ogrlinestring.cpp

用于读取TAB、MIF、SHP文件的类

    char        szToken[OGR_WKT_TOKEN_MAX];
    const char  *pszInput = *ppszInput;

    if( paoPoints != NULL )
    {
        nPointCount = 0;

        CPLFree( paoPoints );
        paoPoints = NULL;
        
        CPLFree( padfZ );
        padfZ = NULL;
    }

/* -------------------------------------------------------------------- */
/*      Read and verify the ``LINESTRING'' keyword token.               */
/* -------------------------------------------------------------------- */
    pszInput = OGRWktReadToken( pszInput, szToken );

    if( !EQUAL(szToken,getGeometryName()) )
        return OGRERR_CORRUPT_DATA;

/* -------------------------------------------------------------------- */
/*      Check for EMPTY or (EMPTY).                                     */
/* -------------------------------------------------------------------- */
    const char *pszPreScan;

    pszPreScan = OGRWktReadToken( pszInput, szToken );
    if( EQUAL(szToken,"EMPTY") )
    {
        *ppszInput = (char *) pszPreScan;
        return OGRERR_NONE;
    }

    if( !EQUAL(szToken,"(") )
        return OGRERR_CORRUPT_DATA;
    
    pszPreScan = OGRWktReadToken( pszPreScan, szToken );
    if( EQUAL(szToken,"EMPTY") )
    {
        pszPreScan = OGRWktReadToken( pszPreScan, szToken );

        *ppszInput = (char *) pszPreScan;
        
        if( !EQUAL(szToken,")") )
            return OGRERR_CORRUPT_DATA;
        else
            return OGRERR_NONE;
    }

/* -------------------------------------------------------------------- */
/*      Read the point list.                                            */
/* -------------------------------------------------------------------- */
    int      nMaxPoint = 0;

    nPointCount = 0;

    pszInput = OGRWktReadPoints( pszInput, &paoPoints, &padfZ, &nMaxPoint,
                                 &nPointCount );
    if( pszInput == NULL )
        return OGRERR_CORRUPT_DATA;

    *ppszInput = (char *) pszInput;

    if( padfZ == NULL )
        nCoordDimension = 2;
    else
        nCoordDimension = 3;
    
    return OGRERR_NONE;
}

/************************************************************************/
/*                            exportToWkt()                             */
/*                                                                      */
/*      Translate this structure into it's well known text format       */
/*      equivelent.  This could be made alot more CPU efficient!        */
/************************************************************************/

OGRErr OGRLineString::exportToWkt( char ** ppszDstText ) const

{
    int         nMaxString = nPointCount * 40 * 3 + 20;
    int         nRetLen = 0;

/* -------------------------------------------------------------------- */
/*      Handle special empty case.                                      */
/* -------------------------------------------------------------------- */
    if( nPointCount == 0 )
    {
        CPLString osEmpty;
        osEmpty.Printf("%s EMPTY",getGeometryName());
        *ppszDstText = CPLStrdup(osEmpty);
        return OGRERR_NONE;
    }

/* -------------------------------------------------------------------- */
/*      General case.                                                   */
/* -------------------------------------------------------------------- */
    *ppszDstText = (char *) VSIMalloc( nMaxString );
    if( *ppszDstText == NULL )
        return OGRERR_NOT_ENOUGH_MEMORY;

    sprintf( *ppszDstText, "%s (", getGeometryName() );

    for( int i = 0; i < nPointCount; i++ )
    {
        if( nMaxString <= (int) strlen(*ppszDstText+nRetLen) + 32 + nRetLen )
        {
            CPLDebug( "OGR", 
                      "OGRLineString::exportToWkt() ... buffer overflow.\n"
                      "nMaxString=%d, strlen(*ppszDstText) = %d, i=%d\n"
                      "*ppszDstText = %s", 
                      nMaxString, strlen(*ppszDstText), i, *ppszDstText );

            VSIFree( *ppszDstText );
            *ppszDstText = NULL;
            return OGRERR_NOT_ENOUGH_MEMORY;
        }
        
        if( i > 0 )
            strcat( *ppszDstText + nRetLen, "," );

        nRetLen += strlen(*ppszDstText + nRetLen);
        if( getCoordinateDimension() == 3 )
            OGRMakeWktCoordinate( *ppszDstText + nRetLen,
                                  paoPoints[i].x,
                                  paoPoints[i].y,
                                  padfZ[i],
                                  nCoordDimension );
        else
            OGRMakeWktCoordinate( *ppszDstText + nRetLen,
                                  paoPoints[i].x,
                                  paoPoints[i].y,
                                  0.0,
                                  nCoordDimension );

        nRetLen += strlen(*ppszDstText + nRetLen);
    }

    strcat( *ppszDstText+nRetLen, ")" );

    return OGRERR_NONE;
}

/************************************************************************/
/*                             get_Length()                             */
/*                                                                      */
/*      For now we return a simple euclidian 2D distance.               */
/************************************************************************/

double OGRLineString::get_Length() const

{
    double      dfLength = 0;
    int         i;

    for( i = 0; i < nPointCount-1; i++ )
    {
        double      dfDeltaX, dfDeltaY;

        dfDeltaX = paoPoints[i+1].x - paoPoints[i].x;
        dfDeltaY = paoPoints[i+1].y - paoPoints[i].y;
        dfLength += sqrt(dfDeltaX*dfDeltaX + dfDeltaY*dfDeltaY);
    }
    
    return dfLength;
}

/************************************************************************/
/*                             StartPoint()                             */
/************************************************************************/

