8343925: [BACKOUT] JDK-8342650 Move getChars to DecimalDigits

Reviewed-by: jpai, alanb, liach

src/java.base/share/classes/java/lang/StringUTF16.java

@@ -35,6 +35,7 @@ import java.util.stream.StreamSupport;
 
 import jdk.internal.misc.Unsafe;
 import jdk.internal.util.ArraysSupport;
+import jdk.internal.util.DecimalDigits;
 import jdk.internal.vm.annotation.ForceInline;
 import jdk.internal.vm.annotation.IntrinsicCandidate;
 
@@ -1512,6 +1513,20 @@ final class StringUTF16 {
         return codePointCount(val, beginIndex, endIndex, true /* checked */);
     }
 
+    public static int getChars(int i, int begin, int end, byte[] value) {
+        checkBoundsBeginEnd(begin, end, value);
+        int pos = getChars(i, end, value);
+        assert begin == pos;
+        return pos;
+    }
+
+    public static int getChars(long l, int begin, int end, byte[] value) {
+        checkBoundsBeginEnd(begin, end, value);
+        int pos = getChars(l, end, value);
+        assert begin == pos;
+        return pos;
+    }
+
     public static boolean contentEquals(byte[] v1, byte[] v2, int len) {
         checkBoundsOffCount(0, len, v2);
         for (int i = 0; i < len; i++) {
@@ -1647,6 +1662,109 @@ final class StringUTF16 {
 
     static final int MAX_LENGTH = Integer.MAX_VALUE >> 1;
 
+    // Used by trusted callers.  Assumes all necessary bounds checks have
+    // been done by the caller.
+
+    /**
+     * This is a variant of {@link StringLatin1#getChars(int, int, byte[])}, but for
+     * UTF-16 coder.
+     *
+     * @param i     value to convert
+     * @param index next index, after the least significant digit
+     * @param buf   target buffer, UTF16-coded.
+     * @return index of the most significant digit or minus sign, if present
+     */
+    static int getChars(int i, int index, byte[] buf) {
+        // Used by trusted callers.  Assumes all necessary bounds checks have been done by the caller.
+        int q, r;
+        int charPos = index;
+
+        boolean negative = (i < 0);
+        if (!negative) {
+            i = -i;
+        }
+
+        // Get 2 digits/iteration using ints
+        while (i <= -100) {
+            q = i / 100;
+            r = (q * 100) - i;
+            i = q;
+            charPos -= 2;
+            putPair(buf, charPos, r);
+        }
+
+        // We know there are at most two digits left at this point.
+        if (i < -9) {
+            charPos -= 2;
+            putPair(buf, charPos, -i);
+        } else {
+            putChar(buf, --charPos, '0' - i);
+        }
+
+        if (negative) {
+            putChar(buf, --charPos, '-');
+        }
+        return charPos;
+    }
+
+    /**
+     * This is a variant of {@link StringLatin1#getChars(long, int, byte[])}, but for
+     * UTF-16 coder.
+     *
+     * @param i     value to convert
+     * @param index next index, after the least significant digit
+     * @param buf   target buffer, UTF16-coded.
+     * @return index of the most significant digit or minus sign, if present
+     */
+    static int getChars(long i, int index, byte[] buf) {
+        // Used by trusted callers.  Assumes all necessary bounds checks have been done by the caller.
+        long q;
+        int charPos = index;
+
+        boolean negative = (i < 0);
+        if (!negative) {
+            i = -i;
+        }
+
+        // Get 2 digits/iteration using longs until quotient fits into an int
+        while (i <= Integer.MIN_VALUE) {
+            q = i / 100;
+            charPos -= 2;
+            putPair(buf, charPos, (int)((q * 100) - i));
+            i = q;
+        }
+
+        // Get 2 digits/iteration using ints
+        int q2;
+        int i2 = (int)i;
+        while (i2 <= -100) {
+            q2 = i2 / 100;
+            charPos -= 2;
+            putPair(buf, charPos, (q2 * 100) - i2);
+            i2 = q2;
+        }
+
+        // We know there are at most two digits left at this point.
+        if (i2 < -9) {
+            charPos -= 2;
+            putPair(buf, charPos, -i2);
+        } else {
+            putChar(buf, --charPos, '0' - i2);
+        }
+
+        if (negative) {
+            putChar(buf, --charPos, '-');
+        }
+        return charPos;
+    }
+
+    private static void putPair(byte[] buf, int charPos, int v) {
+        int packed = (int) DecimalDigits.digitPair(v);
+        putChar(buf, charPos, packed & 0xFF);
+        putChar(buf, charPos + 1, packed >> 8);
+    }
+    // End of trusted methods.
+
     public static void checkIndex(int off, byte[] val) {
         String.checkIndex(off, length(val));
     }