Hi,
That looks like a fairly localized change.
It will need to deal with the risk that the StreamDecoder has cached
byte(s) that have already been pulled from the input stream and not yet
been flushed through, say for example a byte of a multi-byte character.
This might happen if some reads have been done before calling
readAllAsString.
Regards, Roger
On 3/22/26 6:43 AM, Markus KARG wrote:
Dear Core-Lib Developers,
I like to contribute an explicit implementation of
InputStreamReader.readAllAsString() for performance reasons.
I benchmarked InputStreamReader.readAllAsString() vs simplistic custom
code, and the result is pretty clear: Even most trivial custom code
clearly outperforms the original code by more than 30%!
Benchmark Mode Cnt Score Error Units
Demo.jdk thrpt 25 10931.806 ± 535.177 ops/s
Demo.customCode thrpt 25 14775.102 ± 343.829 ops/s
@Benchmark
public String jdk(MyState ms) throws IOException {
return new InputStreamReader(ms.in, UTF_8).readAllAsString();
}
@Benchmark
public String trivialCustomCode(MyState ms) throws IOException {
return new String(ms.in.readAllBytes(), UTF_8);
}
IMHO gaining 30%+ justifies the provision of a custom implementation
like the following one...
public String readAllAsString() throws IOException {
return sd.readAllAsString();
}
and in turn let sd.readAllAsString() return e. g. new
String(in.readAllBytes(), cs)
...to override Reader's default implementation which currently
performs (possibly lots of) several in-builder buffer copies:
public String readAllAsString() throws IOException {
StringBuilder result = new StringBuilder();
char[] cbuf = new char[TRANSFER_BUFFER_SIZE];
int nread;
while ((nread = read(cbuf, 0, cbuf.length)) != -1) {
result.append(cbuf, 0, nread);
}
return result.toString();
}
This minimal change should provide approx. the benchmarked 30%
performance gain, should never be slower, and should not need more
memory than the original implementation.
If the core-libs team is fine with me doing so, I would like to file a
JBS and a PR. Comments very welcome!
-Markus
