lwout_wkb.c

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/**********************************************************************
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.net
 *
 * PostGIS 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.
 *
 * PostGIS 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 PostGIS.  If not, see <http://www.gnu.org/licenses/>.
 *
 **********************************************************************
 *
 * Copyright (C) 2009 Paul Ramsey <pramsey@cleverelephant.ca>
 *
 **********************************************************************/


#include <math.h>

#include "liblwgeom_internal.h"
#include "lwgeom_log.h"

static uint8_t* lwgeom_to_wkb_buf(const LWGEOM *geom, uint8_t *buf, uint8_t variant);
static size_t lwgeom_to_wkb_size(const LWGEOM *geom, uint8_t variant);

/*
* Look-up table for hex writer
*/
static char *hexchr = "0123456789ABCDEF";

char* hexbytes_from_bytes(uint8_t *bytes, size_t size)
{
        char *hex;
        int i;
        if ( ! bytes || ! size )
        {
                lwerror("hexbutes_from_bytes: invalid input");
                return NULL;
        }
        hex = lwalloc(size * 2 + 1);
        hex[2*size] = '\0';
        for( i = 0; i < size; i++ )
        {
                /* Top four bits to 0-F */
                hex[2*i] = hexchr[bytes[i] >> 4];
                /* Bottom four bits to 0-F */
                hex[2*i+1] = hexchr[bytes[i] & 0x0F];
        }
        return hex;
}

/*
* Optional SRID
*/
static int lwgeom_wkb_needs_srid(const LWGEOM *geom, uint8_t variant)
{
        /* Sub-components of collections inherit their SRID from the parent.
           We force that behavior with the WKB_NO_SRID flag */
        if ( variant & WKB_NO_SRID )
                return LW_FALSE;

        /* We can only add an SRID if the geometry has one, and the
           WKB form is extended */
        if ( (variant & WKB_EXTENDED) && lwgeom_has_srid(geom) )
                return LW_TRUE;

        /* Everything else doesn't get an SRID */
        return LW_FALSE;
}

/*
* GeometryType
*/
static uint32_t lwgeom_wkb_type(const LWGEOM *geom, uint8_t variant)
{
        uint32_t wkb_type = 0;

        switch ( geom->type )
        {
        case POINTTYPE:
                wkb_type = WKB_POINT_TYPE;
                break;
        case LINETYPE:
                wkb_type = WKB_LINESTRING_TYPE;
                break;
        case POLYGONTYPE:
                wkb_type = WKB_POLYGON_TYPE;
                break;
        case MULTIPOINTTYPE:
                wkb_type = WKB_MULTIPOINT_TYPE;
                break;
        case MULTILINETYPE:
                wkb_type = WKB_MULTILINESTRING_TYPE;
                break;
        case MULTIPOLYGONTYPE:
                wkb_type = WKB_MULTIPOLYGON_TYPE;
                break;
        case COLLECTIONTYPE:
                wkb_type = WKB_GEOMETRYCOLLECTION_TYPE;
                break;
        case CIRCSTRINGTYPE:
                wkb_type = WKB_CIRCULARSTRING_TYPE;
                break;
        case COMPOUNDTYPE:
                wkb_type = WKB_COMPOUNDCURVE_TYPE;
                break;
        case CURVEPOLYTYPE:
                wkb_type = WKB_CURVEPOLYGON_TYPE;
                break;
        case MULTICURVETYPE:
                wkb_type = WKB_MULTICURVE_TYPE;
                break;
        case MULTISURFACETYPE:
                wkb_type = WKB_MULTISURFACE_TYPE;
                break;
        case POLYHEDRALSURFACETYPE:
                wkb_type = WKB_POLYHEDRALSURFACE_TYPE;
                break;
        case TINTYPE:
                wkb_type = WKB_TIN_TYPE;
                break;
        case TRIANGLETYPE:
                wkb_type = WKB_TRIANGLE_TYPE;
                break;
        default:
                lwerror("Unsupported geometry type: %s [%d]",
                        lwtype_name(geom->type), geom->type);
        }

