/*----------------------------------------------------------------- * * testlo.c * test using large objects with libpq * * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/test/examples/testlo.c * *----------------------------------------------------------------- */ #include <stdio.h> #include <stdlib.h>

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

#include "libpq-fe.h" #include "libpq/libpq-fs.h"

#define BUFSIZE 1024

/* * importFile - * import file "in_filename" into database as large object "lobjOid" * */ static Oid importFile(PGconn *conn, char *filename) { Oid lobjId; int lobj_fd; char buf[BUFSIZE]; int nbytes, tmp; int fd;

/\*
 \* open the file to be read in
 \*/
fd = open(filename, O\_RDONLY, 0666);
if (fd < 0)
{                           /\* error \*/
    fprintf(stderr, "cannot open unix file\\"%s\\"\\n", filename);
}

/\*
 \* create the large object
 \*/
lobjId = lo\_creat(conn, INV\_READ | INV\_WRITE);
if (lobjId == 0)
    fprintf(stderr, "cannot create large object");

lobj\_fd = lo\_open(conn, lobjId, INV\_WRITE);

/\*
 \* read in from the Unix file and write to the inversion file
 \*/
while ((nbytes = read(fd, buf, BUFSIZE)) > 0)
{
    tmp = lo\_write(conn, lobj\_fd, buf, nbytes);
    if (tmp < nbytes)
        fprintf(stderr, "error while reading \\"%s\\"", filename);
}

close(fd);
lo\_close(conn, lobj\_fd);

return lobjId;

}

static void pickout(PGconn *conn, Oid lobjId, int start, int len) { int lobj_fd; char *buf; int nbytes; int nread;

lobj\_fd = lo\_open(conn, lobjId, INV\_READ);
if (lobj\_fd < 0)
    fprintf(stderr, "cannot open large object %u", lobjId);

lo\_lseek(conn, lobj\_fd, start, SEEK\_SET);
buf = malloc(len + 1);

nread = 0;
while (len - nread > 0)
{
    nbytes = lo\_read(conn, lobj\_fd, buf, len - nread);
    buf\[nbytes\] = '\\0';
    fprintf(stderr, ">>> %s", buf);
    nread += nbytes;
    if (nbytes <= 0)
        break;              /\* no more data? \*/
}
free(buf);
fprintf(stderr, "\\n");
lo\_close(conn, lobj\_fd);

}

static void overwrite(PGconn *conn, Oid lobjId, int start, int len) { int lobj_fd; char *buf; int nbytes; int nwritten; int i;

lobj\_fd = lo\_open(conn, lobjId, INV\_WRITE);
if (lobj\_fd < 0)
    fprintf(stderr, "cannot open large object %u", lobjId);

lo\_lseek(conn, lobj\_fd, start, SEEK\_SET);
buf = malloc(len + 1);

for (i = 0; i < len; i++)
    buf\[i\] = 'X';
buf\[i\] = '\\0';

nwritten = 0;
while (len - nwritten > 0)
{
    nbytes = lo\_write(conn, lobj\_fd, buf + nwritten, len - nwritten);
    nwritten += nbytes;
    if (nbytes <= 0)
    {
        fprintf(stderr, "\\nWRITE FAILED!\\n");
        break;
    }
}
free(buf);
fprintf(stderr, "\\n");
lo\_close(conn, lobj\_fd);

}

/* * exportFile - * export large object "lobjOid" to file "out_filename" * */ static void exportFile(PGconn *conn, Oid lobjId, char *filename) { int lobj_fd; char buf[BUFSIZE]; int nbytes, tmp; int fd;

/\*
 \* open the large object
 \*/
lobj\_fd = lo\_open(conn, lobjId, INV\_READ);
if (lobj\_fd < 0)
    fprintf(stderr, "cannot open large object %u", lobjId);

/\*
 \* open the file to be written to
 \*/
fd = open(filename, O\_CREAT | O\_WRONLY | O\_TRUNC, 0666);
if (fd < 0)
{                           /\* error \*/
    fprintf(stderr, "cannot open unix file\\"%s\\"",
            filename);
}

/\*
 \* read in from the inversion file and write to the Unix file
 \*/
while ((nbytes = lo\_read(conn, lobj\_fd, buf, BUFSIZE)) > 0)
{
    tmp = write(fd, buf, nbytes);
    if (tmp < nbytes)
    {
        fprintf(stderr, "error while writing \\"%s\\"",
                filename);
    }
}

lo\_close(conn, lobj\_fd);
close(fd);

}

static void exit_nicely(PGconn *conn) { PQfinish(conn); exit(1); }

int main(int argc, char **argv) { char *in_filename, *out_filename; char *database; Oid lobjOid; PGconn *conn; PGresult *res;

if (argc != 4)
{
    fprintf(stderr, "Usage: %s database\_name in\_filename out\_filename\\n",
            argv\[0\]);
    exit(1);
}

database = argv\[1\];
in\_filename = argv\[2\];
out\_filename = argv\[3\];

/\*
 \* set up the connection
 \*/
conn = PQsetdb(NULL, NULL, NULL, NULL, database);

/\* check to see that the backend connection was successfully made \*/
if (PQstatus(conn) != CONNECTION\_OK)
{
    fprintf(stderr, "%s", PQerrorMessage(conn));
    exit\_nicely(conn);
}

/\* Set always-secure search path, so malicious users can't take control. \*/
res = PQexec(conn,
             "SELECT pg\_catalog.set\_config('search\_path', '', false)");
if (PQresultStatus(res) != PGRES\_TUPLES\_OK)
{
    fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
    PQclear(res);
    exit\_nicely(conn);
}
PQclear(res);

res = PQexec(conn, "begin");
PQclear(res);
printf("importing file \\"%s\\" ...\\n", in\_filename);

/* lobjOid = importFile(conn, in_filename); */ lobjOid = lo_import(conn, in_filename); if (lobjOid == 0) fprintf(stderr, "%s\n", PQerrorMessage(conn)); else { printf("\tas large object %u.\n", lobjOid);

    printf("picking out bytes 1000-2000 of the large object\\n");
    pickout(conn, lobjOid, 1000, 1000);

    printf("overwriting bytes 1000-2000 of the large object with X's\\n");
    overwrite(conn, lobjOid, 1000, 1000);

    printf("exporting large object to file \\"%s\\" ...\\n", out\_filename);

/* exportFile(conn, lobjOid, out_filename); */ if (lo_export(conn, lobjOid, out_filename) < 0) fprintf(stderr, "%s\n", PQerrorMessage(conn)); }

res = PQexec(conn, "end");
PQclear(res);
PQfinish(conn);
return 0;

}