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_slice_new(RrImageCache);
  33     self->ref = 1;
  34     self->max_resized_saved = max_resized_saved;
  35     self->pic_table = g_hash_table_new((GHashFunc)RrImagePicHash,
  36                                        (GEqualFunc)RrImagePicEqual);
  37     self->name_table = g_hash_table_new(g_str_hash, g_str_equal);
  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->pic_table) == 0);
  50         g_hash_table_unref(self->pic_table);
  51         self->pic_table = NULL;
  52
  53         g_assert(g_hash_table_size(self->name_table) == 0);
  54         g_hash_table_destroy(self->name_table);
  55         self->name_table = NULL;
  56
  57         g_slice_free(RrImageCache, self);
  58     }
  59 }
  60
  61 #define hashsize(n) ((RrPixel32)1<<(n))
  62 #define hashmask(n) (hashsize(n)-1)
  63 #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
  64 /* mix -- mix 3 32-bit values reversibly. */
  65 #define mix(a,b,c) \
  66 { \
  67   a -= c;  a ^= rot(c, 4);  c += b; \
  68   b -= a;  b ^= rot(a, 6);  a += c; \
  69   c -= b;  c ^= rot(b, 8);  b += a; \
  70   a -= c;  a ^= rot(c,16);  c += b; \
  71   b -= a;  b ^= rot(a,19);  a += c; \
  72   c -= b;  c ^= rot(b, 4);  b += a; \
  73 }
  74 /* final -- final mixing of 3 32-bit values (a,b,c) into c */
  75 #define final(a,b,c) \
  76 { \
  77   c ^= b; c -= rot(b,14); \
  78   a ^= c; a -= rot(c,11); \
  79   b ^= a; b -= rot(a,25); \
  80   c ^= b; c -= rot(b,16); \
  81   a ^= c; a -= rot(c,4);  \
  82   b ^= a; b -= rot(a,14); \
  83   c ^= b; c -= rot(b,24); \
  84 }
  85
  86 /* This is a fast, reversable hash function called "lookup3", found here:
  87    http://burtleburtle.net/bob/c/lookup3.c, by Bob Jenkins
  88
  89    This hashing algorithm is "reversible", that is, not cryptographically
  90    secure at all.  But we don't care about that, we just want something to
  91    tell when images are the same or different relatively quickly.
  92 */
  93 guint32 hashword(const guint32 *key, gint length, guint32 initval)
  94 {
  95     guint32 a,b,c;
  96
  97     /* Set up the internal state */
  98     a = b = c = 0xdeadbeef + (((guint32)length)<<2) + initval;
  99
 100     /* handle most of the key */
 101     while (length > 3)
 102     {
 103         a += key[0];
 104         b += key[1];
 105         c += key[2];
 106         mix(a,b,c);
 107         length -= 3;
 108         key += 3;
 109     }
 110
 111     /* handle the last 3 guint32's */
 112     switch(length)      /* all the case statements fall through */
 113     {
 114     case 3: c+=key[2];
 115     case 2: b+=key[1];
 116     case 1: a+=key[0];
 117         final(a,b,c);
 118     case 0:             /* case 0: nothing left to add */
 119         break;
 120     }
 121     /* report the result */
 122     return c;
 123 }
 124
 125 /*! This is some arbitrary initial value for the hashing function.  It's
 126   constant so that you get the same result from the same data each time.
 127 */
 128 #define HASH_INITVAL 0xf00d
 129
 130 guint RrImagePicHash(const RrImagePic *p)
 131 {
 132     return hashword(p->data, p->width * p->height, HASH_INITVAL);
 133 }
 134
 135 static gboolean RrImagePicEqual(const RrImagePic *p1,
 136                                 const RrImagePic *p2)
 137 {
 138     return p1->width == p2->width && p1->height == p2->height &&
 139         p1->sum == p2->sum;
 140 }