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