pg_backup_tar.c

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/*-------------------------------------------------------------------------
 *
 * pg_backup_tar.c
 *
 *  This file is copied from the 'files' format file, but dumps data into
 *  one temp file then sends it to the output TAR archive.
 *
 *  The tar format also includes a 'restore.sql' script which is there for
 *  the benefit of humans. This script is never used by pg_restore.
 *
 *  NOTE: If you untar the created 'tar' file, the resulting files are
 *  compatible with the 'directory' format. Please keep the two formats in
 *  sync.
 *
 *  See the headers to pg_backup_directory & pg_restore for more details.
 *
 * Copyright (c) 2000, Philip Warner
 *      Rights are granted to use this software in any way so long
 *      as this notice is not removed.
 *
 *  The author is not responsible for loss or damages that may
 *  result from it's use.
 *
 *
 * IDENTIFICATION
 *      src/bin/pg_dump/pg_backup_tar.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include "pg_backup_archiver.h"
#include "pg_backup_tar.h"
#include "pg_backup_utils.h"
#include "pgtar.h"
#include "common/file_utils.h"
#include "fe_utils/string_utils.h"

#include <sys/stat.h>
#include <ctype.h>
#include <limits.h>
#include <unistd.h>

static void _ArchiveEntry(ArchiveHandle *AH, TocEntry *te);
static void _StartData(ArchiveHandle *AH, TocEntry *te);
static void _WriteData(ArchiveHandle *AH, const void *data, size_t dLen);
static void _EndData(ArchiveHandle *AH, TocEntry *te);
static int  _WriteByte(ArchiveHandle *AH, const int i);
static int  _ReadByte(ArchiveHandle *);
static void _WriteBuf(ArchiveHandle *AH, const void *buf, size_t len);
static void _ReadBuf(ArchiveHandle *AH, void *buf, size_t len);
static void _CloseArchive(ArchiveHandle *AH);
static void _PrintTocData(ArchiveHandle *AH, TocEntry *te);
static void _WriteExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _ReadExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _PrintExtraToc(ArchiveHandle *AH, TocEntry *te);

static void _StartBlobs(ArchiveHandle *AH, TocEntry *te);
static void _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndBlob(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndBlobs(ArchiveHandle *AH, TocEntry *te);

#define K_STD_BUF_SIZE 1024


typedef struct
{
#ifdef HAVE_LIBZ
    gzFile      zFH;
#else
    FILE       *zFH;
#endif
    FILE       *nFH;
    FILE       *tarFH;
    FILE       *tmpFH;
    char       *targetFile;
    char        mode;
    pgoff_t     pos;
    pgoff_t     fileLen;
    ArchiveHandle *AH;
} TAR_MEMBER;

typedef struct
{
    int         hasSeek;
    pgoff_t     filePos;
    TAR_MEMBER *blobToc;
    FILE       *tarFH;
    pgoff_t     tarFHpos;
    pgoff_t     tarNextMember;
    TAR_MEMBER *FH;
    int         isSpecialScript;
    TAR_MEMBER *scriptTH;
} lclContext;

typedef struct
{
    TAR_MEMBER *TH;
    char       *filename;
} lclTocEntry;

/* translator: this is a module name */
static const char *modulename = gettext_noop("tar archiver");

static void _LoadBlobs(ArchiveHandle *AH);

static TAR_MEMBER *tarOpen(ArchiveHandle *AH, const char *filename, char mode);
static void tarClose(ArchiveHandle *AH, TAR_MEMBER *TH);

#ifdef __NOT_USED__
static char *tarGets(char *buf, size_t len, TAR_MEMBER *th);
#endif
static int  tarPrintf(ArchiveHandle *AH, TAR_MEMBER *th, const char *fmt,...) pg_attribute_printf(3, 4);

static void _tarAddFile(ArchiveHandle *AH, TAR_MEMBER *th);
static TAR_MEMBER *_tarPositionTo(ArchiveHandle *AH, const char *filename);
static size_t tarRead(void *buf, size_t len, TAR_MEMBER *th);
static size_t tarWrite(const void *buf, size_t len, TAR_MEMBER *th);
static void _tarWriteHeader(TAR_MEMBER *th);
static int  _tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th);
static size_t _tarReadRaw(ArchiveHandle *AH, void *buf, size_t len, TAR_MEMBER *th, FILE *fh);

static size_t _scriptOut(ArchiveHandle *AH, const void *buf, size_t len);

