Introduce xbps_array_add_first() to insert obj at the head of array.

The behaviour of this routine mimics the existing xbps_array_add() with
the difference that stored objects are moved to the right to insert
our object as the first element on the array.

Use this to add replaced packages in the transaction array at the head
rather than at the end, to preserve the proper sorting order.

include/xbps.h.in

@@ -48,7 +48,7 @@
  *
  * This header documents the full API for the XBPS Library.
  */
-#define XBPS_API_VERSION	"20141107"
+#define XBPS_API_VERSION	"20141113"
 
 #ifndef XBPS_VERSION
  #define XBPS_VERSION		"UNSET"

include/xbps/xbps_array.h

@@ -59,6 +59,7 @@ xbps_object_iterator_t xbps_array_iterator(xbps_array_t);
 xbps_object_t	xbps_array_get(xbps_array_t, unsigned int);
 bool		xbps_array_set(xbps_array_t, unsigned int, xbps_object_t);
 bool		xbps_array_add(xbps_array_t, xbps_object_t);
+bool		xbps_array_add_first(xbps_array_t, xbps_object_t);
 void		xbps_array_remove(xbps_array_t, unsigned int);
 
 bool		xbps_array_equals(xbps_array_t, xbps_array_t);

lib/portableproplib/prop/prop_array.h

@@ -59,6 +59,7 @@ prop_object_iterator_t prop_array_iterator(prop_array_t);
 prop_object_t	prop_array_get(prop_array_t, unsigned int);
 bool		prop_array_set(prop_array_t, unsigned int, prop_object_t);
 bool		prop_array_add(prop_array_t, prop_object_t);
+bool		prop_array_add_first(prop_array_t, prop_object_t);
 void		prop_array_remove(prop_array_t, unsigned int);
 
 bool		prop_array_equals(prop_array_t, prop_array_t);

lib/portableproplib/prop_array.c

@@ -615,6 +615,45 @@ _prop_array_add(prop_array_t pa, prop_object_t po)
 	return (true);
 }
 
+static bool
+_prop_array_add_first(prop_array_t pa, prop_object_t po)
+{
+	unsigned int cnt;
+	/*
+	 * Array must be WRITE-LOCKED.
+	 */
+
+	_PROP_ASSERT(pa->pa_count <= pa->pa_capacity);
+
+	if (prop_array_is_immutable(pa) ||
+	    (pa->pa_count == pa->pa_capacity &&
+	    _prop_array_expand(pa, pa->pa_capacity + EXPAND_STEP) == false))
+		return false;
+
+	prop_object_retain(po);
+	if (pa->pa_count) {
+		cnt = pa->pa_count+1;
+		/* move all stored elements to the right */
+		while (--cnt) {
+			prop_object_t opo = pa->pa_array[cnt-1];
+			_PROP_ASSERT(opo != NULL);
+			prop_object_retain(opo);
+			pa->pa_array[cnt] = opo;
+			prop_object_release(opo);
+			printf("%s: po %p\n", __func__, pa->pa_array[cnt]);
+		}
+		/* passed in object is now the first element */
+		pa->pa_array[0] = po;
+		pa->pa_version++;
+		pa->pa_count++;
+		printf("%s: po %p\n", __func__, pa->pa_array[0]);
+	} else {
+		pa->pa_array[pa->pa_count++] = po;
+		pa->pa_version++;
+	}
+	return true;
+}
+
 /*
  * prop_array_set --
  *	Store a reference to an object at the specified array index.
@@ -679,6 +718,26 @@ prop_array_add(prop_array_t pa, prop_object_t po)
 	return (rv);
 }
 
+/*
+ * prop_array_add_first --
+ *	Add a reference to an object to the specified array, inserting it
+ *	as first element, moving all objects to the right and growing the
+ *	array's capacity, if necessary.
+ */
+bool
+prop_array_add_first(prop_array_t pa, prop_object_t po)
+{
+	bool rv;
+
+	if (! prop_object_is_array(pa))
+		return (false);
+
+	_PROP_RWLOCK_WRLOCK(pa->pa_rwlock);
+	rv = _prop_array_add_first(pa, po);
+	_PROP_RWLOCK_UNLOCK(pa->pa_rwlock);
+
+	return (rv);
+}
 /*
  * prop_array_remove --
  *	Remove the reference to an object from an array at the specified

lib/proplib_wrapper.c

@@ -112,6 +112,12 @@ xbps_array_add(xbps_array_t a, xbps_object_t obj)
 	return prop_array_add(a, obj);
 }
 
+bool
+xbps_array_add_first(xbps_array_t a, xbps_object_t obj)
+{
+	return prop_array_add_first(a, obj);
+}
+
 void
 xbps_array_remove(xbps_array_t a, unsigned int i)
 {

lib/transaction_package_replace.c

@@ -123,7 +123,8 @@ xbps_transaction_package_replace(struct xbps_handle *xhp, xbps_array_t pkgs)
 			 */
 			xbps_dictionary_set_cstring_nocopy(instd,
 			    "transaction", "remove");
-			xbps_array_add(pkgs, instd);
+			if (!xbps_array_add_first(pkgs, instd))
+				return EINVAL;
 			free(curpkgname);
 		}
 		xbps_object_iterator_release(iter);