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Fix variable-byte encoding of large longs #61

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Merged
merged 1 commit into from
Oct 4, 2025
Merged

Fix variable-byte encoding of large longs #61

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4 changes: 2 additions & 2 deletions src/main/java/me/lemire/longcompression/LongVariableByte.java
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ public void headlessCompress(long[] in, IntWrapper inpos, int inlength, long[] o
buf.put((byte) extract7bits(5, val));
buf.put((byte) extract7bits(6, val));
buf.put((byte) (extract7bitsmaskless(7, (val)) | (1 << 7)));
} else if (val >= 0 && val < (1L << 63)) {
} else if (val >= 0) {
buf.put((byte) extract7bits(0, val));
buf.put((byte) extract7bits(1, val));
buf.put((byte) extract7bits(2, val));
Expand Down Expand Up @@ -175,7 +175,7 @@ public void compress(long[] in, IntWrapper inpos, int inlength, byte[] out,
out[outpostmp++] = (byte) extract7bits(5, val);
out[outpostmp++] = (byte) extract7bits(6, val);
out[outpostmp++] = (byte) (extract7bitsmaskless(7, (val)) | (1 << 7));
} else if (val >= 0 && val < (1L << 63)) {
} else if (val >= 0) {
out[outpostmp++] = (byte) extract7bits(0, val);
out[outpostmp++] = (byte) extract7bits(1, val);
out[outpostmp++] = (byte) extract7bits(2, val);
Expand Down
18 changes: 12 additions & 6 deletions src/test/java/me/lemire/longcompression/TestLongVariableByte.java
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Expand Up @@ -24,11 +24,17 @@ public LongCODEC getCodec() {
}

@Test
public void testCodec_intermediateHighPowerOfTwo() {
Assert.assertEquals(1, LongTestUtils.compress((LongCODEC) codec, new long[] { 1L << 42 }).length);
Assert.assertEquals(7, LongTestUtils.compress((ByteLongCODEC) codec, new long[] { 1L << 42 }).length);
Assert.assertEquals(1,
LongTestUtils.compressHeadless((SkippableLongCODEC) codec, new long[] { 1L << 42 }).length);
}
public void testCodec_allBitWidths() {
for (int bitWidth = 0; bitWidth <= 64; bitWidth++) {
long value = bitWidth == 0 ? 0 : 1L << (bitWidth - 1);

int expectedSizeInBytes = Math.max(1, (bitWidth + 6) / 7);
int expectedSizeInLongs = (expectedSizeInBytes > 8) ? 2 : 1;

Assert.assertEquals(expectedSizeInLongs, LongTestUtils.compress((LongCODEC) codec, new long[] { value }).length);
Assert.assertEquals(expectedSizeInBytes, LongTestUtils.compress((ByteLongCODEC) codec, new long[] { value }).length);
Assert.assertEquals(expectedSizeInLongs,
LongTestUtils.compressHeadless((SkippableLongCODEC) codec, new long[] { value }).length);
}
}
}