        if ( variant & WKB_EXTENDED )
        {
                if ( FLAGS_GET_Z(geom->flags) )
                        wkb_type |= WKBZOFFSET;
                if ( FLAGS_GET_M(geom->flags) )
                        wkb_type |= WKBMOFFSET;
/*              if ( geom->srid != SRID_UNKNOWN && ! (variant & WKB_NO_SRID) ) */
                if ( lwgeom_wkb_needs_srid(geom, variant) )
                        wkb_type |= WKBSRIDFLAG;
        }
        else if ( variant & WKB_ISO )
        {
                /* Z types are in the 1000 range */
                if ( FLAGS_GET_Z(geom->flags) )
                        wkb_type += 1000;
                /* M types are in the 2000 range */
                if ( FLAGS_GET_M(geom->flags) )
                        wkb_type += 2000;
                /* ZM types are in the 1000 + 2000 = 3000 range, see above */
        }
        return wkb_type;
}

/*
* Endian
*/
static uint8_t* endian_to_wkb_buf(uint8_t *buf, uint8_t variant)
{
        if ( variant & WKB_HEX )
        {
                buf[0] = '0';
                buf[1] = ((variant & WKB_NDR) ? '1' : '0');
                return buf + 2;
        }
        else
        {
                buf[0] = ((variant & WKB_NDR) ? 1 : 0);
                return buf + 1;
        }
}

/*
* SwapBytes?
*/
static inline int wkb_swap_bytes(uint8_t variant)
{
        /* If requested variant matches machine arch, we don't have to swap! */
        if ( ((variant & WKB_NDR) && (getMachineEndian() == NDR)) ||
             ((! (variant & WKB_NDR)) && (getMachineEndian() == XDR)) )
        {
                return LW_FALSE;
        }
        return LW_TRUE;
}

/*
* Integer32
*/
static uint8_t* integer_to_wkb_buf(const int ival, uint8_t *buf, uint8_t variant)
{
        char *iptr = (char*)(&ival);
        int i = 0;

        if ( sizeof(int) != WKB_INT_SIZE )
        {
                lwerror("Machine int size is not %d bytes!", WKB_INT_SIZE);
        }
        LWDEBUGF(4, "Writing value '%u'", ival);
        if ( variant & WKB_HEX )
        {
                int swap = wkb_swap_bytes(variant);
                /* Machine/request arch mismatch, so flip byte order */
                for ( i = 0; i < WKB_INT_SIZE; i++ )
                {
                        int j = (swap ? WKB_INT_SIZE - 1 - i : i);
                        uint8_t b = iptr[j];
                        /* Top four bits to 0-F */
                        buf[2*i] = hexchr[b >> 4];
                        /* Bottom four bits to 0-F */
                        buf[2*i+1] = hexchr[b & 0x0F];
                }
                return buf + (2 * WKB_INT_SIZE);
        }
        else
        {
                /* Machine/request arch mismatch, so flip byte order */
                if ( wkb_swap_bytes(variant) )
                {
                        for ( i = 0; i < WKB_INT_SIZE; i++ )
                        {
                                buf[i] = iptr[WKB_INT_SIZE - 1 - i];
                        }
                }
                /* If machine arch and requested arch match, don't flip byte order */
                else
                {
                        memcpy(buf, iptr, WKB_INT_SIZE);
                }
                return buf + WKB_INT_SIZE;
        }
}