void OGRLineString::StartPoint( OGRPoint * poPoint ) const

{
    getPoint( 0, poPoint );
}

/************************************************************************/
/*                              EndPoint()                              */
/************************************************************************/

void OGRLineString::EndPoint( OGRPoint * poPoint ) const

{
    getPoint( nPointCount-1, poPoint );
}

/************************************************************************/
/*                               Value()                                */
/*                                                                      */
/*      Get an interpolated point at some distance along the curve.     */
/************************************************************************/

void OGRLineString::Value( double dfDistance, OGRPoint * poPoint ) const

{
    double      dfLength = 0;
    int         i;

    if( dfDistance < 0 )
    {
        StartPoint( poPoint );
        return;
    }

    for( i = 0; i < nPointCount-1; i++ )
    {
        double      dfDeltaX, dfDeltaY, dfSegLength;

        dfDeltaX = paoPoints[i+1].x - paoPoints[i].x;
        dfDeltaY = paoPoints[i+1].y - paoPoints[i].y;
        dfSegLength = sqrt(dfDeltaX*dfDeltaX + dfDeltaY*dfDeltaY);

        if (dfSegLength > 0)
        {
            if( (dfLength <= dfDistance) && ((dfLength + dfSegLength) >= 
                                             dfDistance) )
            {
                double      dfRatio;

                dfRatio = (dfDistance - dfLength) / dfSegLength;

                poPoint->setX( paoPoints[i].x * (1 - dfRatio)
                               + paoPoints[i+1].x * dfRatio );
                poPoint->setY( paoPoints[i].y * (1 - dfRatio)
                               + paoPoints[i+1].y * dfRatio );

                if( getCoordinateDimension() == 3 )
                    poPoint->setZ( padfZ[i] * (1 - dfRatio)
                                   + padfZ[i] * dfRatio );
                
                return;
            }

            dfLength += dfSegLength;
        }
    }
    
    EndPoint( poPoint );
}

/************************************************************************/
/*                            getEnvelope()                             */
/************************************************************************/

void OGRLineString::getEnvelope( OGREnvelope * psEnvelope ) const

{
    double      dfMinX, dfMinY, dfMaxX, dfMaxY;

    if( nPointCount == 0 )
        return;
    
    dfMinX = dfMaxX = paoPoints[0].x;
    dfMinY = dfMaxY = paoPoints[0].y;

    for( int iPoint = 1; iPoint < nPointCount; iPoint++ )
    {
        if( dfMaxX < paoPoints[iPoint].x )
            dfMaxX = paoPoints[iPoint].x;
        if( dfMaxY < paoPoints[iPoint].y )
            dfMaxY = paoPoints[iPoint].y;
        if( dfMinX > paoPoints[iPoint].x )
            dfMinX = paoPoints[iPoint].x;
        if( dfMinY > paoPoints[iPoint].y )
            dfMinY = paoPoints[iPoint].y;
    }

    psEnvelope->MinX = dfMinX;
    psEnvelope->MaxX = dfMaxX;
    psEnvelope->MinY = dfMinY;
    psEnvelope->MaxY = dfMaxY;
}

/************************************************************************/
/*                               Equals()                                */
/************************************************************************/

OGRBoolean OGRLineString::Equals( OGRGeometry * poOther ) const

{
    OGRLineString       *poOLine = (OGRLineString *) poOther;
    
    if( poOLine == this )
        return TRUE;
    
    if( poOther->getGeometryType() != getGeometryType() )
        return FALSE;

    // we should eventually test the SRS.

    if( getNumPoints() != poOLine->getNumPoints() )
        return FALSE;

    for( int iPoint = 0; iPoint < getNumPoints(); iPoint++ )
    {
        if( getX(iPoint) != poOLine->getX(iPoint)
            || getY(iPoint) != poOLine->getY(iPoint) 
            || getZ(iPoint) != poOLine->getZ(iPoint) )
            return FALSE;
    }

    return TRUE;
}

/************************************************************************/
/*                             transform()                              */
/************************************************************************/

OGRErr OGRLineString::transform( OGRCoordinateTransformation *poCT )

{
#ifdef DISABLE_OGRGEOM_TRANSFORM
    return OGRERR_FAILURE;
#else
    double      *xyz;
    int         i;

/* -------------------------------------------------------------------- */
/*      Because we don't want to partially transform this geometry      */
/*      (if some points fail after some have succeeded) we will         */
/*      instead make a copy of the points to operate on.                */
/* -------------------------------------------------------------------- */
    xyz = (double *) CPLMalloc(sizeof(double) * nPointCount * 3);
    if( xyz == NULL )
        return OGRERR_NOT_ENOUGH_MEMORY;

    for( i = 0; i < nPointCount; i++ )
    {
        xyz[i  ] = paoPoints[i].x;
        xyz[i+nPointCount] = paoPoints[i].y;
        if( padfZ )
            xyz[i+nPointCount*2] = padfZ[i];
        else
            xyz[i+nPointCount*2] = 0.0;
    }

/* -------------------------------------------------------------------- */
/*      Transform and reapply.                                          */
/* -------------------------------------------------------------------- */
    if( !poCT->Transform( nPointCount, xyz, xyz + nPointCount, 
                          xyz+nPointCount*2 ) )
    {
        CPLFree( xyz );
        return OGRERR_FAILURE;
    }
    else
    {
        setPoints( nPointCount, xyz, xyz+nPointCount, xyz+nPointCount*2 );
        CPLFree( xyz );

        assignSpatialReference( poCT->GetTargetCS() );

        return OGRERR_NONE;
    }
#endif
}