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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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145
src/java.base/share/classes/java/lang/StringLatin1.java
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@ -33,7 +33,9 @@ import java.util.function.IntConsumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import jdk.internal.util.ArraysSupport;
import jdk.internal.util.ByteArrayLittleEndian;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import jdk.internal.vm.annotation.Stable;
import static java.lang.String.LATIN1;
import static java.lang.String.UTF16;
@ -42,6 +44,40 @@ import static java.lang.String.checkOffset;
final class StringLatin1 {
/**
* Each element of the array represents the packaging of two ascii characters based on little endian:<p>
* <pre>
* 00 -> '0' | ('0' << 8) -> 0x3030
* 01 -> '1' | ('0' << 8) -> 0x3130
* 02 -> '2' | ('0' << 8) -> 0x3230
*
* ...
*
* 10 -> '0' | ('1' << 8) -> 0x3031
* 11 -> '1' | ('1' << 8) -> 0x3131
* 12 -> '2' | ('1' << 8) -> 0x3231
*
* ...
*
* 97 -> '7' | ('9' << 8) -> 0x3739
* 98 -> '8' | ('9' << 8) -> 0x3839
* 99 -> '9' | ('9' << 8) -> 0x3939
* </pre>
*/
@Stable
static final short[] PACKED_DIGITS = new short[] {
0x3030, 0x3130, 0x3230, 0x3330, 0x3430, 0x3530, 0x3630, 0x3730, 0x3830, 0x3930,
0x3031, 0x3131, 0x3231, 0x3331, 0x3431, 0x3531, 0x3631, 0x3731, 0x3831, 0x3931,
0x3032, 0x3132, 0x3232, 0x3332, 0x3432, 0x3532, 0x3632, 0x3732, 0x3832, 0x3932,
0x3033, 0x3133, 0x3233, 0x3333, 0x3433, 0x3533, 0x3633, 0x3733, 0x3833, 0x3933,
0x3034, 0x3134, 0x3234, 0x3334, 0x3434, 0x3534, 0x3634, 0x3734, 0x3834, 0x3934,
0x3035, 0x3135, 0x3235, 0x3335, 0x3435, 0x3535, 0x3635, 0x3735, 0x3835, 0x3935,
0x3036, 0x3136, 0x3236, 0x3336, 0x3436, 0x3536, 0x3636, 0x3736, 0x3836, 0x3936,
0x3037, 0x3137, 0x3237, 0x3337, 0x3437, 0x3537, 0x3637, 0x3737, 0x3837, 0x3937,
0x3038, 0x3138, 0x3238, 0x3338, 0x3438, 0x3538, 0x3638, 0x3738, 0x3838, 0x3938,
0x3039, 0x3139, 0x3239, 0x3339, 0x3439, 0x3539, 0x3639, 0x3739, 0x3839, 0x3939
};
public static char charAt(byte[] value, int index) {
checkIndex(index, value.length);
return (char)(value[index] & 0xff);
@ -79,6 +115,115 @@ final class StringLatin1 {
return ret;
}
/**
* 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) {
// 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;
}
// Generate two digits per iteration
while (i <= -100) {
q = i / 100;
r = (q * 100) - i;
i = q;
charPos -= 2;
ByteArrayLittleEndian.setShort(buf, charPos, PACKED_DIGITS[r]);
}
// We know there are at most two digits left at this point.
if (i < -9) {
charPos -= 2;
ByteArrayLittleEndian.setShort(buf, charPos, PACKED_DIGITS[-i]);
} else {
buf[--charPos] = (byte)('0' - i);
}
if (negative) {
buf[--charPos] = (byte)'-';
}
return charPos;
}
/**
* 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) {
// 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;
ByteArrayLittleEndian.setShort(buf, charPos, PACKED_DIGITS[(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;
ByteArrayLittleEndian.setShort(buf, charPos, PACKED_DIGITS[(q2 * 100) - i2]);
i2 = q2;
}
// We know there are at most two digits left at this point.
if (i2 < -9) {
charPos -= 2;
ByteArrayLittleEndian.setShort(buf, charPos, PACKED_DIGITS[-i2]);
} else {
buf[--charPos] = (byte)('0' - i2);
}
if (negative) {
buf[--charPos] = (byte)'-';
}
return charPos;
}
public static void getChars(byte[] value, int srcBegin, int srcEnd, char[] dst, int dstBegin) {
inflate(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
}