controldata_utils.c

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/*-------------------------------------------------------------------------
 *
 * controldata_utils.c
 *      Common code for control data file output.
 *
 *
 * Portions Copyright (c) 1996-2018, 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, bool *crc_ok_p)
 *
 * Get controlfile values.  The result is returned as a palloc'd copy of the
 * control file data.
 *
 * crc_ok_p can be used by the caller to see whether the CRC of the control
 * file data is correct.
 */
ControlFileData *
get_controlfile(const char *DataDir, const char *progname, bool *crc_ok_p)
{
    ControlFileData *ControlFile;
    int         fd;
    char        ControlFilePath[MAXPGPATH];
    pg_crc32c   crc;

    AssertArg(crc_ok_p);

    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);

    *crc_ok_p = EQ_CRC32C(crc, ControlFile->crc);

    /* 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;
}