Replace old PostODBC driver with new one...

This one is based on an older PostODBC driver, rewritten and maintained by
InsightDist(?)

src/interfaces/odbc/tuplelist.c

@@ -0,0 +1,188 @@
+
+/* Module:          tuplelist.c
+ *
+ * Description:     This module contains functions for creating a manual result set
+ *                  (the TupleList) and retrieving data from it for a specific row/column.
+ *
+ * Classes:         TupleListClass (Functions prefix: "TL_")
+ *
+ * API functions:   none
+ *
+ * Comments:        See "notice.txt" for copyright and license information.
+ *
+ */
+
+#include <stdlib.h>
+#include <malloc.h>
+#include "tuplelist.h"
+#include "tuple.h"
+
+TupleListClass *
+TL_Constructor(UInt4 fieldcnt)
+{
+TupleListClass *rv;
+
+	mylog("in TL_Constructor\n");
+
+	rv = (TupleListClass *) malloc(sizeof(TupleListClass));
+	if (rv) {
+
+        rv->num_fields = fieldcnt;
+        rv->num_tuples = 0;
+        rv->list_start = NULL;
+        rv->list_end = NULL;
+        rv->lastref = NULL;
+        rv->last_indexed = -1;
+	}
+
+	mylog("exit TL_Constructor\n");
+
+	return rv;
+}
+
+void
+TL_Destructor(TupleListClass *self)
+{
+int lf;
+TupleNode *node, *tp;
+
+	mylog("TupleList: in DESTRUCTOR\n");
+
+    node = self->list_start;
+    while(node != NULL) {
+        for (lf=0; lf < self->num_fields; lf++)
+            if (node->tuple[lf].value != NULL) {
+                free(node->tuple[lf].value);
+            }
+        tp = node->next;
+        free(node);
+        node = tp;
+    }
+
+	free(self);
+
+	mylog("TupleList: exit DESTRUCTOR\n");
+}
+			
+
+void *
+TL_get_fieldval(TupleListClass *self, Int4 tupleno, Int2 fieldno)
+{
+Int4 lf;
+Int4 delta, from_end;
+char end_is_closer, start_is_closer;
+TupleNode *rv;
+
+	if (self->last_indexed == -1)
+		/* we have an empty tuple list */
+		return NULL;
+
+	/* some more sanity checks */
+	if ((tupleno >= self->num_tuples) || (tupleno < 0))
+		/* illegal tuple number range */
+		return NULL;
+
+	if ((fieldno >= self->num_fields) || (fieldno < 0))
+		/* illegel field number range */
+		return NULL;
+
+ /* check if we are accessing the same tuple that was used in
+    the last fetch (e.g: for fetching all the fields one after
+    another. Do this to speed things up
+ */
+	if (tupleno == self->last_indexed)
+		return self->lastref->tuple[fieldno].value;
+
+ /* now for the tricky part... */
+
+ /*
+ Since random access is quite inefficient for linked lists we use
+ the lastref pointer that points to the last element referenced
+ by a get_fieldval() call in conjunction with the its index number
+ that is stored in last_indexed. (So we use some locality of
+ reference principle to speed things up)
+ */
+
+	delta = tupleno - self->last_indexed;
+	/* if delta is positive, we have to go forward */
+
+	/* now check if we are closer to the start or the end of the list
+	than to our last_indexed pointer
+	*/
+	from_end = (self->num_tuples - 1) - tupleno;
+
+	start_is_closer = labs(delta) > tupleno;
+	/* true if we are closer to the start of the list than to the
+	last_indexed pointer
+	*/
+
+	end_is_closer = labs(delta) > from_end;
+	/* true if we are closer at the end of the list */
+
+	if (end_is_closer) {
+		/* scanning from the end is the shortest way. so we do that... */
+		rv = self->list_end;
+		for (lf=0; lf < from_end; lf++)
+			rv = rv->prev;
+	} else if (start_is_closer) {
+		/* the shortest way is to start the search from the head of the list */
+		rv = self->list_start;
+		for (lf=0; lf < tupleno; lf++)
+			rv = rv->next;
+	} else {
+		/* the closest way is starting from our lastref - pointer */
+		rv = self->lastref;
+		/* at first determine whether we have to search forward or backwards */
+		if (delta < 0) {
+			/* we have to search backwards */
+			for(lf=0; lf < (-1)*delta; lf++)
+				rv = rv->prev;
+		} else {
+			/* ok, we have to search forward... */
+			for (lf=0; lf < delta; lf++)
+			rv = rv->next;
+		}
+	}
+
+	/* now we have got our return pointer, so update the lastref
+		and the last_indexed values
+	*/
+	self->lastref = rv;
+	self->last_indexed = tupleno;
+
+	return rv->tuple[fieldno].value;
+}
+
+
+
+char
+TL_add_tuple(TupleListClass *self, TupleNode *new_field)
+{
+ /* we append the tuple at the end of the doubly linked list
+    of the tuples we have already read in
+ */
+
+	new_field->prev = NULL;
+	new_field->next = NULL;
+
+	if (self->list_start == NULL) {
+		/* the list is empty, we have to add the first tuple */
+		self->list_start = new_field;
+		self->list_end = new_field;
+		self->lastref = new_field;
+		self->last_indexed = 0;
+	} else {
+		/* there is already an element in the list, so add the new
+			one at the end of the list
+		*/
+		self->list_end->next = new_field;
+		new_field->prev = self->list_end;
+		self->list_end = new_field;
+	}
+	self->num_tuples++;
+
+	/* this method of building a list cannot fail, so we return 1 */
+	return 1;
+}
+
+