EVOLUTION-MANAGER

Edit File: gdalwmsrasterband.cpp

/******************************************************************************
 * $Id: gdalwmsrasterband.cpp 27729 2014-09-24 00:40:16Z goatbar $
 *
 * Project:  WMS Client Driver
 * Purpose:  GDALWMSRasterBand implementation.
 * Author:   Adam Nowacki, nowak@xpam.de
 *
 ******************************************************************************
 * Copyright (c) 2007, Adam Nowacki
 * Copyright (c) 2008-2013, Even Rouault <even dot rouault at mines-paris dot org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "wmsdriver.h"

GDALWMSRasterBand::GDALWMSRasterBand(GDALWMSDataset *parent_dataset, int band, double scale) {
    //	printf("[%p] GDALWMSRasterBand::GDALWMSRasterBand(%p, %d, %f)\n", this, parent_dataset, band, scale);
    m_parent_dataset = parent_dataset;
    m_scale = scale;
    m_overview = -1;
    m_color_interp = GCI_Undefined;

poDS = parent_dataset;
    nRasterXSize = static_cast<int>(m_parent_dataset->m_data_window.m_sx * scale + 0.5);
    nRasterYSize = static_cast<int>(m_parent_dataset->m_data_window.m_sy * scale + 0.5);
    nBand = band;
    eDataType = m_parent_dataset->m_data_type;
    nBlockXSize = m_parent_dataset->m_block_size_x;
    nBlockYSize = m_parent_dataset->m_block_size_y;
}

GDALWMSRasterBand::~GDALWMSRasterBand() {
    for (std::vector<GDALWMSRasterBand *>::iterator it = m_overviews.begin(); it != m_overviews.end(); ++it) {
        GDALWMSRasterBand *p = *it;
        delete p;
    }
}

char** GDALWMSRasterBand::BuildHTTPRequestOpts()
{
    char **http_request_opts = NULL;
    if (m_parent_dataset->m_http_timeout != -1) {
        CPLString http_request_optstr;
        http_request_optstr.Printf("TIMEOUT=%d", m_parent_dataset->m_http_timeout);
        http_request_opts = CSLAddString(http_request_opts, http_request_optstr.c_str());
    }

if (m_parent_dataset->m_osUserAgent.size() != 0)
    {
        CPLString osUserAgentOptStr("USERAGENT=");
        osUserAgentOptStr += m_parent_dataset->m_osUserAgent;
        http_request_opts = CSLAddString(http_request_opts, osUserAgentOptStr.c_str());
    }
    if (m_parent_dataset->m_osReferer.size() != 0)
    {
        CPLString osRefererOptStr("REFERER=");
        osRefererOptStr += m_parent_dataset->m_osReferer;
        http_request_opts = CSLAddString(http_request_opts, osRefererOptStr.c_str());
    }
    if (m_parent_dataset->m_unsafeSsl >= 1) {
        http_request_opts = CSLAddString(http_request_opts, "UNSAFESSL=1");
    }
    if (m_parent_dataset->m_osUserPwd.size() != 0) 
    {
        CPLString osUserPwdOptStr("USERPWD=");
        osUserPwdOptStr += m_parent_dataset->m_osUserPwd;
        http_request_opts = CSLAddString(http_request_opts, osUserPwdOptStr.c_str());
    }

return http_request_opts;
}

CPLErr GDALWMSRasterBand::ReadBlocks(int x, int y, void *buffer, int bx0, int by0, int bx1, int by1, int advise_read) {
    CPLErr ret = CE_None;
    int i;

int max_request_count = (bx1 - bx0 + 1) * (by1 - by0 + 1);
    int request_count = 0;
    CPLHTTPRequest *download_requests = NULL;
    GDALWMSCache *cache = m_parent_dataset->m_cache;
    struct BlockXY {
        int x, y;
    } *download_blocks = NULL;
    if (!m_parent_dataset->m_offline_mode) {
        download_requests = new CPLHTTPRequest[max_request_count];
        download_blocks = new BlockXY[max_request_count];
    }

char **http_request_opts = BuildHTTPRequestOpts();

