Set up work for making a 3.5 prerelease.

[chaz/openbox] / obrender / imagecache.c

diff --git a/obrender/imagecache.c b/obrender/imagecache.c
new file mode 100644 (file)
index 0000000..9c605f9
--- /dev/null
+++ b/obrender/imagecache.c
@@ -0,0 +1,144 @@
+/* -*- indent-tabs-mode: nil; tab-width: 4; c-basic-offset: 4; -*-
+
+   imagecache.c for the Openbox window manager
+   Copyright (c) 2008        Dana Jansens
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   See the COPYING file for a copy of the GNU General Public License.
+*/
+
+#include "render.h"
+#include "imagecache.h"
+#include "image.h"
+
+static gboolean RrImagePicEqual(const RrImagePic *p1,
+                                const RrImagePic *p2);
+
+RrImageCache* RrImageCacheNew(gint max_resized_saved)
+{
+    RrImageCache *self;
+
+    g_assert(max_resized_saved >= 0);
+
+    self = g_new(RrImageCache, 1);
+    self->ref = 1;
+    self->max_resized_saved = max_resized_saved;
+    self->table = g_hash_table_new((GHashFunc)RrImagePicHash,
+                                   (GEqualFunc)RrImagePicEqual);
+    return self;
+}
+
+void RrImageCacheRef(RrImageCache *self)
+{
+    ++self->ref;
+}
+
+void RrImageCacheUnref(RrImageCache *self)
+{
+    if (self && --self->ref == 0) {
+        g_assert(g_hash_table_size(self->table) == 0);
+        g_hash_table_unref(self->table);
+
+        g_free(self);
+    }
+}
+
+/*! Finds an image in the cache, if it is already in there */
+RrImage* RrImageCacheFind(RrImageCache *self,
+                          RrPixel32 *data, gint w, gint h)
+{
+    RrImagePic pic;
+
+    RrImagePicInit(&pic, w, h, data);
+    return g_hash_table_lookup(self->table, &pic);
+}
+
+#define hashsize(n) ((RrPixel32)1<<(n))
+#define hashmask(n) (hashsize(n)-1)
+#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+/* mix -- mix 3 32-bit values reversibly. */
+#define mix(a,b,c) \
+{ \
+  a -= c;  a ^= rot(c, 4);  c += b; \
+  b -= a;  b ^= rot(a, 6);  a += c; \
+  c -= b;  c ^= rot(b, 8);  b += a; \
+  a -= c;  a ^= rot(c,16);  c += b; \
+  b -= a;  b ^= rot(a,19);  a += c; \
+  c -= b;  c ^= rot(b, 4);  b += a; \
+}
+/* final -- final mixing of 3 32-bit values (a,b,c) into c */
+#define final(a,b,c) \
+{ \
+  c ^= b; c -= rot(b,14); \
+  a ^= c; a -= rot(c,11); \
+  b ^= a; b -= rot(a,25); \
+  c ^= b; c -= rot(b,16); \
+  a ^= c; a -= rot(c,4);  \
+  b ^= a; b -= rot(a,14); \
+  c ^= b; c -= rot(b,24); \
+}
+
+/* This is a fast, reversable hash function called "lookup3", found here:
+   http://burtleburtle.net/bob/c/lookup3.c, by Bob Jenkins
+
+   This hashing algorithm is "reversible", that is, not cryptographically
+   secure at all.  But we don't care about that, we just want something to
+   tell when images are the same or different relatively quickly.
+*/
+guint32 hashword(const guint32 *key, gint length, guint32 initval)
+{
+    guint32 a,b,c;
+
+    /* Set up the internal state */
+    a = b = c = 0xdeadbeef + (((guint32)length)<<2) + initval;
+
+    /* handle most of the key */
+    while (length > 3)
+    {
+        a += key[0];
+        b += key[1];
+        c += key[2];
+        mix(a,b,c);
+        length -= 3;
+        key += 3;
+    }
+
+    /* handle the last 3 guint32's */
+    switch(length)      /* all the case statements fall through */
+    { 
+    case 3: c+=key[2];
+    case 2: b+=key[1];
+    case 1: a+=key[0];
+        final(a,b,c);
+    case 0:             /* case 0: nothing left to add */
+        break;
+    }
+    /* report the result */
+    return c;
+}
+
+/*! This is some arbitrary initial value for the hashing function.  It's
+  constant so that you get the same result from the same data each time.
+*/
+#define HASH_INITVAL 0xf00d
+
+guint RrImagePicHash(const RrImagePic *p)
+{
+    return hashword(p->data, p->width * p->height, HASH_INITVAL);
+}
+
+static gboolean RrImagePicEqual(const RrImagePic *p1,
+                                const RrImagePic *p2)
+{
+    return p1->width == p2->width && p1->height == p2->height &&
+        p1->sum == p2->sum;
+}