fix for libpq choking on varlen fields

I broke it, I'm guilty :-(. Here's the fix.

In view of recent discussions about eliminating the fixed limit
on tuple sizes, a better long-term solution would be to increase
the width of field size values from 2 bytes to 4 in the FE/BE
protocol. I suspect we will end up doing that someday, so maybe
we should bite the bullet and do it now as part of the "2.0" FE/BE
protocol revision. On the other hand, we did promise a few weeks ago
that we were done changing the FE/BE protocol for 6.4. Comments?

regards, tom lane

*** src/interfaces/libpq/fe-exec.c.orig Wed Sep 9 22:01:38 1998
--- src/interfaces/libpq/fe-exec.c Wed Sep 9 22:45:53 1998
***************
*** 541,546 ****
--- 541,556 ----
PQclear(result);
return EOF;
}
+ /*
+ * Since pqGetInt treats 2-byte integers as unsigned, we need to
+ * coerce the special value "-1" to signed form. (-1 is sent for
+ * variable-length fields.) Formerly, libpq effectively did a
+ * sign-extension on the 2-byte value by storing it in a signed short.
+ * Now we only coerce the single value 65535 == -1; values
+ * 32768..65534 are taken as valid field lengths.
+ */
+ if (typlen == 0xFFFF)
+ typlen = -1;
result->attDescs[i].name = strdup(typName);
result->attDescs[i].typid = typid;
result->attDescs[i].typlen = typlen;
***************
*** 1488,1494 ****
if (strncmp(res->cmdStatus, "INSERT ", 7) != 0)
return "";

! /*
* The cmdStatus string looks like
* INSERT oid count\0
* In order to be able to return an ordinary C string without
--- 1498,1504 ----
if (strncmp(res->cmdStatus, "INSERT ", 7) != 0)
return "";

! /*----------
* The cmdStatus string looks like
* INSERT oid count\0
* In order to be able to return an ordinary C string without
***************
*** 1498,1503 ****
--- 1508,1514 ----
* INSERT oid count\0oid\0
* ^ our return value points here
* Pretty klugy eh? This routine should've just returned an Oid value.
+ *----------
*/

slen = strlen(res->cmdStatus);