On Tue, 25 Jun 2024 17:29:04 GMT, Shaojin Wen <d...@openjdk.org> wrote:
>> The current versions of FloatToDecimal and DoubleToDecimal allocate
>> additional objects. Reducing these allocations can improve the performance
>> of Float/Double.toString and AbstractStringBuilder's append(float/double).
>>
>> This patch is just a code refactoring to reduce object allocation, but does
>> not change the Float/Double to decimal algorithm.
>>
>> The following code comments the allocated objects to be removed.
>>
>>
>> class FloatToDecimal {
>> public static String toString(float v) {
>> // allocate object FloatToDecimal
>> return new FloatToDecimal().toDecimalString(v);
>> }
>>
>> public static Appendable appendTo(float v, Appendable app)
>> throws IOException {
>> // allocate object FloatToDecimal
>> return new FloatToDecimal().appendDecimalTo(v, app);
>> }
>>
>> private Appendable appendDecimalTo(float v, Appendable app)
>> throws IOException {
>> switch (toDecimal(v)) {
>> case NON_SPECIAL:
>> // allocate object char[]
>> char[] chars = new char[index + 1];
>> for (int i = 0; i < chars.length; ++i) {
>> chars[i] = (char) bytes[i];
>> }
>> if (app instanceof StringBuilder builder) {
>> return builder.append(chars);
>> }
>> if (app instanceof StringBuffer buffer) {
>> return buffer.append(chars);
>> }
>> for (char c : chars) {
>> app.append(c);
>> }
>> return app;
>> // ...
>> }
>> }
>> }
>>
>> class DoubleToDecimal {
>> public static String toString(double v) {
>> // allocate object DoubleToDecimal
>> return new DoubleToDecimal(false).toDecimalString(v);
>> }
>>
>> public static Appendable appendTo(double v, Appendable app)
>> throws IOException {
>> // allocate object DoubleToDecimal
>> return new DoubleToDecimal(false).appendDecimalTo(v, app);
>> }
>>
>> private Appendable appendDecimalTo(double v, Appendable app)
>> throws IOException {
>> switch (toDecimal(v, null)) {
>> case NON_SPECIAL:
>> // allocate object char[]
>> char[] chars = new char[index + 1];
>> for (int i = 0; i < chars.length; ++i) {
>> chars[i] = (char) bytes[i];
>> }
>> ...
>
> Shaojin Wen has updated the pull request incrementally with one additional
> commit since the last revision:
>
> from @liach: use s.getBytes for performance
src/java.base/share/classes/jdk/internal/math/ToDecimal.java line 47:
> 45: static final int NAN = 5 << 8;
> 46:
> 47: static final byte LATIN1 = 0;
I think this somewhat unnecessarily copies names and internal implementation
details from `String` (where the `coder` value is used both as a pseudo-boolean
and as a shift operand, which is not applicable here). In this context we could
use something like `private final boolean latin1;` (all uses of `coder` are
just `if (coder == LATIN1)` so it would be simplified to `if (latin1)`)
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/19730#discussion_r1654812101
