0] = 0xff;
                    tmpBuf[1] = com_;

                    if (comment_.length() + 3 > 0xffff) throw Error(37, "JPEG comment");
                    us2Data(tmpBuf + 2, static_cast<uint16_t>(comment_.length() + 3), bigEndian);

                    if (outIo.write(tmpBuf, 4) != 4) throw Error(21);
                    if (outIo.write((byte*)comment_.data(), (long)comment_.length())
                        != (long)comment_.length()) throw Error(21);
                    if (outIo.putb(0)==EOF) throw Error(21);
                    if (outIo.error()) throw Error(21);
                    --search;
                }
                --search;
            }
            if (marker == eoi_) {
                break;
            }
            else if (   skipApp1Exif == count
                     || skipApp1Xmp  == count
                     || std::find(skipApp13Ps3.begin(), skipApp13Ps3.end(), count) != skipApp13Ps3.end()
                     || skipCom      == count) {
                --search;
                io_->seek(size-bufRead, BasicIo::cur);
            }
            else {
                if (size < 2) throw Error(22);
                buf.alloc(size+2);
                io_->seek(-bufRead-2, BasicIo::cur);
                io_->read(buf.pData_, size+2);
                if (io_->error() || io_->eof()) throw Error(20);
                if (outIo.write(buf.pData_, size+2) != size+2) throw Error(21);
                if (outIo.error()) throw Error(21);
            }

            // Next marker
            marker = advanceToMarker();
            if (marker < 0) throw Error(22);
            ++count;
        }

        // Populate the fake data, only make sense for remoteio, httpio and sshio.
        // it avoids allocating memory for parts of the file that contain image-date.
        io_->populateFakeData();

        // Copy rest of the Io
        io_->seek(-2, BasicIo::cur);
        buf.alloc(4096);
        long readSize = 0;
        while ((readSize=io_->read(buf.pData_, buf.size_))) {
            if (outIo.write(buf.pData_, readSize) != readSize) throw Error(21);
        }
        if (outIo.error()) throw Error(21);

    } // JpegBase::doWriteMetadata

    const byte JpegImage::soi_ = 0xd8;
    const byte JpegImage::blank_[] = {
        0xFF,0xD8,0xFF,0xDB,0x00,0x84,0x00,0x10,0x0B,0x0B,0x0B,0x0C,0x0B,0x10,0x0C,0x0C,
        0x10,0x17,0x0F,0x0D,0x0F,0x17,0x1B,0x14,0x10,0x10,0x14,0x1B,0x1F,0x17,0x17,0x17,
        0x17,0x17,0x1F,0x1E,0x17,0x1A,0x1A,0x1A,0x1A,0x17,0x1E,0x1E,0x23,0x25,0x27,0x25,
        0x23,0x1E,0x2F,0x2F,0x33,0x33,0x2F,0x2F,0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x40,
        0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x01,0x11,0x0F,0x0F,0x11,0x13,0x11,0x15,0x12,
        0x12,0x15,0x14,0x11,0x14,0x11,0x14,0x1A,0x14,0x16,0x16,0x14,0x1A,0x26,0x1A,0x1A,
        0x1C,0x1A,0x1A,0x26,0x30,0x23,0x1E,0x1E,0x1E,0x1E,0x23,0x30,0x2B,0x2E,0x27,0x27,
        0x27,0x2E,0x2B,0x35,0x35,0x30,0x30,0x35,0x35,0x40,0x40,0x3F,0x40,0x40,0x40,0x40,
        0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x40,0xFF,0xC0,0x00,0x11,0x08,0x00,0x01,0x00,
        0x01,0x03,0x01,0x22,0x00,0x02,0x11,0x01,0x03,0x11,0x01,0xFF,0xC4,0x00,0x4B,0x00,
        0x01,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
        0x00,0x07,0x01,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
        0x00,0x00,0x00,0x00,0x10,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
        0x00,0x00,0x00,0x00,0x00,0x00,0x11,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
        0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xFF,0xDA,0x00,0x0C,0x03,0x01,0x00,0x02,
        0x11,0x03,0x11,0x00,0x3F,0x00,0xA0,0x00,0x0F,0xFF,0xD9 };

    JpegImage::JpegImage(BasicIo::AutoPtr io, bool create)
        : JpegBase(ImageType::jpeg, io, create, blank_, sizeof(blank_))
    {
    }

    std::string JpegImage::mimeType() const
    {
        return "image/jpeg";
    }

    int JpegImage::writeHeader(BasicIo& outIo) const
    {
        // Jpeg header
        byte tmpBuf[2];
        tmpBuf[0] = 0xff;
        tmpBuf[1] = soi_;
        if (outIo.write(tmpBuf, 2) != 2) return 4;
        if (outIo.error()) return 4;
        return 0;
    }

    bool JpegImage::isThisType(BasicIo& iIo, bool advance) const
    {
        return isJpegType(iIo, advance);
    }

    Image::AutoPtr newJpegInstance(BasicIo::AutoPtr io, bool create)
    {
        Image::AutoPtr image(new JpegImage(io, create));
        if (!image->good()) {
            image.reset();
        }
        return image;
    }

    bool isJpegType(BasicIo& iIo, bool advance)
    {
        bool result = true;
        byte tmpBuf[2];
        iIo.read(tmpBuf, 2);
        if (iIo.error() || iIo.eof()) return false;

        if (0xff != tmpBuf[0] || JpegImage::soi_ != tmpBuf[1]) {
            result = false;
        }
        if (!advance || !result ) iIo.seek(-2, BasicIo::cur);
        return result;
    }

    const char ExvImage::exiv2Id_[] = "Exiv2";
    const byte ExvImage::blank_[] = { 0xff,0x01,'E','x','i','v','2',0xff,0xd9 };

    ExvImage::ExvImage(BasicIo::AutoPtr io, bool create)
        : JpegBase(ImageType::exv, io, create, blank_, sizeof(blank_))
    {
    }

    std::string ExvImage::mimeType() const
    {
        return "image/x-exv";
    }

    int ExvImage::writeHeader(BasicIo& outIo) const
    {
        // Exv header
        byte tmpBuf[7];
        tmpBuf[0] = 0xff;
        tmpBuf[1] = 0x01;
        std::memcpy(tmpBuf + 2, exiv2Id_, 5);
        if (outIo.write(tmpBuf, 7) != 7) return 4;
        if (outIo.error()) return 4;
        return 0;
    }

    bool ExvImage::isThisType(BasicIo& iIo, bool advance) const
    {
        return isExvType(iIo, advance);
    }

    Image::AutoPtr newExvInstance(BasicIo::AutoPtr io, bool create)
    {
        Image::AutoPtr image;
        image = Image::AutoPtr(new ExvImage(io, create));
        if (!image->good()) image.reset();
        return image;
    }

    bool isExvType(BasicIo& iIo, bool advance)
    {
        bool result = true;
        byte tmpBuf[7];
        iIo.read(tmpBuf, 7);
        if (iIo.error() || iIo.eof()) return false;

        if (   0xff != tmpBuf[0] || 0x01 != tmpBuf[1]
            || memcmp(tmpBuf + 2, ExvImage::exiv2Id_, 5) != 0) {
            result = false;
        }
        if (!advance || !result) iIo.seek(-7, BasicIo::cur);
        return result;
    }

}                                       // namespace Exiv2