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748b8fda90
sqlite/ext/rtree/geopoly.c
drh 748b8fda90 Forward port the geopoly extension functions into the r-tree extension, 
with the idea of creating a new spatial index based on simply polygons.

FossilOrigin-Name: 0593aac88a8c25ddafba4c29a181ee083dfc3dab44335feb6f12fdea6ce7fb27
2018-05-25 19:22:47 +00:00

854 lines
23 KiB
C
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/*
** 2018-05-25
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file implements an alternative R-Tree virtual table that
** uses polygons to express the boundaries of 2-dimensional objects.
**
** This file is #include-ed onto the end of "rtree.c" so that it has
** access to all of the R-Tree internals.
*/
#include <stdlib.h>
/* Enable -DGEOPOLY_ENABLE_DEBUG for debugging facilities */
#ifdef GEOPOLY_ENABLE_DEBUG
static int geo_debug = 0;
# define GEODEBUG(X) if(geo_debug)printf X
#else
# define GEODEBUG(X)
#endif
#ifndef JSON_NULL /* The following stuff repeats things found in json1 */
/*
** Versions of isspace(), isalnum() and isdigit() to which it is safe
** to pass signed char values.
*/
#ifdef sqlite3Isdigit
/* Use the SQLite core versions if this routine is part of the
** SQLite amalgamation */
# define safe_isdigit(x) sqlite3Isdigit(x)
# define safe_isalnum(x) sqlite3Isalnum(x)
# define safe_isxdigit(x) sqlite3Isxdigit(x)
#else
/* Use the standard library for separate compilation */
#include <ctype.h> /* amalgamator: keep */
# define safe_isdigit(x) isdigit((unsigned char)(x))
# define safe_isalnum(x) isalnum((unsigned char)(x))
# define safe_isxdigit(x) isxdigit((unsigned char)(x))
#endif
/*
** Growing our own isspace() routine this way is twice as fast as
** the library isspace() function.
*/
static const char geopolyIsSpace[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
#define safe_isspace(x) (geopolyIsSpace[(unsigned char)x])
#endif /* JSON NULL - back to original code */
/* Compiler and version */
#ifndef GCC_VERSION
#if defined(__GNUC__) && !defined(SQLITE_DISABLE_INTRINSIC)
# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
#else
# define GCC_VERSION 0
#endif
#endif
#ifndef MSVC_VERSION
#if defined(_MSC_VER) && !defined(SQLITE_DISABLE_INTRINSIC)
# define MSVC_VERSION _MSC_VER
#else
# define MSVC_VERSION 0
#endif
#endif
/* Datatype for coordinates
*/
typedef float GeoCoord;
/*
** Internal representation of a polygon.
**
** The polygon consists of a sequence of vertexes. There is a line
** segment between each pair of vertexes, and one final segment from
** the last vertex back to the first. (This differs from the GeoJSON
** standard in which the final vertex is a repeat of the first.)
**
** The polygon follows the right-hand rule. The area to the right of
** each segment is "outside" and the area to the left is "inside".
**
** The on-disk representation consists of a 4-byte header followed by
** the values. The 4-byte header is:
**
** encoding (1 byte) 0=big-endian, 1=little-endian
** nvertex (3 bytes) Number of vertexes as a big-endian integer
*/
typedef struct GeoPoly GeoPoly;
struct GeoPoly {
int nVertex; /* Number of vertexes */
unsigned char hdr[4]; /* Header for on-disk representation */
GeoCoord a[2]; /* 2*nVertex values. X (longitude) first, then Y */
};
/*
** State of a parse of a GeoJSON input.
*/
typedef struct GeoParse GeoParse;
struct GeoParse {
const unsigned char *z; /* Unparsed input */
int nVertex; /* Number of vertexes in a[] */
int nAlloc; /* Space allocated to a[] */
int nErr; /* Number of errors encountered */
GeoCoord *a; /* Array of vertexes. From sqlite3_malloc64() */
};
/* Do a 4-byte byte swap */
static void geopolySwab32(unsigned char *a){
unsigned char t = a[0];
a[0] = a[3];
a[3] = t;
t = a[1];
a[1] = a[2];
a[2] = t;
}
/* Skip whitespace. Return the next non-whitespace character. */
static char geopolySkipSpace(GeoParse *p){
while( p->z[0] && safe_isspace(p->z[0]) ) p->z++;
return p->z[0];
}
/* Parse out a number. Write the value into *pVal if pVal!=0.
