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Fix overflow error in parsing of long geohashes #29418

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merged 2 commits into from
Apr 16, 2018
Merged

Fix overflow error in parsing of long geohashes #29418

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8e7b895
Fix overflow error in parsing of long geohashes
imotov Apr 6, 2018
474eaa6
Add a note about geohash precision limitations
imotov Apr 10, 2018
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19 changes: 14 additions & 5 deletions server/src/main/java/org/elasticsearch/common/geo/GeoHashUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -72,15 +72,19 @@ public static final long longEncode(final double lon, final double lat, final in
/**
* Encode from geohash string to the geohash based long format (lon/lat interleaved, 4 least significant bits = level)
*/
public static final long longEncode(final String hash) {
int level = hash.length()-1;
private static long longEncode(final String hash, int length) {
int level = length - 1;
long b;
long l = 0L;
for(char c : hash.toCharArray()) {
b = (long)(BASE_32_STRING.indexOf(c));
l |= (b<<(level--*5));
if (level < 0) {
// We cannot handle more than 12 levels
break;
}
}
return (l<<4)|hash.length();
return (l << 4) | length;
}

/**
Expand Down Expand Up @@ -173,6 +177,10 @@ public static final long mortonEncode(final String hash) {
for(char c : hash.toCharArray()) {
b = (long)(BASE_32_STRING.indexOf(c));
l |= (b<<((level--*5) + MORTON_OFFSET));
if (level < 0) {
// We cannot handle more than 12 levels
break;
}
}
return BitUtil.flipFlop(l);
}
Expand Down Expand Up @@ -200,13 +208,14 @@ private static char encode(int x, int y) {
public static Rectangle bbox(final String geohash) {
// bottom left is the coordinate
GeoPoint bottomLeft = GeoPoint.fromGeohash(geohash);
long ghLong = longEncode(geohash);
int len = Math.min(12, geohash.length());
long ghLong = longEncode(geohash, len);
// shift away the level
ghLong >>>= 4;
// deinterleave and add 1 to lat and lon to get topRight
long lat = BitUtil.deinterleave(ghLong >>> 1) + 1;
long lon = BitUtil.deinterleave(ghLong) + 1;
GeoPoint topRight = GeoPoint.fromGeohash(BitUtil.interleave((int)lon, (int)lat) << 4 | geohash.length());
GeoPoint topRight = GeoPoint.fromGeohash(BitUtil.interleave((int)lon, (int)lat) << 4 | len);

return new Rectangle(bottomLeft.lat(), topRight.lat(), bottomLeft.lon(), topRight.lon());
}
Expand Down
16 changes: 16 additions & 0 deletions server/src/test/java/org/elasticsearch/common/geo/GeoHashTests.java
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Expand Up @@ -82,4 +82,20 @@ public void testGeohashExtremes() {
assertEquals("xbpbpbpbpbpb", GeoHashUtils.stringEncode(180, 0));
assertEquals("zzzzzzzzzzzz", GeoHashUtils.stringEncode(180, 90));
}

public void testLongGeohashes() {
for (int i = 0; i < 100000; i++) {
String geohash = randomGeohash(12, 12);
GeoPoint expected = GeoPoint.fromGeohash(geohash);
// Adding some random geohash characters at the end
String extendedGeohash = geohash + randomGeohash(1, 10);
GeoPoint actual = GeoPoint.fromGeohash(extendedGeohash);
assertEquals("Additional data points above 12 should be ignored [" + extendedGeohash + "]" , expected, actual);

Rectangle expectedBbox = GeoHashUtils.bbox(geohash);
Rectangle actualBbox = GeoHashUtils.bbox(extendedGeohash);
assertEquals("Additional data points above 12 should be ignored [" + extendedGeohash + "]" , expectedBbox, actualBbox);

}
}
}