/*
* Float64
*/
static uint8_t* double_to_wkb_buf(const double d, uint8_t *buf, uint8_t variant)
{
        char *dptr = (char*)(&d);
        int i = 0;

        if ( sizeof(double) != WKB_DOUBLE_SIZE )
        {
                lwerror("Machine double size is not %d bytes!", WKB_DOUBLE_SIZE);
        }

        if ( variant & WKB_HEX )
        {
                int swap =  wkb_swap_bytes(variant);
                /* Machine/request arch mismatch, so flip byte order */
                for ( i = 0; i < WKB_DOUBLE_SIZE; i++ )
                {
                        int j = (swap ? WKB_DOUBLE_SIZE - 1 - i : i);
                        uint8_t b = dptr[j];
                        /* Top four bits to 0-F */
                        buf[2*i] = hexchr[b >> 4];
                        /* Bottom four bits to 0-F */
                        buf[2*i+1] = hexchr[b & 0x0F];
                }
                return buf + (2 * WKB_DOUBLE_SIZE);
        }
        else
        {
                /* Machine/request arch mismatch, so flip byte order */
                if ( wkb_swap_bytes(variant) )
                {
                        for ( i = 0; i < WKB_DOUBLE_SIZE; i++ )
                        {
                                buf[i] = dptr[WKB_DOUBLE_SIZE - 1 - i];
                        }
                }
                /* If machine arch and requested arch match, don't flip byte order */
                else
                {
                        memcpy(buf, dptr, WKB_DOUBLE_SIZE);
                }
                return buf + WKB_DOUBLE_SIZE;
        }
}


/*
* Empty
*/
static size_t empty_to_wkb_size(const LWGEOM *geom, uint8_t variant)
{
        /* endian byte + type integer */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE;

        /* optional srid integer */
        if ( lwgeom_wkb_needs_srid(geom, variant) )
                size += WKB_INT_SIZE;

        /* Represent POINT EMPTY as POINT(NaN NaN) */
        if ( geom->type == POINTTYPE )
        {
                const LWPOINT *pt = (LWPOINT*)geom;
                size += WKB_DOUBLE_SIZE * FLAGS_NDIMS(pt->point->flags);
        }
        /* num-elements */
        else
        {
                size += WKB_INT_SIZE;
        }

        return size;
}

static uint8_t* empty_to_wkb_buf(const LWGEOM *geom, uint8_t *buf, uint8_t variant)
{
        uint32_t wkb_type = lwgeom_wkb_type(geom, variant);

        /* Set the endian flag */
        buf = endian_to_wkb_buf(buf, variant);

        /* Set the geometry type */
        buf = integer_to_wkb_buf(wkb_type, buf, variant);

        /* Set the SRID if necessary */
        if ( lwgeom_wkb_needs_srid(geom, variant) )
                buf = integer_to_wkb_buf(geom->srid, buf, variant);

        /* Represent POINT EMPTY as POINT(NaN NaN) */
        if ( geom->type == POINTTYPE )
        {
                const LWPOINT *pt = (LWPOINT*)geom;
                static double nn = NAN;
                int i;
                for ( i = 0; i < FLAGS_NDIMS(pt->point->flags); i++ )
                {
                        buf = double_to_wkb_buf(nn, buf, variant);
                }
        }
        /* Everything else is flagged as empty using num-elements == 0 */
        else
        {
                /* Set nrings/npoints/ngeoms to zero */
                buf = integer_to_wkb_buf(0, buf, variant);
        }

        return buf;
}

/*
* POINTARRAY
*/
static size_t ptarray_to_wkb_size(const POINTARRAY *pa, uint8_t variant)
{
        int dims = 2;
        size_t size = 0;

        if ( variant & (WKB_ISO | WKB_EXTENDED) )
                dims = FLAGS_NDIMS(pa->flags);

        /* Include the npoints if it's not a POINT type) */
        if ( ! ( variant & WKB_NO_NPOINTS ) )
                size += WKB_INT_SIZE;

        /* size of the double list */
        size += pa->npoints * dims * WKB_DOUBLE_SIZE;

        return size;
}

static uint8_t* ptarray_to_wkb_buf(const POINTARRAY *pa, uint8_t *buf, uint8_t variant)
{
        int dims = 2;
        int pa_dims = FLAGS_NDIMS(pa->flags);
        int i, j;
        double *dbl_ptr;

        /* SFSQL is always 2-d. Extended and ISO use all available dimensions */
        if ( (variant & WKB_ISO) || (variant & WKB_EXTENDED) )
                dims = pa_dims;