/*
 *  Initializer
 */
void
InitArchiveFmt_Tar(ArchiveHandle *AH)
{
    lclContext *ctx;

    /* Assuming static functions, this can be copied for each format. */
    AH->ArchiveEntryPtr = _ArchiveEntry;
    AH->StartDataPtr = _StartData;
    AH->WriteDataPtr = _WriteData;
    AH->EndDataPtr = _EndData;
    AH->WriteBytePtr = _WriteByte;
    AH->ReadBytePtr = _ReadByte;
    AH->WriteBufPtr = _WriteBuf;
    AH->ReadBufPtr = _ReadBuf;
    AH->ClosePtr = _CloseArchive;
    AH->ReopenPtr = NULL;
    AH->PrintTocDataPtr = _PrintTocData;
    AH->ReadExtraTocPtr = _ReadExtraToc;
    AH->WriteExtraTocPtr = _WriteExtraToc;
    AH->PrintExtraTocPtr = _PrintExtraToc;

    AH->StartBlobsPtr = _StartBlobs;
    AH->StartBlobPtr = _StartBlob;
    AH->EndBlobPtr = _EndBlob;
    AH->EndBlobsPtr = _EndBlobs;
    AH->ClonePtr = NULL;
    AH->DeClonePtr = NULL;

    AH->WorkerJobDumpPtr = NULL;
    AH->WorkerJobRestorePtr = NULL;

    /*
     * Set up some special context used in compressing data.
     */
    ctx = (lclContext *) pg_malloc0(sizeof(lclContext));
    AH->formatData = (void *) ctx;
    ctx->filePos = 0;
    ctx->isSpecialScript = 0;

    /* Initialize LO buffering */
    AH->lo_buf_size = LOBBUFSIZE;
    AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);

    /*
     * Now open the tar file, and load the TOC if we're in read mode.
     */
    if (AH->mode == archModeWrite)
    {
        if (AH->fSpec && strcmp(AH->fSpec, "") != 0)
        {
            ctx->tarFH = fopen(AH->fSpec, PG_BINARY_W);
            if (ctx->tarFH == NULL)
                exit_horribly(modulename,
                              "could not open TOC file \"%s\" for output: %s\n",
                              AH->fSpec, strerror(errno));
        }
        else
        {
            ctx->tarFH = stdout;
            if (ctx->tarFH == NULL)
                exit_horribly(modulename,
                              "could not open TOC file for output: %s\n",
                              strerror(errno));
        }

        ctx->tarFHpos = 0;

        /*
         * Make unbuffered since we will dup() it, and the buffers screw each
         * other
         */
        /* setvbuf(ctx->tarFH, NULL, _IONBF, 0); */

        ctx->hasSeek = checkSeek(ctx->tarFH);

        /*
         * We don't support compression because reading the files back is not
         * possible since gzdopen uses buffered IO which totally screws file
         * positioning.
         */
        if (AH->compression != 0)
            exit_horribly(modulename,
                          "compression is not supported by tar archive format\n");
    }
    else
    {                           /* Read Mode */
        if (AH->fSpec && strcmp(AH->fSpec, "") != 0)
        {
            ctx->tarFH = fopen(AH->fSpec, PG_BINARY_R);
            if (ctx->tarFH == NULL)
                exit_horribly(modulename, "could not open TOC file \"%s\" for input: %s\n",
                              AH->fSpec, strerror(errno));
        }
        else
        {
            ctx->tarFH = stdin;
            if (ctx->tarFH == NULL)
                exit_horribly(modulename, "could not open TOC file for input: %s\n",
                              strerror(errno));
        }

        /*
         * Make unbuffered since we will dup() it, and the buffers screw each
         * other
         */
        /* setvbuf(ctx->tarFH, NULL, _IONBF, 0); */

        ctx->tarFHpos = 0;

        ctx->hasSeek = checkSeek(ctx->tarFH);

        /*
         * Forcibly unmark the header as read since we use the lookahead
         * buffer
         */
        AH->readHeader = 0;

        ctx->FH = (void *) tarOpen(AH, "toc.dat", 'r');
        ReadHead(AH);
        ReadToc(AH);
        tarClose(AH, ctx->FH);  /* Nothing else in the file... */
    }
}

