lwin_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 "../postgis_config.h"
/*#define POSTGIS_DEBUG_LEVEL 4*/
#include "liblwgeom_internal.h" /* NOTE: includes lwgeom_log.h */
#include "lwgeom_log.h"
#include <math.h>
#include <limits.h>
 
#define LW_PARSER_MAX_DEPTH 200
 
typedef struct
{
        const uint8_t *wkb; /* Points to start of WKB */
        size_t wkb_size; /* Expected size of WKB */
        int swap_bytes; /* Do an endian flip? */
        int check; /* Simple validity checks on geometries */
        uint32_t lwtype; /* Current type we are handling */
        uint32_t srid; /* Current SRID we are handling */
        int has_z; /* Z? */
        int has_m; /* M? */
        int has_srid; /* SRID? */
        uint8_t depth;      /* Current recursion level (to prevent stack overflows). Maxes at LW_PARSER_MAX_DEPTH */
        const uint8_t *pos; /* Current parse position */
} wkb_parse_state;
 
 
LWGEOM* lwgeom_from_wkb_state(wkb_parse_state *s);
 
 
 
/**********************************************************************/
 
/* Our static character->number map. Anything > 15 is invalid */
static uint8_t hex2char[256] = {
    /* not Hex characters */
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    /* 0-9 */
    0,1,2,3,4,5,6,7,8,9,20,20,20,20,20,20,
    /* A-F */
    20,10,11,12,13,14,15,20,20,20,20,20,20,20,20,20,
    /* not Hex characters */
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
        /* a-f */
    20,10,11,12,13,14,15,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    /* not Hex characters (upper 128 characters) */
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20
    };
 
 
uint8_t* bytes_from_hexbytes(const char *hexbuf, size_t hexsize)
{
        uint8_t *buf = NULL;
        register uint8_t h1, h2;
        uint32_t i;
 
        if( hexsize % 2 )
                lwerror("Invalid hex string, length (%d) has to be a multiple of two!", hexsize);
 
        buf = lwalloc(hexsize/2);
 
        if( ! buf )
                lwerror("Unable to allocate memory buffer.");
 
        for( i = 0; i < hexsize/2; i++ )
        {
                h1 = hex2char[(int)hexbuf[2*i]];
                h2 = hex2char[(int)hexbuf[2*i+1]];
                if( h1 > 15 )
                        lwerror("Invalid hex character (%c) encountered", hexbuf[2*i]);
                if( h2 > 15 )
                        lwerror("Invalid hex character (%c) encountered", hexbuf[2*i+1]);
                /* First character is high bits, second is low bits */
                buf[i] = ((h1 & 0x0F) << 4) | (h2 & 0x0F);
        }
        return buf;
}
 
 
/**********************************************************************/
 
 
 
 
 
static inline void wkb_parse_state_check(wkb_parse_state *s, size_t next)
{
        if( (s->pos + next) > (s->wkb + s->wkb_size) )
        {
                lwerror("WKB structure does not match expected size!");
                return;
        }
}
 
static void lwtype_from_wkb_state(wkb_parse_state *s, uint32_t wkb_type)
{
        uint32_t wkb_simple_type;
 
        LWDEBUG(4, "Entered function");
 
        s->has_z = LW_FALSE;
        s->has_m = LW_FALSE;
        s->has_srid = LW_FALSE;
 
        /* If any of the higher bits are set, this is probably an extended type. */
        if( wkb_type & 0xF0000000 )
        {
                if( wkb_type & WKBZOFFSET ) s->has_z = LW_TRUE;
                if( wkb_type & WKBMOFFSET ) s->has_m = LW_TRUE;
                if( wkb_type & WKBSRIDFLAG ) s->has_srid = LW_TRUE;
                LWDEBUGF(4, "Extended type: has_z=%d has_m=%d has_srid=%d", s->has_z, s->has_m, s->has_srid);
        }
 