for (int iy = by0; iy <= by1; ++iy) {
        for (int ix = bx0; ix <= bx1; ++ix) {
            bool need_this_block = false;
            if (!advise_read) {
                for (int ib = 1; ib <= m_parent_dataset->nBands; ++ib) {
                    if ((ix == x) && (iy == y) && (ib == nBand)) {
                        need_this_block = true;
                    } else {
                        GDALWMSRasterBand *band = static_cast<GDALWMSRasterBand *>(m_parent_dataset->GetRasterBand(ib));
                        if (m_overview >= 0) band = static_cast<GDALWMSRasterBand *>(band->GetOverview(m_overview));
                        if (!band->IsBlockInCache(ix, iy)) need_this_block = true;
                    }
                }
            } else {
                need_this_block = true;
            }
            CPLString url;
            if (need_this_block) {
                CPLString file_name;
                AskMiniDriverForBlock(&url, ix, iy);
                if ((cache != NULL) && (cache->Read(url.c_str(), &file_name) == CE_None)) {
                    if (advise_read) {
                        need_this_block = false;
                    } else {
                        void *p = 0;
                        if ((ix == x) && (iy == y)) p = buffer;
                        if (ReadBlockFromFile(ix, iy, file_name.c_str(), nBand, p, 0) == CE_None) need_this_block = false;
                    }
                }
            }
            if (need_this_block) {
                if (m_parent_dataset->m_offline_mode) {
                    if (!advise_read) {
                        void *p = 0;
                        if ((ix == x) && (iy == y)) p = buffer;
                        if (ZeroBlock(ix, iy, nBand, p) != CE_None) {
                            CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: ZeroBlock failed.");
                            ret = CE_Failure;
                        }
                    }
                } else {
                    CPLHTTPInitializeRequest(&download_requests[request_count], url.c_str(), http_request_opts);
                    download_blocks[request_count].x = ix;
                    download_blocks[request_count].y = iy;
                    ++request_count;
                }
            }
        }
    }
    if (http_request_opts != NULL) {
        CSLDestroy(http_request_opts);
    }

if (request_count > 0) {
        char **opts = NULL;
        CPLString optstr;
        if (m_parent_dataset->m_http_max_conn != -1) {
            optstr.Printf("MAXCONN=%d", m_parent_dataset->m_http_max_conn);
            opts = CSLAddString(opts, optstr.c_str());
        }
        if (CPLHTTPFetchMulti(download_requests, request_count, opts) != CE_None) {
            CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: CPLHTTPFetchMulti failed.");
            ret = CE_Failure;
        }
        if (opts != NULL) {
            CSLDestroy(opts);
        }
    }

for (i = 0; i < request_count; ++i) {
        if (ret == CE_None) {
            if ((download_requests[i].nStatus == 200) && (download_requests[i].pabyData != NULL) && (download_requests[i].nDataLen > 0)) {
                CPLString file_name(BufferToVSIFile(download_requests[i].pabyData, download_requests[i].nDataLen));
                if (file_name.size() > 0) {
                    bool wms_exception = false;
                    /* check for error xml */
                    if (download_requests[i].nDataLen >= 20) {
                        const char *download_data = reinterpret_cast<char *>(download_requests[i].pabyData);
                        if (EQUALN(download_data, "<?xml ", 6) 
                        || EQUALN(download_data, "<!DOCTYPE ", 10)
                        || EQUALN(download_data, "<ServiceException", 17)) {
                            if (ReportWMSException(file_name.c_str()) != CE_None) {
                                CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: The server returned unknown exception.");
                            }
                            wms_exception = true;
                            ret = CE_Failure;
                        }
                    }
                    if (ret == CE_None) {
                        if (advise_read && !m_parent_dataset->m_verify_advise_read) {
                            if (cache != NULL) {
                                cache->Write(download_requests[i].pszURL, file_name);
                            }
                        } else {
                            void *p = 0;
                            if ((download_blocks[i].x == x) && (download_blocks[i].y == y)) p = buffer;
                            if (ReadBlockFromFile(download_blocks[i].x, download_blocks[i].y, file_name.c_str(), nBand, p, advise_read) == CE_None) {
                                if (cache != NULL) {
                                    cache->Write(download_requests[i].pszURL, file_name);
                                }
                            } else {
                                CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: ReadBlockFromFile (%s) failed.",
                                         download_requests[i].pszURL);
                                ret = CE_Failure;
                            }
                        }
                    } else if( wms_exception && m_parent_dataset->m_zeroblock_on_serverexceptions ) {
                         void *p = 0;
                         if ((download_blocks[i].x == x) && (download_blocks[i].y == y)) p = buffer;
                         if (ZeroBlock(download_blocks[i].x, download_blocks[i].y, nBand, p) != CE_None) {
                             CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: ZeroBlock failed.");
                         } else {
                             ret = CE_None;
                         }

