591d0c69ba
This reverts commit 0696fa4669.
I'm not sure what I did there, it seems like I pushed smaller commits
instead of a squashed one, and then did a revert that undid everything.
References #4623
140 lines
4.1 KiB
C
140 lines
4.1 KiB
C
/**********************************************************************
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*
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* PostGIS - Spatial Types for PostgreSQL
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* http://postgis.net
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*
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* PostGIS is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* PostGIS is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with PostGIS. If not, see <http://www.gnu.org/licenses/>.
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*
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**********************************************************************
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*
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* Copyright 2014 Kashif Rasul <kashif.rasul@gmail.com> and
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* Shoaib Burq <saburq@gmail.com>
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*
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**********************************************************************/
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#include "stringbuffer.h"
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#include "liblwgeom_internal.h"
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static lwvarlena_t *lwline_to_encoded_polyline(const LWLINE *, int precision);
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static lwvarlena_t *lwmmpoint_to_encoded_polyline(const LWMPOINT *, int precision);
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static lwvarlena_t *pointarray_to_encoded_polyline(const POINTARRAY *, int precision);
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/* takes a GEOMETRY and returns an Encoded Polyline representation */
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extern lwvarlena_t *
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lwgeom_to_encoded_polyline(const LWGEOM *geom, int precision)
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{
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int type = geom->type;
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switch (type)
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{
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case LINETYPE:
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return lwline_to_encoded_polyline((LWLINE*)geom, precision);
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case MULTIPOINTTYPE:
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return lwmmpoint_to_encoded_polyline((LWMPOINT*)geom, precision);
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default:
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lwerror("lwgeom_to_encoded_polyline: '%s' geometry type not supported",
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lwtype_name(type));
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return NULL;
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}
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}
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static lwvarlena_t *
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lwline_to_encoded_polyline(const LWLINE *line, int precision)
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{
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return pointarray_to_encoded_polyline(line->points, precision);
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}
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static lwvarlena_t *
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lwmmpoint_to_encoded_polyline(const LWMPOINT *mpoint, int precision)
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{
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LWLINE* line = lwline_from_lwmpoint(mpoint->srid, mpoint);
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lwvarlena_t *encoded_polyline = lwline_to_encoded_polyline(line, precision);
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lwline_free(line);
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return encoded_polyline;
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}
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static lwvarlena_t *
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pointarray_to_encoded_polyline(const POINTARRAY *pa, int precision)
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{
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uint32_t i;
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const POINT2D* prevPoint;
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int* delta;
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stringbuffer_t* sb;
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double scale = pow(10, precision);
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/* Empty input is empty string */
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if (pa->npoints == 0)
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{
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lwvarlena_t *v = lwalloc(LWVARHDRSZ);
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LWSIZE_SET(v->size, LWVARHDRSZ);
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return v;
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}
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delta = lwalloc(2 * sizeof(int) * pa->npoints);
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/* Take the double value and multiply it by 1x10^precision, rounding the
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* result */
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prevPoint = getPoint2d_cp(pa, 0);
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delta[0] = round(prevPoint->y * scale);
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delta[1] = round(prevPoint->x * scale);
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/* Points only include the offset from the previous point */
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for (i = 1; i < pa->npoints; i++)
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{
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const POINT2D* point = getPoint2d_cp(pa, i);
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delta[2 * i] = round(point->y * scale) - round(prevPoint->y * scale);
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delta[(2 * i) + 1] =
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round(point->x * scale) - round(prevPoint->x * scale);
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prevPoint = point;
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}
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/* value to binary: a negative value must be calculated using its two's
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* complement */
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for (i = 0; i < pa->npoints * 2; i++)
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{
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/* Multiply by 2 for a signed left shift */
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delta[i] *= 2;
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/* if value is negative, invert this encoding */
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if (delta[i] < 0) {
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delta[i] = ~(delta[i]);
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}
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}
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sb = stringbuffer_create();
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for (i = 0; i < pa->npoints * 2; i++)
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{
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int numberToEncode = delta[i];
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while (numberToEncode >= 0x20)
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{
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/* Place the 5-bit chunks into reverse order or
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each value with 0x20 if another bit chunk follows and add 63*/
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int nextValue = (0x20 | (numberToEncode & 0x1f)) + 63;
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stringbuffer_aprintf(sb, "%c", (char)nextValue);
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/* Break the binary value out into 5-bit chunks */
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numberToEncode >>= 5;
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}
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numberToEncode += 63;
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stringbuffer_aprintf(sb, "%c", (char)numberToEncode);
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}
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lwfree(delta);
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lwvarlena_t *v = stringbuffer_getvarlenacopy(sb);
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stringbuffer_destroy(sb);
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return v;
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}
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