palette: delay sorted radius vectors construction until needed

In babl-palette, when C11 atomic operations are available, don't
construct the sorted radius vectors on palette setup, but rather
when first converting from RGB to the palette format.  This avoids
the costly vector-construction step for palettes that are never
used as the destination format of a conversion.

diff --git a/babl/babl-palette.c b/babl/babl-palette.c
index f0eecc59b2b1c738daa5d8c253e24de914bc5e41..c4d3068f3d9f4becfe1d4f2df1cfa460e62424e0 100644 (file)
--- a/babl/babl-palette.c
+++ b/babl/babl-palette.c
@@ -27,6 +27,10 @@
 #include "babl.h"
 #include "babl-memory.h"
 
+#ifdef HAVE_STDATOMIC_H
+#include <stdatomic.h>
+#endif
+
 #define HASH_TABLE_SIZE 1111
 
 
@@ -110,7 +114,8 @@ babl_palette_radius_compare (const void *r1,
 }
 
 static void
-babl_palette_init_radii (BablPalette *pal)
+babl_palette_init_radii (BablPalette       *pal,
+                         BablPaletteRadius *radii)
 {
   int i, j;
 
@@ -122,12 +127,12 @@ babl_palette_init_radii (BablPalette *pal)
 
   for (i = 0; i < pal->count; i++)
     {
-      BablPaletteRadius   *radii1 = pal->radii + (pal->count - 1) * i;
+      BablPaletteRadius   *radii1 = radii + (pal->count - 1) * i;
       const unsigned char *p1     = pal->data_u8 + 4 * i;
 
       for (j = i + 1; j < pal->count; j++)
         {
-          BablPaletteRadius   *radii2 = pal->radii + (pal->count - 1) * j;
+          BablPaletteRadius   *radii2 = radii + (pal->count - 1) * j;
           const unsigned char *p2     = pal->data_u8 + 4 * j;
           unsigned short       diff;
 
@@ -145,6 +150,53 @@ babl_palette_init_radii (BablPalette *pal)
     }
 }
 
+static BablPaletteRadius *
+babl_palette_create_radii (BablPalette *pal)
+{
+  BablPaletteRadius *radii;
+
+  radii = babl_malloc (sizeof (BablPaletteRadius) *
+                       (pal->count - 1)           *
+                       pal->count);
+
+  babl_palette_init_radii (pal, radii);
+
+  return radii;
+}
+
+static const BablPaletteRadius *
+babl_palette_get_radii (BablPalette *pal,
+                        int          entry)
+{
+  BablPaletteRadius *radii;
+
+#ifdef HAVE_STDATOMIC_H
+  radii = atomic_load_explicit (&pal->radii, memory_order_consume);
+
+  if (! radii)
+    {
+      BablPaletteRadius *existing_radii;
+
+      existing_radii = NULL;
+      radii          = babl_palette_create_radii (pal);
+
+      if (! atomic_compare_exchange_strong_explicit (&pal->radii,
+                                                     &existing_radii, radii,
+                                                     memory_order_acq_rel,
+                                                     memory_order_consume))
+        {
+          babl_free (radii);
+
+          radii = existing_radii;
+        }
+    }
+#else
+  radii = pal->radii;
+#endif
+
+  return radii + (pal->count - 1) * entry;
+}
+
 static void
 babl_palette_reset_hash (BablPalette *pal)
 {
@@ -181,7 +233,7 @@ babl_palette_lookup (BablPalette         *pal,
     }
   else
     {
-      const BablPaletteRadius *radii = pal->radii + (pal->count - 1) * best_idx;
+      const BablPaletteRadius *radii = babl_palette_get_radii (pal, best_idx);
       const unsigned char     *q;
       int                      best_diff2;
       int                      best_diff;
@@ -256,9 +308,7 @@ make_pal (const Babl *pal_space,
   pal->data = babl_malloc (bpp * count);
   pal->data_double = babl_malloc (4 * sizeof(double) * count);
   pal->data_u8 = babl_malloc (4 * sizeof(char) * count);
-  pal->radii = babl_malloc (sizeof (BablPaletteRadius) *
-                            (pal->count - 1)           *
-                            pal->count);
+  pal->radii = NULL;
 
   memcpy (pal->data, data, bpp * count);
 
@@ -267,7 +317,9 @@ make_pal (const Babl *pal_space,
   babl_process (babl_fish (format, babl_format_with_space ("R'G'B'A u8", pal_space)),
                 data, pal->data_u8, count);
 
-  babl_palette_init_radii (pal);
+#ifndef HAVE_STDATOMIC_H
+  pal->radii = babl_palette_create_radii (pal);
+#endif
 
   babl_palette_reset_hash (pal);
 
@@ -315,7 +367,7 @@ default_palette (void)
   babl_process (babl_fish (pal.format, babl_format ("RGBA double")),
                 pal.data, pal.data_double, pal.count);
 
-  babl_palette_init_radii (&pal);
+  babl_palette_init_radii (&pal, pal.radii);
 
   babl_palette_reset_hash (&pal);
 

diff --git a/meson.build b/meson.build
index be9779c8bac7eb071b38947e5b4b0d3900527f27..1ededd110ecdbde5b268ea2f337e91fdeb484810 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -260,6 +260,7 @@ endif
 
 # Check headers
 check_headers = [
+  ['HAVE_STDATOMIC_H', 'stdatomic.h']
 ]
 # Don't check for dynamic load on windows
 if not platform_win32