        /* Mask off the flags */
        wkb_type = wkb_type & 0x0FFFFFFF;
        /* Strip out just the type number (1-12) from the ISO number (eg 3001-3012) */
        wkb_simple_type = wkb_type % 1000;
 
        /* Extract the Z/M information from ISO style numbers */
        if( wkb_type >= 3000 && wkb_type < 4000 )
        {
                s->has_z = LW_TRUE;
                s->has_m = LW_TRUE;
        }
        else if ( wkb_type >= 2000 && wkb_type < 3000 )
        {
                s->has_m = LW_TRUE;
        }
        else if ( wkb_type >= 1000 && wkb_type < 2000 )
        {
                s->has_z = LW_TRUE;
        }
 
        switch (wkb_simple_type)
        {
                case WKB_POINT_TYPE:
                        s->lwtype = POINTTYPE;
                        break;
                case WKB_LINESTRING_TYPE:
                        s->lwtype = LINETYPE;
                        break;
                case WKB_POLYGON_TYPE:
                        s->lwtype = POLYGONTYPE;
                        break;
                case WKB_MULTIPOINT_TYPE:
                        s->lwtype = MULTIPOINTTYPE;
                        break;
                case WKB_MULTILINESTRING_TYPE:
                        s->lwtype = MULTILINETYPE;
                        break;
                case WKB_MULTIPOLYGON_TYPE:
                        s->lwtype = MULTIPOLYGONTYPE;
                        break;
                case WKB_GEOMETRYCOLLECTION_TYPE:
                        s->lwtype = COLLECTIONTYPE;
                        break;
                case WKB_CIRCULARSTRING_TYPE:
                        s->lwtype = CIRCSTRINGTYPE;
                        break;
                case WKB_COMPOUNDCURVE_TYPE:
                        s->lwtype = COMPOUNDTYPE;
                        break;
                case WKB_CURVEPOLYGON_TYPE:
                        s->lwtype = CURVEPOLYTYPE;
                        break;
                case WKB_MULTICURVE_TYPE:
                        s->lwtype = MULTICURVETYPE;
                        break;
                case WKB_MULTISURFACE_TYPE:
                        s->lwtype = MULTISURFACETYPE;
                        break;
                case WKB_POLYHEDRALSURFACE_TYPE:
                        s->lwtype = POLYHEDRALSURFACETYPE;
                        break;
                case WKB_TIN_TYPE:
                        s->lwtype = TINTYPE;
                        break;
                case WKB_TRIANGLE_TYPE:
                        s->lwtype = TRIANGLETYPE;
                        break;
 
                /* PostGIS 1.5 emits 13, 14 for CurvePolygon, MultiCurve */
                /* These numbers aren't SQL/MM (numbers currently only */
                /* go up to 12. We can handle the old data here (for now??) */
                /* converting them into the lwtypes that are intended. */
                case WKB_CURVE_TYPE:
                        s->lwtype = CURVEPOLYTYPE;
                        break;
                case WKB_SURFACE_TYPE:
                        s->lwtype = MULTICURVETYPE;
                        break;
 
                default: /* Error! */
                        lwerror("Unknown WKB type (%d)! Full WKB type number was (%d).", wkb_simple_type, wkb_type);
                        break;
        }
 
        LWDEBUGF(4,"Got lwtype %s (%u)", lwtype_name(s->lwtype), s->lwtype);
 
        return;
}
 
static char byte_from_wkb_state(wkb_parse_state *s)
{
        char char_value = 0;
        LWDEBUG(4, "Entered function");
 
        wkb_parse_state_check(s, WKB_BYTE_SIZE);
        LWDEBUG(4, "Passed state check");
 
        char_value = s->pos[0];
        LWDEBUGF(4, "Read byte value: %x", char_value);
        s->pos += WKB_BYTE_SIZE;
 
        return char_value;
}
 
static uint32_t integer_from_wkb_state(wkb_parse_state *s)
{
        uint32_t i = 0;
 
        wkb_parse_state_check(s, WKB_INT_SIZE);
 
        memcpy(&i, s->pos, WKB_INT_SIZE);
 