}
                    VSIUnlink(file_name.c_str());
                }
            } else {
               std::vector<int>::iterator zero_it = std::find(
                     m_parent_dataset->m_http_zeroblock_codes.begin(),
                     m_parent_dataset->m_http_zeroblock_codes.end(),
                     download_requests[i].nStatus);
               if ( zero_it != m_parent_dataset->m_http_zeroblock_codes.end() ) {
                    if (!advise_read) {
                        void *p = 0;
                        if ((download_blocks[i].x == x) && (download_blocks[i].y == y)) p = buffer;
                        if (ZeroBlock(download_blocks[i].x, download_blocks[i].y, nBand, p) != CE_None) {
                            CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: ZeroBlock failed.");
                            ret = CE_Failure;
                        }
                    }
                } else {
                    CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Unable to download block %d, %d.\n  URL: %s\n  HTTP status code: %d, error: %s.",
                        download_blocks[i].x, download_blocks[i].y, download_requests[i].pszURL, download_requests[i].nStatus, 
		    download_requests[i].pszError ? download_requests[i].pszError : "(null)");
                    ret = CE_Failure;
                }
            }
        }
        CPLHTTPCleanupRequest(&download_requests[i]);
    }
    if (!m_parent_dataset->m_offline_mode) {
        delete[] download_blocks;
        delete[] download_requests;
    }

return ret;
}

CPLErr GDALWMSRasterBand::IReadBlock(int x, int y, void *buffer) {
    int bx0 = x;
    int by0 = y;
    int bx1 = x;
    int by1 = y;

if ((m_parent_dataset->m_hint.m_valid) && (m_parent_dataset->m_hint.m_overview == m_overview)) {
        int tbx0 = m_parent_dataset->m_hint.m_x0 / nBlockXSize;
        int tby0 = m_parent_dataset->m_hint.m_y0 / nBlockYSize;
        int tbx1 = (m_parent_dataset->m_hint.m_x0 + m_parent_dataset->m_hint.m_sx - 1) / nBlockXSize;
        int tby1 = (m_parent_dataset->m_hint.m_y0 + m_parent_dataset->m_hint.m_sy - 1) / nBlockYSize;
        if ((tbx0 <= bx0) && (tby0 <= by0) && (tbx1 >= bx1) && (tby1 >= by1)) {
            bx0 = tbx0;
            by0 = tby0;
            bx1 = tbx1;
            by1 = tby1;
        }
    }

CPLErr eErr = ReadBlocks(x, y, buffer, bx0, by0, bx1, by1, 0);

if ((m_parent_dataset->m_hint.m_valid) && (m_parent_dataset->m_hint.m_overview == m_overview))
    {
        m_parent_dataset->m_hint.m_valid = false;
    }

return eErr;
}

CPLErr GDALWMSRasterBand::IRasterIO(GDALRWFlag rw, int x0, int y0, int sx, int sy, void *buffer, int bsx, int bsy, GDALDataType bdt, int pixel_space, int line_space) {
    CPLErr ret;

if (rw != GF_Read) return CE_Failure;
    if (buffer == NULL) return CE_Failure;
    if ((sx == 0) || (sy == 0) || (bsx == 0) || (bsy == 0)) return CE_None;

m_parent_dataset->m_hint.m_x0 = x0;
    m_parent_dataset->m_hint.m_y0 = y0;
    m_parent_dataset->m_hint.m_sx = sx;
    m_parent_dataset->m_hint.m_sy = sy;
    m_parent_dataset->m_hint.m_overview = m_overview;
    m_parent_dataset->m_hint.m_valid = true;
    ret = GDALRasterBand::IRasterIO(rw, x0, y0, sx, sy, buffer, bsx, bsy, bdt, pixel_space, line_space);
    m_parent_dataset->m_hint.m_valid = false;

return ret;
}

int GDALWMSRasterBand::HasArbitraryOverviews() {
//    return m_parent_dataset->m_mini_driver_caps.m_has_arb_overviews;
    return 0; // not implemented yet
}

int GDALWMSRasterBand::GetOverviewCount() {
    return m_overviews.size();
}

GDALRasterBand *GDALWMSRasterBand::GetOverview(int n) {
    if ((m_overviews.size() > 0) && (static_cast<size_t>(n) < m_overviews.size())) return m_overviews[n];
    else return NULL;
}

