empire/empserver
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Store sequence numbers more compactly

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Store them and ef_type in bit-fields.

Allocate eight bits for ef_type.  Values range from 0 to EF_GAME
(currently 16), so this is plenty.

Allocate twelve bits for sequence numbers.  Sequence number mismatches
are now missed when the numbers are equal modulo 2^12.  Still
sufficiently improbable.

Common machines store the bit-fields in a 32 bit word.  There are
twelve bits left in that word for future use.  Total savings 16 bits,
which is exactly what the previous commit spent on wider uids on
common machines.
This commit is contained in:
Markus Armbruster 2009-12-31 10:30:54 +01:00
parent ba2044be18
commit 358aee203e
15 changed files with 33 additions and 34 deletions
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8
include/nat.h
View file

@ -70,9 +70,9 @@ enum nat_status {
*/
struct realmstr {
/* initial part must match struct empobj */
short ef_type;
signed ef_type: 8;
unsigned r_seqno: 12;
int r_uid; /* realm table index */
unsigned r_seqno;
time_t r_timestamp; /* Last time this realm was touched */
natid r_cnum; /* country number */
/* end of part matching struct empobj */
@ -83,9 +83,9 @@ struct realmstr {
struct natstr {
/* initial part must match struct empobj */
short ef_type;
signed ef_type: 8;
unsigned nat_seqno: 12;
int nat_uid; /* equals nat_cnum */
unsigned nat_seqno;
time_t nat_timestamp;
natid nat_cnum; /* our country number */
/* end of part matching struct empobj */