lwgeom_dump.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 2001-2009 Refractions Research Inc.
 *
 **********************************************************************/
 
 
#include <math.h>
#include <float.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
 
#include "postgres.h"
#include "fmgr.h"
#include "utils/elog.h"
#include "utils/array.h"
#include "utils/geo_decls.h"
#include "funcapi.h"
 
#include "../postgis_config.h"
#include "liblwgeom.h"
#include "lwgeom_pg.h"
 
 
Datum LWGEOM_dump(PG_FUNCTION_ARGS);
Datum LWGEOM_dump_rings(PG_FUNCTION_ARGS);
Datum ST_Subdivide(PG_FUNCTION_ARGS);
 
typedef struct GEOMDUMPNODE_T
{
        uint32_t idx;
        LWGEOM *geom;
}
GEOMDUMPNODE;
 
#define MAXDEPTH 32
typedef struct GEOMDUMPSTATE
{
        int stacklen;
        GEOMDUMPNODE *stack[MAXDEPTH];
        LWGEOM *root;
}
GEOMDUMPSTATE;
 
#define PUSH(x,y) ((x)->stack[(x)->stacklen++]=(y))
#define LAST(x) ((x)->stack[(x)->stacklen-1])
#define POP(x) (--((x)->stacklen))
 
 
PG_FUNCTION_INFO_V1(LWGEOM_dump);
Datum LWGEOM_dump(PG_FUNCTION_ARGS)
{
        GSERIALIZED *pglwgeom;
        LWCOLLECTION *lwcoll;
        LWGEOM *lwgeom;
        FuncCallContext *funcctx;
        GEOMDUMPSTATE *state;
        GEOMDUMPNODE *node;
        TupleDesc tupdesc;
        HeapTuple tuple;
        MemoryContext oldcontext, newcontext;
        Datum result;
        char address[256];
        char *ptr;
        int i;
        char *values[2];
 
        if (SRF_IS_FIRSTCALL())
        {
                funcctx = SRF_FIRSTCALL_INIT();
                newcontext = funcctx->multi_call_memory_ctx;
 
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                pglwgeom = PG_GETARG_GSERIALIZED_P_COPY(0);
                lwgeom = lwgeom_from_gserialized(pglwgeom);
 
                /* Create function state */
                state = lwalloc(sizeof(GEOMDUMPSTATE));
                state->root = lwgeom;
                state->stacklen=0;
 
                if ( lwgeom_is_collection(lwgeom) )
                {
                        /*
                         * Push a GEOMDUMPNODE on the state stack
                         */
                        node = lwalloc(sizeof(GEOMDUMPNODE));
                        node->idx=0;
                        node->geom = lwgeom;
                        PUSH(state, node);
                }
 
                funcctx->user_fctx = state;
 
                /*
                 * Build a tuple description for an
                 * geometry_dump tuple
                 */
                get_call_result_type(fcinfo, 0, &tupdesc);
                BlessTupleDesc(tupdesc);
 
                /*
                 * generate attribute metadata needed later to produce
                 * tuples from raw C strings
                 */
                funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);;
 
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        newcontext = funcctx->multi_call_memory_ctx;
 
        /* get state */
        state = funcctx->user_fctx;
 
        /* Handled simple geometries */
        if ( ! state->root ) SRF_RETURN_DONE(funcctx);
        /* Return nothing for empties */
        if ( lwgeom_is_empty(state->root) ) SRF_RETURN_DONE(funcctx);
        if ( ! lwgeom_is_collection(state->root) )
        {
                values[0] = "{}";
                values[1] = lwgeom_to_hexwkb_buffer(state->root, WKB_EXTENDED);
                tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
                result = HeapTupleGetDatum(tuple);
 
                state->root = NULL;
                SRF_RETURN_NEXT(funcctx, result);
        }
 
        while (1)
        {
                node = LAST(state);
                lwcoll = (LWCOLLECTION*)node->geom;
 
                if ( node->idx < lwcoll->ngeoms )
                {
                        lwgeom = lwcoll->geoms[node->idx];
                        if ( ! lwgeom_is_collection(lwgeom) )
                        {
                                /* write address of current geom */
                                ptr=address;
                                *ptr++='{';
                                for (i=0; i<state->stacklen; i++)
                                {
                                        if ( i ) ptr += sprintf(ptr, ",");
                                        ptr += sprintf(ptr, "%d", state->stack[i]->idx+1);
                                }
                                *ptr++='}';
                                *ptr='\0';
 
                                break;
                        }
 
                        /*
                         * It's a collection, increment index
                         * of current node, push a new one on the
                         * stack
                         */
 
                        if (state->stacklen > MAXDEPTH)
                                elog(ERROR, "Unable to dump overly nested collection.");
 
                        oldcontext = MemoryContextSwitchTo(newcontext);
 
                        node = lwalloc(sizeof(GEOMDUMPNODE));
                        node->idx=0;
                        node->geom = lwgeom;
                        PUSH(state, node);
 
                        MemoryContextSwitchTo(oldcontext);
 
                        continue;
                }
 
                if ( ! POP(state) ) SRF_RETURN_DONE(funcctx);
                LAST(state)->idx++;
        }
 
        lwgeom->srid = state->root->srid;
 
        values[0] = address;
        values[1] = lwgeom_to_hexwkb_buffer(lwgeom, WKB_EXTENDED);
        tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
        result = TupleGetDatum(funcctx->slot, tuple);
        node->idx++;
        SRF_RETURN_NEXT(funcctx, result);
}
 
struct POLYDUMPSTATE
{
        uint32_t ringnum;
        LWPOLY *poly;
};
 
