/*-------------------------------------------------------------------------
 *
 * controldata_utils.c
 *		Common code for control data file output.
 *
 *
 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/common/controldata_utils.c
 *
 *-------------------------------------------------------------------------
 */

#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif

#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "catalog/pg_control.h"
#include "common/controldata_utils.h"
#include "port/pg_crc32c.h"

/*
 * get_controlfile(char *DataDir, const char *progname)
 *
 * Get controlfile values. The caller is responsible
 * for pfreeing the result.
 *
 * Returns NULL if the CRC did not match.
 */
ControlFileData *
get_controlfile(const char *DataDir, const char *progname)
{
	ControlFileData *ControlFile;
	int			fd;
	char		ControlFilePath[MAXPGPATH];
	pg_crc32c	crc;

	ControlFile = palloc(sizeof(ControlFileData));
	snprintf(ControlFilePath, MAXPGPATH, "%s/global/pg_control", DataDir);

	if ((fd = open(ControlFilePath, O_RDONLY | PG_BINARY, 0)) == -1)
#ifndef FRONTEND
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not open file \"%s\" for reading: %m",
						ControlFilePath)));
#else
	{
		fprintf(stderr, _("%s: could not open file \"%s\" for reading: %s\n"),
				progname, ControlFilePath, strerror(errno));
		exit(EXIT_FAILURE);
	}
#endif

	if (read(fd, ControlFile, sizeof(ControlFileData)) != sizeof(ControlFileData))
#ifndef FRONTEND
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not read file \"%s\": %m", ControlFilePath)));
#else
	{
		fprintf(stderr, _("%s: could not read file \"%s\": %s\n"),
				progname, ControlFilePath, strerror(errno));
		exit(EXIT_FAILURE);
	}
#endif

	close(fd);

	/* Check the CRC. */
	INIT_CRC32C(crc);
	COMP_CRC32C(crc,
				(char *) ControlFile,
				offsetof(ControlFileData, crc));
	FIN_CRC32C(crc);

	if (!EQ_CRC32C(crc, ControlFile->crc))
	{
		pfree(ControlFile);
		return NULL;
	}

	/* Make sure the control file is valid byte order. */
	if (ControlFile->pg_control_version % 65536 == 0 &&
		ControlFile->pg_control_version / 65536 != 0)
#ifndef FRONTEND
		elog(ERROR, _("byte ordering mismatch"));
#else
		printf(_("WARNING: possible byte ordering mismatch\n"
				 "The byte ordering used to store the pg_control file might not match the one\n"
				 "used by this program.  In that case the results below would be incorrect, and\n"
				 "the PostgreSQL installation would be incompatible with this data directory.\n"));
#endif

	return ControlFile;
}