src/java.base/share/classes/java/util/UUID.java

rev 58210 : 8196334: Optimize UUID#fromString
Reviewed-by: TBD
Contributed-by: plokhotnyuk@gmail.com, jon.chambers@gmail.com, claes.redestad@oracle.com

*** 178,187 ****
--- 178,226 ----
          md5Bytes[8]  &= 0x3f;  /* clear variant        */
          md5Bytes[8]  |= 0x80;  /* set to IETF variant  */
          return new UUID(md5Bytes);
      }
  
+     private static final byte[] NIBBLES;
+     static {
+         byte[] ns = new byte[256];
+         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;
+         NIBBLES = ns;
+     }
+ 
+     private static long parse4Nibbles(String name, int pos) {
+         byte[] ns = NIBBLES;
+         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];
+     }
+ 
      /**
       * Creates a {@code UUID} from the string standard representation as
       * described in the {@link #toString} method.
       *
       * @param  name
*** 193,202 ****
--- 232,266 ----
       *          If name does not conform to the string representation as
       *          described in {@link #toString}
       *
       */
      public static UUID fromString(String name) {
+         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 (ch1 == '-' && ch2 == '-' && ch3 == '-' && ch4 == '-') {
+                 long msb1 = parse4Nibbles(name, 0);
+                 long msb2 = parse4Nibbles(name, 4);
+                 long msb3 = parse4Nibbles(name, 9);
+                 long msb4 = parse4Nibbles(name, 14);
+                 long lsb1 = parse4Nibbles(name, 19);
+                 long lsb2 = parse4Nibbles(name, 24);
+                 long lsb3 = parse4Nibbles(name, 28);
+                 long lsb4 = parse4Nibbles(name, 32);
+                 if ((msb1 | msb2 | msb3 | msb4 | lsb1 | lsb2 | lsb3 | lsb4) >= 0) {
+                     return new UUID(
+                             msb1 << 48 | msb2 << 32 | msb3 << 16 | msb4,
+                             lsb1 << 48 | lsb2 << 32 | lsb3 << 16 | lsb4);
+                 }
+             }
+         }
+         return fromString1(name);
+     }
+ 
+     private static UUID fromString1(String name) {
          int len = name.length();
          if (len > 36) {
              throw new IllegalArgumentException("UUID string too large");
          }