/*
 * - Start a new TOC entry
 *   Setup the output file name.
 */
static void
_ArchiveEntry(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *ctx;
    char        fn[K_STD_BUF_SIZE];

    ctx = (lclTocEntry *) pg_malloc0(sizeof(lclTocEntry));
    if (te->dataDumper != NULL)
    {
#ifdef HAVE_LIBZ
        if (AH->compression == 0)
            sprintf(fn, "%d.dat", te->dumpId);
        else
            sprintf(fn, "%d.dat.gz", te->dumpId);
#else
        sprintf(fn, "%d.dat", te->dumpId);
#endif
        ctx->filename = pg_strdup(fn);
    }
    else
    {
        ctx->filename = NULL;
        ctx->TH = NULL;
    }
    te->formatData = (void *) ctx;
}

static void
_WriteExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *ctx = (lclTocEntry *) te->formatData;

    if (ctx->filename)
        WriteStr(AH, ctx->filename);
    else
        WriteStr(AH, "");
}

static void
_ReadExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *ctx = (lclTocEntry *) te->formatData;

    if (ctx == NULL)
    {
        ctx = (lclTocEntry *) pg_malloc0(sizeof(lclTocEntry));
        te->formatData = (void *) ctx;
    }

    ctx->filename = ReadStr(AH);
    if (strlen(ctx->filename) == 0)
    {
        free(ctx->filename);
        ctx->filename = NULL;
    }
    ctx->TH = NULL;
}

static void
_PrintExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *ctx = (lclTocEntry *) te->formatData;

    if (AH->public.verbose && ctx->filename != NULL)
        ahprintf(AH, "-- File: %s\n", ctx->filename);
}

static void
_StartData(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;

    tctx->TH = tarOpen(AH, tctx->filename, 'w');
}

static TAR_MEMBER *
tarOpen(ArchiveHandle *AH, const char *filename, char mode)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    TAR_MEMBER *tm;

#ifdef HAVE_LIBZ
    char        fmode[10];
#endif

    if (mode == 'r')
    {
        tm = _tarPositionTo(AH, filename);
        if (!tm)                /* Not found */
        {
            if (filename)
            {
                /*
                 * Couldn't find the requested file. Future: do SEEK(0) and
                 * retry.
                 */
                exit_horribly(modulename, "could not find file \"%s\" in archive\n", filename);
            }
            else
            {
                /* Any file OK, none left, so return NULL */
                return NULL;
            }
        }

#ifdef HAVE_LIBZ

        if (AH->compression == 0)
            tm->nFH = ctx->tarFH;
        else
            exit_horribly(modulename, "compression is not supported by tar archive format\n");
        /* tm->zFH = gzdopen(dup(fileno(ctx->tarFH)), "rb"); */
#else
        tm->nFH = ctx->tarFH;
#endif
    }
    else
    {
        int         old_umask;

        tm = pg_malloc0(sizeof(TAR_MEMBER));

        /*
         * POSIX does not require, but permits, tmpfile() to restrict file
         * permissions.  Given an OS crash after we write data, the filesystem
         * might retain the data but forget tmpfile()'s unlink().  If so, the
         * file mode protects confidentiality of the data written.
         */
        old_umask = umask(S_IRWXG | S_IRWXO);

#ifndef WIN32
        tm->tmpFH = tmpfile();
#else

        /*
         * On WIN32, tmpfile() generates a filename in the root directory,
         * which requires administrative permissions on certain systems. Loop
         * until we find a unique file name we can create.
         */
        while (1)
        {
            char       *name;
            int         fd;

            name = _tempnam(NULL, "pg_temp_");
            if (name == NULL)
                break;
            fd = open(name, O_RDWR | O_CREAT | O_EXCL | O_BINARY |
                      O_TEMPORARY, S_IRUSR | S_IWUSR);
            free(name);

            if (fd != -1)       /* created a file */
            {
                tm->tmpFH = fdopen(fd, "w+b");
                break;
            }
            else if (errno != EEXIST)   /* failure other than file exists */
                break;
        }
#endif

        if (tm->tmpFH == NULL)
            exit_horribly(modulename, "could not generate temporary file name: %s\n", strerror(errno));

        umask(old_umask);

