iverase commented on code in PR #12625:
URL: https://github.com/apache/lucene/pull/12625#discussion_r1358473230
##########
lucene/core/src/java/org/apache/lucene/index/TermsHashPerField.java:
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@@ -255,6 +255,81 @@ final void writeBytes(int stream, byte[] b, int offset,
int len) {
}
}
+ // Size of each slice. These arrays should be at most 16
+ // elements (index is encoded with 4 bits). First array
+ // is just a compact way to encode X+1 with a max. Second
+ // array is the length of each slice, ie first slice is 5
+ // bytes, next slice is 14 bytes, etc.
+
+ /**
+ * An array holding the offset into the {@link #LEVEL_SIZE_ARRAY} to quickly
navigate to the next
+ * slice level.
+ */
+ static final int[] NEXT_LEVEL_ARRAY = {1, 2, 3, 4, 5, 6, 7, 8, 9, 9};
+
+ /** An array holding the level sizes for byte slices. */
+ static final int[] LEVEL_SIZE_ARRAY = {5, 14, 20, 30, 40, 40, 80, 80, 120,
200};
+
+ /** The first level size for new slices */
+ static final int FIRST_LEVEL_SIZE = LEVEL_SIZE_ARRAY[0];
+
+ /**
+ * Allocates a new slice with the given size. As each slice is filled with
0's initially, we mark
+ * the end with a non-zero byte. This way we don't need to record its length
and instead allocate
+ * new slice once they hit a non-zero byte.
+ */
+ // pkg private for access by tests
+ static int newSlice(ByteBlockPool bytePool, final int size, final int level)
{
+ assert LEVEL_SIZE_ARRAY[level] == size;
Review Comment:
I think it is just a micro optimization to avoid looking twice into the
array. This is a copy paste of the original code.
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