vector uuid toString

Author: wenshao

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

@@ -31,7 +31,7 @@
 
 import jdk.internal.access.JavaLangAccess;
 import jdk.internal.access.SharedSecrets;
-import jdk.internal.util.HexDigits;
+import jdk.internal.misc.Unsafe;
 
 /**
  * A class that represents an immutable universally unique identifier (UUID).
@@ -76,6 +76,7 @@
  * @since   1.5
  */
 public final class UUID implements java.io.Serializable, Comparable<UUID> {
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
 
     /**
      * Explicit serialVersionUID for interoperability.
@@ -466,31 +467,59 @@ public long node() {
      */
     @Override
     public String toString() {
-        int i0 = (int) (mostSigBits >> 32);
-        int i1 = (int) mostSigBits;
-        int i2 = (int) (leastSigBits >> 32);
-        int i3 = (int) leastSigBits;
-
+        long lsb = leastSigBits;
+        long msb = mostSigBits;
         byte[] buf = new byte[36];
-        HexDigits.put4(buf, 0, i0 >> 16);
-        HexDigits.put4(buf, 4, i0);
         buf[8] = '-';
-        HexDigits.put4(buf, 9, i1 >> 16);
         buf[13] = '-';
-        HexDigits.put4(buf, 14, i1);
         buf[18] = '-';
-        HexDigits.put4(buf, 19, i2 >> 16);
         buf[23] = '-';
-        HexDigits.put4(buf, 24, i2);
-        HexDigits.put4(buf, 28, i3 >> 16);
-        HexDigits.put4(buf, 32, i3);
+        putHex8(buf, 0, msb >> 32, false);
+        putHex8(buf, 9, msb, true);
+        putHex8(buf, 19, lsb >> 32, true);
+        putHex8(buf, 28, lsb, false);
+
         try {
             return jla.newStringNoRepl(buf, StandardCharsets.ISO_8859_1);
         } catch (CharacterCodingException cce) {
             throw new AssertionError(cce);
         }
     }
 
+    private static void putHex8(byte[] bytes, int off, long i, boolean separator) {
+        long e = Long.expand(i, 0x0F0F_0F0F_0F0F_0F0FL);
+        /*
+            Use long to simulate vector operations and generate 8 hexadecimal characters at a time.
+            ------------
+            0  = 0b0000_0000 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '0'
+            1  = 0b0000_0001 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '1'
+            2  = 0b0000_0010 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '2'
+            3  = 0b0000_0011 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '3'
+            4  = 0b0000_0100 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '4'
+            5  = 0b0000_0101 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '5'
+            6  = 0b0000_0110 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '6'
+            7  = 0b0000_0111 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '7'
+            8  = 0b0000_1000 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '8'
+            9  = 0b0000_1001 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 0  + 0x30 + (i & 0xF) => '9'
+            10 = 0b0000_1010 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'a'
+            11 = 0b0000_1011 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'b'
+            12 = 0b0000_1100 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'c'
+            13 = 0b0000_1101 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'd'
+            14 = 0b0000_1110 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'e'
+            15 = 0b0000_1111 => m = ((i + 6) & 0x10); (m << 1) + (m >> 1) - (m >> 4) => 39 + 0x30 + (i & 0xF) => 'f'
+         */
+        long m = (e + 0x0606_0606_0606_0606L) & 0x1010_1010_1010_1010L;
+        long x = ((m << 1) + (m >> 1) - (m >> 4))
+                + 0x3030_3030_3030_3030L
+                + (e & 0x0F0F_0F0F_0F0F_0F0FL);
+        if (separator) {
+            UNSAFE.putIntUnaligned(bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET + off, (int) x, true);
+            UNSAFE.putIntUnaligned(bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET + off + 5, (int) (x >>> 32), true);
+        } else {
+            UNSAFE.putLongUnaligned(bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET + off, x, true);
+        }
+    }
+
     /**
      * Returns a hash code for this {@code UUID}.
      *

src/java.base/share/classes/jdk/internal/util/HexDigits.java

@@ -113,22 +113,6 @@ public static short digitPair(int i, boolean ucase) {
                 : v;
     }
 
-    /**
-     * Insert the unsigned 2-byte integer into the buffer as 4 hexadecimal digit ASCII bytes,
-     * only least significant 16 bits of {@code value} are used.
-     * @param buffer byte buffer to copy into
-     * @param index insert point
-     * @param value to convert
-     */
-    public static void put4(byte[] buffer, int index, int value) {
-        // Prepare an int value so C2 generates a 4-byte write instead of two 2-byte writes
-        int v = (DIGITS[value & 0xff] << 16) | DIGITS[(value >> 8) & 0xff];
-        buffer[index]     = (byte)  v;
-        buffer[index + 1] = (byte) (v >> 8);
-        buffer[index + 2] = (byte) (v >> 16);
-        buffer[index + 3] = (byte) (v >> 24);
-    }
-
     /**
      * Insert digits for long value in buffer from high index to low index.
      *