Change DBCLOB+GetSubString to work from first null instead of backwards

GetSubString with an oversized buffer (like from i5_dbcs_alloc) can
sometimes add garbage to the end of the buffer when using DBCLOB locators
with SQL_C_CHAR outputs. The old code seemed to scan backwards, which is
bad if it hits the garbage. As such, try to scan from the first null
and then clear out spaces only after getting everything after the null.
Since the PASE driver implies DBCLOB is for strings and not binary data,
this should be OK?

Author: NattyNarwhal

ibm_db2.c

@@ -5708,10 +5708,35 @@ static RETCODE _php_db2_get_data2(stmt_handle *stmt_res, SQLUSMALLINT col_num, S
     }
 #ifdef PASE /* trim i5/OS SQLGetSubString DBCLOB cases extra nulls -- no harm to simply remove */
     else if (*out_length > 1 && stmt_res->column_info[col_num-1].loc_type == SQL_DBCLOB_LOCATOR) {
-        int ib = *out_length - 1;
-        char * ibc = (char *) buff;
-        for (; ib && (ibc[ib] == 0x00 || ibc[ib] == 0x20); ib--) ibc[ib] = '\0';
-        *out_length = ib + 1;
+        /*
+         * CB 201210111: The combination of using *LOCAL (but DRDA to localhost
+         * is OK) and i5_dbcs_alloc causes garbage in addition to the nulls,
+         * usually 0x1A (ASCII replacement) and some @. I suspect there might
+         * be a buffer overrun kind of situation going on. However, this did
+         * impact users using i5_dbcs_alloc, so we'll just clean up the nulls.
+         * Tony wrote one, but it went backwards from the end, so the garbage
+         * after the first null would confuse it. Since the PASE version of the
+         * driver seems to treat DBCLOBs as strings, it should be OK as unlike
+         * a binary, trimming nulls should be safe.
+         */
+        char *str_buff = (char *) buff;
+        int i = 0, first_null;
+        while (str_buff[i] != '\0' && i < *out_length) {
+            i++;
+        }
+        first_null = i;
+        while (i < *out_length) {
+            str_buff[i++] = '\0';
+        }
+        *out_length = first_null;
+        /* avoid a regression in db2_statistics tests, trim end spaces */
+        for (i = first_null - 1; i >= 0; i--) {
+            if (str_buff[i] != ' ') {
+                *out_length = i + 1; /* XXX: ok to assume +1? */
+                break;
+            }
+            str_buff[i] = '\0';
+        }
     }
 #endif /* PASE */
     SQLFreeHandle(SQL_HANDLE_STMT, new_hstmt);