I checked this question, but it's not what I'm looking for.
I'm trying to figure out how to cap a log file's size (say, 10MB), and as soon as it's hit, either:
Don't really care about language - as long as it's possible :)
Note: I am aware of the rolling log files approach (hit a target size, rename, and continue logging). I am looking to avoid such a roll.
If you are implementing both the writer and the reader, then you can do something like this:
struct logentry {
timestamp ts;
char msg [4000];
};
class logger {
private:
int write_recordnum; // next record number to write
int max_recordnum; // controls maximum size of file
FILE *logfile;
public:
logger (const char *filename, int max_records)
{
max_recordnum = max_records;
logfile = fopen (filename, "a+");
}
void write_next_entry (const char *msg, ...)
{
struct logentry ent;
// format message into entry
va_list ap;
va_start (ap, msg);
vsnprintf (ent.msg, sizeof(ent.msg), msg, ap);
va_end (ap);
ent.ts = gettimestamp();
// position logfile
if (write_recordnum > max_recordnum)
write_recordnum = 0;
fseek (logfile, write_recordnum * sizeof (ent), 0);
fwrite (&ent, 1, sizeof(ent), logfile);
}
bool read_entry (int recnum, char *msg)
{
struct logentry ent;
if (recnum >= max_recordnum)
return false;
fseek (logfile, recnum * sizeof (ent), 0);
fread (&ent, 1, sizeof(ent), logfile);
strcpy (msg, ent.msg);
return true;
}
};
The idea is to manage a circular buffer by explicit fixed-size record numbers. Needed is logic to manage whether record N exists, and to check errors.