[cairo-path-fixed] Avoid malloc for small paths

We do this by including an initial op and arg buf in cairo_path_fixed_t,
so for small paths we don't have to alloc those buffers.

The way this is done is a bit unusual.  Specifically, using an array of
length one instead of a normal member:

-    cairo_path_op_buf_t *op_buf_head;
+    cairo_path_op_buf_t  op_buf_head[1];

Has the advantage that read-only use of the buffers does not need any
change as arrays act like pointers syntactically.  All manipulation code
however needs to be updates, which the patch supposed does.  Still, there
seems to be bugs remaining as cairo-perf quits with a Bad X Request error
with this patch.

1 files changed, 38 insertions, 28 deletions

diff --git a/src/cairo-path-fixed.c b/src/cairo-path-fixed.c
index 3505c668..b4579102 100644
--- a/src/cairo-path-fixed.c
+++ b/src/cairo-path-fixed.c
@@ -79,11 +79,15 @@ _cairo_path_arg_buf_add_points (cairo_path_arg_buf_t *arg_buf,
 void
 _cairo_path_fixed_init (cairo_path_fixed_t *path)
 {
-    path->op_buf_head = NULL;
-    path->op_buf_tail = NULL;
+    path->op_buf_head->num_ops = 0;
+    path->op_buf_head->next = NULL;
+    path->op_buf_head->prev = NULL;
+    path->op_buf_tail = path->op_buf_head;
 
-    path->arg_buf_head = NULL;
-    path->arg_buf_tail = NULL;
+    path->arg_buf_head->num_points = 0;
+    path->arg_buf_head->next = NULL;
+    path->arg_buf_head->prev = NULL;
+    path->arg_buf_tail = path->arg_buf_head;
 
     path->current_point.x = 0;
     path->current_point.y = 0;
@@ -105,7 +109,10 @@ _cairo_path_fixed_init_copy (cairo_path_fixed_t *path,
     path->has_curve_to = other->has_curve_to;
     path->last_move_point = other->last_move_point;
 
-    for (other_op_buf = other->op_buf_head;
+    path->op_buf_head->num_ops = other->op_buf_head->num_ops;
+    memcpy (path->op_buf_head->op, other->op_buf_head->op,
+	    other->op_buf_head->num_ops * sizeof (cairo_path_op_t));
+    for (other_op_buf = other->op_buf_head->next;
 	 other_op_buf;
 	 other_op_buf = other_op_buf->next)
     {
@@ -118,7 +125,10 @@ _cairo_path_fixed_init_copy (cairo_path_fixed_t *path,
 	_cairo_path_fixed_add_op_buf (path, op_buf);
     }
 
-    for (other_arg_buf = other->arg_buf_head;
+    path->arg_buf_head->num_points = other->arg_buf_head->num_points;
+    memcpy (path->arg_buf_head->points, other->arg_buf_head->points,
+	    other->arg_buf_head->num_points * sizeof (cairo_point_t));
+    for (other_arg_buf = other->arg_buf_head->next;
 	 other_arg_buf;
 	 other_arg_buf = other_arg_buf->next)
     {
@@ -151,19 +161,27 @@ _cairo_path_fixed_fini (cairo_path_fixed_t *path)
     cairo_path_op_buf_t *op_buf;
     cairo_path_arg_buf_t *arg_buf;
 
-    while (path->op_buf_head) {
-	op_buf = path->op_buf_head;
-	path->op_buf_head = op_buf->next;
-	_cairo_path_op_buf_destroy (op_buf);
+    op_buf = path->op_buf_head->next;
+    while (op_buf) {
+	cairo_path_op_buf_t *this = op_buf;
+	op_buf = op_buf->next;
+	_cairo_path_op_buf_destroy (this);
     }
-    path->op_buf_tail = NULL;
+    path->op_buf_head->num_ops = 0;
+    path->op_buf_head->next = NULL;
+    path->op_buf_head->prev = NULL;
+    path->op_buf_tail = path->op_buf_head;
 
-    while (path->arg_buf_head) {
-	arg_buf = path->arg_buf_head;
-	path->arg_buf_head = arg_buf->next;
-	_cairo_path_arg_buf_destroy (arg_buf);
+    arg_buf = path->arg_buf_head->next;
+    while (arg_buf) {
+	cairo_path_arg_buf_t *this = arg_buf;
+	arg_buf = arg_buf->next;
+	_cairo_path_arg_buf_destroy (this);
     }
-    path->arg_buf_tail = NULL;
+    path->arg_buf_head->num_points = 0;
+    path->arg_buf_head->next = NULL;
+    path->arg_buf_head->prev = NULL;
+    path->arg_buf_tail = path->arg_buf_head;
 
     path->has_current_point = FALSE;
     path->has_curve_to = FALSE;
@@ -415,12 +433,7 @@ _cairo_path_fixed_add_op_buf (cairo_path_fixed_t  *path,
     op_buf->next = NULL;
     op_buf->prev = path->op_buf_tail;
 
-    if (path->op_buf_tail) {
-	path->op_buf_tail->next = op_buf;
-    } else {
-	path->op_buf_head = op_buf;
-    }
-
+    path->op_buf_tail->next = op_buf;
     path->op_buf_tail = op_buf;
 }
 
@@ -431,12 +444,7 @@ _cairo_path_fixed_add_arg_buf (cairo_path_fixed_t   *path,
     arg_buf->next = NULL;
     arg_buf->prev = path->arg_buf_tail;
 
-    if (path->arg_buf_tail) {
-	path->arg_buf_tail->next = arg_buf;
-    } else {
-	path->arg_buf_head = arg_buf;
-    }
-
+    path->arg_buf_tail->next = arg_buf;
     path->arg_buf_tail = arg_buf;
 }
 
@@ -450,6 +458,7 @@ _cairo_path_op_buf_create (void)
     if (op_buf) {
 	op_buf->num_ops = 0;
 	op_buf->next = NULL;
+	op_buf->prev = NULL;
     }
 
     return op_buf;
@@ -478,6 +487,7 @@ _cairo_path_arg_buf_create (void)
     if (arg_buf) {
 	arg_buf->num_points = 0;
 	arg_buf->next = NULL;
+	arg_buf->prev = NULL;
     }
 
     return arg_buf;