void GDALWMSRasterBand::AddOverview(double scale) {
    GDALWMSRasterBand *overview = new GDALWMSRasterBand(m_parent_dataset, nBand, scale);
    std::vector<GDALWMSRasterBand *>::iterator it = m_overviews.begin();
    for (; it != m_overviews.end(); ++it) {
        GDALWMSRasterBand *p = *it;
        if (p->m_scale < scale) break;
    }
    m_overviews.insert(it, overview);
    it = m_overviews.begin();
    for (int i = 0; it != m_overviews.end(); ++it, ++i) {
        GDALWMSRasterBand *p = *it;
        p->m_overview = i;
    }
}

bool GDALWMSRasterBand::IsBlockInCache(int x, int y) {
    bool ret = false;
    GDALRasterBlock *b = TryGetLockedBlockRef(x, y);
    if (b != NULL) {
        ret = true;
        b->DropLock();
    }
    return ret;
}

// This is the function that calculates the block coordinates for the fetch
void GDALWMSRasterBand::AskMiniDriverForBlock(CPLString *url, int x, int y)
{
    GDALWMSImageRequestInfo iri;
    GDALWMSTiledImageRequestInfo tiri;

ComputeRequestInfo(iri, tiri, x, y);

m_parent_dataset->m_mini_driver->TiledImageRequest(url, iri, tiri);
}

void GDALWMSRasterBand::ComputeRequestInfo(GDALWMSImageRequestInfo &iri,
                                           GDALWMSTiledImageRequestInfo &tiri,
                                           int x, int y)
{
    int x0 = MAX(0, x * nBlockXSize);
    int y0 = MAX(0, y * nBlockYSize);
    int x1 = MAX(0, (x + 1) * nBlockXSize);
    int y1 = MAX(0, (y + 1) * nBlockYSize);
    if (m_parent_dataset->m_clamp_requests) {
	x0 = MIN(x0, nRasterXSize);
	y0 = MIN(y0, nRasterYSize);
	x1 = MIN(x1, nRasterXSize);
	y1 = MIN(y1, nRasterYSize);
    }
    
    const double rx = (m_parent_dataset->m_data_window.m_x1 - m_parent_dataset->m_data_window.m_x0) / static_cast<double>(nRasterXSize);
    const double ry = (m_parent_dataset->m_data_window.m_y1 - m_parent_dataset->m_data_window.m_y0) / static_cast<double>(nRasterYSize);
    /* Use different method for x0,y0 and x1,y1 to make sure calculated values are exact for corner requests */
    iri.m_x0 = x0 * rx + m_parent_dataset->m_data_window.m_x0;
    iri.m_y0 = y0 * ry + m_parent_dataset->m_data_window.m_y0;
    iri.m_x1 = m_parent_dataset->m_data_window.m_x1 - (nRasterXSize - x1) * rx;
    iri.m_y1 = m_parent_dataset->m_data_window.m_y1 - (nRasterYSize - y1) * ry;
    iri.m_sx = x1 - x0;
    iri.m_sy = y1 - y0;

int level = m_overview + 1;
    tiri.m_x = (m_parent_dataset->m_data_window.m_tx >> level) + x;
    tiri.m_y = (m_parent_dataset->m_data_window.m_ty >> level) + y;
    tiri.m_level = m_parent_dataset->m_data_window.m_tlevel - level;
}

/************************************************************************/
/*                      GetMetadataDomainList()                         */
/************************************************************************/

char **GDALWMSRasterBand::GetMetadataDomainList()
{
    return CSLAddString(GDALPamRasterBand::GetMetadataDomainList(), "LocationInfo");
}

const char *GDALWMSRasterBand::GetMetadataItem( const char * pszName,
                                                const char * pszDomain )
{
/* ==================================================================== */
/*      LocationInfo handling.                                          */
/* ==================================================================== */
    if( pszDomain != NULL
        && EQUAL(pszDomain,"LocationInfo")
        && (EQUALN(pszName,"Pixel_",6) || EQUALN(pszName,"GeoPixel_",9)) )
    {
        int iPixel, iLine;

/* -------------------------------------------------------------------- */
/*      What pixel are we aiming at?                                    */
/* -------------------------------------------------------------------- */
        if( EQUALN(pszName,"Pixel_",6) )
        {
            if( sscanf( pszName+6, "%d_%d", &iPixel, &iLine ) != 2 )
                return NULL;
        }
        else if( EQUALN(pszName,"GeoPixel_",9) )
        {
            double adfGeoTransform[6];
            double adfInvGeoTransform[6];
            double dfGeoX, dfGeoY;

