Improve error detection and recovery in lo_import()/lo_export().

Problems noted while experimenting with new control-C code for psql.

diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 5d81a6ea3391d6f4ad55fa226d2a47354c4fae18..5e11b0e3059bd857efd409d5f1adba1547d85f10 100644 (file)
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.56 2006/03/05 15:59:09 momjian Exp $
+ *       $PostgreSQL: pgsql/src/interfaces/libpq/fe-lobj.c,v 1.57 2006/06/14 01:28:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,6 +58,12 @@ lo_open(PGconn *conn, Oid lobjId, int mode)
        PQArgBlock      argv[2];
        PGresult   *res;
 
+       if (conn->lobjfuncs == NULL)
+       {
+               if (lo_initialize(conn) < 0)
+                       return -1;
+       }
+
        argv[0].isint = 1;
        argv[0].len = 4;
        argv[0].u.integer = lobjId;
@@ -66,12 +72,6 @@ lo_open(PGconn *conn, Oid lobjId, int mode)
        argv[1].len = 4;
        argv[1].u.integer = mode;
 
-       if (conn->lobjfuncs == NULL)
-       {
-               if (lo_initialize(conn) < 0)
-                       return -1;
-       }
-
        res = PQfn(conn, conn->lobjfuncs->fn_lo_open, &fd, &result_len, 1, argv, 2);
        if (PQresultStatus(res) == PGRES_COMMAND_OK)
        {
@@ -438,6 +438,7 @@ lo_import(PGconn *conn, const char *filename)
        char            buf[LO_BUFSIZE];
        Oid                     lobjOid;
        int                     lobj;
+       char            sebuf[256];
 
        /*
         * open the file to be read in
@@ -445,8 +446,6 @@ lo_import(PGconn *conn, const char *filename)
        fd = open(filename, O_RDONLY | PG_BINARY, 0666);
        if (fd < 0)
        {                                                       /* error */
-               char            sebuf[256];
-
                printfPQExpBuffer(&conn->errorMessage,
                                                  libpq_gettext("could not open file \"%s\": %s\n"),
                                                  filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
@@ -454,7 +453,7 @@ lo_import(PGconn *conn, const char *filename)
        }
 
        /*
-        * create an inversion "object"
+        * create an inversion object
         */
        lobjOid = lo_creat(conn, INV_READ | INV_WRITE);
        if (lobjOid == InvalidOid)
@@ -477,24 +476,46 @@ lo_import(PGconn *conn, const char *filename)
        }
 
        /*
-        * read in from the Unix file and write to the inversion file
+        * read in from the file and write to the large object
         */
        while ((nbytes = read(fd, buf, LO_BUFSIZE)) > 0)
        {
                tmp = lo_write(conn, lobj, buf, nbytes);
-               if (tmp < nbytes)
+               if (tmp != nbytes)
                {
+                       /*
+                        * If the lo_write failed, we are probably in an aborted
+                        * transaction and so lo_close will fail.  Try it anyway for
+                        * cleanliness, but don't let it determine the returned error
+                        * message.
+                        */
+                       (void) lo_close(conn, lobj);
+
                        printfPQExpBuffer(&conn->errorMessage,
-                                                 libpq_gettext("error while reading file \"%s\"\n"),
-                                                         filename);
+                                               libpq_gettext("error while writing large object %u\n"),
+                                                         lobjOid);
                        (void) close(fd);
-                       (void) lo_close(conn, lobj);
                        return InvalidOid;
                }
        }
 
+       if (nbytes < 0)
+       {
+               printfPQExpBuffer(&conn->errorMessage,
+                                               libpq_gettext("could not read from file \"%s\": %s\n"),
+                                                 filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
+               lobjOid = InvalidOid;
+       }
+
        (void) close(fd);
-       (void) lo_close(conn, lobj);
+
+       if (lo_close(conn, lobj) != 0)
+       {
+               printfPQExpBuffer(&conn->errorMessage,
+                                               libpq_gettext("error while writing large object %u\n"),
+                                                 lobjOid);
+               return InvalidOid;
+       }
 
        return lobjOid;
 }
@@ -502,16 +523,18 @@ lo_import(PGconn *conn, const char *filename)
 /*
  * lo_export -
  *       exports an (inversion) large object.
- * returns -1 upon failure, 1 otherwise
+ * returns -1 upon failure, 1 if OK
  */
 int
 lo_export(PGconn *conn, Oid lobjId, const char *filename)
 {
+       int                     result = 1;
        int                     fd;
        int                     nbytes,
                                tmp;
        char            buf[LO_BUFSIZE];
        int                     lobj;
+       char            sebuf[256];
 
        /*
         * open the large object.
@@ -530,8 +553,6 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
        fd = open(filename, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY, 0666);
        if (fd < 0)
        {                                                       /* error */
-               char            sebuf[256];
-
                printfPQExpBuffer(&conn->errorMessage,
                                                  libpq_gettext("could not open file \"%s\": %s\n"),
                                                  filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
@@ -540,33 +561,39 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
        }
 
        /*
-        * read in from the inversion file and write to the Unix file
+        * read in from the large object and write to the file
         */
        while ((nbytes = lo_read(conn, lobj, buf, LO_BUFSIZE)) > 0)
        {
                tmp = write(fd, buf, nbytes);
-               if (tmp < nbytes)
+               if (tmp != nbytes)
                {
                        printfPQExpBuffer(&conn->errorMessage,
-                                          libpq_gettext("error while writing to file \"%s\"\n"),
-                                                         filename);
+                                          libpq_gettext("error while writing to file \"%s\": %s\n"),
+                                                 filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
                        (void) lo_close(conn, lobj);
                        (void) close(fd);
                        return -1;
                }
        }
 
-       (void) lo_close(conn, lobj);
+       if (lo_close(conn, lobj) != 0 || nbytes < 0)
+       {
+               printfPQExpBuffer(&conn->errorMessage,
+                                               libpq_gettext("error while reading large object %u\n"),
+                                                 lobjId);
+               result = -1;
+       }
 
        if (close(fd))
        {
                printfPQExpBuffer(&conn->errorMessage,
-                                          libpq_gettext("error while writing to file \"%s\"\n"),
-                                                 filename);
-               return -1;
+                                          libpq_gettext("error while writing to file \"%s\": %s\n"),
+                                                 filename, pqStrerror(errno, sebuf, sizeof(sebuf)));
+               result = -1;
        }
 
-       return 1;
+       return result;
 }