Convert function to read from string instead of file in C
- by Dusty
I've been tasked with updating a function which currently reads in a configuration file from disk and populates a structure:
static int LoadFromFile(FILE *Stream, ConfigStructure *cs)
{
int tempInt;
...
if ( fscanf( Stream, "Version: %d\n",&tempInt) != 1 )
{
printf("Unable to read version number\n");
return 0;
}
cs->Version = tempInt;
...
}
to one which allows us to bypass writing the configuration to disk and instead pass it directly in memory, roughly equivalent to this:
static int LoadFromString(char *Stream, ConfigStructure *cs)
A few things to note:
The current LoadFromFile function is incredibly dense and complex, reading dozens of versions of the config file in a backward compatible manner, which makes duplication of the overall logic quite a pain.
The functions that generate the config file and those that read it originate in totally different parts of the old system and therefore don't share any data structures so I can't pass those directly. I could potentially write a wrapper, but again, it would need to handle any structure passed in in a backwards compatible manner.
I'm tempted to just pass the file as is in as a string (as in the prototype above) and convert all the fscanf's to sscanf's but then I have to handle incrementing the pointer along (and potentially dealing with buffer overrun errors) manually.
This has to remain in C, so no C++ functionality like streams can help here
Am I missing a better option? Is there some way to create a FILE * that actually just points to a location in memory instead of on disk? Any pointers, suggestions or other help is greatly appreciated.