        /* Set the number of points (if it's not a POINT type) */
        if ( ! ( variant & WKB_NO_NPOINTS ) )
                buf = integer_to_wkb_buf(pa->npoints, buf, variant);

        /* Bulk copy the coordinates when: dimensionality matches, output format */
        /* is not hex, and output endian matches internal endian. */
        if ( pa->npoints && (dims == pa_dims) && ! wkb_swap_bytes(variant) && ! (variant & WKB_HEX)  )
        {
                size_t size = pa->npoints * dims * WKB_DOUBLE_SIZE;
                memcpy(buf, getPoint_internal(pa, 0), size);
                buf += size;
        }
        /* Copy coordinates one-by-one otherwise */
        else
        {
                for ( i = 0; i < pa->npoints; i++ )
                {
                        LWDEBUGF(4, "Writing point #%d", i);
                        dbl_ptr = (double*)getPoint_internal(pa, i);
                        for ( j = 0; j < dims; j++ )
                        {
                                LWDEBUGF(4, "Writing dimension #%d (buf = %p)", j, buf);
                                buf = double_to_wkb_buf(dbl_ptr[j], buf, variant);
                        }
                }
        }
        LWDEBUGF(4, "Done (buf = %p)", buf);
        return buf;
}

/*
* POINT
*/
static size_t lwpoint_to_wkb_size(const LWPOINT *pt, uint8_t variant)
{
        /* Endian flag + type number */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE;

        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)pt) )
                return empty_to_wkb_size((LWGEOM*)pt, variant);

        /* Extended WKB needs space for optional SRID integer */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)pt, variant) )
                size += WKB_INT_SIZE;

        /* Points */
        size += ptarray_to_wkb_size(pt->point, variant | WKB_NO_NPOINTS);
        return size;
}

static uint8_t* lwpoint_to_wkb_buf(const LWPOINT *pt, uint8_t *buf, uint8_t variant)
{
        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)pt) )
                return empty_to_wkb_buf((LWGEOM*)pt, buf, variant);

        /* Set the endian flag */
        LWDEBUGF(4, "Entering function, buf = %p", buf);
        buf = endian_to_wkb_buf(buf, variant);
        LWDEBUGF(4, "Endian set, buf = %p", buf);
        /* Set the geometry type */
        buf = integer_to_wkb_buf(lwgeom_wkb_type((LWGEOM*)pt, variant), buf, variant);
        LWDEBUGF(4, "Type set, buf = %p", buf);
        /* Set the optional SRID for extended variant */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)pt, variant) )
        {
                buf = integer_to_wkb_buf(pt->srid, buf, variant);
                LWDEBUGF(4, "SRID set, buf = %p", buf);
        }
        /* Set the coordinates */
        buf = ptarray_to_wkb_buf(pt->point, buf, variant | WKB_NO_NPOINTS);
        LWDEBUGF(4, "Pointarray set, buf = %p", buf);
        return buf;
}

/*
* LINESTRING, CIRCULARSTRING
*/
static size_t lwline_to_wkb_size(const LWLINE *line, uint8_t variant)
{
        /* Endian flag + type number */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE;

        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)line) )
                return empty_to_wkb_size((LWGEOM*)line, variant);

        /* Extended WKB needs space for optional SRID integer */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)line, variant) )
                size += WKB_INT_SIZE;

        /* Size of point array */
        size += ptarray_to_wkb_size(line->points, variant);
        return size;
}

static uint8_t* lwline_to_wkb_buf(const LWLINE *line, uint8_t *buf, uint8_t variant)
{
        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)line) )
                return empty_to_wkb_buf((LWGEOM*)line, buf, variant);

