archive.c

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/*-------------------------------------------------------------------------
 *
 * archive.c
 *    Common WAL archive routines
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/common/archive.c
 *
 *-------------------------------------------------------------------------
 */

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

#include "common/archive.h"
#include "lib/stringinfo.h"

/*
 * BuildRestoreCommand
 *
 * Builds a restore command to retrieve a file from WAL archives, replacing
 * the supported aliases with values supplied by the caller as defined by
 * the GUC parameter restore_command: xlogpath for %p, xlogfname for %f and
 * lastRestartPointFname for %r.
 *
 * The result is a palloc'd string for the restore command built.  The
 * caller is responsible for freeing it.  If any of the required arguments
 * is NULL and that the corresponding alias is found in the command given
 * by the caller, then NULL is returned.
 */
char *
BuildRestoreCommand(const char *restoreCommand,
                    const char *xlogpath,
                    const char *xlogfname,
                    const char *lastRestartPointFname)
{
    StringInfoData result;
    const char *sp;

    /*
     * Build the command to be executed.
     */
    initStringInfo(&result);

    for (sp = restoreCommand; *sp; sp++)
    {
        if (*sp == '%')
        {
            switch (sp[1])
            {
                case 'p':
                    {
                        char       *nativePath;

                        /* %p: relative path of target file */
                        if (xlogpath == NULL)
                        {
                            pfree(result.data);
                            return NULL;
                        }
                        sp++;

                        /*
                         * This needs to use a placeholder to not modify the
                         * input with the conversion done via
                         * make_native_path().
                         */
                        nativePath = pstrdup(xlogpath);
                        make_native_path(nativePath);
                        appendStringInfoString(&result,
                                               nativePath);
                        pfree(nativePath);
                        break;
                    }
                case 'f':
                    /* %f: filename of desired file */
                    if (xlogfname == NULL)
                    {
                        pfree(result.data);
                        return NULL;
                    }
                    sp++;
                    appendStringInfoString(&result, xlogfname);
                    break;
                case 'r':
                    /* %r: filename of last restartpoint */
                    if (lastRestartPointFname == NULL)
                    {
                        pfree(result.data);
                        return NULL;
                    }
                    sp++;
                    appendStringInfoString(&result,
                                           lastRestartPointFname);
                    break;
                case '%':
                    /* convert %% to a single % */
                    sp++;
                    appendStringInfoChar(&result, *sp);
                    break;
                default:
                    /* otherwise treat the % as not special */
                    appendStringInfoChar(&result, *sp);
                    break;
            }
        }
        else
        {
            appendStringInfoChar(&result, *sp);
        }
    }

    return result.data;
}