Dogcows Code - chaz/openbox/blob - obrender/imagecache.c

   1 /* -*- indent-tabs-mode: nil; tab-width: 4; c-basic-offset: 4; -*-
   2
   3    imagecache.c for the Openbox window manager
   4    Copyright (c) 2008        Dana Jansens
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    See the COPYING file for a copy of the GNU General Public License.
  17 */
  18
  19 #include "render.h"
  20 #include "imagecache.h"
  21 #include "image.h"
  22
  23 static gboolean RrImagePicEqual(const RrImagePic *p1,
  24                                 const RrImagePic *p2);
  25
  26 RrImageCache* RrImageCacheNew(gint max_resized_saved)
  27 {
  28     RrImageCache *self;
  29
  30     g_assert(max_resized_saved >= 0);
  31
  32     self = g_new(RrImageCache, 1);
  33     self->ref = 1;
  34     self->max_resized_saved = max_resized_saved;
  35     self->table = g_hash_table_new((GHashFunc)RrImagePicHash,
  36                                    (GEqualFunc)RrImagePicEqual);
  37     self->file_name_table = NULL;
  38     return self;
  39 }
  40
  41 void RrImageCacheRef(RrImageCache *self)
  42 {
  43     ++self->ref;
  44 }
  45
  46 void RrImageCacheUnref(RrImageCache *self)
  47 {
  48     if (self && --self->ref == 0) {
  49         g_assert(g_hash_table_size(self->table) == 0);
  50         g_assert(self->file_name_table == NULL);
  51         g_hash_table_unref(self->table);
  52
  53         g_free(self);
  54     }
  55 }
  56
  57 /*! Finds an image in the cache, if it is already in there */
  58 RrImage* RrImageCacheFind(RrImageCache *self,
  59                           RrPixel32 *data, gint w, gint h)
  60 {
  61     RrImagePic pic;
  62
  63     RrImagePicInit(&pic, w, h, data);
  64     return g_hash_table_lookup(self->table, &pic);
  65 }
  66
  67 #define hashsize(n) ((RrPixel32)1<<(n))
  68 #define hashmask(n) (hashsize(n)-1)
  69 #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
  70 /* mix -- mix 3 32-bit values reversibly. */
  71 #define mix(a,b,c) \
  72 { \
  73   a -= c;  a ^= rot(c, 4);  c += b; \
  74   b -= a;  b ^= rot(a, 6);  a += c; \
  75   c -= b;  c ^= rot(b, 8);  b += a; \
  76   a -= c;  a ^= rot(c,16);  c += b; \
  77   b -= a;  b ^= rot(a,19);  a += c; \
  78   c -= b;  c ^= rot(b, 4);  b += a; \
  79 }
  80 /* final -- final mixing of 3 32-bit values (a,b,c) into c */
  81 #define final(a,b,c) \
  82 { \
  83   c ^= b; c -= rot(b,14); \
  84   a ^= c; a -= rot(c,11); \
  85   b ^= a; b -= rot(a,25); \
  86   c ^= b; c -= rot(b,16); \
  87   a ^= c; a -= rot(c,4);  \
  88   b ^= a; b -= rot(a,14); \
  89   c ^= b; c -= rot(b,24); \
  90 }
  91
  92 /* This is a fast, reversable hash function called "lookup3", found here:
  93    http://burtleburtle.net/bob/c/lookup3.c, by Bob Jenkins
  94
  95    This hashing algorithm is "reversible", that is, not cryptographically
  96    secure at all.  But we don't care about that, we just want something to
  97    tell when images are the same or different relatively quickly.
  98 */
  99 guint32 hashword(const guint32 *key, gint length, guint32 initval)
 100 {
 101     guint32 a,b,c;
 102
 103     /* Set up the internal state */
 104     a = b = c = 0xdeadbeef + (((guint32)length)<<2) + initval;
 105
 106     /* handle most of the key */
 107     while (length > 3)
 108     {
 109         a += key[0];
 110         b += key[1];
 111         c += key[2];
 112         mix(a,b,c);
 113         length -= 3;
 114         key += 3;
 115     }
 116
 117     /* handle the last 3 guint32's */
 118     switch(length)      /* all the case statements fall through */
 119     {
 120     case 3: c+=key[2];
 121     case 2: b+=key[1];
 122     case 1: a+=key[0];
 123         final(a,b,c);
 124     case 0:             /* case 0: nothing left to add */
 125         break;
 126     }
 127     /* report the result */
 128     return c;
 129 }
 130
 131 /*! This is some arbitrary initial value for the hashing function.  It's
 132   constant so that you get the same result from the same data each time.
 133 */
 134 #define HASH_INITVAL 0xf00d
 135
 136 guint RrImagePicHash(const RrImagePic *p)
 137 {
 138     return hashword(p->data, p->width * p->height, HASH_INITVAL);
 139 }
 140
 141 static gboolean RrImagePicEqual(const RrImagePic *p1,
 142                                 const RrImagePic *p2)
 143 {
 144     return p1->width == p2->width && p1->height == p2->height &&
 145         p1->sum == p2->sum;
 146 }