C saving game state, reducing passed variables - c

Question

I've been wondering if there's a way to do a function that saves game state but in transparent way. It's not a question about actual saving (I know how to save to file etc), it's about writing it in a clear, simple and understandable way.
So far I've came to three ideas (remember, I wish it could be a function or some easy thing like savegame()), none is perfect:
Put every variable I want to save into a struct like:
struct state{
int hp;
pos position;
int x;
int y;
...
};
...
if(savegame==1) {
state game;
game.hp=hp;
game.position=position;
game.x=x;
game.y=y;
...
savegame(game);
}
as you can see, it's not looking any good, it takes so many lines to do just a saving: what if I would like to save like 40 variables? What if I want to do saving in like 5-6 places in a code?
Make my function long as snake (this gives a problem with loading it back, so for example I also put a loadgame func):
void savegame(int hp, pos position, int x, int y,...) // too long
{ ... }
void loadgame(int &hp, pos &position, int &x, int &y,...) // too long
{ ... }
...
int main()
{
...
savegame(hp, pos, x, y, ...) // too long
...
loadgame(hp, pos, x, y, ...) // too long
}
again, if it would have 40 variables inside(and i also would like to call savegame or loadgame like 5-6 times), it would take like 4 lines of code each(i just skip an idea to put it in 1 line)
Start my program with struct containing game state, and make all calculations, actually all game on that struct
struct gamestate{
int hp;
pos position;
int x;
int y;
}
...
int main()
{
struct gamestate s;
s.x++;
...
}
but this leads to a problem where everytime I make calculations I have to add this 's' at beggining.
Conclusion:
My idea was to maybe change second option just to reduce every call of savegame(...); to simple savegame();, is there a way to do it? Without define?

Answer 1

Here is a dynamic way to do something similar to what you describe in your 1st option, i.e. track a game state using pointer to struct but that also stores and recovers that data to and from a binary file...
The following .c and .h files illustrate the idea that you can use a compound struct, i.e. one containing several other structs, that at any one time contain all of the values representing states in your program. This is very easily passed via a function(s) with very few arguments (prototyped eg. as char *GetState(state *in, const char *filespec); and char *SetState(state *out, const char *filespec); ) which in turn would write or read the contents of the struct into/out of a binary buffer. I have used this method to store and retrieve multiple sets of state data within files.
Note, the structs have random fields that of course you will modify as needed, but the idea is that you can pass a single pointer value that points to all the state data, in every function where state date is updated, or needs to be stored.
so_SaveGameState.c
#include <so_SaveGameState.h>
unsigned char *pByteA;
GAME_STATE game = {{{"jim", "C:\\ico1.ico", {10, 120, 3}}, {"joe", "C:\\ico2.ico", {80, 10, -5}},{"larry", "C:\\ico3.ico", {15, -45, -45}},{"sue", "C:\\ico4.ico", {-100, -45, 45}}}, ENVR_3};
GAME_STATE *pGame = NULL;
int main(void)
{
pGame = &game;//point to populated memory
printf("Player 3 position\nx = %d\ny = %d\nz = %d\n", game.plyr[2].pos.x, game.plyr[2].pos.y, game.plyr[2].pos.z);
//example function that changes game state
UpdatePlayerPosition(&pGame, 2);
printf("Player 3 position\nx = %d\ny = %d\nz = %d\n", game.plyr[2].pos.x, game.plyr[2].pos.y, game.plyr[2].pos.z);
UpdatePlayerPosition(&pGame, 2);
printf("Player 3 position\nx = %d\ny = %d\nz = %d\n", game.plyr[2].pos.x, game.plyr[2].pos.y, game.plyr[2].pos.z);
UpdatePlayerPosition(&pGame, 2);
printf("Player 3 position\nx = %d\ny = %d\nz = %d\n", game.plyr[2].pos.x, game.plyr[2].pos.y, game.plyr[2].pos.z);
//prepare an instance of game state for storeing
(const GAME_STATE *)pByteA = &game;
int len1 = sizeof(game);
BOOL status = storeState("C:\\tempextract\\binFileStruct.bin", pByteA, len1);
//recover a stored state
unsigned char *buf = recoverState("C:\\tempextract\\binFileStruct.bin");
GAME_STATE *game_2 = (GAME_STATE *)buf;
free(game_2);
return 0;
}
unsigned char * recoverState(const char *filespec)
{
size_t sz = 0;
int n = 0;
unsigned char *binBuf = NULL;
FILE *fp = fopen(filespec, "rb");
if(fp)
{
fseek(fp, 0L, SEEK_END);
sz = ftell(fp);
fseek(fp, 0L, SEEK_SET);
rewind(fp);
binBuf = calloc(sz, sizeof(*binBuf));
n = fread(binBuf, sizeof(unsigned char), sz, fp);
fclose(fp);
}
if(n == sz)
{
return binBuf;
}
else
{
return NULL;
}
}
int storeState(const char *filespec, const unsigned char *buf, size_t sz)
{
int count = 0;
FILE *fp = fopen(filespec, "wb");
if(fp)
{
count = fwrite(buf, sizeof(unsigned char), sz, fp);
fclose(fp);
}
return (count == sz) ? 1 : 0;
}
void UpdatePlayerPosition(GAME_STATE **game, int player)
{
static int x=0, y=0, z=0;
static BOOL toggle = TRUE;
toggle = (toggle == 1) ? -1 : 1;
srand(clock());
//using fake assignment here
//i.e. you would have other criteria to set actual position
x += toggle * rand()%300;
y += toggle * rand()%300;
z += toggle * rand()%300;
(*game)->plyr[player].pos.x = x;
(*game)->plyr[player].pos.y = y;
(*game)->plyr[player].pos.y = z;
}
so_StoreGameState.h
typedef enum {//environment
ENVR_1, //bad weather
ENVR_2, //hill
ENVR_3, //pit
ENVR_4, //angry birds
ENVR_5, //enemy guard
MAX_OBST
}ENVR_TYPE;
typedef struct {
int x;
int y;
int z;
}POS;
typedef struct {
ENVR_TYPE envir;
//...
}ENVIR;
typedef struct {
char name[20];
char iconFile[260];
POS pos;
//...
}PLAYER;
typedef struct {
PLAYER plyr[4];
ENVIR env;
//...
}GAME_STATE;
extern GAME_STATE game;
unsigned char * recoverState(const char *filespec);
int storeState(const char *filespec, const unsigned char *buf, size_t sz);