        /* Swap? Copy into a stack-allocated integer. */
        if( s->swap_bytes )
        {
                int j = 0;
                uint8_t tmp;
 
                for( j = 0; j < WKB_INT_SIZE/2; j++ )
                {
                        tmp = ((uint8_t*)(&i))[j];
                        ((uint8_t*)(&i))[j] = ((uint8_t*)(&i))[WKB_INT_SIZE - j - 1];
                        ((uint8_t*)(&i))[WKB_INT_SIZE - j - 1] = tmp;
                }
        }
 
        s->pos += WKB_INT_SIZE;
        return i;
}
 
static double double_from_wkb_state(wkb_parse_state *s)
{
        double d = 0;
 
        wkb_parse_state_check(s, WKB_DOUBLE_SIZE);
 
        memcpy(&d, s->pos, WKB_DOUBLE_SIZE);
 
        /* Swap? Copy into a stack-allocated integer. */
        if( s->swap_bytes )
        {
                int i = 0;
                uint8_t tmp;
 
                for( i = 0; i < WKB_DOUBLE_SIZE/2; i++ )
                {
                        tmp = ((uint8_t*)(&d))[i];
                        ((uint8_t*)(&d))[i] = ((uint8_t*)(&d))[WKB_DOUBLE_SIZE - i - 1];
                        ((uint8_t*)(&d))[WKB_DOUBLE_SIZE - i - 1] = tmp;
                }
 
        }
 
        s->pos += WKB_DOUBLE_SIZE;
        return d;
}
 
static POINTARRAY* ptarray_from_wkb_state(wkb_parse_state *s)
{
        POINTARRAY *pa = NULL;
        size_t pa_size;
        uint32_t ndims = 2;
        uint32_t npoints = 0;
        static uint32_t maxpoints = UINT_MAX / WKB_DOUBLE_SIZE / 4;
 
        /* Calculate the size of this point array. */
        npoints = integer_from_wkb_state(s);
        if (npoints > maxpoints)
        {
                lwerror("Pointarray length (%d) is too large");
                return NULL;
        }
 
        LWDEBUGF(4,"Pointarray has %d points", npoints);
 
        if( s->has_z ) ndims++;
        if( s->has_m ) ndims++;
        pa_size = npoints * ndims * WKB_DOUBLE_SIZE;
 
        /* Empty! */
        if( npoints == 0 )
                return ptarray_construct(s->has_z, s->has_m, npoints);
 
        /* Does the data we want to read exist? */
        wkb_parse_state_check(s, pa_size);
 
        /* If we're in a native endianness, we can just copy the data directly! */
        if( ! s->swap_bytes )
        {
                pa = ptarray_construct_copy_data(s->has_z, s->has_m, npoints, (uint8_t*)s->pos);
                s->pos += pa_size;
        }
        /* Otherwise we have to read each double, separately. */
        else
        {
                uint32_t i = 0;
                double *dlist;
                pa = ptarray_construct(s->has_z, s->has_m, npoints);
                dlist = (double*)(pa->serialized_pointlist);
                for( i = 0; i < npoints * ndims; i++ )
                {
                        dlist[i] = double_from_wkb_state(s);
                }
        }
 
        return pa;
}
 
static LWPOINT* lwpoint_from_wkb_state(wkb_parse_state *s)
{
        static uint32_t npoints = 1;
        POINTARRAY *pa = NULL;
        size_t pa_size;
        uint32_t ndims = 2;
        const POINT2D *pt;
 
        /* Count the dimensions. */
        if( s->has_z ) ndims++;
        if( s->has_m ) ndims++;
        pa_size = ndims * WKB_DOUBLE_SIZE;
 
        /* Does the data we want to read exist? */
        wkb_parse_state_check(s, pa_size);
 