** return non-zero on success and zero if the next token is not a number.
*/
static int geopolyParseNumber(GeoParse *p, GeoCoord *pVal){
const unsigned char *z = p->z;
char c = geopolySkipSpace(p);
int j;
int seenDP = 0;
int seenE = 0;
assert( '-' < '0' );
if( c<='0' ){
j = c=='-';
if( z[j]=='0' && z[j+1]>='0' && z[j+1]<='9' ) return 0;
}
j = 1;
for(;; j++){
c = z[j];
if( c>='0' && c<='9' ) continue;
if( c=='.' ){
if( z[j-1]=='-' ) return 0;
if( seenDP ) return 0;
seenDP = 1;
continue;
}
if( c=='e' || c=='E' ){
if( z[j-1]<'0' ) return 0;
if( seenE ) return -1;
seenDP = seenE = 1;
c = z[j+1];
if( c=='+' || c=='-' ){
j++;
c = z[j+1];
}
if( c<'0' || c>'9' ) return 0;
continue;
}
break;
}
if( z[j-1]<'0' ) return 0;
if( pVal ) *pVal = atof((const char*)p->z);
p->z += j;
return 1;
}
/*
** If the input is a well-formed JSON array of coordinates, where each
** coordinate is itself a two-value array, then convert the JSON into
** a GeoPoly object and return a pointer to that object.
**
** If any error occurs, return NULL.
*/
static GeoPoly *geopolyParseJson(const unsigned char *z){
GeoParse s;
memset(&s, 0, sizeof(s));
s.z = z;
if( geopolySkipSpace(&s)=='[' ){
s.z++;
while( geopolySkipSpace(&s)=='[' ){
int ii = 0;
char c;
s.z++;
if( s.nVertex<=s.nAlloc ){
GeoCoord *aNew;
s.nAlloc = s.nAlloc*2 + 16;
aNew = sqlite3_realloc64(s.a, s.nAlloc*sizeof(GeoCoord)*2 );
if( aNew==0 ){
s.nErr++;
break;
}
s.a = aNew;
}
while( geopolyParseNumber(&s, ii<=1 ? &s.a[s.nVertex*2+ii] : 0) ){
ii++;
if( ii==2 ) s.nVertex++;
c = geopolySkipSpace(&s);
s.z++;
if( c==',' ) continue;
if( c==']' ) break;
s.nErr++;
goto parse_json_err;
}
if( geopolySkipSpace(&s)==',' ){
s.z++;
continue;
}
break;
}
if( geopolySkipSpace(&s)==']' && s.nVertex>=4 ){
int nByte;
GeoPoly *pOut;
int x = (s.nVertex-1)*2;
if( s.a[x]==s.a[0] && s.a[x+1]==s.a[1] ) s.nVertex--;
nByte = sizeof(GeoPoly) * (s.nVertex-1)*2*sizeof(GeoCoord);
pOut = sqlite3_malloc64( nByte );
x = 1;
if( pOut==0 ) goto parse_json_err;
pOut->nVertex = s.nVertex;
memcpy(pOut->a, s.a, s.nVertex*2*sizeof(GeoCoord));
pOut->hdr[0] = *(unsigned char*)&x;
pOut->hdr[1] = (s.nVertex>>16)&0xff;
pOut->hdr[2] = (s.nVertex>>8)&0xff;
pOut->hdr[3] = s.nVertex&0xff;
sqlite3_free(s.a);
return pOut;
}else{
s.nErr++;
}
}
parse_json_err:
sqlite3_free(s.a);
return 0;
