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