        /* If we're in a native endianness, we can just copy the data directly! */
        if( ! s->swap_bytes )
        {
                pa = ptarray_construct_copy_data(s->has_z, s->has_m, npoints, (uint8_t*)s->pos);
                s->pos += pa_size;
        }
        /* Otherwise we have to read each double, separately */
        else
        {
                uint32_t i = 0;
                double *dlist;
                pa = ptarray_construct(s->has_z, s->has_m, npoints);
                dlist = (double*)(pa->serialized_pointlist);
                for( i = 0; i < ndims; i++ )
                {
                        dlist[i] = double_from_wkb_state(s);
                }
        }
 
        /* Check for POINT(NaN NaN) ==> POINT EMPTY */
        pt = getPoint2d_cp(pa, 0);
        if ( isnan(pt->x) && isnan(pt->y) )
        {
                ptarray_free(pa);
                return lwpoint_construct_empty(s->srid, s->has_z, s->has_m);
        }
        else
        {
                return lwpoint_construct(s->srid, NULL, pa);
        }
}
 
static LWLINE* lwline_from_wkb_state(wkb_parse_state *s)
{
        POINTARRAY *pa = ptarray_from_wkb_state(s);
 
        if( pa == NULL || pa->npoints == 0 )
        {
                ptarray_free(pa);
                return lwline_construct_empty(s->srid, s->has_z, s->has_m);
        }
 
        if( s->check & LW_PARSER_CHECK_MINPOINTS && pa->npoints < 2 )
        {
                lwerror("%s must have at least two points", lwtype_name(s->lwtype));
                return NULL;
        }
 
        return lwline_construct(s->srid, NULL, pa);
}
 
static LWCIRCSTRING* lwcircstring_from_wkb_state(wkb_parse_state *s)
{
        POINTARRAY *pa = ptarray_from_wkb_state(s);
 
        if( pa == NULL || pa->npoints == 0 )
                return lwcircstring_construct_empty(s->srid, s->has_z, s->has_m);
 
        if( s->check & LW_PARSER_CHECK_MINPOINTS && pa->npoints < 3 )
        {
                lwerror("%s must have at least three points", lwtype_name(s->lwtype));
                return NULL;
        }
 
        if( s->check & LW_PARSER_CHECK_ODD && ! (pa->npoints % 2) )
        {
                lwerror("%s must have an odd number of points", lwtype_name(s->lwtype));
                return NULL;
        }
 
        return lwcircstring_construct(s->srid, NULL, pa);
}
 
static LWPOLY* lwpoly_from_wkb_state(wkb_parse_state *s)
{
        uint32_t nrings = integer_from_wkb_state(s);
        uint32_t i = 0;
        LWPOLY *poly = lwpoly_construct_empty(s->srid, s->has_z, s->has_m);
 
        LWDEBUGF(4,"Polygon has %d rings", nrings);
 
        /* Empty polygon? */
        if( nrings == 0 )
                return poly;
 
        for( i = 0; i < nrings; i++ )
        {
                POINTARRAY *pa = ptarray_from_wkb_state(s);
                if( pa == NULL )
                        continue;
 
                /* Check for at least four points. */
                if( s->check & LW_PARSER_CHECK_MINPOINTS && pa->npoints < 4 )
                {
                        LWDEBUGF(2, "%s must have at least four points in each ring", lwtype_name(s->lwtype));
                        lwerror("%s must have at least four points in each ring", lwtype_name(s->lwtype));
                        return NULL;
                }
 
                /* Check that first and last points are the same. */
                if( s->check & LW_PARSER_CHECK_CLOSURE && ! ptarray_is_closed_2d(pa) )
                {
                        LWDEBUGF(2, "%s must have closed rings", lwtype_name(s->lwtype));
                        lwerror("%s must have closed rings", lwtype_name(s->lwtype));
                        return NULL;
                }
 
                /* Add ring to polygon */
                if ( lwpoly_add_ring(poly, pa) == LW_FAILURE )
                {
                        LWDEBUG(2, "Unable to add ring to polygon");
                        lwerror("Unable to add ring to polygon");
                }
 