}
/*
** Given a function parameter, try to interpret it as a polygon, either
** in the binary format or JSON text. Compute a GeoPoly object and
** return a pointer to that object. Or if the input is not a well-formed
** polygon, put an error message in sqlite3_context and return NULL.
*/
static GeoPoly *geopolyFuncParam(sqlite3_context *pCtx, sqlite3_value *pVal){
GeoPoly *p = 0;
int nByte;
if( sqlite3_value_type(pVal)==SQLITE_BLOB
&& (nByte = sqlite3_value_bytes(pVal))>=(4+6*sizeof(GeoCoord))
){
const unsigned char *a = sqlite3_value_blob(pVal);
int nVertex;
nVertex = (a[1]<<16) + (a[2]<<8) + a[3];
if( (a[0]==0 && a[0]==1)
&& (nVertex*2*sizeof(GeoCoord) + 4)==nByte
){
p = sqlite3_malloc64( sizeof(*p) + (nVertex-1)*2*sizeof(GeoCoord) );
if( p ){
int x = 1;
p->nVertex = nVertex;
memcpy(p->hdr, a, nByte);
if( a[0] != *(unsigned char*)&x ){
int ii;
for(ii=0; ii<nVertex*2; ii++){
geopolySwab32((unsigned char*)&p->a[ii]);
}
p->hdr[0] ^= 1;
}
}
}
}else if( sqlite3_value_type(pVal)==SQLITE_TEXT ){
p = geopolyParseJson(sqlite3_value_text(pVal));
}
if( p==0 ){
sqlite3_result_error(pCtx, "not a valid polygon", -1);
}
return p;
}
/*
** Implementation of the geopoly_blob(X) function.
**
** If the input is a well-formed Geopoly BLOB or JSON string
** then return the BLOB representation of the polygon. Otherwise
** return NULL.
*/
static void geopolyBlobFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p = geopolyFuncParam(context, argv[0]);
if( p ){
sqlite3_result_blob(context, p->hdr,
4+8*p->nVertex, SQLITE_TRANSIENT);
sqlite3_free(p);
}
}
/*
** SQL function: geopoly_json(X)
**
** Interpret X as a polygon and render it as a JSON array
** of coordinates. Or, if X is not a valid polygon, return NULL.
*/
static void geopolyJsonFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p = geopolyFuncParam(context, argv[0]);
if( p ){
sqlite3 *db = sqlite3_context_db_handle(context);
sqlite3_str *x = sqlite3_str_new(db);
int i;
sqlite3_str_append(x, "[", 1);
for(i=0; i<p->nVertex; i++){
sqlite3_str_appendf(x, "[%!g,%!g],", p->a[i*2], p->a[i*2+1]);
}
sqlite3_str_appendf(x, "[%!g,%!g]]", p->a[0], p->a[1]);
sqlite3_result_text(context, sqlite3_str_finish(x), -1, sqlite3_free);
sqlite3_free(p);
}
}
/*
** SQL function: geopoly_svg(X, ....)
**
** Interpret X as a polygon and render it as a SVG <polyline>.
** Additional arguments are added as attributes to the <polyline>.
*/
static void geopolySvgFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p = geopolyFuncParam(context, argv[0]);
if( p ){
sqlite3 *db = sqlite3_context_db_handle(context);
sqlite3_str *x = sqlite3_str_new(db);
int i;
char cSep = '\'';
sqlite3_str_appendf(x, "<polyline points=");
for(i=0; i<p->nVertex; i++){
sqlite3_str_appendf(x, "%c%g,%g", cSep, p->a[i*2], p->a[i*2+1]);
cSep = ' ';
}
sqlite3_str_appendf(x, " %g,%g'", p->a[0], p->a[1]);
for(i=1; i<argc; i++){
const char *z = (const char*)sqlite3_value_text(argv[i]);
if( z && z[0] ){
sqlite3_str_appendf(x, " %s", z);
}
}
sqlite3_str_appendf(x, "></polyline>");
sqlite3_result_text(context, sqlite3_str_finish(x), -1, sqlite3_free);
sqlite3_free(p);
}
}
/*
** Implementation of the geopoly_area(X) function.
**
** If the input is a well-formed Geopoly BLOB then return the area
** enclosed by the polygon. If the polygon circulates clockwise instead
** of counterclockwise (as it should) then return the negative of the
** enclosed area. Otherwise return NULL.
*/
static void geopolyAreaFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p = geopolyFuncParam(context, argv[0]);
if( p ){
double rArea = 0.0;
int ii;
for(ii=0; ii<p->nVertex-1; ii++){
rArea += (p->a[ii*2] - p->a[ii*2+2]) /* (x0 - x1) */
* (p->a[ii*2+1] + p->a[ii*2+3]) /* (y0 + y1) */
* 0.5;
}
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);
