Hi David,
please don't CC to me. Otherwise I get your message twice. I read the list.
....
Am 25.06.2008 17:55, David M. Lloyd schrieb:
On 06/25/2008 03:57 AM, Ulf Zibis wrote:
Hi David,
can you show an example using a 'switch' statement which is shorter
or faster than:
char c = c2bMap.charAt(c2bMapIndex[(current & MASK1) >>
SHIFT] + (current & MASK2));
Faster - maybe or maybe not; but the "c2bMap", being sparse, can be
represented possibly more space-efficiently using a lookupswitch (I'm
thinking of all the \u0000 entries, which can be handled with a
"default" branch):
public static final c2bMapper(int idx) {
switch (idx) {
case 1: return 1;
case 2: return 2;
...
default: return 0;
}
}
The primary disadvantage being, I guess, that the table cannot then be
stored in e.g. a properties file.
- DML
Let me correct:
public static final byte c2bMapper(char inChar) {
int idx = (int)inChar;
switch (idx) {
case 0x0001: return (byte)0x01;
case 0x0002: return (byte)0x02;
...
case 0x015F: return (byte)0x8F;
...
case 0x02DD: return (byte)0x64;
default: return 0;
}
}
Internally this will be compiled as a looong if () else if () else if ()
.... chain, because the cases are NOT consecutive. Executing such a
chain will never be faster, than calculating the index as I posted.
Additionally this code would not be space-efficient. Think about 256
times {else if (idx == x) return (byte)y;}
Not to forget: each of the around 100 encoders will need such an
individual custom switch-case block. :-(
- Ulf