#ifdef HAVE_LIBZ

        if (AH->compression != 0)
        {
            sprintf(fmode, "wb%d", AH->compression);
            tm->zFH = gzdopen(dup(fileno(tm->tmpFH)), fmode);
            if (tm->zFH == NULL)
                exit_horribly(modulename, "could not open temporary file\n");
        }
        else
            tm->nFH = tm->tmpFH;
#else

        tm->nFH = tm->tmpFH;
#endif

        tm->AH = AH;
        tm->targetFile = pg_strdup(filename);
    }

    tm->mode = mode;
    tm->tarFH = ctx->tarFH;

    return tm;
}

static void
tarClose(ArchiveHandle *AH, TAR_MEMBER *th)
{
    /*
     * Close the GZ file since we dup'd. This will flush the buffers.
     */
    if (AH->compression != 0)
        if (GZCLOSE(th->zFH) != 0)
            exit_horribly(modulename, "could not close tar member\n");

    if (th->mode == 'w')
        _tarAddFile(AH, th);    /* This will close the temp file */

    /*
     * else Nothing to do for normal read since we don't dup() normal file
     * handle, and we don't use temp files.
     */

    if (th->targetFile)
        free(th->targetFile);

    th->nFH = NULL;
    th->zFH = NULL;
}

#ifdef __NOT_USED__
static char *
tarGets(char *buf, size_t len, TAR_MEMBER *th)
{
    char       *s;
    size_t      cnt = 0;
    char        c = ' ';
    int         eof = 0;

    /* Can't read past logical EOF */
    if (len > (th->fileLen - th->pos))
        len = th->fileLen - th->pos;

    while (cnt < len && c != '\n')
    {
        if (_tarReadRaw(th->AH, &c, 1, th, NULL) <= 0)
        {
            eof = 1;
            break;
        }
        buf[cnt++] = c;
    }

    if (eof && cnt == 0)
        s = NULL;
    else
    {
        buf[cnt++] = '\0';
        s = buf;
    }

    if (s)
    {
        len = strlen(s);
        th->pos += len;
    }

    return s;
}
#endif

/*
 * Just read bytes from the archive. This is the low level read routine
 * that is used for ALL reads on a tar file.
 */
static size_t
_tarReadRaw(ArchiveHandle *AH, void *buf, size_t len, TAR_MEMBER *th, FILE *fh)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    size_t      avail;
    size_t      used = 0;
    size_t      res = 0;

    avail = AH->lookaheadLen - AH->lookaheadPos;
    if (avail > 0)
    {
        /* We have some lookahead bytes to use */
        if (avail >= len)       /* Just use the lookahead buffer */
            used = len;
        else
            used = avail;

        /* Copy, and adjust buffer pos */
        memcpy(buf, AH->lookahead + AH->lookaheadPos, used);
        AH->lookaheadPos += used;

        /* Adjust required length */
        len -= used;
    }

    /* Read the file if len > 0 */
    if (len > 0)
    {
        if (fh)
        {
            res = fread(&((char *) buf)[used], 1, len, fh);
            if (res != len && !feof(fh))
                READ_ERROR_EXIT(fh);
        }
        else if (th)
        {
            if (th->zFH)
            {
                res = GZREAD(&((char *) buf)[used], 1, len, th->zFH);
                if (res != len && !GZEOF(th->zFH))
                {
#ifdef HAVE_LIBZ
                    int         errnum;
                    const char *errmsg = gzerror(th->zFH, &errnum);

                    exit_horribly(modulename,
                                  "could not read from input file: %s\n",
                                  errnum == Z_ERRNO ? strerror(errno) : errmsg);
#else
                    exit_horribly(modulename,
                                  "could not read from input file: %s\n",
                                  strerror(errno));
#endif
                }
            }
            else
            {
                res = fread(&((char *) buf)[used], 1, len, th->nFH);
                if (res != len && !feof(th->nFH))
                    READ_ERROR_EXIT(th->nFH);
            }
        }
        else
            exit_horribly(modulename, "internal error -- neither th nor fh specified in tarReadRaw()\n");
    }

    ctx->tarFHpos += res + used;

    return (res + used);
}

static size_t
tarRead(void *buf, size_t len, TAR_MEMBER *th)
{
    size_t      res;

    if (th->pos + len > th->fileLen)
        len = th->fileLen - th->pos;

    if (len <= 0)
        return 0;

    res = _tarReadRaw(th->AH, buf, len, th, NULL);

    th->pos += res;

    return res;
}

static size_t
tarWrite(const void *buf, size_t len, TAR_MEMBER *th)
{
    size_t      res;

    if (th->zFH != NULL)
        res = GZWRITE(buf, 1, len, th->zFH);
    else
        res = fwrite(buf, 1, len, th->nFH);

    th->pos += res;
    return res;
}

static void
_WriteData(ArchiveHandle *AH, const void *data, size_t dLen)
{
    lclTocEntry *tctx = (lclTocEntry *) AH->currToc->formatData;

    if (tarWrite(data, dLen, tctx->TH) != dLen)
        WRITE_ERROR_EXIT;

    return;
}

static void
_EndData(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;