        /* Set the endian flag */
        buf = endian_to_wkb_buf(buf, variant);
        /* Set the geometry type */
        buf = integer_to_wkb_buf(lwgeom_wkb_type((LWGEOM*)line, variant), buf, variant);
        /* Set the optional SRID for extended variant */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)line, variant) )
                buf = integer_to_wkb_buf(line->srid, buf, variant);
        /* Set the coordinates */
        buf = ptarray_to_wkb_buf(line->points, buf, variant);
        return buf;
}

/*
* TRIANGLE
*/
static size_t lwtriangle_to_wkb_size(const LWTRIANGLE *tri, uint8_t variant)
{
        /* endian flag + type number + number of rings */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE + WKB_INT_SIZE;

        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)tri) )
                return empty_to_wkb_size((LWGEOM*)tri, variant);

        /* Extended WKB needs space for optional SRID integer */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)tri, variant) )
                size += WKB_INT_SIZE;

        /* How big is this point array? */
        size += ptarray_to_wkb_size(tri->points, variant);

        return size;
}

static uint8_t* lwtriangle_to_wkb_buf(const LWTRIANGLE *tri, uint8_t *buf, uint8_t variant)
{
        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)tri) )
                return empty_to_wkb_buf((LWGEOM*)tri, buf, variant);

        /* Set the endian flag */
        buf = endian_to_wkb_buf(buf, variant);

        /* Set the geometry type */
        buf = integer_to_wkb_buf(lwgeom_wkb_type((LWGEOM*)tri, variant), buf, variant);

        /* Set the optional SRID for extended variant */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)tri, variant) )
                buf = integer_to_wkb_buf(tri->srid, buf, variant);

        /* Set the number of rings (only one, it's a triangle, buddy) */
        buf = integer_to_wkb_buf(1, buf, variant);

        /* Write that ring */
        buf = ptarray_to_wkb_buf(tri->points, buf, variant);

        return buf;
}

/*
* POLYGON
*/
static size_t lwpoly_to_wkb_size(const LWPOLY *poly, uint8_t variant)
{
        /* endian flag + type number + number of rings */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE + WKB_INT_SIZE;
        int i = 0;

        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)poly) )
                return empty_to_wkb_size((LWGEOM*)poly, variant);

        /* Extended WKB needs space for optional SRID integer */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)poly, variant) )
                size += WKB_INT_SIZE;

        for ( i = 0; i < poly->nrings; i++ )
        {
                /* Size of ring point array */
                size += ptarray_to_wkb_size(poly->rings[i], variant);
        }

        return size;
}

static uint8_t* lwpoly_to_wkb_buf(const LWPOLY *poly, uint8_t *buf, uint8_t variant)
{
        int i;

        /* Only process empty at this level in the EXTENDED case */
        if ( (variant & WKB_EXTENDED) && lwgeom_is_empty((LWGEOM*)poly) )
                return empty_to_wkb_buf((LWGEOM*)poly, buf, variant);

        /* Set the endian flag */
        buf = endian_to_wkb_buf(buf, variant);
        /* Set the geometry type */
        buf = integer_to_wkb_buf(lwgeom_wkb_type((LWGEOM*)poly, variant), buf, variant);
        /* Set the optional SRID for extended variant */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)poly, variant) )
                buf = integer_to_wkb_buf(poly->srid, buf, variant);
        /* Set the number of rings */
        buf = integer_to_wkb_buf(poly->nrings, buf, variant);

        for ( i = 0; i < poly->nrings; i++ )
        {
                buf = ptarray_to_wkb_buf(poly->rings[i], buf, variant);
        }

        return buf;
}


/*
* MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION
* MULTICURVE, COMPOUNDCURVE, MULTISURFACE, CURVEPOLYGON, TIN,
* POLYHEDRALSURFACE
*/
static size_t lwcollection_to_wkb_size(const LWCOLLECTION *col, uint8_t variant)
{
        /* Endian flag + type number + number of subgeoms */
        size_t size = WKB_BYTE_SIZE + WKB_INT_SIZE + WKB_INT_SIZE;
        int i = 0;