{
                CPLLocaleC oLocaleEnforcer;
                if( sscanf( pszName+9, "%lf_%lf", &dfGeoX, &dfGeoY ) != 2 )
                    return NULL;
            }

if( GetDataset() == NULL )
                return NULL;

if( GetDataset()->GetGeoTransform( adfGeoTransform ) != CE_None )
                return NULL;

if( !GDALInvGeoTransform( adfGeoTransform, adfInvGeoTransform ) )
                return NULL;

iPixel = (int) floor(
                adfInvGeoTransform[0]
                + adfInvGeoTransform[1] * dfGeoX
                + adfInvGeoTransform[2] * dfGeoY );
            iLine = (int) floor(
                adfInvGeoTransform[3]
                + adfInvGeoTransform[4] * dfGeoX
                + adfInvGeoTransform[5] * dfGeoY );

/* The GetDataset() for the WMS driver is always the main overview level, so rescale */
            /* the values if we are an overview */
            if (m_overview >= 0)
            {
                iPixel = (int) (1.0 * iPixel * GetXSize() / GetDataset()->GetRasterBand(1)->GetXSize());
                iLine = (int) (1.0 * iLine * GetYSize() / GetDataset()->GetRasterBand(1)->GetYSize());
            }
        }
        else
            return NULL;

if( iPixel < 0 || iLine < 0
            || iPixel >= GetXSize()
            || iLine >= GetYSize() )
            return NULL;

if (nBand != 1)
        {
            GDALRasterBand* poFirstBand = m_parent_dataset->GetRasterBand(1);
            if (m_overview >= 0)
                poFirstBand = poFirstBand->GetOverview(m_overview);
            if (poFirstBand)
                return poFirstBand->GetMetadataItem(pszName, pszDomain);
        }

GDALWMSImageRequestInfo iri;
        GDALWMSTiledImageRequestInfo tiri;
        int nBlockXOff = iPixel / nBlockXSize;
        int nBlockYOff = iLine / nBlockYSize;

ComputeRequestInfo(iri, tiri, nBlockXOff, nBlockYOff);

CPLString url;
        m_parent_dataset->m_mini_driver->GetTiledImageInfo(&url,
                                                           iri, tiri,
                                                           iPixel % nBlockXSize,
                                                           iLine % nBlockXSize);

char* pszRes = NULL;

if (url.size() != 0)
        {
            if (url == osMetadataItemURL)
            {
                return osMetadataItem.size() != 0 ? osMetadataItem.c_str() : NULL;
            }
            osMetadataItemURL = url;

char **http_request_opts = BuildHTTPRequestOpts();
            CPLHTTPResult* psResult = CPLHTTPFetch( url.c_str(), http_request_opts);
            if( psResult && psResult->pabyData )
                pszRes = CPLStrdup((const char*) psResult->pabyData);
            CPLHTTPDestroyResult(psResult);
            CSLDestroy(http_request_opts);
        }

if (pszRes)
        {
            osMetadataItem = "<LocationInfo>";
            CPLPushErrorHandler(CPLQuietErrorHandler);
            CPLXMLNode* psXML = CPLParseXMLString(pszRes);
            CPLPopErrorHandler();
            if (psXML != NULL && psXML->eType == CXT_Element)
            {
                if (strcmp(psXML->pszValue, "?xml") == 0)
                {
                    if (psXML->psNext)
                    {
                        char* pszXML = CPLSerializeXMLTree(psXML->psNext);
                        osMetadataItem += pszXML;
                        CPLFree(pszXML);
                    }
                }
                else
                {
                    osMetadataItem += pszRes;
                }
            }
            else
            {
                char* pszEscapedXML = CPLEscapeString(pszRes, -1, CPLES_XML_BUT_QUOTES);
                osMetadataItem += pszEscapedXML;
                CPLFree(pszEscapedXML);
            }
            if (psXML != NULL)
                CPLDestroyXMLNode(psXML);

osMetadataItem += "</LocationInfo>";
            CPLFree(pszRes);
            return osMetadataItem.c_str();
        }
        else
        {
            osMetadataItem = "";
            return NULL;
        }
    }

return GDALPamRasterBand::GetMetadataItem(pszName, pszDomain);
}

CPLErr GDALWMSRasterBand::ReadBlockFromFile(int x, int y, const char *file_name, int to_buffer_band, void *buffer, int advise_read) {
    CPLErr ret = CE_None;
    GDALDataset *ds = 0;
    GByte *color_table = NULL;
    int i;