    /* Close the file */
    tarClose(AH, tctx->TH);
    tctx->TH = NULL;
}

/*
 * Print data for a given file
 */
static void
_PrintFileData(ArchiveHandle *AH, char *filename)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        buf[4096];
    size_t      cnt;
    TAR_MEMBER *th;

    if (!filename)
        return;

    th = tarOpen(AH, filename, 'r');
    ctx->FH = th;

    while ((cnt = tarRead(buf, 4095, th)) > 0)
    {
        buf[cnt] = '\0';
        ahwrite(buf, 1, cnt, AH);
    }

    tarClose(AH, th);
}


/*
 * Print data for a given TOC entry
*/
static void
_PrintTocData(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    int         pos1;

    if (!tctx->filename)
        return;

    /*
     * If we're writing the special restore.sql script, emit a suitable
     * command to include each table's data from the corresponding file.
     *
     * In the COPY case this is a bit klugy because the regular COPY command
     * was already printed before we get control.
     */
    if (ctx->isSpecialScript)
    {
        if (te->copyStmt)
        {
            /* Abort the COPY FROM stdin */
            ahprintf(AH, "\\.\n");

            /*
             * The COPY statement should look like "COPY ... FROM stdin;\n",
             * see dumpTableData().
             */
            pos1 = (int) strlen(te->copyStmt) - 13;
            if (pos1 < 6 || strncmp(te->copyStmt, "COPY ", 5) != 0 ||
                strcmp(te->copyStmt + pos1, " FROM stdin;\n") != 0)
                exit_horribly(modulename,
                              "unexpected COPY statement syntax: \"%s\"\n",
                              te->copyStmt);

            /* Emit all but the FROM part ... */
            ahwrite(te->copyStmt, 1, pos1, AH);
            /* ... and insert modified FROM */
            ahprintf(AH, " FROM '$$PATH$$/%s';\n\n", tctx->filename);
        }
        else
        {
            /* --inserts mode, no worries, just include the data file */
            ahprintf(AH, "\\i $$PATH$$/%s\n\n", tctx->filename);
        }

        return;
    }

    if (strcmp(te->desc, "BLOBS") == 0)
        _LoadBlobs(AH);
    else
        _PrintFileData(AH, tctx->filename);
}

static void
_LoadBlobs(ArchiveHandle *AH)
{
    Oid         oid;
    lclContext *ctx = (lclContext *) AH->formatData;
    TAR_MEMBER *th;
    size_t      cnt;
    bool        foundBlob = false;
    char        buf[4096];

    StartRestoreBlobs(AH);

    th = tarOpen(AH, NULL, 'r');    /* Open next file */
    while (th != NULL)
    {
        ctx->FH = th;

        if (strncmp(th->targetFile, "blob_", 5) == 0)
        {
            oid = atooid(&th->targetFile[5]);
            if (oid != 0)
            {
                ahlog(AH, 1, "restoring large object with OID %u\n", oid);

                StartRestoreBlob(AH, oid, AH->public.ropt->dropSchema);

                while ((cnt = tarRead(buf, 4095, th)) > 0)
                {
                    buf[cnt] = '\0';
                    ahwrite(buf, 1, cnt, AH);
                }
                EndRestoreBlob(AH, oid);
                foundBlob = true;
            }
            tarClose(AH, th);
        }
        else
        {
            tarClose(AH, th);

            /*
             * Once we have found the first blob, stop at the first non-blob
             * entry (which will be 'blobs.toc').  This coding would eat all
             * the rest of the archive if there are no blobs ... but this
             * function shouldn't be called at all in that case.
             */
            if (foundBlob)
                break;
        }

        th = tarOpen(AH, NULL, 'r');
    }
    EndRestoreBlobs(AH);
}


static int
_WriteByte(ArchiveHandle *AH, const int i)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        b = i;          /* Avoid endian problems */

    if (tarWrite(&b, 1, ctx->FH) != 1)
        WRITE_ERROR_EXIT;

    ctx->filePos += 1;
    return 1;
}

static int
_ReadByte(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    size_t      res;
    unsigned char c;

    res = tarRead(&c, 1, ctx->FH);
    if (res != 1)
        /* We already would have exited for errors on reads, must be EOF */
        exit_horribly(modulename,
                      "could not read from input file: end of file\n");
    ctx->filePos += 1;
    return c;
}

