> hmm a write32 is still about 10 times slower than a write8, but a write16
> is about twice as fast as write8.
Hey guys, I've been lurking here a while (don't have a setup to run jJOS
- sure would be nice when you no longer need the Etherboot stuff), but
was wondering...
How about if you added a feature to allow arrays to be created that had
their values in particular regions of memory..something like:
byte[] getBytes(long address, long length);
so you could write code like (just off the top of my head..don't really
know the details of VGA):
byte[] vgaBuffer = jos.system.machine.getBytes(0xa0000, 0x10000);
for (int i = 0; i < 0x10000; i++)
vgaBuffer[i] = 0;
The only trick would be to make sure that when such an array was GC'd,
the underlying bytes were left alone and not reallocated.
I'd think you'd save a fair amount of function call overhead, you'd be
able to use standard methods like java.lang.System.arraycopy(), and
you'd get the builtin Java array bounds checking for free.
Speaking of bounds checking, I understand that in at least some JVMs,
it'd be even faster to write code like:
try
{
byte[] vgaBuffer = jos.system.machine.getBytes(0xa0000, 0x10000);
int i = 0;
while (true)
vgaBuffer[i++] = 0;
}
catch (ArrayIndexOutOfBoundsException aioobe)
{
}
basically, don't bother explicitly checking the value of i (like the
"for" loop does) since the JVM will be checking it itself anyhow.
Barry
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