PG_FUNCTION_INFO_V1(LWGEOM_dump_rings);
Datum LWGEOM_dump_rings(PG_FUNCTION_ARGS)
{
        GSERIALIZED *pglwgeom;
        LWGEOM *lwgeom;
        FuncCallContext *funcctx;
        struct POLYDUMPSTATE *state;
        TupleDesc tupdesc;
        HeapTuple tuple;
        MemoryContext oldcontext, newcontext;
        Datum result;
        char address[256];
        char *values[2];
 
        if (SRF_IS_FIRSTCALL())
        {
                funcctx = SRF_FIRSTCALL_INIT();
                newcontext = funcctx->multi_call_memory_ctx;
 
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                pglwgeom = PG_GETARG_GSERIALIZED_P_COPY(0);
                if ( gserialized_get_type(pglwgeom) != POLYGONTYPE )
                {
                        elog(ERROR, "Input is not a polygon");
                }
 
                lwgeom = lwgeom_from_gserialized(pglwgeom);
 
                /* Create function state */
                state = lwalloc(sizeof(struct POLYDUMPSTATE));
                state->poly = lwgeom_as_lwpoly(lwgeom);
                assert (state->poly);
                state->ringnum=0;
 
                funcctx->user_fctx = state;
 
                /*
                 * Build a tuple description for an
                 * geometry_dump tuple
                 */
                get_call_result_type(fcinfo, 0, &tupdesc);
                BlessTupleDesc(tupdesc);
 
                /*
                 * generate attribute metadata needed later to produce
                 * tuples from raw C strings
                 */
                funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);;
 
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        newcontext = funcctx->multi_call_memory_ctx;
 
        /* get state */
        state = funcctx->user_fctx;
 
        /* Loop through polygon rings */
        while (state->ringnum < state->poly->nrings )
        {
                LWPOLY* poly = state->poly;
                POINTARRAY *ring;
                LWGEOM* ringgeom;
 
                /* Switch to an appropriate memory context for POINTARRAY
                 * cloning and hexwkb allocation */
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                /* We need a copy of input ring here */
                ring = ptarray_clone_deep(poly->rings[state->ringnum]);
 
                /* Construct another polygon with shell only */
                ringgeom = (LWGEOM*)lwpoly_construct(
                               poly->srid,
                               NULL, /* TODO: could use input bounding box here */
                               1, /* one ring */
                               &ring);
 
                /* Write path as ``{ <ringnum> }'' */
                sprintf(address, "{%d}", state->ringnum);
 
                values[0] = address;
                values[1] = lwgeom_to_hexwkb_buffer(ringgeom, WKB_EXTENDED);
 
                MemoryContextSwitchTo(oldcontext);
 
                tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
                result = HeapTupleGetDatum(tuple);
                ++state->ringnum;
                SRF_RETURN_NEXT(funcctx, result);
        }
 
        SRF_RETURN_DONE(funcctx);
 
}
 
 
/*
* Break an object up into smaller objects of no more than N vertices
*/
PG_FUNCTION_INFO_V1(ST_Subdivide);
Datum ST_Subdivide(PG_FUNCTION_ARGS)
{
        typedef struct
        {
                int nextgeom;
                int numgeoms;
                LWCOLLECTION *col;
        } collection_fctx;
 
        FuncCallContext *funcctx;
        collection_fctx *fctx;
        MemoryContext oldcontext;
 
        /* stuff done only on the first call of the function */
        if (SRF_IS_FIRSTCALL())
        {
                GSERIALIZED *gser;
                LWGEOM *geom;
                LWCOLLECTION *col;
                /* default to maxvertices < page size */
                int maxvertices = 128;
                double gridSize = -1;
 
                /* create a function context for cross-call persistence */
                funcctx = SRF_FIRSTCALL_INIT();
 
                /*
                * switch to memory context appropriate for multiple function calls
                */
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
                /*
                * Get the geometry value
                */
                gser = PG_GETARG_GSERIALIZED_P(0);
                geom = lwgeom_from_gserialized(gser);
 
                /*
                * Get the max vertices value
                */
                if ( PG_NARGS() > 1 && ! PG_ARGISNULL(1) )
                        maxvertices = PG_GETARG_INT32(1);
 
                /*
                * Get the gridSize value
                */
                if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                        gridSize = PG_GETARG_FLOAT8(2);
 
                /*
                * Compute the subdivision of the geometry
                */
                col = lwgeom_subdivide_prec(geom, maxvertices, gridSize);
 
                if ( ! col )
                        SRF_RETURN_DONE(funcctx);
 
                /* allocate memory for user context */
                fctx = (collection_fctx *) palloc(sizeof(collection_fctx));
 
                /* initialize state */
                fctx->nextgeom = 0;
                fctx->numgeoms = col->ngeoms;
                fctx->col = col;
 
                /* save user context, switch back to function context */
                funcctx->user_fctx = fctx;
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        fctx = funcctx->user_fctx;
 
        if (fctx->nextgeom < fctx->numgeoms)
        {
                GSERIALIZED *gpart = geometry_serialize(fctx->col->geoms[fctx->nextgeom]);
                fctx->nextgeom++;
                SRF_RETURN_NEXT(funcctx, PointerGetDatum(gpart));
        }
        else
        {
                /* do when there is no more left */
                SRF_RETURN_DONE(funcctx);
        }
}