        }
        return poly;
}
 
static LWTRIANGLE* lwtriangle_from_wkb_state(wkb_parse_state *s)
{
        uint32_t nrings = integer_from_wkb_state(s);
        LWTRIANGLE *tri = lwtriangle_construct_empty(s->srid, s->has_z, s->has_m);
        POINTARRAY *pa = NULL;
 
        /* Empty triangle? */
        if( nrings == 0 )
                return tri;
 
        /* Should be only one ring. */
        if ( nrings != 1 )
                lwerror("Triangle has wrong number of rings: %d", nrings);
 
        /* There's only one ring, we hope? */
        pa = ptarray_from_wkb_state(s);
 
        /* If there's no points, return an empty triangle. */
        if( pa == NULL )
                return tri;
 
        /* Check for at least four points. */
        if( s->check & LW_PARSER_CHECK_MINPOINTS && pa->npoints < 4 )
        {
                LWDEBUGF(2, "%s must have at least four points", lwtype_name(s->lwtype));
                lwerror("%s must have at least four points", lwtype_name(s->lwtype));
                return NULL;
        }
 
        if( s->check & LW_PARSER_CHECK_ZCLOSURE && ! ptarray_is_closed_z(pa) )
        {
                lwerror("%s must have closed rings", lwtype_name(s->lwtype));
                return NULL;
        }
 
        /* Empty TRIANGLE starts w/ empty POINTARRAY, free it first */
        if (tri->points)
                ptarray_free(tri->points);
 
        tri->points = pa;
        return tri;
}
 
static LWCURVEPOLY* lwcurvepoly_from_wkb_state(wkb_parse_state *s)
{
        uint32_t ngeoms = integer_from_wkb_state(s);
        LWCURVEPOLY *cp = lwcurvepoly_construct_empty(s->srid, s->has_z, s->has_m);
        LWGEOM *geom = NULL;
        uint32_t i;
 
        /* Empty collection? */
        if ( ngeoms == 0 )
                return cp;
 
        for ( i = 0; i < ngeoms; i++ )
        {
                geom = lwgeom_from_wkb_state(s);
                if ( lwcurvepoly_add_ring(cp, geom) == LW_FAILURE )
                {
                        lwgeom_free(geom);
                        lwgeom_free((LWGEOM *)cp);
                        lwerror("Unable to add geometry (%p) to curvepoly (%p)", geom, cp);
                        return NULL;
                }
        }
 
        return cp;
}
 
static LWCOLLECTION* lwcollection_from_wkb_state(wkb_parse_state *s)
{
        uint32_t ngeoms = integer_from_wkb_state(s);
        LWCOLLECTION *col = lwcollection_construct_empty(s->lwtype, s->srid, s->has_z, s->has_m);
        LWGEOM *geom = NULL;
        uint32_t i;
 
        LWDEBUGF(4,"Collection has %d components", ngeoms);
 
        /* Empty collection? */
        if ( ngeoms == 0 )
                return col;
 
        /* Be strict in polyhedral surface closures */
        if ( s->lwtype == POLYHEDRALSURFACETYPE )
                s->check |= LW_PARSER_CHECK_ZCLOSURE;
 
        s->depth++;
        if (s->depth >= LW_PARSER_MAX_DEPTH)
        {
                lwcollection_free(col);
                lwerror("Geometry has too many chained collections");
                return NULL;
        }
        for ( i = 0; i < ngeoms; i++ )
        {
                geom = lwgeom_from_wkb_state(s);
                if ( lwcollection_add_lwgeom(col, geom) == NULL )
                {
                        lwgeom_free(geom);
                        lwgeom_free((LWGEOM *)col);
                        lwerror("Unable to add geometry (%p) to collection (%p)", geom, col);
                        return NULL;
                }
        }
        s->depth--;
 
        return col;
}
 
 
LWGEOM* lwgeom_from_wkb_state(wkb_parse_state *s)
{
        char wkb_little_endian;
        uint32_t wkb_type;
 
        LWDEBUG(4,"Entered function");
 
