Markus Gaisbauer a écrit :
A bug in java.lang.StringCoding causes a full and unnecessary copy of
the byte array given as the first argument.
it's not a bug, it's a feature :)
i think this copy is a defensive copy to avoid malicious charser
(decoder) to
access the underlying buffer.
By the way, using clone() seams better than Arrays.copyOf() here.
byte[] b = ba.clone();
This results in severe slow down of the Constructor if the byte array is
big.
Rémi
The attached patch, should fix the problem.
Unfortunately I do not (yet) have an official bug id for this, as this
seems to take a while (reported 2 weeks ago).
To reproduce the problem run the following test program:
import java.nio.charset.Charset;
public class StringTest {
public static void main(String[] args) throws Exception {
long before;
long after;
byte[] data;
data = new byte[1024*1024*16]; // 16 megabyte
data[0] = 'X';
// warmup
new String(data, 0, 1);
new String(data, 0, 1, Charset.forName("UTF8"));
new String(data, 0, 1, "UTF8");
before = System.nanoTime();
new String(data, 0, 1);
after = System.nanoTime();
System.out.println((after - before) / 1000000 + "ms");
before = System.nanoTime();
new String(data, 0, 1, Charset.forName("UTF8"));
after = System.nanoTime();
System.out.println((after - before) / 1000000 + "ms");
before = System.nanoTime();
new String(data, 0, 1, "UTF8");
after = System.nanoTime();
System.out.println((after - before) / 1000000 + "ms");
}
}
------------------------------------------------------------------------
Index: StringCoding.java
===================================================================
--- StringCoding.java (revision 258)
+++ StringCoding.java (working copy)
@@ -193,7 +193,6 @@
static char[] decode(Charset cs, byte[] ba, int off, int len) {
StringDecoder sd = new StringDecoder(cs, cs.name());
- byte[] b = Arrays.copyOf(ba, ba.length);
return sd.decode(b, off, len);
}
