angband-import
commented
4 years ago Comment by pmac on 22 Mar 2007 04:17 UTC I have a different model of how to write a save file, using generated code. The following is done with the C preprocessor, but you can use perl or m4 to generate C files from a class definition just as well. The methods are equivalent; it's just that the perl input can be cleaner-looking than c preprocessor macros.
Define two sets of macros that have the same names but different actions as follows:
gen_types.h:
#define F(type, var) type var;
#define C(type, var) type var;
#SERIALIZATION(clazz, fields) \
struct clazz { fields };gen_serialization.h:
#define F(type, var) {"type", "var", TRUE},
#define C(type, var) {"type", "var", FALSE},
#define SERIALIZABLE(type, fields) \
serialization type [] = { \
fields \
{0, 0, 0} \
};Then when you define a serializable type, you can generate either the struct or the names of the types (and thus offsets) of the fields in that struct. To save the struct, you just read the field values, then go to the appropriated computed offset. This can be recursive for saving equipment in the pack or in the store.
So, unless there is a significant structural change from one release to another, save files are compatible without any effort, so long as you initialize default values in a sane manner. (That can be done programmatically, or by adding another argument to the F() macros.
For example, the following macro header file:
SERIALIZABLE(player_t,
F(char,name[100])
F(byte,race)
C(int,computed)
F(u8b,inven_count)
F(object_t,inventory[24])
)Can generate either of the following, depending on which macros are included:
struct player_t {
char name[100];
byte race;
int computed;
u8b inven_count;
object_t inventory[24];
};OR this, which defines a (mostly) backwards-compatible serialization of the above structure. Just read or write the data structures, as tuples of (name, type, value)
serialization player_t [] = {
{"char", "name[100]", TRUE},
{"byte", "race", TRUE},
{"int", "computed", FALSE},
{"u8b", "inven_count", TRUE},
{"object_t", "inventory[24]", TRUE},
{0, 0, 0}
};
Reported by takkaria on 21 Mar 2007 14:48 UTC There are comments at the top of save.c (see #ifdef FUTURE_SAVEFILES), which indicate plans to create a modular and better-versioned savefile format. I used that as a base to create a new format, which has better versioning support, and is probably a whole lot more future-proof than what's currently there. It also unified save/load code as far as possible.
The new savefile is constructed of a header, followed by a number of blocks, followed by a special "end block". For a fuller description, see [http://ajps.mine.nu/angband/wiki/SavefileCode].
It's also possible to compress this savefile in-memory, should the need be felt. sfuerst was working on this for Z, but I can't find a link for it right now.