forums.ps2dev.org

[kgsws]

I dont know if it is somewhere on net ...
I wanted to update all 3 ports (hexen, heretic, doom) with PSP's system functions, and i discovered bug in SceUtilitySavedataParam, i found correct things in memory of original game, there is fix:

[johnmph]

Here's the modified psputility_savedata.h that i use if you want :

[kgsws]

i am not sure about this line:
char **saveNameMultiple;
it is pointer to pointer to char(s), but what i use is just:
char *saveNameMultiple;
pointer to char(s)
and with this:
savedata->saveNameMultiple = (char **) nameMultiple;
isnt better to do
savedata->saveNameMultiple = &nameMultiple;
of course if you use only one pointer (not pointer to pointer)

[johnmph]

[kgsws]

but, in first post is this:
in struct SceUtilitySavedataParam:

char *saveNames;
pointer to char(s), is it right?

and after i defined new struct
typedef struct
{
char name1[20];
char name2[20];
char name3[20];
char name4[20];
char name5[20];
char nothing[20]; // Terminator
} savenames_t;
no pointers, is it right?
after i create:
savenames_t savenames;
and this is not pointer too, is it right?

and on this line:
data.saveNames = &savenames;
i am making pointer to chars from char[120], is it right?

that means, you dont need to define:
savenames_t savenames;
but only:
char savenames[120];
but you must fill it in correct order

[johnmph]

[kgsws]

but if i define pointer to something, an non pointer, then i must use & character ...

char *point; // 4 bytes
char nonpoint // 1 byte

i can do:
nonpoint = 'X';
but i cant do:
point = 'X'; // becouse pointer is not set, and it will try to write to address 0x00000000
i can use:
point = malloc(1);
and after it, i can use that ...
if i do:
point = &nonpoint;
it will set address of point to address of nonpoint, so when i try:
nonpoint = 'A';
point = 'X'; // or point[0] = 'X';
nonpoint will be 'X' there ...

that is way i am thinking about pointers :P

i am not sure with:
x = (char **)y; // conversion
so, i dont use it, if i dont need

[johnmph]

[johnmph]

and you can found many tutorials on pointers on internet

[kgsws]

great, now i understant it more, but if i create:

[johnmph]

Yes you are right and it's because i use :

savedata->saveNameMultiple = (char **) nameMultiple;

instead :

savedata->saveNameMultiple = (char **) &nameMultiple;

The savegame function takes a pointer to char and not a pointer to pointer to chars and it's why i use a large string (char nameMultiple[][20]) but when i reversed this function, i wrote it as char** instead char* because i think that it's more representive for the meaning of how it's used.

But you can also write it like (in structure) :

int nameMultiple;

and after use it like :

char name[120] = "...";
struct.nameMultiple = (int) name;

It's valid too but it's not very good to understand lol

So the savedata function takes a pointer to chars and reads the chars by 20 until he finds 0 as first char (terminator).

[kgsws]

i still dont understand why:
savedata->saveNameMultiple = (char **) nameMultiple;
and no:
savedata->saveNameMultiple = &nameMultiple;
(it is just pointer = pointer) (becouse & makes pointer from non pointer)

becouse there are two '**' markers, every marker means pointer, so it is pointer to pointer to ...

if i do:
char **something;
then it is pointer to pointer to char(s), so:
something = malloc(x * 4) // x = num pointers, 4 is size of pointer
and then i can do:
something[0] = malloc(10); // 10 chars
something[1] = malloc(20); // 20 chars
.....
and then:
printf(something[0]); // 10 chars
printf(something[1]); // 20 chars
.....

it is strange, becouse of compiler ...
sprintf accepts pointer to char (so char*)
but when i do:
char some[20];
and then:
printf(some); it automaticaly converts non pointer to pointer
(becouse if not, it will try to use first 4 chars as address of pointer, and that is bad)

[johnmph]

Because an array = a pointer :

char some[20];

some is a pointer to 20 bytes data allocated statically.

char *some2 = some;

some2 is a pointer which points to the same memory, it's the same !

[kgsws]

yes, but compiler can handle it diffrend way than creating a pointer by using *.

if you thing that way, then everything is pointer to some location in memory (yes, data must be stored somewhere)

int is array of 4 chars:
int somenum;
char somechars[4];

char is pointer without using *?
and why int isnt?

but compiler can make pointer from somechars automaticaly by using it as x = somechars; but if i use x = &somechars; it does not create pointer to pointer, then savedata

Size is same, i thing, everything hadles compiler, like MSVC .NET, it does not allow some things, what DEV C++ does. (yes i had some problems with it)

isnt '(char*)' just fake conversion, for using variable as diffrend type?

tested:
char text[] = "test text";
printf("0x%08X\n",text);
printf("0x%08X\n",&text);
both lines shown same hex number, so it does not depends on '&'
then i dont need to use it, but 'char *saveNames;' is right (only one pointer)

[Jim]

Right, because if you have

char x[]="foo";
Then

x is type pointer to char
&x is type pointer to array of char

They're both point to the same address, but they have different types.

I don't know what you're all on about, this is utterly basic C programming.

Jim
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