        /* Extended WKB needs space for optional SRID integer */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)col, variant) )
                size += WKB_INT_SIZE;

        for ( i = 0; i < col->ngeoms; i++ )
        {
                /* size of subgeom */
                size += lwgeom_to_wkb_size((LWGEOM*)col->geoms[i], variant | WKB_NO_SRID);
        }

        return size;
}

static uint8_t* lwcollection_to_wkb_buf(const LWCOLLECTION *col, uint8_t *buf, uint8_t variant)
{
        int i;

        /* Set the endian flag */
        buf = endian_to_wkb_buf(buf, variant);
        /* Set the geometry type */
        buf = integer_to_wkb_buf(lwgeom_wkb_type((LWGEOM*)col, variant), buf, variant);
        /* Set the optional SRID for extended variant */
        if ( lwgeom_wkb_needs_srid((LWGEOM*)col, variant) )
                buf = integer_to_wkb_buf(col->srid, buf, variant);
        /* Set the number of sub-geometries */
        buf = integer_to_wkb_buf(col->ngeoms, buf, variant);

        /* Write the sub-geometries. Sub-geometries do not get SRIDs, they
           inherit from their parents. */
        for ( i = 0; i < col->ngeoms; i++ )
        {
                buf = lwgeom_to_wkb_buf(col->geoms[i], buf, variant | WKB_NO_SRID);
        }

        return buf;
}

/*
* GEOMETRY
*/
static size_t lwgeom_to_wkb_size(const LWGEOM *geom, uint8_t variant)
{
        size_t size = 0;

        if ( geom == NULL )
                return 0;

        /* Short circuit out empty geometries */
        if ( (!(variant & WKB_EXTENDED)) && lwgeom_is_empty(geom) )
        {
                return empty_to_wkb_size(geom, variant);
        }

        switch ( geom->type )
        {
                case POINTTYPE:
                        size += lwpoint_to_wkb_size((LWPOINT*)geom, variant);
                        break;

                /* LineString and CircularString both have points elements */
                case CIRCSTRINGTYPE:
                case LINETYPE:
                        size += lwline_to_wkb_size((LWLINE*)geom, variant);
                        break;

                /* Polygon has nrings and rings elements */
                case POLYGONTYPE:
                        size += lwpoly_to_wkb_size((LWPOLY*)geom, variant);
                        break;

                /* Triangle has one ring of three points */
                case TRIANGLETYPE:
                        size += lwtriangle_to_wkb_size((LWTRIANGLE*)geom, variant);
                        break;

                /* All these Collection types have ngeoms and geoms elements */
                case MULTIPOINTTYPE:
                case MULTILINETYPE:
                case MULTIPOLYGONTYPE:
                case COMPOUNDTYPE:
                case CURVEPOLYTYPE:
                case MULTICURVETYPE:
                case MULTISURFACETYPE:
                case COLLECTIONTYPE:
                case POLYHEDRALSURFACETYPE:
                case TINTYPE:
                        size += lwcollection_to_wkb_size((LWCOLLECTION*)geom, variant);
                        break;

                /* Unknown type! */
                default:
                        lwerror("Unsupported geometry type: %s [%d]", lwtype_name(geom->type), geom->type);
        }

        return size;
}

/* TODO handle the TRIANGLE type properly */

static uint8_t* lwgeom_to_wkb_buf(const LWGEOM *geom, uint8_t *buf, uint8_t variant)
{

        /* Do not simplify empties when outputting to canonical form */
        if ( lwgeom_is_empty(geom) & ! (variant & WKB_EXTENDED) )
                return empty_to_wkb_buf(geom, buf, variant);

        switch ( geom->type )
        {
                case POINTTYPE:
                        return lwpoint_to_wkb_buf((LWPOINT*)geom, buf, variant);

                /* LineString and CircularString both have 'points' elements */
                case CIRCSTRINGTYPE:
                case LINETYPE:
                        return lwline_to_wkb_buf((LWLINE*)geom, buf, variant);

