From 87dee43c428c20a54ad9ad7cfd46ca18ef656254 Mon Sep 17 00:00:00 2001
From: Christian Hergert <christian@hergert.me>
Date: Sun, 13 Sep 2015 03:52:59 -0700
Subject: [PATCH] arraylist: add g_array_list_prepend()

Not the most optimized way to do this, but we need it to make incremental
porting easier. We can also look at changing directions based on the
common access pattern (since we have O(1) access to head and tail).
---
 glib/garraylist.c      | 79 +++++++++++++++++++++++++++++++++++-------
 glib/garraylist.h      |  4 +++
 glib/tests/arraylist.c |  4 +++
 3 files changed, 74 insertions(+), 13 deletions(-)

diff --git a/glib/garraylist.c b/glib/garraylist.c
index a08462289..945666f8c 100644
--- a/glib/garraylist.c
+++ b/glib/garraylist.c
@@ -183,12 +183,31 @@ g_array_list_index (GArrayList *self,
   return items [index].data;
 }
 
+static inline void
+_g_array_list_update_pointers (GList *array,
+                               gsize  array_len)
+{
+  gsize i;
+
+  if (array_len > 0)
+    array [0].next = &array [1];
+
+  for (i = 1; i < (array_len - 1); i++)
+    {
+      array [i].prev = &array [i - 1];
+      array [i].next = &array [i + 1];
+    }
+
+  if (array_len > 1)
+    array [array_len- 1].prev = &array [array_len - 1 - 1];
+}
+
 static void
-_g_array_list_grow (GArrayList *self)
+_g_array_list_grow (GArrayList *self,
+                    gboolean    update_pointers)
 {
   GArrayListAlloc *alloc = (GArrayListAlloc *)self;
   gpointer old_items;
-  gsize i;
 
   DEBUG_ASSERT (self != NULL);
   DEBUG_ASSERT (alloc->mode == MODE_ALLOC);
@@ -203,17 +222,10 @@ _g_array_list_grow (GArrayList *self)
   if (G_LIKELY (old_items == alloc->items))
     return;
 
-  if (alloc->len > 0)
-    alloc->items [0].next = &alloc->items [1];
+  if (!update_pointers)
+    return;
 
-  for (i = 1; i < (alloc->len - 1); i++)
-    {
-      alloc->items [i].prev = &alloc->items [i-1];
-      alloc->items [i].next = &alloc->items [i+1];
-    }
-
-  if (alloc->len > 1)
-    alloc->items [alloc->len - 1].prev = &alloc->items [alloc->len - 1 - 1];
+  _g_array_list_update_pointers (alloc->items, alloc->len);
 }
 
 static void
@@ -301,7 +313,7 @@ g_array_list_add (GArrayList *self,
   DEBUG_ASSERT (any->mode == MODE_ALLOC);
 
   if (G_UNLIKELY (alloc->len == alloc->items_len))
-    _g_array_list_grow (self);
+    _g_array_list_grow (self, TRUE);
 
   item = &alloc->items [alloc->len];
   prev = (alloc->len > 0) ? &alloc->items [alloc->len - 1] : NULL;
@@ -320,6 +332,47 @@ g_array_list_add (GArrayList *self,
   DEBUG_ASSERT (alloc->items [alloc->len - 1].data == data);
 }
 
+void
+g_array_list_prepend (GArrayList *self,
+                      gpointer    data)
+{
+  GArrayListAny *any = (GArrayListAny *)self;
+  GArrayListEmbed *embed = (GArrayListEmbed *)self;
+  GArrayListAlloc *alloc = (GArrayListAlloc *)self;
+
+  g_return_if_fail (self != NULL);
+
+  if (G_LIKELY (any->mode == MODE_EMBED))
+    {
+      if (G_LIKELY (embed->len < G_N_ELEMENTS (embed->items)))
+        {
+          memmove (&embed->items [1], &embed->items [0], sizeof (GList) * embed->len);
+          embed->items [0].prev = NULL;
+          embed->items [0].next = &embed->items [1];
+          embed->items [0].data = data;
+          embed->len++;
+          return;
+        }
+
+      _g_array_list_transition (self);
+    }
+
+  DEBUG_ASSERT (any->mode == MODE_ALLOC);
+
+  if (G_UNLIKELY (alloc->len == alloc->items_len))
+    _g_array_list_grow (self, FALSE);
+
+  memmove (&alloc->items [1], &alloc->items [0], sizeof (GList) * alloc->len);
+
+  alloc->items [0].data = data;
+
+  _g_array_list_update_pointers (alloc->items, alloc->len);
+
+  DEBUG_ASSERT (alloc->len <= alloc->items_len);
+  DEBUG_ASSERT (alloc->len > 0);
+  DEBUG_ASSERT (alloc->items [0].data == data);
+}
+
 void
 g_array_list_remove_index (GArrayList *self,
                            guint       index)
diff --git a/glib/garraylist.h b/glib/garraylist.h
index 30fb108c1..cd2b5f6c6 100644
--- a/glib/garraylist.h
+++ b/glib/garraylist.h
@@ -74,6 +74,10 @@ void         g_array_list_destroy      (GArrayList     *list);
 GLIB_AVAILABLE_IN_2_46
 const GList *g_array_list_last_link    (GArrayList     *list);
 
+GLIB_AVAILABLE_IN_2_46
+void         g_array_list_prepend      (GArrayList     *list,
+                                        gpointer        data);
+
 #define g_array_list_first(list) (((list)->len == 0) ? NULL : g_array_list_index((list),0))
 #define g_array_list_last(list) (((list)->len == 0) ? NULL : g_array_list_index((list),(list)->len-1))
 
diff --git a/glib/tests/arraylist.c b/glib/tests/arraylist.c
index a716dc6a6..328088d07 100644
--- a/glib/tests/arraylist.c
+++ b/glib/tests/arraylist.c
@@ -73,6 +73,10 @@ test_basic (GArrayList *al)
 
   g_assert_cmpint (al->len, ==, 500);
   g_assert_cmpint (test_basic_counter, ==, 500);
+
+  g_array_list_prepend (al, GSIZE_TO_POINTER (191919));
+  g_assert_cmpint (GPOINTER_TO_SIZE (g_array_list_index (al, 0)), ==, 191919);
+
   g_array_list_destroy (al);
   g_assert_cmpint (test_basic_counter, ==, 1000);