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In the Programmer's Guide, the sample code for accessing large objects

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from libpq has two functions with memory leaks.

The functions pickout() and overwrite() malloc space for buf which is
never freed.

See
http://www.postgresql.org/users-lounge/docs/7.0/programmer/largeobjects3207.htm

This problem is also in the 6.5 docs at
http://www.postgresql.org/users-lounge/docs/6.5/programmer/x3184.htm

Nishad Prakash
This commit is contained in:
Bruce Momjian 2001-01-20 00:05:54 +00:00
parent a7ea9f46e1
commit d128852358
1 changed files with 117 additions and 96 deletions
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213
doc/src/sgml/lobj.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/lobj.sgml,v 1.14 2000/12/21 22:55:27 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/lobj.sgml,v 1.15 2001/01/20 00:05:54 momjian Exp $
-->
<chapter id="largeObjects">
@ -316,48 +316,52 @@ SELECT lo_export(image.raster, '/tmp/motd') from image
*--------------------------------------------------------------
*/
#include &lt;stdio.h&gt;
#include "libpq-fe.h"
#include "libpq/libpq-fs.h"
#include &quot;libpq-fe.h&quot;
#include &quot;libpq/libpq-fs.h&quot;
#define BUFSIZE 1024
/*
* importFile * import file "in_filename" into database as large object "lobjOid"
* importFile * import file &quot;in_filename&quot; into database as large object &quot;lob
jOid&quot;
*
*/
Oid importFile(PGconn *conn, char *filename)
Oid
importFile(PGconn *conn, char *filename)
{
Oid lobjId;
int lobj_fd;
char buf[BUFSIZE];
int nbytes, tmp;
int fd;
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 &lt; 0) { /* error */
fprintf(stderr, "can't open unix file %s\n", filename);
if (fd &lt; 0)
{ /* error */
fprintf(stderr, &quot;can't open unix file %s\n&quot;, filename);
}
/*
* create the large object
*/
lobjId = lo_creat(conn, INV_READ|INV_WRITE);
if (lobjId == 0) {
fprintf(stderr, "can't create large object\n");
}
lobjId = lo_creat(conn, INV_READ | INV_WRITE);
if (lobjId == 0)
fprintf(stderr, &quot;can't create large object\n&quot;);
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)) &gt; 0) {
tmp = lo_write(conn, lobj_fd, buf, nbytes);
if (tmp &lt; nbytes) {
fprintf(stderr, "error while reading large object\n");
}
while ((nbytes = read(fd, buf, BUFSIZE)) &gt; 0)
{
tmp = lo_write(conn, lobj_fd, buf, nbytes);
if (tmp &lt; nbytes)
fprintf(stderr, &quot;error while reading large object\n&quot;);
}
(void) close(fd);
@ -366,101 +370,115 @@ Oid importFile(PGconn *conn, char *filename)
return lobjId;
}
void pickout(PGconn *conn, Oid lobjId, int start, int len)
void
pickout(PGconn *conn, Oid lobjId, int start, int len)
{
int lobj_fd;
char* buf;
int nbytes;
int nread;
int lobj_fd;
char *buf;
int nbytes;
int nread;
lobj_fd = lo_open(conn, lobjId, INV_READ);
if (lobj_fd &lt; 0) {
fprintf(stderr,"can't open large object %d\n",
lobjId);
if (lobj_fd &lt; 0)
{
fprintf(stderr, &quot;can't open large object %d\n&quot;,
lobjId);
}
lo_lseek(conn, lobj_fd, start, SEEK_SET);
buf = malloc(len+1);
buf = malloc(len + 1);
nread = 0;
while (len - nread &gt; 0) {
nbytes = lo_read(conn, lobj_fd, buf, len - nread);
buf[nbytes] = ' ';
fprintf(stderr,"&gt;&gt;&gt; %s", buf);
nread += nbytes;
while (len - nread &gt; 0)
{
nbytes = lo_read(conn, lobj_fd, buf, len - nread);
buf[nbytes] = ' ';
fprintf(stderr, &quot;&gt;&gt;&gt; %s&quot;, buf);
nread += nbytes;
}
fprintf(stderr,"\n");
free(buf);
fprintf(stderr, &quot;\n&quot;);
lo_close(conn, lobj_fd);
}
void overwrite(PGconn *conn, Oid lobjId, int start, int len)
void
overwrite(PGconn *conn, Oid lobjId, int start, int len)
{
int lobj_fd;
char* buf;
int nbytes;
int nwritten;
int i;
int lobj_fd;
char *buf;
int nbytes;
int nwritten;
int i;
lobj_fd = lo_open(conn, lobjId, INV_READ);
if (lobj_fd &lt; 0) {
fprintf(stderr,"can't open large object %d\n",
lobjId);
if (lobj_fd &lt; 0)
{
fprintf(stderr, &quot;can't open large object %d\n&quot;,
lobjId);
}
lo_lseek(conn, lobj_fd, start, SEEK_SET);
buf = malloc(len+1);
