Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/7533#discussion_r35181937
--- Diff:
unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java ---
@@ -352,6 +352,69 @@ public int indexOf(UTF8String v, int start) {
return -1;
}
+ private enum ByteType {FIRSTBYTE, MIDBYTE, SINGLEBYTECHAR};
+
+ private ByteType checkByteType(Byte b) {
+ int firstTwoBits = (b >>> 6) & 0x03;
+ if (firstTwoBits == 3) {
+ return ByteType.FIRSTBYTE;
+ } else if (firstTwoBits == 2) {
+ return ByteType.MIDBYTE;
+ } else {
+ return ByteType.SINGLEBYTECHAR;
+ }
+ }
+
+ /**
+ * Return the first byte position for a given byte which shared the same
code point.
+ * @param bytePos any byte within the code point
+ * @return the first byte position of a given code point, throw
exception if not a valid UTF8 str
+ */
+ private int firstOfCurrentCodePoint(int bytePos) {
+ while (bytePos >= 0) {
+ if (ByteType.FIRSTBYTE == checkByteType(getByte(bytePos))
+ || ByteType.SINGLEBYTECHAR == checkByteType(getByte(bytePos))) {
+ return bytePos;
+ }
+ bytePos--;
+ }
+ throw new RuntimeException("Invalid utf8 string");
+ }
+
+ private int indexEnd(int startCodePoint) {
+ int i = numBytes -1; // position in byte
+ int c = numChars() - 1; // position in character
--- End diff --
`numChars()` is actually very expensive. as the `indexEnd` (or
`lastIndexOf`) will be called multiple times for the `substring_index`, we need
to think about how to optimize that by removing the function calls.
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