static void
_WriteBuf(ArchiveHandle *AH, const void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    if (tarWrite(buf, len, ctx->FH) != len)
        WRITE_ERROR_EXIT;

    ctx->filePos += len;
}

static void
_ReadBuf(ArchiveHandle *AH, void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    if (tarRead(buf, len, ctx->FH) != len)
        /* We already would have exited for errors on reads, must be EOF */
        exit_horribly(modulename,
                      "could not read from input file: end of file\n");

    ctx->filePos += len;
    return;
}

static void
_CloseArchive(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    TAR_MEMBER *th;
    RestoreOptions *ropt;
    RestoreOptions *savRopt;
    DumpOptions *savDopt;
    int         savVerbose,
                i;

    if (AH->mode == archModeWrite)
    {
        /*
         * Write the Header & TOC to the archive FIRST
         */
        th = tarOpen(AH, "toc.dat", 'w');
        ctx->FH = th;
        WriteHead(AH);
        WriteToc(AH);
        tarClose(AH, th);       /* Not needed any more */

        /*
         * Now send the data (tables & blobs)
         */
        WriteDataChunks(AH, NULL);

        /*
         * Now this format wants to append a script which does a full restore
         * if the files have been extracted.
         */
        th = tarOpen(AH, "restore.sql", 'w');

        tarPrintf(AH, th, "--\n"
                  "-- NOTE:\n"
                  "--\n"
                  "-- File paths need to be edited. Search for $$PATH$$ and\n"
                  "-- replace it with the path to the directory containing\n"
                  "-- the extracted data files.\n"
                  "--\n");

        AH->CustomOutPtr = _scriptOut;

        ctx->isSpecialScript = 1;
        ctx->scriptTH = th;

        ropt = NewRestoreOptions();
        memcpy(ropt, AH->public.ropt, sizeof(RestoreOptions));
        ropt->filename = NULL;
        ropt->dropSchema = 1;
        ropt->compression = 0;
        ropt->superuser = NULL;
        ropt->suppressDumpWarnings = true;

        savDopt = AH->public.dopt;
        savRopt = AH->public.ropt;

        SetArchiveOptions((Archive *) AH, NULL, ropt);

        savVerbose = AH->public.verbose;
        AH->public.verbose = 0;

        RestoreArchive((Archive *) AH);

        SetArchiveOptions((Archive *) AH, savDopt, savRopt);

        AH->public.verbose = savVerbose;

        tarClose(AH, th);

        ctx->isSpecialScript = 0;

        /*
         * EOF marker for tar files is two blocks of NULLs.
         */
        for (i = 0; i < 512 * 2; i++)
        {
            if (fputc(0, ctx->tarFH) == EOF)
                WRITE_ERROR_EXIT;
        }

        /* Sync the output file if one is defined */
        if (AH->dosync && AH->fSpec)
            (void) fsync_fname(AH->fSpec, false, progname);
    }

    AH->FH = NULL;
}

static size_t
_scriptOut(ArchiveHandle *AH, const void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    return tarWrite(buf, len, ctx->scriptTH);
}

/*
 * BLOB support
 */

/*
 * Called by the archiver when starting to save all BLOB DATA (not schema).
 * This routine should save whatever format-specific information is needed
 * to read the BLOBs back into memory.
 *
 * It is called just prior to the dumper's DataDumper routine.
 *
 * Optional, but strongly recommended.
 *
 */
static void
_StartBlobs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        fname[K_STD_BUF_SIZE];

    sprintf(fname, "blobs.toc");
    ctx->blobToc = tarOpen(AH, fname, 'w');
}

/*
 * Called by the archiver when the dumper calls StartBlob.
 *
 * Mandatory.
 *
 * Must save the passed OID for retrieval at restore-time.
 */
static void
_StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    char        fname[255];
    char       *sfx;

    if (oid == 0)
        exit_horribly(modulename, "invalid OID for large object (%u)\n", oid);

    if (AH->compression != 0)
        sfx = ".gz";
    else
        sfx = "";

    sprintf(fname, "blob_%u.dat%s", oid, sfx);

    tarPrintf(AH, ctx->blobToc, "%u %s\n", oid, fname);

    tctx->TH = tarOpen(AH, fname, 'w');
}

/*
 * Called by the archiver when the dumper calls EndBlob.
 *
 * Optional.
 *
 */
static void
_EndBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;

    tarClose(AH, tctx->TH);
}

/*
 * Called by the archiver when finishing saving all BLOB DATA.
 *
 * Optional.
 *
 */
static void
_EndBlobs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    /* Write out a fake zero OID to mark end-of-blobs. */
    /* WriteInt(AH, 0); */

    tarClose(AH, ctx->blobToc);
}



/*------------
 * TAR Support
 *------------
 */

static int
tarPrintf(ArchiveHandle *AH, TAR_MEMBER *th, const char *fmt,...)
{
    char       *p;
    size_t      len = 128;      /* initial assumption about buffer size */
    size_t      cnt;

    for (;;)
    {
        va_list     args;