//CPLDebug("WMS", "ReadBlockFromFile: to_buffer_band=%d, (x,y)=(%d, %d)", to_buffer_band, x, y);

/* expected size */
    const int esx = MIN(MAX(0, (x + 1) * nBlockXSize), nRasterXSize) - MIN(MAX(0, x * nBlockXSize), nRasterXSize);
    const int esy = MIN(MAX(0, (y + 1) * nBlockYSize), nRasterYSize) - MIN(MAX(0, y * nBlockYSize), nRasterYSize);
    ds = reinterpret_cast<GDALDataset*>(GDALOpen(file_name, GA_ReadOnly));
    if (ds != NULL) {
        int sx = ds->GetRasterXSize();
        int sy = ds->GetRasterYSize();
        bool accepted_as_no_alpha = false;  // if the request is for 4 bands but the wms returns 3  
        /* Allow bigger than expected so pre-tiled constant size images work on corners */
        if ((sx > nBlockXSize) || (sy > nBlockYSize) || (sx < esx) || (sy < esy)) {
            CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Incorrect size %d x %d of downloaded block, expected %d x %d, max %d x %d.",
                sx, sy, esx, esy, nBlockXSize, nBlockYSize);
            ret = CE_Failure;
        }
        if (ret == CE_None) {
            int nDSRasterCount = ds->GetRasterCount();
            if (nDSRasterCount != m_parent_dataset->nBands) {
                /* Maybe its an image with color table */
                bool accepted_as_ct = false;
                if ((eDataType == GDT_Byte) && (ds->GetRasterCount() == 1)) {
                    GDALRasterBand *rb = ds->GetRasterBand(1);
                    if (rb->GetRasterDataType() == GDT_Byte) {
                        GDALColorTable *ct = rb->GetColorTable();
                        if (ct != NULL) {
                            accepted_as_ct = true;
                            if (!advise_read) {
                                color_table = new GByte[256 * 4];
                                const int count = MIN(256, ct->GetColorEntryCount());
                                for (i = 0; i < count; ++i) {
                                    GDALColorEntry ce;
                                    ct->GetColorEntryAsRGB(i, &ce);
                                    color_table[i] = static_cast<GByte>(ce.c1);
                                    color_table[i + 256] = static_cast<GByte>(ce.c2);
                                    color_table[i + 512] = static_cast<GByte>(ce.c3);
                                    color_table[i + 768] = static_cast<GByte>(ce.c4);
                                }
                                for (i = count; i < 256; ++i) {
                                    color_table[i] = 0;
                                    color_table[i + 256] = 0;
                                    color_table[i + 512] = 0;
                                    color_table[i + 768] = 0;
                                }
                            }
                        }
                    }
                }

