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8310929: Optimization for Integer.toString

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Reviewed-by: redestad, rriggs
This commit is contained in:
shaojin.wensj 2023-09-08 02:13:52 +00:00 • committed by Yi Yang
parent 111ecdbaf5
commit 4b43c25fe3
8 changed files with 215 additions and 172 deletions
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76
src/java.base/share/classes/java/lang/Integer.java
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@ -414,33 +414,6 @@ public final class Integer extends Number
} while (charPos > 0);
}
static final byte[] DigitTens = {
'0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
'1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
'2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
'3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
'4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
'5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
'6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
'7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
'8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
'9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
} ;
static final byte[] DigitOnes = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
} ;
/**
* Returns a {@code String} object representing the
* specified integer. The argument is converted to signed decimal
@ -456,7 +429,7 @@ public final class Integer extends Number
int size = stringSize(i);
if (COMPACT_STRINGS) {
byte[] buf = new byte[size];
getChars(i, size, buf);
StringLatin1.getChars(i, size, buf);
return new String(buf, LATIN1);
} else {
byte[] buf = new byte[size * 2];
@ -483,53 +456,6 @@ public final class Integer extends Number
return Long.toString(toUnsignedLong(i));
}
/**
* Places characters representing the integer i into the
* character array buf. The characters are placed into
* the buffer backwards starting with the least significant
* digit at the specified index (exclusive), and working
* backwards from there.
*
* @implNote This method converts positive inputs into negative
* values, to cover the Integer.MIN_VALUE case. Converting otherwise
* (negative to positive) will expose -Integer.MIN_VALUE that overflows
* integer.
*
* @param i value to convert
* @param index next index, after the least significant digit
* @param buf target buffer, Latin1-encoded
* @return index of the most significant digit or minus sign, if present
*/
static int getChars(int i, int index, byte[] buf) {
int q, r;
int charPos = index;
boolean negative = i < 0;
if (!negative) {
i = -i;
}
// Generate two digits per iteration
while (i <= -100) {
q = i / 100;
r = (q * 100) - i;
i = q;
buf[--charPos] = DigitOnes[r];
buf[--charPos] = DigitTens[r];
}
// We know there are at most two digits left at this point.
buf[--charPos] = DigitOnes[-i];
if (i < -9) {
buf[--charPos] = DigitTens[-i];
}
if (negative) {
buf[--charPos] = (byte)'-';
}
return charPos;
}
/**
* Returns the string representation size for a given int value.
*