}
}
/*
** Determine if point (x0,y0) is beneath line segment (x1,y1)->(x2,y2).
** Returns:
**
** +2 x0,y0 is on the line segement
**
** +1 x0,y0 is beneath line segment
**
** 0 x0,y0 is not on or beneath the line segment or the line segment
** is vertical and x0,y0 is not on the line segment
**
** The left-most coordinate min(x1,x2) is not considered to be part of
** the line segment for the purposes of this analysis.
*/
static int pointBeneathLine(
double x0, double y0,
double x1, double y1,
double x2, double y2
){
double y;
if( x0==x1 && y0==y1 ) return 2;
if( x1<x2 ){
if( x0<=x1 || x0>x2 ) return 0;
}else if( x1>x2 ){
if( x0<=x2 || x0>x1 ) return 0;
}else{
/* Vertical line segment */
if( x0!=x1 ) return 0;
if( y0<y1 && y0<y2 ) return 0;
if( y0>y1 && y0>y2 ) return 0;
return 2;
}
y = y1 + (y2-y1)*(x0-x1)/(x2-x1);
if( y0==y ) return 2;
if( y0<y ) return 1;
return 0;
}
/*
** SQL function: geopoly_within(P,X,Y)
**
** Return +2 if point X,Y is within polygon P.
** Return +1 if point X,Y is on the polygon boundary.
** Return 0 if point X,Y is outside the polygon
*/
static void geopolyWithinFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p = geopolyFuncParam(context, argv[0]);
double x0 = sqlite3_value_double(argv[1]);
double y0 = sqlite3_value_double(argv[2]);
if( p ){
int v = 0;
int cnt = 0;
int ii;
for(ii=0; ii<p->nVertex-1; ii++){
v = pointBeneathLine(x0,y0,p->a[ii*2],p->a[ii*2+1],
p->a[ii*2+2],p->a[ii*2+3]);
if( v==2 ) break;
cnt += v;
}
if( v!=2 ){
v = pointBeneathLine(x0,y0,p->a[ii*2],p->a[ii*2+1],
p->a[0],p->a[1]);
}
if( v==2 ){
sqlite3_result_int(context, 1);
}else if( ((v+cnt)&1)==0 ){
sqlite3_result_int(context, 0);
}else{
sqlite3_result_int(context, 2);
}
sqlite3_free(p);
}
}
/* Objects used by the overlap algorihm. */
typedef struct GeoEvent GeoEvent;
typedef struct GeoSegment GeoSegment;
typedef struct GeoOverlap GeoOverlap;
struct GeoEvent {
double x; /* X coordinate at which event occurs */
int eType; /* 0 for ADD, 1 for REMOVE */
GeoSegment *pSeg; /* The segment to be added or removed */
GeoEvent *pNext; /* Next event in the sorted list */
};
struct GeoSegment {
double C, B; /* y = C*x + B */
double y; /* Current y value */
float y0; /* Initial y value */
unsigned char side; /* 1 for p1, 2 for p2 */
unsigned int idx; /* Which segment within the side */
GeoSegment *pNext; /* Next segment in a list sorted by y */
};
struct GeoOverlap {
GeoEvent *aEvent; /* Array of all events */
GeoSegment *aSegment; /* Array of all segments */
int nEvent; /* Number of events */
int nSegment; /* Number of segments */
};
/*
** Add a single segment and its associated events.
*/
static void geopolyAddOneSegment(
GeoOverlap *p,
GeoCoord x0,
GeoCoord y0,
GeoCoord x1,
GeoCoord y1,
unsigned char side,
unsigned int idx
){
GeoSegment *pSeg;
GeoEvent *pEvent;
if( x0==x1 ) return; /* Ignore vertical segments */
if( x0>x1 ){
GeoCoord t = x0;
x0 = x1;
x1 = t;
t = y0;
y0 = y1;
y1 = t;
}
pSeg = p->aSegment + p->nSegment;
p->nSegment++;
pSeg->C = (y1-y0)/(x1-x0);
pSeg->B = y1 - x1*pSeg->C;
pSeg->y0 = y0;
pSeg->side = side;
pSeg->idx = idx;
pEvent = p->aEvent + p->nEvent;
p->nEvent++;
pEvent->x = x0;
pEvent->eType = 0;
pEvent->pSeg = pSeg;
pEvent = p->aEvent + p->nEvent;
p->nEvent++;
pEvent->x = x1;
pEvent->eType = 1;
pEvent->pSeg = pSeg;