        /* Allocate work buffer. */
        p = (char *) pg_malloc(len);

        /* Try to format the data. */
        va_start(args, fmt);
        cnt = pvsnprintf(p, len, fmt, args);
        va_end(args);

        if (cnt < len)
            break;              /* success */

        /* Release buffer and loop around to try again with larger len. */
        free(p);
        len = cnt;
    }

    cnt = tarWrite(p, cnt, th);
    free(p);
    return (int) cnt;
}

bool
isValidTarHeader(char *header)
{
    int         sum;
    int         chk = tarChecksum(header);

    sum = read_tar_number(&header[148], 8);

    if (sum != chk)
        return false;

    /* POSIX tar format */
    if (memcmp(&header[257], "ustar\0", 6) == 0 &&
        memcmp(&header[263], "00", 2) == 0)
        return true;
    /* GNU tar format */
    if (memcmp(&header[257], "ustar  \0", 8) == 0)
        return true;
    /* not-quite-POSIX format written by pre-9.3 pg_dump */
    if (memcmp(&header[257], "ustar00\0", 8) == 0)
        return true;

    return false;
}

/* Given the member, write the TAR header & copy the file */
static void
_tarAddFile(ArchiveHandle *AH, TAR_MEMBER *th)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    FILE       *tmp = th->tmpFH;    /* Grab it for convenience */
    char        buf[32768];
    size_t      cnt;
    pgoff_t     len = 0;
    size_t      res;
    size_t      i,
                pad;

    /*
     * Find file len & go back to start.
     */
    fseeko(tmp, 0, SEEK_END);
    th->fileLen = ftello(tmp);
    if (th->fileLen < 0)
        exit_horribly(modulename, "could not determine seek position in archive file: %s\n",
                      strerror(errno));
    fseeko(tmp, 0, SEEK_SET);

    _tarWriteHeader(th);

    while ((cnt = fread(buf, 1, sizeof(buf), tmp)) > 0)
    {
        if ((res = fwrite(buf, 1, cnt, th->tarFH)) != cnt)
            WRITE_ERROR_EXIT;
        len += res;
    }
    if (!feof(tmp))
        READ_ERROR_EXIT(tmp);

    if (fclose(tmp) != 0)       /* This *should* delete it... */
        exit_horribly(modulename, "could not close temporary file: %s\n",
                      strerror(errno));

    if (len != th->fileLen)
    {
        char        buf1[32],
                    buf2[32];

        snprintf(buf1, sizeof(buf1), INT64_FORMAT, (int64) len);
        snprintf(buf2, sizeof(buf2), INT64_FORMAT, (int64) th->fileLen);
        exit_horribly(modulename, "actual file length (%s) does not match expected (%s)\n",
                      buf1, buf2);
    }

    pad = ((len + 511) & ~511) - len;
    for (i = 0; i < pad; i++)
    {
        if (fputc('\0', th->tarFH) == EOF)
            WRITE_ERROR_EXIT;
    }

    ctx->tarFHpos += len + pad;
}

/* Locate the file in the archive, read header and position to data */
static TAR_MEMBER *
_tarPositionTo(ArchiveHandle *AH, const char *filename)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    TAR_MEMBER *th = pg_malloc0(sizeof(TAR_MEMBER));
    char        c;
    char        header[512];
    size_t      i,
                len,
                blks;
    int         id;

    th->AH = AH;

    /* Go to end of current file, if any */
    if (ctx->tarFHpos != 0)
    {
        char        buf1[100],
                    buf2[100];

        snprintf(buf1, sizeof(buf1), INT64_FORMAT, (int64) ctx->tarFHpos);
        snprintf(buf2, sizeof(buf2), INT64_FORMAT, (int64) ctx->tarNextMember);
        ahlog(AH, 4, "moving from position %s to next member at file position %s\n",
              buf1, buf2);

        while (ctx->tarFHpos < ctx->tarNextMember)
            _tarReadRaw(AH, &c, 1, NULL, ctx->tarFH);
    }