                /* Polygon has 'nrings' and 'rings' elements */
                case POLYGONTYPE:
                        return lwpoly_to_wkb_buf((LWPOLY*)geom, buf, variant);

                /* Triangle has one ring of three points */
                case TRIANGLETYPE:
                        return lwtriangle_to_wkb_buf((LWTRIANGLE*)geom, buf, variant);

                /* All these Collection types have 'ngeoms' and 'geoms' elements */
                case MULTIPOINTTYPE:
                case MULTILINETYPE:
                case MULTIPOLYGONTYPE:
                case COMPOUNDTYPE:
                case CURVEPOLYTYPE:
                case MULTICURVETYPE:
                case MULTISURFACETYPE:
                case COLLECTIONTYPE:
                case POLYHEDRALSURFACETYPE:
                case TINTYPE:
                        return lwcollection_to_wkb_buf((LWCOLLECTION*)geom, buf, variant);

                /* Unknown type! */
                default:
                        lwerror("Unsupported geometry type: %s [%d]", lwtype_name(geom->type), geom->type);
        }
        /* Return value to keep compiler happy. */
        return 0;
}

uint8_t* lwgeom_to_wkb(const LWGEOM *geom, uint8_t variant, size_t *size_out)
{
        size_t buf_size;
        uint8_t *buf = NULL;
        uint8_t *wkb_out = NULL;

        /* Initialize output size */
        if ( size_out ) *size_out = 0;

        if ( geom == NULL )
        {
                LWDEBUG(4,"Cannot convert NULL into WKB.");
                lwerror("Cannot convert NULL into WKB.");
                return NULL;
        }

        /* Calculate the required size of the output buffer */
        buf_size = lwgeom_to_wkb_size(geom, variant);
        LWDEBUGF(4, "WKB output size: %d", buf_size);

        if ( buf_size == 0 )
        {
                LWDEBUG(4,"Error calculating output WKB buffer size.");
                lwerror("Error calculating output WKB buffer size.");
                return NULL;
        }

        /* Hex string takes twice as much space as binary + a null character */
        if ( variant & WKB_HEX )
        {
                buf_size = 2 * buf_size + 1;
                LWDEBUGF(4, "Hex WKB output size: %d", buf_size);
        }

        /* If neither or both variants are specified, choose the native order */
        if ( ! (variant & WKB_NDR || variant & WKB_XDR) ||
               (variant & WKB_NDR && variant & WKB_XDR) )
        {
                if ( getMachineEndian() == NDR )
                        variant = variant | WKB_NDR;
                else
                        variant = variant | WKB_XDR;
        }

        /* Allocate the buffer */
        buf = lwalloc(buf_size);

        if ( buf == NULL )
        {
                LWDEBUGF(4,"Unable to allocate %d bytes for WKB output buffer.", buf_size);
                lwerror("Unable to allocate %d bytes for WKB output buffer.", buf_size);
                return NULL;
        }

        /* Retain a pointer to the front of the buffer for later */
        wkb_out = buf;

        /* Write the WKB into the output buffer */
        buf = lwgeom_to_wkb_buf(geom, buf, variant);

        /* Null the last byte if this is a hex output */
        if ( variant & WKB_HEX )
        {
                *buf = '\0';
                buf++;
        }

        LWDEBUGF(4,"buf (%p) - wkb_out (%p) = %d", buf, wkb_out, buf - wkb_out);

        /* The buffer pointer should now land at the end of the allocated buffer space. Let's check. */
        if ( buf_size != (buf - wkb_out) )
        {
                LWDEBUG(4,"Output WKB is not the same size as the allocated buffer.");
                lwerror("Output WKB is not the same size as the allocated buffer.");
                lwfree(wkb_out);
                return NULL;
        }

        /* Report output size */
        if ( size_out ) *size_out = buf_size;

        return wkb_out;
}

char* lwgeom_to_hexwkb(const LWGEOM *geom, uint8_t variant, size_t *size_out)
{
        return (char*)lwgeom_to_wkb(geom, variant | WKB_HEX, size_out);
}