From d4506f8a041385f7695b04b1ddfacb894d05da5c Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Mon, 26 Jan 2015 11:04:46 +0100
Subject: support variable-size results

---
 src/include/taler_db_lib.h | 90 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 72 insertions(+), 18 deletions(-)

(limited to 'src/include/taler_db_lib.h')

diff --git a/src/include/taler_db_lib.h b/src/include/taler_db_lib.h
index 41b46264e..6e2b2b2c0 100644
--- a/src/include/taler_db_lib.h
+++ b/src/include/taler_db_lib.h
@@ -13,13 +13,12 @@
   You should have received a copy of the GNU General Public License along with
   TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
 */
-
-
 /**
  * @file include/taler_db_lib.h
  * @brief helper functions for DB interactions
  * @author Sree Harsha Totakura <sreeharsha@totakura.in>
  * @author Florian Dold
+ * @author Christian Grothoff
  */
 
 #ifndef TALER_DB_LIB_H_
@@ -28,16 +27,6 @@
 #include <libpq-fe.h>
 #include "taler_util.h"
 
-#define TALER_DB_QUERY_PARAM_END { NULL, 0, 0 }
-#define TALER_DB_QUERY_PARAM_PTR(x) { (x), sizeof (*(x)), 1 }
-#define TALER_DB_QUERY_PARAM_PTR_SIZED(x, s) { (x), (s), 1 }
-
-
-#define TALER_DB_RESULT_SPEC_END { NULL, 0, NULL }
-#define TALER_DB_RESULT_SPEC(name, dst) { (void *) (dst), sizeof (*(dst)), (name) }
-#define TALER_DB_RESULT_SPEC_SIZED(name, dst, s) { (void *) (dst), (s), (name) }
-
-
 /**
  * Description of a DB query parameter.
  */
@@ -47,10 +36,12 @@ struct TALER_DB_QueryParam
    * Data or NULL
    */
   const void *data;
+
   /**
-   * Size of 'data'
+   * Size of @e data
    */
   size_t size;
+
   /**
    * Non-null if this is not the last parameter.
    * This allows for null as sentinal value.
@@ -58,6 +49,27 @@ struct TALER_DB_QueryParam
   int more;
 };
 
+/**
+ * End of query parameter specification.
+ */
+#define TALER_DB_QUERY_PARAM_END { NULL, 0, 0 }
+
+/**
+ * Generate fixed-size query parameter with size given explicitly.
+ *
+ * @param x pointer to the query parameter to pass
+ * @param s number of bytes of @a x to use for the query
+ */
+#define TALER_DB_QUERY_PARAM_PTR_SIZED(x, s) { (x), (s), 1 }
+
+/**
+ * Generate fixed-size query parameter with size determined
+ * by variable type.
+ *
+ * @param x pointer to the query parameter to pass.
+ */
+#define TALER_DB_QUERY_PARAM_PTR(x) TALER_DB_QUERY_PARAM_PTR_SIZED(x, sizeof (*(x)))
+
 
 /**
  * Description of a DB result cell.
@@ -70,7 +82,9 @@ struct TALER_DB_ResultSpec
   void *dst;
 
   /**
-   * Allowed size for the data.
+   * Allowed size for the data, 0 for variable-size
+   * (in this case, the type of @e dst is a `void **`
+   * and we need to allocate a buffer of the right size).
    */
   size_t dst_size;
 
@@ -78,9 +92,47 @@ struct TALER_DB_ResultSpec
    * Field name of the desired result.
    */
   char *fname;
+
+  /**
+   * Actual size of the result.
+   */
+  size_t *result_size;
+
 };
 
 
+/**
+ * End of result parameter specification.
+ */
+#define TALER_DB_RESULT_SPEC_END { NULL, 0, NULL, NULL }
+
+/**
+ * We expect a fixed-size result, with size given explicitly
+ *
+ * @param name name of the field in the table
+ * @param dst point to where to store the result
+ * @param s number of bytes we should use in @a dst
+ */
+#define TALER_DB_RESULT_SPEC_SIZED(name, dst, s) { (void *) (dst), (s), (name), NULL }
+
+/**
+ * We expect a fixed-size result, with size determined by the type of `* dst`
+ *
+ * @param name name of the field in the table
+ * @param dst point to where to store the result, type fits expected result size
+ */
+#define TALER_DB_RESULT_SPEC(name, dst) TALER_DB_RESULT_SPEC_SIZED(name, dst, sizeof (*(dst)))
+
+/**
+ * Variable-size result expected.
+ *
+ * @param name name of the field in the table
+ * @param dst where to store the result (of type void **), to be allocated
+ * @param sptr pointer to a `size_t` for where to store the size of @a dst
+ */
+#define TALER_DB_RESULT_SPEC_VAR(name, dst, sptr) { (void *) (dst), 0, (name), sptr }
+
+
 /**
  * Execute a prepared statement.
  */
@@ -96,12 +148,14 @@ TALER_DB_exec_prepared (PGconn *db_conn,
  * is returned.
  *
  * @return
- *   GNUNET_YES if all results could be extracted
- *   GNUNET_NO if at least one result was NULL
- *   GNUNET_SYSERR if a result was invalid (non-existing field)
+ *   #GNUNET_YES if all results could be extracted
+ *   #GNUNET_NO if at least one result was NULL
+ *   #GNUNET_SYSERR if a result was invalid (non-existing field)
  */
 int
-TALER_DB_extract_result (PGresult *result, struct TALER_DB_ResultSpec *rs, int row);
+TALER_DB_extract_result (PGresult *result,
+                         struct TALER_DB_ResultSpec *rs,
+                         int row);
 
 
 int
-- 
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