if (nDSRasterCount == 4 && m_parent_dataset->nBands == 3)
                {
                    /* metacarta TMS service sometimes return a 4 band PNG instead of the expected 3 band... */
                }
                else if (!accepted_as_ct) {
                   if (ds->GetRasterCount()==3 && m_parent_dataset->nBands == 4 && (eDataType == GDT_Byte))
                   { // WMS returned a file with no alpha so we will fill the alpha band with "opaque" 
                      accepted_as_no_alpha = true;
                   }
                   else
                   {
                      CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Incorrect bands count %d in downloaded block, expected %d.",
                         nDSRasterCount, m_parent_dataset->nBands);
                      ret = CE_Failure;
                   }
                }
            }
        }
        if (!advise_read) {
            for (int ib = 1; ib <= m_parent_dataset->nBands; ++ib) {
                if (ret == CE_None) {
                    void *p = NULL;
                    GDALRasterBlock *b = NULL;
                    if ((buffer != NULL) && (ib == to_buffer_band)) {
                        p = buffer;
                    } else {
                        GDALWMSRasterBand *band = static_cast<GDALWMSRasterBand *>(m_parent_dataset->GetRasterBand(ib));
                        if (m_overview >= 0) band = static_cast<GDALWMSRasterBand *>(band->GetOverview(m_overview));
                        if (!band->IsBlockInCache(x, y)) {
                            b = band->GetLockedBlockRef(x, y, true);
                            if (b != NULL) {
                                p = b->GetDataRef();
                                if (p == NULL) {
                                  CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: GetDataRef returned NULL.");
                                  ret = CE_Failure;
                                }
                            }
                        }
                        else
                        {
                            //CPLDebug("WMS", "Band %d, block (x,y)=(%d, %d) already in cache", band->GetBand(), x, y);
                        }
                    }
                    if (p != NULL) {
                        int pixel_space = GDALGetDataTypeSize(eDataType) / 8;
                        int line_space = pixel_space * nBlockXSize;
                        if (color_table == NULL) {
                            if( ib <= ds->GetRasterCount()) {
				GDALDataType dt=eDataType;
				// Get the data from the PNG as stored instead of converting, if the server asks for that
                                // TODO: This hack is from #3493 - not sure it really belongs here.
				if ((GDT_Int16==dt)&&(GDT_UInt16==ds->GetRasterBand(ib)->GetRasterDataType()))
				    dt=GDT_UInt16;
				if (ds->RasterIO(GF_Read, 0, 0, sx, sy, p, sx, sy, dt, 1, &ib, pixel_space, line_space, 0) != CE_None) {
				    CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: RasterIO failed on downloaded block.");
				    ret = CE_Failure;
				}
                            }
                            else
                            {  // parent expects 4 bands but file only has 3 so generate a all "opaque" 4th band
                               if (accepted_as_no_alpha)
                               {
                                  // the file had 3 bands and we are reading band 4 (Alpha) so fill with 255 (no alpha)
                                  GByte *byte_buffer = reinterpret_cast<GByte *>(p);
                                  for (int y = 0; y < sy; ++y) {
                                     for (int x = 0; x < sx; ++x) {
                                        const int offset = x + y * line_space;
                                        byte_buffer[offset] = 255;  // fill with opaque
                                     }
                                  }
                               }
                               else
                               {  // we should never get here because this case was caught above
                                  CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Incorrect bands count %d in downloaded block, expected %d.",
                                     ds->GetRasterCount(), m_parent_dataset->nBands);
                                  ret = CE_Failure;
                               }     
                            }
                        } else if (ib <= 4) {
                            if (ds->RasterIO(GF_Read, 0, 0, sx, sy, p, sx, sy, eDataType, 1, NULL, pixel_space, line_space, 0) != CE_None) {
                                CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: RasterIO failed on downloaded block.");
                                ret = CE_Failure;
                            }
                            if (ret == CE_None) {
                                GByte *band_color_table = color_table + 256 * (ib - 1);
                                GByte *byte_buffer = reinterpret_cast<GByte *>(p);
                                for (int y = 0; y < sy; ++y) {
                                    for (int x = 0; x < sx; ++x) {
                                        const int offset = x + y * line_space;
                                        byte_buffer[offset] = band_color_table[byte_buffer[offset]];
                                    }
                                }
                            }
                        } else {
                            CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Color table supports at most 4 components.");
                            ret = CE_Failure;
                        }
                    }
                    if (b != NULL) {
                        b->DropLock();
                    }
                }
            }
        }
        GDALClose(ds);
    } else {
        CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: Unable to open downloaded block.");
        ret = CE_Failure;
    }

if (color_table != NULL) {
        delete[] color_table;
    }

return ret;
}

CPLErr GDALWMSRasterBand::ZeroBlock(int x, int y, int to_buffer_band, void *buffer) {
    CPLErr ret = CE_None;

for (int ib = 1; ib <= m_parent_dataset->nBands; ++ib) {
        if (ret == CE_None) {
            void *p = NULL;
            GDALRasterBlock *b = NULL;
            if ((buffer != NULL) && (ib == to_buffer_band)) {
                p = buffer;
            } else {
                GDALWMSRasterBand *band = static_cast<GDALWMSRasterBand *>(m_parent_dataset->GetRasterBand(ib));
                if (m_overview >= 0) band = static_cast<GDALWMSRasterBand *>(band->GetOverview(m_overview));
                if (!band->IsBlockInCache(x, y)) {
                    b = band->GetLockedBlockRef(x, y, true);
                    if (b != NULL) {
                        p = b->GetDataRef();
                        if (p == NULL) {
                          CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: GetDataRef returned NULL.");
                          ret = CE_Failure;
                        }
                    }
                }
            }
            if (p != NULL) {
                unsigned char *b = reinterpret_cast<unsigned char *>(p);
                int block_size = nBlockXSize * nBlockYSize * (GDALGetDataTypeSize(eDataType) / 8);
                for (int i = 0; i < block_size; ++i) b[i] = 0;
            }
            if (b != NULL) {
                b->DropLock();
            }
        }
    }

return ret;
}

CPLErr GDALWMSRasterBand::ReportWMSException(const char *file_name) {
    CPLErr ret = CE_None;
    int reported_errors_count = 0;