        /* Fail when handed incorrect starting byte */
        wkb_little_endian = byte_from_wkb_state(s);
        if( wkb_little_endian != 1 && wkb_little_endian != 0 )
        {
                LWDEBUG(4,"Leaving due to bad first byte!");
                lwerror("Invalid endian flag value encountered.");
                return NULL;
        }
 
        /* Check the endianness of our input  */
        s->swap_bytes = LW_FALSE;
        if( getMachineEndian() == NDR ) /* Machine arch is little */
        {
                if ( ! wkb_little_endian )    /* Data is big! */
                        s->swap_bytes = LW_TRUE;
        }
        else                              /* Machine arch is big */
        {
                if ( wkb_little_endian )      /* Data is little! */
                        s->swap_bytes = LW_TRUE;
        }
 
        /* Read the type number */
        wkb_type = integer_from_wkb_state(s);
        LWDEBUGF(4,"Got WKB type number: 0x%X", wkb_type);
        lwtype_from_wkb_state(s, wkb_type);
 
        /* Read the SRID, if necessary */
        if( s->has_srid )
        {
                s->srid = clamp_srid(integer_from_wkb_state(s));
                /* TODO: warn on explicit UNKNOWN srid ? */
                LWDEBUGF(4,"Got SRID: %u", s->srid);
        }
 
        /* Do the right thing */
        switch( s->lwtype )
        {
                case POINTTYPE:
                        return (LWGEOM*)lwpoint_from_wkb_state(s);
                        break;
                case LINETYPE:
                        return (LWGEOM*)lwline_from_wkb_state(s);
                        break;
                case CIRCSTRINGTYPE:
                        return (LWGEOM*)lwcircstring_from_wkb_state(s);
                        break;
                case POLYGONTYPE:
                        return (LWGEOM*)lwpoly_from_wkb_state(s);
                        break;
                case TRIANGLETYPE:
                        return (LWGEOM*)lwtriangle_from_wkb_state(s);
                        break;
                case CURVEPOLYTYPE:
                        return (LWGEOM*)lwcurvepoly_from_wkb_state(s);
                        break;
                case MULTIPOINTTYPE:
                case MULTILINETYPE:
                case MULTIPOLYGONTYPE:
                case COMPOUNDTYPE:
                case MULTICURVETYPE:
                case MULTISURFACETYPE:
                case POLYHEDRALSURFACETYPE:
                case TINTYPE:
                case COLLECTIONTYPE:
                        return (LWGEOM*)lwcollection_from_wkb_state(s);
                        break;
 
                /* Unknown type! */
                default:
                        lwerror("Unsupported geometry type: %s [%d]", lwtype_name(s->lwtype), s->lwtype);
        }
 
        /* Return value to keep compiler happy. */
        return NULL;
 
}
 
/* TODO add check for SRID consistency */
 
LWGEOM* lwgeom_from_wkb(const uint8_t *wkb, const size_t wkb_size, const char check)
{
        wkb_parse_state s;
 
        /* Initialize the state appropriately */
        s.wkb = wkb;
        s.wkb_size = wkb_size;
        s.swap_bytes = LW_FALSE;
        s.check = check;
        s.lwtype = 0;
        s.srid = SRID_UNKNOWN;
        s.has_z = LW_FALSE;
        s.has_m = LW_FALSE;
        s.has_srid = LW_FALSE;
        s.pos = wkb;
        s.depth = 1;
 
        return lwgeom_from_wkb_state(&s);
}
 
LWGEOM* lwgeom_from_hexwkb(const char *hexwkb, const char check)
{
        int hexwkb_len;
        uint8_t *wkb;
        LWGEOM *lwgeom;
 
        if ( ! hexwkb )
        {
                lwerror("lwgeom_from_hexwkb: null input");
                return NULL;
        }
 
        hexwkb_len = strlen(hexwkb);
        wkb = bytes_from_hexbytes(hexwkb, hexwkb_len);
        lwgeom = lwgeom_from_wkb(wkb, hexwkb_len/2, check);
        lwfree(wkb);
        return lwgeom;
}