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Fix theta preamble count for legacy single-item images #774

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Merged
leerho merged 1 commit into from
Oct 1, 2026
Merged

Fix theta preamble count for legacy single-item images #774

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2 changes: 1 addition & 1 deletion src/main/java/org/apache/datasketches/theta/PreambleUtil.java
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Original file line number Diff line number Diff line change
Expand Up @@ -278,7 +278,7 @@ static String preambleToString(final MemorySegment seg) {
final int seedHash = extractSeedHash(seg);

//assumes preLongs == 1; empty or singleItem
int curCount = singleItem ? 1 : 0;
int curCount = empty ? 0 : 1;
float p = (float) 1.0; //preLongs 1 or 2
long thetaLong = Long.MAX_VALUE; //preLongs 1 or 2
long thetaULong = thetaLong; //preLongs 1, 2 or 3
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10 changes: 10 additions & 0 deletions src/test/java/org/apache/datasketches/theta/PreambleUtilTest.java
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Expand Up @@ -106,6 +106,16 @@ public void checkToStringWithPrelongsOf2() {
println(ThetaSketch.toString(bytes));
}

@Test
public void checkHistoricalSingleItemToString() {
final byte[] bytes = SingleItemSketch.create(1).toByteArray();
bytes[5] &= (byte) ~PreambleUtil.SINGLEITEM_FLAG_MASK;

final String summary = PreambleUtil.preambleToString(bytes);
assertTrue(summary.contains(" 5 SINGLE_ITEM : false"));
assertTrue(summary.contains("Bytes 8-11 : CurrentCount : 1"));
}

@Test
public void checkPreambleToStringExceptions() {
byte[] byteArr = new byte[7];
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