vnc: palette: use a pool to reduce memory allocations

We now that the palette will never have more than 256
elements. Let's use a pool to reduce malloc calls.
Signed-off-by: NCorentin Chary <corentincj@iksaif.net>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

ui/vnc-palette.c

@@ -63,23 +63,9 @@ VncPalette *palette_new(size_t max, int bpp)
 
 void palette_destroy(VncPalette *palette)
 {
-    int i;
-
     if (palette == NULL) {
-        return ;
+        qemu_free(palette);
     }
-
-    for (i = 0; i < VNC_PALETTE_HASH_SIZE; i++) {
-        VncPaletteEntry *entry = QLIST_FIRST(&palette->table[i]);
-        while (entry) {
-            VncPaletteEntry *tmp = QLIST_NEXT(entry, next);
-            QLIST_REMOVE(entry, next);
-            qemu_free(entry);
-            entry = tmp;
-        }
-    }
-
-    qemu_free(palette);
 }
 
 int palette_put(VncPalette *palette, uint32_t color)
@@ -97,7 +83,7 @@ int palette_put(VncPalette *palette, uint32_t color)
     if (!entry) {
         VncPaletteEntry *entry;
 
-        entry = qemu_mallocz(sizeof(*entry));
+        entry = &palette->pool[palette->size];
         entry->color = color;
         entry->idx = idx;
         QLIST_INSERT_HEAD(&palette->table[hash], entry, next);

ui/vnc-palette.h

@@ -34,6 +34,7 @@
 #include <stdint.h>
 
 #define VNC_PALETTE_HASH_SIZE 256
+#define VNC_PALETTE_MAX_SIZE  256
 
 typedef struct VncPaletteEntry {
     int idx;
@@ -42,7 +43,7 @@ typedef struct VncPaletteEntry {
 } VncPaletteEntry;
 
 typedef struct VncPalette {
-    QObject_HEAD;
+    VncPaletteEntry pool[VNC_PALETTE_MAX_SIZE];
     size_t size;
     size_t max;
     int bpp;