/*
 * dumpstat --- simple standalone program to read and analyze a PG stats
 * file.  Based on pgstat_read_statsfile() from 8.1 sources.
 *
 * Currently works with either 8.0 or 8.1 formats depending on which
 * headers it is compiled against.
 */
#include "postgres.h"

#include "pgstat.h"


int
main(int argc, char **argv)
{
	PgStat_StatDBEntry dbbuf;
	PgStat_StatTabEntry tabbuf;
	PgStat_StatBeEntry beentry;
	FILE	   *fpin;
	int32		format_id;
	int			maxbackends = 0;
	int			havebackends = 0;
	int			havedbs = 0;
	int			havetabs = 0;

	/*
	 * Try to open the status file. If it doesn't exist, the backends simply
	 * return zero for anything and the collector simply starts from scratch
	 * with empty counters.
	 */
	if ((fpin = fopen(argv[1], "rb")) == NULL)
	{
		perror(argv[1]);
		return 1;
	}

	/*
	 * Verify it's of the expected format.
	 */
#ifdef PGSTAT_FILE_FORMAT_ID
	if (fread(&format_id, 1, sizeof(format_id), fpin) != sizeof(format_id)
		|| format_id != PGSTAT_FILE_FORMAT_ID)
	{
		fprintf(stderr, "corrupted pgstat.stat file\n");
		goto done;
	}
#endif

	/*
	 * We found an existing collector stats file. Read it and put all the
	 * hashtable entries into place.
	 */
	for (;;)
	{
		switch (fgetc(fpin))
		{
				/*
				 * 'D'	A PgStat_StatDBEntry struct describing a database
				 * follows. Subsequently, zero to many 'T' entries will follow
				 * until a 'd' is encountered.
				 */
			case 'D':
				if (fread(&dbbuf, 1, sizeof(dbbuf), fpin) != sizeof(dbbuf))
				{
					fprintf(stderr, "corrupted pgstat.stat file\n");
					goto done;
				}
				havedbs++;
				break;

				/*
				 * 'd'	End of this database.
				 */
			case 'd':
				break;

				/*
				 * 'T'	A PgStat_StatTabEntry follows.
				 */
			case 'T':
				if (fread(&tabbuf, 1, sizeof(tabbuf), fpin) != sizeof(tabbuf))
				{
					fprintf(stderr, "corrupted pgstat.stat file\n");
					goto done;
				}
				havetabs++;
				break;

				/*
				 * 'M'	The maximum number of backends to expect follows.
				 */
			case 'M':
				if (fread(&maxbackends, 1, sizeof(maxbackends), fpin) !=
					sizeof(maxbackends))
				{
					fprintf(stderr, "corrupted pgstat.stat file\n");
					goto done;
				}
				if (maxbackends == 0)
					goto done;
				break;

				/*
				 * 'B'	A PgStat_StatBeEntry follows.
				 */
			case 'B':
				/*
				 * Read it directly into the table.
				 */
				if (fread(&beentry, 1, sizeof(PgStat_StatBeEntry), fpin) !=
					sizeof(PgStat_StatBeEntry))
				{
					fprintf(stderr, "corrupted pgstat.stat file\n");
					goto done;
				}

				havebackends++;
				break;

				/*
				 * 'E'	The EOF marker of a complete stats file.
				 */
			case 'E':
				goto done;

			default:
				fprintf(stderr, "corrupted pgstat.stat file at %ld\n",
						ftell(fpin) - 1);
				goto done;
		}
	}

done:
	fclose(fpin);

	printf("found %d backends of %d (%ld bytes)\n", havebackends, maxbackends,
		   havebackends * (long) sizeof(PgStat_StatBeEntry));
	printf("%d databases (%ld bytes)\n", havedbs,
		   havedbs * (long) sizeof(PgStat_StatDBEntry));
	printf("%d tables (%ld bytes)\n", havetabs,
		   havetabs * (long) sizeof(PgStat_StatTabEntry));

	return 0;
}