ptarray_locate_between_m()

static POINTARRAYSET ptarray_locate_between_m ( POINTARRAY *  ipa, double  m0, double  m1  )

static

Definition at line 436 of file lwgeom_functions_lrs.c.

{
        POINTARRAYSET ret;
        POINTARRAY *dpa=NULL;
        uint32_t i;
 
        ret.nptarrays=0;
 
        /*
         * We allocate space for as many pointarray as
         * segments in the input POINTARRAY, as worst
         * case is for each segment to cross the M range
         * window.
         * TODO: rework this to reduce used memory
         */
        ret.ptarrays=lwalloc(sizeof(POINTARRAY *)*ipa->npoints-1);
 
        POSTGIS_DEBUGF(2, "ptarray_locate...: called for pointarray %p, m0:%g, m1:%g",
                 ipa, m0, m1);
 
 
        for (i=1; i<ipa->npoints; i++)
        {
                POINT4D p1, p2;
                int clipval;
 
                getPoint4d_p(ipa, i-1, &p1);
                getPoint4d_p(ipa, i, &p2);
 
                POSTGIS_DEBUGF(3, " segment %d-%d [ %g %g %g %g -  %g %g %g %g ]",
                         i-1, i,
                         p1.x, p1.y, p1.z, p1.m,
                         p2.x, p2.y, p2.z, p2.m);
 
                clipval = clip_seg_by_m_range(&p1, &p2, m0, m1);
 
                /* segment completely outside, nothing to do */
                if (! clipval ) continue;
 
                POSTGIS_DEBUGF(3, " clipped to: [ %g %g %g %g - %g %g %g %g ]   clipval: %d", p1.x, p1.y, p1.z, p1.m,
                         p2.x, p2.y, p2.z, p2.m, clipval);
 
                /* If no points have been accumulated so far, then if clipval != 0 the first point must be the
                   start of the intersection */
                if (dpa == NULL)
                {
                        POSTGIS_DEBUGF(3, " 1 creating new POINTARRAY with first point %g,%g,%g,%g", p1.x, p1.y, p1.z, p1.m);
 
                        dpa = ptarray_construct_empty(FLAGS_GET_Z(ipa->flags), FLAGS_GET_M(ipa->flags), ipa->npoints-i);
                        ptarray_append_point(dpa, &p1, LW_TRUE);
                }
 
                /* Otherwise always add the next point, avoiding duplicates */
                if (dpa)
                        ptarray_append_point(dpa, &p2, LW_FALSE);
 
                /*
                 * second point has been clipped
                 */
                if ( clipval & 0x0100 || i == ipa->npoints-1 )
                {
                        POSTGIS_DEBUGF(3, " closing pointarray %p with %d points", dpa, dpa->npoints);
 
                        ret.ptarrays[ret.nptarrays++] = dpa;
                        dpa = NULL;
                }
        }
 
        /*
         * if dpa!=NULL it means we didn't close it yet.
         * this should never happen.
         */
        if ( dpa != NULL ) lwpgerror("Something wrong with algorithm");
 
        return ret;
}

References clip_seg_by_m_range(), POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, getPoint4d_p(), LW_FALSE, LW_TRUE, lwalloc(), POINT4D::m, POINTARRAY::npoints, POINTARRAYSET::nptarrays, ptarray_append_point(), ptarray_construct_empty(), POINTARRAYSET::ptarrays, POINT4D::x, POINT4D::y, and POINT4D::z.

Referenced by lwline_locate_between_m().

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