    {
        char        buf[100];

        snprintf(buf, sizeof(buf), INT64_FORMAT, (int64) ctx->tarFHpos);
        ahlog(AH, 4, "now at file position %s\n", buf);
    }

    /* We are at the start of the file, or at the next member */

    /* Get the header */
    if (!_tarGetHeader(AH, th))
    {
        if (filename)
            exit_horribly(modulename, "could not find header for file \"%s\" in tar archive\n", filename);
        else
        {
            /*
             * We're just scanning the archive for the next file, so return
             * null
             */
            free(th);
            return NULL;
        }
    }

    while (filename != NULL && strcmp(th->targetFile, filename) != 0)
    {
        ahlog(AH, 4, "skipping tar member %s\n", th->targetFile);

        id = atoi(th->targetFile);
        if ((TocIDRequired(AH, id) & REQ_DATA) != 0)
            exit_horribly(modulename, "restoring data out of order is not supported in this archive format: "
                          "\"%s\" is required, but comes before \"%s\" in the archive file.\n",
                          th->targetFile, filename);

        /* Header doesn't match, so read to next header */
        len = ((th->fileLen + 511) & ~511); /* Padded length */
        blks = len >> 9;        /* # of 512 byte blocks */

        for (i = 0; i < blks; i++)
            _tarReadRaw(AH, &header[0], 512, NULL, ctx->tarFH);

        if (!_tarGetHeader(AH, th))
            exit_horribly(modulename, "could not find header for file \"%s\" in tar archive\n", filename);
    }

    ctx->tarNextMember = ctx->tarFHpos + ((th->fileLen + 511) & ~511);
    th->pos = 0;

    return th;
}

/* Read & verify a header */
static int
_tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        h[512];
    char        tag[100 + 1];
    int         sum,
                chk;
    pgoff_t     len;
    pgoff_t     hPos;
    bool        gotBlock = false;

    while (!gotBlock)
    {
        /* Save the pos for reporting purposes */
        hPos = ctx->tarFHpos;

        /* Read a 512 byte block, return EOF, exit if short */
        len = _tarReadRaw(AH, h, 512, NULL, ctx->tarFH);
        if (len == 0)           /* EOF */
            return 0;

        if (len != 512)
            exit_horribly(modulename,
                          ngettext("incomplete tar header found (%lu byte)\n",
                                   "incomplete tar header found (%lu bytes)\n",
                                   len),
                          (unsigned long) len);

        /* Calc checksum */
        chk = tarChecksum(h);
        sum = read_tar_number(&h[148], 8);

        /*
         * If the checksum failed, see if it is a null block. If so, silently
         * continue to the next block.
         */
        if (chk == sum)
            gotBlock = true;
        else
        {
            int         i;

            for (i = 0; i < 512; i++)
            {
                if (h[i] != 0)
                {
                    gotBlock = true;
                    break;
                }
            }
        }
    }

    /* Name field is 100 bytes, might not be null-terminated */
    strlcpy(tag, &h[0], 100 + 1);

    len = read_tar_number(&h[124], 12);

    {
        char        posbuf[32];
        char        lenbuf[32];

        snprintf(posbuf, sizeof(posbuf), UINT64_FORMAT, (uint64) hPos);
        snprintf(lenbuf, sizeof(lenbuf), UINT64_FORMAT, (uint64) len);
        ahlog(AH, 3, "TOC Entry %s at %s (length %s, checksum %d)\n",
              tag, posbuf, lenbuf, sum);
    }

    if (chk != sum)
    {
        char        posbuf[32];

        snprintf(posbuf, sizeof(posbuf), UINT64_FORMAT,
                 (uint64) ftello(ctx->tarFH));
        exit_horribly(modulename,
                      "corrupt tar header found in %s "
                      "(expected %d, computed %d) file position %s\n",
                      tag, sum, chk, posbuf);
    }

    th->targetFile = pg_strdup(tag);
    th->fileLen = len;

    return 1;
}


static void
_tarWriteHeader(TAR_MEMBER *th)
{
    char        h[512];

    tarCreateHeader(h, th->targetFile, NULL, th->fileLen,
                    0600, 04000, 02000, time(NULL));

    /* Now write the completed header. */
    if (fwrite(h, 1, 512, th->tarFH) != 512)
        WRITE_ERROR_EXIT;
}