jasonk000 commented on a change in pull request #11721:
URL: https://github.com/apache/kafka/pull/11721#discussion_r801255679
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File path: clients/src/main/java/org/apache/kafka/common/utils/ByteUtils.java
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@@ -386,18 +386,39 @@ public static void writeDouble(double value, ByteBuffer
buffer) {
buffer.putDouble(value);
}
+ final static int[] LEADING_ZEROS_TO_U_VARINT_SIZE = new int[] {
+ // 32 bits, and each 7-bits adds one byte to the output
+ 5, 5, 5, 5, // 32
+ 4, 4, 4, 4, 4, 4, 4, // 28
+ 3, 3, 3, 3, 3, 3, 3, // 21
+ 2, 2, 2, 2, 2, 2, 2, // 14
+ 1, 1, 1, 1, 1, 1, 1, // 7
+ 1 // 0
+ };
+
+ final static int[] LEADING_ZEROS_TO_U_VARLONG_SIZE = new int[] {
+ // 64 bits, and each 7-bits adds one byte to the output
+ 10, // 64
+ 9, 9, 9, 9, 9, 9, 9, // 63
+ 8, 8, 8, 8, 8, 8, 8, // 56
+ 7, 7, 7, 7, 7, 7, 7, // 49
+ 6, 6, 6, 6, 6, 6, 6, // 42
+ 5, 5, 5, 5, 5, 5, 5, // 35
+ 4, 4, 4, 4, 4, 4, 4, // 28
+ 3, 3, 3, 3, 3, 3, 3, // 21
+ 2, 2, 2, 2, 2, 2, 2, // 14
+ 1, 1, 1, 1, 1, 1, 1, // 7
+ 1 // 0
+ };
+
/**
* Number of bytes needed to encode an integer in unsigned variable-length
format.
*
* @param value The signed value
*/
public static int sizeOfUnsignedVarint(int value) {
- int bytes = 1;
- while ((value & 0xffffff80) != 0L) {
- bytes += 1;
- value >>>= 7;
- }
- return bytes;
+ int leadingZeros = Integer.numberOfLeadingZeros(value);
+ return LEADING_ZEROS_TO_U_VARINT_SIZE[leadingZeros];
Review comment:
I like your approach here, and it's something that _should_ be possible,
but, I don't see it being applied, the below still includes the cmp/mov
```
final static byte[] LEADING_ZEROS_TO_U_VARINT_SIZE = new byte[4096];
```
Byte is -127 to +128 in Java, so 4096 should be plenty.
```
byte leadingZeros = (byte) Integer.numberOfLeadingZeros(inputInt);
return LEADING_ZEROS_TO_U_VARINT_SIZE[leadingZeros];
````
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