Circular file

Hi everybody,
I need to write a file that i want to limit the size to 800 Kb and when have this size, start to write from the top of the file and
deleting this first line and so on.
How can i do it.

Who is Participating?
snypConnect With a Mentor Commented:
why not just keep track of how much you've written to the file and then fseek() your file when you hit your limit?

however.. let's say you're at position 0xC7FFF and you want to write 0x1000 bytes.. try the following..
you'll need to know the size of the data you're writing obviously..

#define SIZELIMIT 0xC8000
char dataArray[512];
unsigned long dataSize;
unsigned long writeSize;
unsigned long filePos;


filePos = ftell(filePtr);

if (filePos + dataSize >= SIZELIMIT) {

writeSize = dataSize - ((filePos + dataSize) % SIZELIMIT); // write as much as we can up to the end of the 800kb
fwrite(&dataArray[0], writeSize, 1, filePtr);

fteek(filePtr, 0, 0); // back to the start of the file
fwrite(&dataArray[((filePos + dataSize) % SIZELIMIT)], dataSize - writeSize, filePtr); // write the remainder at 0


fwrite(&dataArray[0], dataSize, 1, filePtr); // data is small enough to fit, just write it all
Store your data in an array first.  Declare an array of that size in your program.  Write to the array and starting at the beginning when you get to the end.  When you are ready to write the file, just reference the array.
i'm sorry, i need to correct the code there..

fseek(filePtr, 0, 0); // back to the start of the file
fwrite(&dataArray[writeSize], dataSize - writeSize, filePtr); // write the remainder at 0
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