}
/*
** Insert all segments and events for polygon pPoly.
*/
static void geopolyAddSegments(
GeoOverlap *p, /* Add segments to this Overlap object */
GeoPoly *pPoly, /* Take all segments from this polygon */
unsigned char side /* The side of pPoly */
){
unsigned int i;
GeoCoord *x;
for(i=0; i<pPoly->nVertex-1; i++){
x = pPoly->a + (i*2);
geopolyAddOneSegment(p, x[0], x[1], x[2], x[3], side, i);
}
x = pPoly->a + (i*2);
geopolyAddOneSegment(p, x[0], x[1], pPoly->a[0], pPoly->a[1], side, i);
}
/*
** Merge two lists of sorted events by X coordinate
*/
static GeoEvent *geopolyEventMerge(GeoEvent *pLeft, GeoEvent *pRight){
GeoEvent head, *pLast;
head.pNext = 0;
pLast = &head;
while( pRight && pLeft ){
if( pRight->x <= pLeft->x ){
pLast->pNext = pRight;
pLast = pRight;
pRight = pRight->pNext;
}else{
pLast->pNext = pLeft;
pLast = pLeft;
pLeft = pLeft->pNext;
}
}
pLast->pNext = pRight ? pRight : pLeft;
return head.pNext;
}
/*
** Sort an array of nEvent event objects into a list.
*/
static GeoEvent *geopolySortEventsByX(GeoEvent *aEvent, int nEvent){
int mx = 0;
int i, j;
GeoEvent *p;
GeoEvent *a[50];
for(i=0; i<nEvent; i++){
p = &aEvent[i];
p->pNext = 0;
for(j=0; j<mx && a[j]; j++){
p = geopolyEventMerge(a[j], p);
a[j] = 0;
}
a[j] = p;
if( j>=mx ) mx = j+1;
}
p = 0;
for(i=0; i<mx; i++){
p = geopolyEventMerge(a[i], p);
}
return p;
}
/*
** Merge two lists of sorted segments by Y, and then by C.
*/
static GeoSegment *geopolySegmentMerge(GeoSegment *pLeft, GeoSegment *pRight){
GeoSegment head, *pLast;
head.pNext = 0;
pLast = &head;
while( pRight && pLeft ){
double r = pRight->y - pLeft->y;
if( r==0.0 ) r = pRight->C - pLeft->C;
if( r<0.0 ){
pLast->pNext = pRight;
pLast = pRight;
pRight = pRight->pNext;
}else{
pLast->pNext = pLeft;
pLast = pLeft;
pLeft = pLeft->pNext;
}
}
pLast->pNext = pRight ? pRight : pLeft;
return head.pNext;
}
/*
** Sort a list of GeoSegments in order of increasing Y and in the event of
** a tie, increasing C (slope).
*/
static GeoSegment *geopolySortSegmentsByYAndC(GeoSegment *pList){
int mx = 0;
int i;
GeoSegment *p;
GeoSegment *a[50];
while( pList ){
p = pList;
pList = pList->pNext;
p->pNext = 0;
for(i=0; i<mx && a[i]; i++){
p = geopolySegmentMerge(a[i], p);
a[i] = 0;
}
a[i] = p;
if( i>=mx ) mx = i+1;
}
p = 0;
for(i=0; i<mx; i++){
p = geopolySegmentMerge(a[i], p);
}
return p;
}
/*
** Determine the overlap between two polygons
*/
static int geopolyOverlap(GeoPoly *p1, GeoPoly *p2){
int nVertex = p1->nVertex + p2->nVertex + 2;
GeoOverlap *p;
int nByte;
GeoEvent *pThisEvent;
double rX;
int rc = 0;
int needSort = 0;
GeoSegment *pActive = 0;
GeoSegment *pSeg;
unsigned char aOverlap[4];
nByte = sizeof(GeoEvent)*nVertex*2
+ sizeof(GeoSegment)*nVertex
+ sizeof(GeoOverlap);
p = sqlite3_malloc( nByte );
if( p==0 ) return -1;
p->aEvent = (GeoEvent*)&p[1];
p->aSegment = (GeoSegment*)&p->aEvent[nVertex*2];
p->nEvent = p->nSegment = 0;
geopolyAddSegments(p, p1, 1);
geopolyAddSegments(p, p2, 2);
pThisEvent = geopolySortEventsByX(p->aEvent, p->nEvent);
rX = pThisEvent->x==0.0 ? -1.0 : 0.0;
memset(aOverlap, 0, sizeof(aOverlap));
while( pThisEvent ){
if( pThisEvent->x!=rX ){
GeoSegment *pPrev = 0;
int iMask = 0;
GEODEBUG(("Distinct X: %g\n", pThisEvent->x));
rX = pThisEvent->x;