buf = malloc(len + 1);
for (i=0;i&lt;len;i++)
buf[i] = 'X';
for (i = 0; i &lt; len; i++)
buf[i] = 'X';
buf[i] = ' ';
nwritten = 0;
while (len - nwritten &gt; 0) {
nbytes = lo_write(conn, lobj_fd, buf + nwritten, len - nwritten);
nwritten += nbytes;
while (len - nwritten &gt; 0)
{
nbytes = lo_write(conn, lobj_fd, buf + nwritten, len - nwritten);
nwritten += nbytes;
}
fprintf(stderr,"\n");
free(buf);
fprintf(stderr, &quot;\n&quot;);
lo_close(conn, lobj_fd);
}
/*
* exportFile * export large object "lobjOid" to file "out_filename"
* exportFile * export large object &quot;lobjOid&quot; to file &quot;out_filename&quot;
*
*/
void exportFile(PGconn *conn, Oid lobjId, char *filename)
void
exportFile(PGconn *conn, Oid lobjId, char *filename)
{
int lobj_fd;
char buf[BUFSIZE];
int nbytes, tmp;
int fd;
int lobj_fd;
char buf[BUFSIZE];
int nbytes,
tmp;
int fd;
/*
* create an inversion "object"
* create an inversion &quot;object&quot;
*/
lobj_fd = lo_open(conn, lobjId, INV_READ);
if (lobj_fd &lt; 0) {
fprintf(stderr,"can't open large object %d\n",
lobjId);
if (lobj_fd &lt; 0)
{
fprintf(stderr, &quot;can't open large object %d\n&quot;,
lobjId);
}
/*
* open the file to be written to
*/
fd = open(filename, O_CREAT|O_WRONLY, 0666);
if (fd &lt; 0) { /* error */
fprintf(stderr, "can't open unix file %s\n",
filename);
fd = open(filename, O_CREAT | O_WRONLY, 0666);
if (fd &lt; 0)
{ /* error */
fprintf(stderr, &quot;can't open unix file %s\n&quot;,
filename);
}
/*
* read in from the Unix file and write to the inversion file
*/
while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) &gt; 0) {
tmp = write(fd, buf, nbytes);
if (tmp &lt; nbytes) {
fprintf(stderr,"error while writing %s\n",
filename);
}
while ((nbytes = lo_read(conn, lobj_fd, buf, BUFSIZE)) &gt; 0)
{
tmp = write(fd, buf, nbytes);
if (tmp &lt; nbytes)
{
fprintf(stderr, &quot;error while writing %s\n&quot;,
filename);
}
}
(void) lo_close(conn, lobj_fd);
@ -470,25 +488,27 @@ void exportFile(PGconn *conn, Oid lobjId, char *filename)
}
void
exit_nicely(PGconn* conn)
exit_nicely(PGconn *conn)
{
PQfinish(conn);
exit(1);
PQfinish(conn);
exit(1);
}
int
main(int argc, char **argv)
{
char *in_filename, *out_filename;
char *database;
Oid lobjOid;
PGconn *conn;
PGresult *res;
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);
if (argc != 4)
{
fprintf(stderr, &quot;Usage: %s database_name in_filename out_filename\n&quot;,
argv[0]);
exit(1);
}
database = argv[1];
@ -501,33 +521,34 @@ main(int argc, char **argv)
conn = PQsetdb(NULL, NULL, NULL, NULL, database);
/* check to see that the backend connection was successfully made */
if (PQstatus(conn) == CONNECTION_BAD) {
fprintf(stderr,"Connection to database '%s' failed.\n", database);
fprintf(stderr,"%s",PQerrorMessage(conn));
exit_nicely(conn);
if (PQstatus(conn) == CONNECTION_BAD)
{
fprintf(stderr, &quot;Connection to database '%s' failed.\n&quot;, database);
fprintf(stderr, &quot;%s&quot;, PQerrorMessage(conn));
exit_nicely(conn);
}
res = PQexec(conn, "begin");
res = PQexec(conn, &quot;begin&quot;);
PQclear(res);
printf("importing file %s\n", in_filename);
printf(&quot;importing file %s\n&quot;, in_filename);
/* lobjOid = importFile(conn, in_filename); */
lobjOid = lo_import(conn, in_filename);
/*
printf("as large object %d.\n", lobjOid);
printf(&quot;as large object %d.\n&quot;, lobjOid);
printf("picking out bytes 1000-2000 of the large object\n");
printf(&quot;picking out bytes 1000-2000 of the large object\n&quot;);
pickout(conn, lobjOid, 1000, 1000);
printf("overwriting bytes 1000-2000 of the large object with X's\n");
printf(&quot;overwriting bytes 1000-2000 of the large object with X's\n&quot;);
overwrite(conn, lobjOid, 1000, 1000);
*/
printf("exporting large object to file %s\n", out_filename);
printf(&quot;exporting large object to file %s\n&quot;, out_filename);
/* exportFile(conn, lobjOid, out_filename); */
lo_export(conn, lobjOid,out_filename);
lo_export(conn, lobjOid, out_filename);
res = PQexec(conn, "end");
res = PQexec(conn, &quot;end&quot;);
PQclear(res);
PQfinish(conn);
exit(0);