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More efficient parsing of UUIDs from strings #192

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merged 2 commits into from
Jun 8, 2020
Merged

More efficient parsing of UUIDs from strings #192

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3e6282c
More efficient parsing of UUIDs from strings
plokhotnyuk Jun 6, 2020
7956ad6
Fix inefficiency of RNG-based benchmarks
plokhotnyuk Jun 6, 2020
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13 changes: 5 additions & 8 deletions bench/src/main/scala/UUIDBench.scala
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Original file line number Diff line number Diff line change
@@ -1,26 +1,22 @@
package memeid4s.bench

import java.util.concurrent.ThreadLocalRandom
import java.util.concurrent.TimeUnit

import scala.util.Random

import memeid4s.UUID
import org.openjdk.jmh.annotations._

object UUIDStates {
val namespace = UUID.V1.next

val gen = new Random()

@SuppressWarnings(Array("scalafix:Disable.toString"))
val uuids: List[String] = (1 to 100).map(_ => UUID.V1.next.toString).toList
val uuids: Array[String] = (1 to 100).map(_ => UUID.V1.next.toString).toArray

@State(Scope.Benchmark)
class RNG {

def uuid: String =
uuids(gen.nextInt(uuids.length))
def uuid: String = uuids(ThreadLocalRandom.current().nextInt(uuids.length))
}

}

@Warmup(
Expand All @@ -34,6 +30,7 @@ object UUIDStates {
timeUnit = TimeUnit.SECONDS
)
class UUIDBenchmark {

import UUIDStates._

@Benchmark
Expand Down
81 changes: 65 additions & 16 deletions memeid/src/main/java/memeid/UUID.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@
import java.util.Optional;
import java.util.function.Function;
import java.util.function.LongSupplier;
import java.util.regex.Pattern;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static memeid.Bits.*;
Expand All @@ -34,7 +33,33 @@
* @see <a href="https://tools.ietf.org/html/rfc4122">RFC-4122</a>
*/
public class UUID implements Comparable<UUID> {
public static final Pattern uuidRegex = Pattern.compile("\\p{XDigit}{8}-\\p{XDigit}{4}-\\p{XDigit}{4}-\\p{XDigit}{4}-\\p{XDigit}{12}");
public static final byte [] nibbles = new byte[256];

static {
java.util.Arrays.fill(nibbles, (byte) -1);
nibbles['0'] = 0;
nibbles['1'] = 1;
nibbles['2'] = 2;
nibbles['3'] = 3;
nibbles['4'] = 4;
nibbles['5'] = 5;
nibbles['6'] = 6;
nibbles['7'] = 7;
nibbles['8'] = 8;
nibbles['9'] = 9;
nibbles['A'] = 10;
nibbles['B'] = 11;
nibbles['C'] = 12;
nibbles['D'] = 13;
nibbles['E'] = 14;
nibbles['F'] = 15;
nibbles['a'] = 10;
nibbles['b'] = 11;
nibbles['c'] = 12;
nibbles['d'] = 13;
nibbles['e'] = 14;
nibbles['f'] = 15;
}

/**
* The nil UUID is special form of UUID that is specified to have all 128 bits set to zero.
Expand Down Expand Up @@ -62,16 +87,15 @@ public static UUID from(long msb, long lsb) {
* @return a valid {@link UUID} created from a {@link java.util.UUID}
*/
public static UUID fromUUID(java.util.UUID juuid) {
if (juuid.version() == 0 && juuid == NIL.juuid)
return NIL;

if (juuid.version() == 1) return new V1(juuid);
if (juuid.version() == 2) return new V2(juuid);
if (juuid.version() == 3) return new V3(juuid);
if (juuid.version() == 4) return new V4(juuid);
if (juuid.version() == 5) return new V5(juuid);

return new UnknownVersion(juuid);
switch(juuid.version()) {
case 5: return new V5(juuid);
case 4: return new V4(juuid);
case 3: return new V3(juuid);
case 2: return new V2(juuid);
case 1: return new V1(juuid);
case 0: if (juuid == NIL.juuid) return NIL;
default: return new UnknownVersion(juuid);
}
}

/**
Expand All @@ -84,10 +108,35 @@ public static UUID fromUUID(java.util.UUID juuid) {
* described in {@link #toString}
*/
public static UUID fromString(String name) {
if (uuidRegex.matcher(name).matches())
return fromUUID(java.util.UUID.fromString(name));
else
throw new IllegalArgumentException("Invalid UUID string: " + name);
byte[] ns = nibbles;
if (name.length() == 36 &&
name.charAt(8) == '-' &&
name.charAt(13) == '-' &&
name.charAt(18) == '-' &&
name.charAt(23) == '-') {
int msb1 = parse4Nibbles(name, ns, 0);
int msb2 = parse4Nibbles(name, ns, 4);
int msb3 = parse4Nibbles(name, ns, 9);
int msb4 = parse4Nibbles(name, ns, 14);
if ((msb1 | msb2 | msb3 | msb4) >= 0) {
int lsb1 = parse4Nibbles(name, ns, 19);
int lsb2 = parse4Nibbles(name, ns, 24);
int lsb3 = parse4Nibbles(name, ns, 28);
int lsb4 = parse4Nibbles(name, ns, 32);
if ((lsb1 | lsb2 | lsb3 | lsb4) >= 0) return from(
(long) msb1 << 48 | (long) msb2 << 32 | (long) msb3 << 16 | msb4,
(long) lsb1 << 48 | (long) lsb2 << 32 | (long) lsb3 << 16 | lsb4);
}
}
throw new IllegalArgumentException("Invalid UUID string: " + name);
}

private static int parse4Nibbles(String name, byte[] ns, int pos) {
char ch1 = name.charAt(pos);
char ch2 = name.charAt(pos + 1);
char ch3 = name.charAt(pos + 2);
char ch4 = name.charAt(pos + 3);
return (ch1 | ch2 | ch3 | ch4) > 0xFF ? -1 : ns[ch1] << 12 | ns[ch2] << 8 | ns[ch3] << 4 | ns[ch4];
}

/**
Expand Down