render/imagecache.c (raw)
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/* -*- 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" static gboolean RrImagePicEqual(const RrImagePic *p1, const RrImagePic *p2); RrImageCache* RrImageCacheNew() { RrImageCache *self; self = g_new(RrImageCache, 1); self->ref = 1; 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; pic.width = w; pic.height = h; pic.data = data; return g_hash_table_lookup(self->table, &pic); } /* This is a fast, reversable hash function called "lookup3", found here: http://burtleburtle.net/bob/c/lookup3.c */ #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); \ } 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; } #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) { guint s1, s2; RrPixel32 *data1, *data2; gint i; if (p1->width != p2->width || p1->height != p2->height) return FALSE; /* strcmp() would probably suck on 4k of data.. sum all their values and see if they get the same thing. they already matched on their hashes at this point. */ s1 = s2 = 0; data1 = p1->data; data2 = p2->data; for (i = 0; i < p1->width * p1->height; ++i, ++data1) s1 += *data1; for (i = 0; i < p2->width * p2->height; ++i, ++data2) s2 += *data2; return s1 == s2; } |