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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Add the geopoly_reverse() function to the GeoPoly extension.
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SHA3-256: 690dd18a5768c5a8cdfa92d5b01901c1a7b1fb6ebb90399f56a3112e41609f92
User & Date: drh 2018-10-08 12:58:59
Context
2018-10-08
18:58
Merge latest trunk changes into this branch. check-in: 2ac72114 user: dan tags: reuse-schema
18:55
Replace the new geopoly_reverse() function with geopoly_ccw(). The geopoly_ccw() function only reverses the vertex order if doing so is necessary to get the correct right-hand winding rule on the polygon. check-in: 07506694 user: drh tags: trunk
12:58
Add the geopoly_reverse() function to the GeoPoly extension. check-in: 690dd18a user: drh tags: trunk
2018-10-06
14:38
Fix the ".help -all" option in the command-line shell. check-in: aac8f1df user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to ext/rtree/geopoly.c.

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    rArea += (p->a[ii*2] - p->a[0])                  /* (xN - x0) */
             * (p->a[ii*2+1] + p->a[1])              /* (yN + y0) */
             * 0.5;
    sqlite3_result_double(context, rArea);
    sqlite3_free(p);
  }            
}































#define GEOPOLY_PI 3.1415926535897932385

/* Fast approximation for cosine(X) for X between -0.5*pi and 2*pi
*/
static double geopolyCosine(double r){
  assert( r>=-0.5*GEOPOLY_PI && r<=2.0*GEOPOLY_PI );
................................................................................
     { geopolyWithinFunc,        2, 1,    "geopoly_within"           },
     { geopolyContainsPointFunc, 3, 1,    "geopoly_contains_point"   },
     { geopolyOverlapFunc,       2, 1,    "geopoly_overlap"          },
     { geopolyDebugFunc,         1, 0,    "geopoly_debug"            },
     { geopolyBBoxFunc,          1, 1,    "geopoly_bbox"             },
     { geopolyXformFunc,         7, 1,    "geopoly_xform"            },
     { geopolyRegularFunc,       4, 1,    "geopoly_regular"          },

  };
  static const struct {
    void (*xStep)(sqlite3_context*,int,sqlite3_value**);
    void (*xFinal)(sqlite3_context*);
    const char *zName;
  } aAgg[] = {
     { geopolyBBoxStep, geopolyBBoxFinal, "geopoly_group_bbox"    },







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    rArea += (p->a[ii*2] - p->a[0])                  /* (xN - x0) */
             * (p->a[ii*2+1] + p->a[1])              /* (yN + y0) */
             * 0.5;
    sqlite3_result_double(context, rArea);
    sqlite3_free(p);
  }            
}

/*
** Implementation of the geopoly_reverse(X) function.
**
** Reverse the order of the vertexes in polygon X.  This can be used
** to convert an historical polygon that uses a clockwise rotation into
** a well-formed GeoJSON polygon that uses counter-clockwise rotation.
*/
static void geopolyReverseFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  GeoPoly *p = geopolyFuncParam(context, argv[0], 0);
  if( p ){
    int ii, jj;
    for(ii=2, jj=p->nVertex*2 - 4; ii<jj; ii+=2, jj-=2){
      GeoCoord t = p->a[ii];
      p->a[ii] = p->a[jj];
      p->a[jj] = t;
      t = p->a[ii+1];
      p->a[ii+1] = p->a[jj+1];
      p->a[jj+1] = t;

    }
    sqlite3_result_blob(context, p->hdr, 
       4+8*p->nVertex, SQLITE_TRANSIENT);
    sqlite3_free(p);
  }            
}

#define GEOPOLY_PI 3.1415926535897932385

/* Fast approximation for cosine(X) for X between -0.5*pi and 2*pi
*/
static double geopolyCosine(double r){
  assert( r>=-0.5*GEOPOLY_PI && r<=2.0*GEOPOLY_PI );
................................................................................
     { geopolyWithinFunc,        2, 1,    "geopoly_within"           },
     { geopolyContainsPointFunc, 3, 1,    "geopoly_contains_point"   },
     { geopolyOverlapFunc,       2, 1,    "geopoly_overlap"          },
     { geopolyDebugFunc,         1, 0,    "geopoly_debug"            },
     { geopolyBBoxFunc,          1, 1,    "geopoly_bbox"             },
     { geopolyXformFunc,         7, 1,    "geopoly_xform"            },
     { geopolyRegularFunc,       4, 1,    "geopoly_regular"          },
     { geopolyReverseFunc,       1, 1,    "geopoly_reverse"          },
  };
  static const struct {
    void (*xStep)(sqlite3_context*,int,sqlite3_value**);
    void (*xFinal)(sqlite3_context*);
    const char *zName;
  } aAgg[] = {
     { geopolyBBoxStep, geopolyBBoxFinal, "geopoly_group_bbox"    },