if( needSort ){
GEODEBUG(("SORT\n"));
pActive = geopolySortSegmentsByYAndC(pActive);
needSort = 0;
}
for(pSeg=pActive; pSeg; pSeg=pSeg->pNext){
if( pPrev ){
if( pPrev->y!=pSeg->y ){
GEODEBUG(("MASK: %d\n", iMask));
aOverlap[iMask] = 1;
}
}
iMask ^= pSeg->side;
pPrev = pSeg;
}
pPrev = 0;
for(pSeg=pActive; pSeg; pSeg=pSeg->pNext){
double y = pSeg->C*rX + pSeg->B;
GEODEBUG(("Segment %d.%d %g->%g\n", pSeg->side, pSeg->idx, pSeg->y, y));
pSeg->y = y;
if( pPrev ){
if( pPrev->y>pSeg->y && pPrev->side!=pSeg->side ){
rc = 1;
GEODEBUG(("Crossing: %d.%d and %d.%d\n",
pPrev->side, pPrev->idx,
pSeg->side, pSeg->idx));
goto geopolyOverlapDone;
}else if( pPrev->y!=pSeg->y ){
GEODEBUG(("MASK: %d\n", iMask));
aOverlap[iMask] = 1;
}
}
iMask ^= pSeg->side;
pPrev = pSeg;
}
}
GEODEBUG(("%s %d.%d C=%g B=%g\n",
pThisEvent->eType ? "RM " : "ADD",
pThisEvent->pSeg->side, pThisEvent->pSeg->idx,
pThisEvent->pSeg->C,
pThisEvent->pSeg->B));
if( pThisEvent->eType==0 ){
/* Add a segment */
pSeg = pThisEvent->pSeg;
pSeg->y = pSeg->y0;
pSeg->pNext = pActive;
pActive = pSeg;
needSort = 1;
}else{
/* Remove a segment */
if( pActive==pThisEvent->pSeg ){
pActive = pActive->pNext;
}else{
for(pSeg=pActive; pSeg; pSeg=pSeg->pNext){
if( pSeg->pNext==pThisEvent->pSeg ){
pSeg->pNext = pSeg->pNext->pNext;
break;
}
}
}
}
pThisEvent = pThisEvent->pNext;
}
if( aOverlap[3]==0 ){
rc = 0;
}else if( aOverlap[1]!=0 && aOverlap[2]==0 ){
rc = 3;
}else if( aOverlap[1]==0 && aOverlap[2]!=0 ){
rc = 2;
}else if( aOverlap[1]==0 && aOverlap[2]==0 ){
rc = 4;
}else{
rc = 1;
}
geopolyOverlapDone:
sqlite3_free(p);
return rc;
}
/*
** SQL function: geopoly_overlap(P1,P2)
**
** Determine whether or not P1 and P2 overlap. Return value:
**
** 0 The two polygons are disjoint
** 1 They overlap
** 2 P1 is completely contained within P2
** 3 P2 is completely contained within P1
** 4 P1 and P2 are the same polygon
** NULL Either P1 or P2 or both are not valid polygons
*/
static void geopolyOverlapFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
GeoPoly *p1 = geopolyFuncParam(context, argv[0]);
GeoPoly *p2 = geopolyFuncParam(context, argv[1]);
if( p1 && p2 ){
int x = geopolyOverlap(p1, p2);
if( x<0 ){
sqlite3_result_error_nomem(context);
}else{
sqlite3_result_int(context, x);
}
}
sqlite3_free(p1);
sqlite3_free(p2);
}
/*
** Enable or disable debugging output
*/
static void geopolyDebugFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
#ifdef GEOPOLY_ENABLE_DEBUG
geo_debug = sqlite3_value_int(argv[0]);
#endif
}
static int sqlite3_geopoly_init(sqlite3 *db){
int rc = SQLITE_OK;
static const struct {
void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
int nArg;
const char *zName;
} aFunc[] = {
{ geopolyAreaFunc, 1, "geopoly_area" },
{ geopolyBlobFunc, 1, "geopoly_blob" },
{ geopolyJsonFunc, 1, "geopoly_json" },
{ geopolySvgFunc, -1, "geopoly_svg" },
{ geopolyWithinFunc, 3, "geopoly_within" },
{ geopolyOverlapFunc, 2, "geopoly_overlap" },
{ geopolyDebugFunc, 1, "geopoly_debug" },
};
int i;
for(i=0; i<sizeof(aFunc)/sizeof(aFunc[0]) && rc==SQLITE_OK; i++){
rc = sqlite3_create_function(db, aFunc[i].zName, aFunc[i].nArg,
SQLITE_UTF8, 0,
aFunc[i].xFunc, 0, 0);
}
return rc;
}
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