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UUID.fromString improvement to be more efficient when parsing 36-byte valid values #4

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UUID.fromString improvement to be more efficient when parsing 36-byte valid values #4

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70 changes: 70 additions & 0 deletions src/java.base/share/classes/java/util/UUID.java
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,34 @@ public final class UUID implements java.io.Serializable, Comparable<UUID> {

private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();

private static final byte[] nibbles = new byte[256];

static {
byte[] ns = nibbles;
java.util.Arrays.fill(ns, (byte) -1);
ns['0'] = 0;
ns['1'] = 1;
ns['2'] = 2;
ns['3'] = 3;
ns['4'] = 4;
ns['5'] = 5;
ns['6'] = 6;
ns['7'] = 7;
ns['8'] = 8;
ns['9'] = 9;
ns['A'] = 10;
ns['B'] = 11;
ns['C'] = 12;
ns['D'] = 13;
ns['E'] = 14;
ns['F'] = 15;
ns['a'] = 10;
ns['b'] = 11;
ns['c'] = 12;
ns['d'] = 13;
ns['e'] = 14;
ns['f'] = 15;
}
/*
* The random number generator used by this class to create random
* based UUIDs. In a holder class to defer initialization until needed.
Expand Down Expand Up @@ -195,6 +223,48 @@ public static UUID nameUUIDFromBytes(byte[] name) {
*
*/
public static UUID fromString(String name) {
byte[] ns = nibbles;
long msb;
long lsb;
if (name.length() == 36) {
char ch1 = name.charAt(8);
char ch2 = name.charAt(13);
char ch3 = name.charAt(18);
char ch4 = name.charAt(23);
if (((((long) ch1) << 48) | (((long) ch2) << 32) |
(((long) ch3) << 16) | ch4) == 0x2d002d002d002dL) {
long msb1 = parse4Nibbles(name, ns, 0);
long msb2 = parse4Nibbles(name, ns, 4);
long msb3 = parse4Nibbles(name, ns, 9);
long msb4 = parse4Nibbles(name, ns, 14);
msb = (msb1 << 48) | (msb2 << 32) | (msb3 << 16) | msb4;
if ((msb1 | msb2 | msb3 | msb4) >= 0) {
long lsb1 = parse4Nibbles(name, ns, 0);
long lsb2 = parse4Nibbles(name, ns, 4);
long lsb3 = parse4Nibbles(name, ns, 9);
long lsb4 = parse4Nibbles(name, ns, 14);
lsb = (lsb1 << 48) | (lsb2 << 32) | (lsb3 << 16) | lsb4;
if ((lsb1 | lsb2 | lsb3 | lsb4) >= 0) {
return new UUID(msb, lsb);
}
}
}
}
return fromString1(name);
}

private static long 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 (((((long) ch1) << 48) | (((long) ch2) << 32) |
(((long) ch3) << 16) | ch4) & 0xff00ff00ff00ff00L) != 0 ?
-1L : (ns[ch1 & 0xff] << 12) | (ns[ch2 & 0xff] << 8) |
(ns[ch3 & 0xff] << 4) | ns[ch4 & 0xff];
}

private static UUID fromString1(String name) {
int len = name.length();
if (len > 36) {
throw new IllegalArgumentException("UUID string too large");
Expand Down
6 changes: 4 additions & 2 deletions test/jdk/java/util/UUID/UUIDTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -95,8 +95,9 @@ private static void nameUUIDFromBytesTest() throws Exception {
private static void stringTest() throws Exception {
for (int i=0; i<100; i++) {
UUID u1 = UUID.randomUUID();
UUID u2 = UUID.fromString(u1.toString());
if (!u1.equals(u2))
UUID u2 = UUID.fromString(u1.toString().toLowerCase());
UUID u3 = UUID.fromString(u1.toString().toUpperCase());
if (!u1.equals(u2) || !u1.equals(u3))
throw new Exception("UUID -> string -> UUID failed");
}

Expand All @@ -107,6 +108,7 @@ private static void stringTest() throws Exception {
testFromStringError("0-0-0-0-");
testFromStringError("0-0-0-0-0-");
testFromStringError("0-0-0-0-x");
testFromStringError("аааааааа-аааа-аааа-аааа-аааааааааааа");
}

private static void testFromStringError(String str) {
Expand Down