CPLXMLNode *orig_root = CPLParseXMLFile(file_name);
    CPLXMLNode *root = orig_root;
    if (root != NULL) {
        root = CPLGetXMLNode(root, "=ServiceExceptionReport");
    }
    if (root != NULL) {
        CPLXMLNode *n = CPLGetXMLNode(root, "ServiceException");
        while (n != NULL) {
            const char *exception = CPLGetXMLValue(n, "=ServiceException", "");
            const char *exception_code = CPLGetXMLValue(n, "=ServiceException.code", "");
            if (exception[0] != '\0') {
                if (exception_code[0] != '\0') {
                    CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: The server returned exception code '%s': %s", exception_code, exception);
                    ++reported_errors_count;
                } else {
                    CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: The server returned exception: %s", exception);
                    ++reported_errors_count;
                }
            } else if (exception_code[0] != '\0') {
                CPLError(CE_Failure, CPLE_AppDefined, "GDALWMS: The server returned exception code '%s'.", exception_code);
                ++reported_errors_count;
            }

n = n->psNext;
            if (n != NULL) {
                n = CPLGetXMLNode(n, "=ServiceException");
            }
        }
    } else {
        ret = CE_Failure;
    }
    if (orig_root != NULL) {
        CPLDestroyXMLNode(orig_root);
    }

if (reported_errors_count == 0) {
        ret = CE_Failure;
    }

return ret;
}

CPLErr GDALWMSRasterBand::AdviseRead(int x0, int y0,
                                     int sx, int sy,
                                     CPL_UNUSED int bsx, CPL_UNUSED int bsy,
                                     CPL_UNUSED GDALDataType bdt, CPL_UNUSED char **options) {
    if (m_parent_dataset->m_offline_mode || !m_parent_dataset->m_use_advise_read) return CE_None;
    if (m_parent_dataset->m_cache == NULL) return CE_Failure;

int bx0 = x0 / nBlockXSize;
    int by0 = y0 / nBlockYSize;
    int bx1 = (x0 + sx - 1) / nBlockXSize;
    int by1 = (y0 + sy - 1) / nBlockYSize;

return ReadBlocks(0, 0, NULL, bx0, by0, bx1, by1, 1);
}

GDALColorInterp GDALWMSRasterBand::GetColorInterpretation() {
    return m_color_interp;
}

CPLErr GDALWMSRasterBand::SetColorInterpretation( GDALColorInterp eNewInterp )
{
    m_color_interp = eNewInterp;
    return CE_None;
}

// Utility function, returns a value from a vector corresponding to the band index
// or the first entry
static double getBandValue(std::vector<double> &v,size_t idx)
{
    idx--;
    if (v.size()>idx) return v[idx];
    return v[0];
}

double GDALWMSRasterBand::GetNoDataValue( int *pbSuccess)
{
    std::vector<double> &v=m_parent_dataset->vNoData;
    if (v.size()==0)
        return GDALPamRasterBand::GetNoDataValue(pbSuccess);
    if (pbSuccess) *pbSuccess=TRUE;
    return getBandValue(v,nBand);
}

double GDALWMSRasterBand::GetMinimum( int *pbSuccess)
{
    std::vector<double> &v=m_parent_dataset->vMin;
    if (v.size()==0)
        return GDALPamRasterBand::GetMinimum(pbSuccess);
    if (pbSuccess) *pbSuccess=TRUE;
    return getBandValue(v,nBand);
}

double GDALWMSRasterBand::GetMaximum( int *pbSuccess)
{
    std::vector<double> &v=m_parent_dataset->vMax;
    if (v.size()==0)
        return GDALPamRasterBand::GetMaximum(pbSuccess);
    if (pbSuccess) *pbSuccess=TRUE;
    return getBandValue(v,nBand);
}

GDALColorTable *GDALWMSRasterBand::GetColorTable()
{
    return m_parent_dataset->m_poColorTable;
}