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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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61
src/java.base/share/classes/java/lang/Long.java
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@ -459,7 +459,7 @@ public final class Long 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];
@ -486,65 +486,6 @@ public final class Long extends Number
return toUnsignedString(i, 10);
}
/**
* Places characters representing the long 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 Long.MIN_VALUE case. Converting otherwise
* (negative to positive) will expose -Long.MIN_VALUE that overflows
* long.
*
* @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(long i, int index, byte[] buf) {
long q;
int r;
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;
r = (int)((q * 100) - i);
i = q;
buf[--charPos] = Integer.DigitOnes[r];
buf[--charPos] = Integer.DigitTens[r];
}
// Get 2 digits/iteration using ints
int q2;
int i2 = (int)i;
while (i2 <= -100) {
q2 = i2 / 100;
r = (q2 * 100) - i2;
i2 = q2;
buf[--charPos] = Integer.DigitOnes[r];
buf[--charPos] = Integer.DigitTens[r];
}
// We know there are at most two digits left at this point.
buf[--charPos] = Integer.DigitOnes[-i2];
if (i2 < -9) {
buf[--charPos] = Integer.DigitTens[-i2];
}
if (negative) {
buf[--charPos] = (byte)'-';
}
return charPos;
}
/**
* Returns the string representation size for a given long value.
*