text: /*-------------------------------------------------------------------------
   *
   * 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.
   */
  ControlFileData *
  get_controlfile(char *DataDir, const char *progname)
  {
  	ControlFileData *ControlFile;
  	int			fd;
  	char		ControlFilePath[MAXPGPATH];
  	pg_crc32c	crc;
  	int			r;
  
  	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
  
  	r = read(fd, ControlFile, sizeof(ControlFileData));
  	if (r != sizeof(ControlFileData))
  	{
  		if (r < 0)
  #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
  		else
  #ifndef FRONTEND
  			ereport(ERROR,
  					(errmsg("could not read file \"%s\": read %d of %d",
  							ControlFilePath, r, (int) sizeof(ControlFileData))));
  #else
  		{
  			fprintf(stderr, _("%s: could not read file \"%s\": read %d of %d\n"),
  					progname, ControlFilePath, r, (int) sizeof(ControlFileData));
  			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))
  #ifndef FRONTEND
  		elog(ERROR, _("calculated CRC checksum does not match value stored in file"));
  #else
  		printf(_("WARNING: Calculated CRC checksum does not match value stored in file.\n"
  				 "Either the file is corrupt, or it has a different layout than this program\n"
  				 "is expecting.  The results below are untrustworthy.\n\n"));
  #endif
  
  	/* 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;
  }
  