package mil.nga.giat.geowave.index.sfc.zorder;
import java.util.BitSet;
import mil.nga.giat.geowave.index.sfc.SFCDimensionDefinition;
import mil.nga.giat.geowave.index.sfc.data.NumericRange;
/**
* Convenience methods used to decode/encode Z-Order space filling curve values
* (using a simple bit-interleaving approach).
*
*/
public class ZOrderUtils
{
public static NumericRange[] decodeRanges(
final byte[] bytes,
final int bitsPerDimension,
final SFCDimensionDefinition[] dimensionDefinitions ) {
final byte[] littleEndianBytes = swapEndianFormat(bytes);
final BitSet bitSet = BitSet.valueOf(littleEndianBytes);
final NumericRange[] normalizedValues = new NumericRange[dimensionDefinitions.length];
for (int d = 0; d < dimensionDefinitions.length; d++) {
final BitSet dimensionSet = new BitSet();
int j = 0;
for (int i = d; i < (bitsPerDimension * dimensionDefinitions.length); i += dimensionDefinitions.length) {
dimensionSet.set(
j++,
bitSet.get(i));
}
normalizedValues[d] = decode(
dimensionSet,
0,
1,
dimensionDefinitions[d]);
}
return normalizedValues;
}
public static long[] decodeIndices(
final byte[] bytes,
final int bitsPerDimension,
final int numDimensions ) {
final byte[] littleEndianBytes = swapEndianFormat(bytes);
final BitSet bitSet = BitSet.valueOf(littleEndianBytes);
final long[] coordinates = new long[numDimensions];
final long rangePerDimension = (long) Math.pow(
2,
bitsPerDimension);
for (int d = 0; d < numDimensions; d++) {
final BitSet dimensionSet = new BitSet();
int j = 0;
for (int i = d; i < (bitsPerDimension * numDimensions); i += numDimensions) {
dimensionSet.set(
j++,
bitSet.get(i));
}
coordinates[d] = decodeIndex(
dimensionSet,
rangePerDimension);
}
return coordinates;
}
private static long decodeIndex(
final BitSet bs,
final long rangePerDimension ) {
long floor = 0;
long ceiling = rangePerDimension;
long mid = 0;
for (int i = 0; i < bs.length(); i++) {
mid = (floor + ceiling) / 2;
if (bs.get(i)) {
floor = mid;
}
else {
ceiling = mid;
}
}
return mid;
}
private static NumericRange decode(
final BitSet bs,
double floor,
double ceiling,
final SFCDimensionDefinition dimensionDefinition ) {
double mid = 0;
for (int i = 0; i < bs.length(); i++) {
mid = (floor + ceiling) / 2;
if (bs.get(i)) {
floor = mid;
}
else {
ceiling = mid;
}
}
return new NumericRange(
dimensionDefinition.denormalize(floor),
dimensionDefinition.denormalize(ceiling));
}
public static byte[] encode(
final double[] normalizedValues,
final int bitsPerDimension,
final int numDimensions ) {
final BitSet[] bitSets = new BitSet[numDimensions];
for (int d = 0; d < numDimensions; d++) {
bitSets[d] = getBits(
normalizedValues[d],
0,
1,
bitsPerDimension);
}
final BitSet combinedBitSet = new BitSet(
bitsPerDimension * numDimensions);
int j = 0;
for (int i = 0; i < bitsPerDimension; i++) {
for (int d = 0; d < numDimensions; d++) {
combinedBitSet.set(
j++,
bitSets[d].get(i));
}
}
final byte[] littleEndianBytes = combinedBitSet.toByteArray();
return swapEndianFormat(littleEndianBytes);
}
public static byte[] swapEndianFormat(
final byte[] b ) {
final byte[] endianSwappedBytes = new byte[b.length];
for (int i = 0; i < b.length; i++) {
endianSwappedBytes[i] = swapEndianFormat(b[i]);
}
return endianSwappedBytes;
}
private static byte swapEndianFormat(
final byte b ) {
int converted = 0x00;
converted ^= (b & 0b1000_0000) >> 7;
converted ^= (b & 0b0100_0000) >> 5;
converted ^= (b & 0b0010_0000) >> 3;
converted ^= (b & 0b0001_0000) >> 1;
converted ^= (b & 0b0000_1000) << 1;
converted ^= (b & 0b0000_0100) << 3;
converted ^= (b & 0b0000_0010) << 5;
converted ^= (b & 0b0000_0001) << 7;
return (byte) (converted & 0xFF);
}
private static BitSet getBits(
final double value,
double floor,
double ceiling,
final int bitsPerDimension ) {
final BitSet buffer = new BitSet(
bitsPerDimension);
for (int i = 0; i < bitsPerDimension; i++) {
final double mid = (floor + ceiling) / 2;
if (value >= mid) {
buffer.set(i);
floor = mid;
}
else {
ceiling = mid;
}
}
return buffer;
}
}