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#ActualKaptein

Posted 05 December 2012 - 03:44 PM

well, in java you could serialize objects, and get perfect replicas (with data element and class -exceptions of your own choosing)
in C i would define structures that consist primarily of what i want, and the offsets between the specific data, so that my saves never get "old"
for example, a small int table in a savefile tells me where this and that starts (in bytes), and ill just grab some generic tables from these positions
assuming you have made changes to the internal structures recently, it will get complicated in C, but there may be tricks you can use in C++ (i don't know the language)

anyways, define structs (classes if you will) that contains pertinent information on the data, and let these structs be so generic that you won't have to go back and look at them ever again =)
harddisk space is .. the least of your problems :) make room for improvements!
when this is done, just put the structs one by one into the file at the locations you'd want them to be in, and disregard completely "open spaces between structs"
the only requirement here is that you know where they are, and that they don't overlap
if you use sizeof(struct) you can pack them well together, and you might still be able to load the structs later, if you consider the differences between any old and new scheme
i recommend discarding old data though, if you make any changes

so, if A is the main savefile struct, and B is a container for where some additional structs are stored, the file layout could be:
ABBBBBBB C C C C C C C C C C C C C C C
the procedure:

// tell our future selves what size A had when we made this file
put (sizeof(A))

// tell A what kind of size B had when we saved
A.container_size = sizeof(B)

// declare a position for where we are in the file, which simplifies things greatly,
// both for loading and saving
int position = 0; // (or 1, depending on if its 0- or 1-based file offsets, its ALWAYS in bytes though!)

// put the entire struct directly into the file
// and increase position by the size of this structure (note that the sizes of structs vary between compilers!)
// (however, differences between compilers is something we don't care about now, and sometimes the language is consistent :P)
put(A); position += sizeof(A);

// put each struct that tells us location of data, and its size
for (int i = 0; i < a.containers; i++)
{ put(B); position += sizeof(B);
}

// for each B, we put each C (for each collection of data, we put each data)
for each B for each C in B
{
// we want to remember the size of each data item, including what type it is, and any other information
// that you would need to know now, or in the future
B.data_size[index] = sizeof©; // for example..!
// put to file, advance position
put© : position += sizeof©
}
close()

and so on .. and so forth =)
now the position you are in the file is incremented for each structure, packed tightly
and there is no confusion about where anything is located
this is an ultra-basic system, that leaves less room for problems in your code, but is still not completely resistant to future updates and changes
to compensate for future changes, a version system could be used, but then you'd need backwards compatibility in your games loading system
personally, i say if you make any changes to the saving system - make all the changes, and scrap the old system, if you can :)
i hope this helps

#1Kaptein

Posted 05 December 2012 - 03:37 PM

well, in java you could serialize objects, and get perfect replicas (with data element and class -exceptions of your own choosing)
in C i would define structures that consist primarily of what i want, and the offsets between the specific data, so that my saves never get "old"
for example, a small int table in a savefile tells me where this and that starts (in bytes), and ill just grab some generic tables from these positions
assuming you have made changes to the internal structures recently, it will get complicated in C, but there may be tricks you can use in C++ (i don't know the language)

anyways, define structs (classes if you will) that contains pertinent information on the data, and let these structs be so generic that you won't have to go back and look at them ever again =)
harddisk space is .. the least of your problems :) make room for improvements!
when this is done, just put the structs one by one into the file at the locations you'd want them to be in, and disregard completely "open spaces between structs"
the only requirement here is that you know where they are, and that they don't overlap
if you use sizeof(struct) you can pack them well together, and you might still be able to load the structs later, if you consider the differences between any old and new scheme
i recommend discarding old data though, if you make any changes

so, if A is the main savefile struct, and B is a container for where some additional structs are stored, the file layout could be:
ABBBBBBB C C C C C C C C C C C C C C C
the procedure:

// tell our future selves what size A had when we made this file
put (sizeof(A))

// tell A what kind of size B had when we saved
A.container_size = sizeof(B)

put(A); position += sizeof(A);
for (int i = 0; i < a.containers; i++)
{ put(B); position += sizeof(B);
}
for each B for each C in B
{
B.data_size[index] = sizeof©; // for example.. unless the C structs are generic too (they usually aren't)
put© : position += sizeof©

and so on .. and so forth =)
now the position you are in the file is incremented for each structure, packed tightly
and there is no confusion about where anything is located
this is an ultra-basic system, that leaves less room for problems in your code, but is still not completely resistant to future updates and changes
to compensate for future changes, a version system could be used, but then you'd need backwards compatibility in your games loading system
personally, i say if you make any changes to the saving system - make all the changes, and scrap the old system, if you can :)
i hope this helps

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