load_images.c

   1 /* Copyright (C) <2010> Douglas Bagnall <douglas@halo.gen.nz>
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Library General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Library General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Library General Public
  14  * License along with this library; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 02111-1307, USA.
  17  */
  18
  19 #include "sparrow.h"
  20 #include "gstsparrow.h"
  21
  22 #include <string.h>
  23 #include <math.h>
  24
  25 #include <sys/mman.h>
  26
  27
  28 static void
  29 load_images(GstSparrow *sparrow){
  30   int fd = open(sparrow->jpeg_blob, O_RDONLY);
  31   off_t length = lseek(fd, 0, SEEK_END);
  32   off_t start = lseek(fd, 0, SEEK_SET);
  33
  34   void *mem = mmap(NULL, length, PROT_READ, MAP_PRIVATE | MAP_POPULATE, fd, 0);
  35   madvise(mem, length, POSIX_MADV_WILLNEED);
  36
  37   sparrow->shared->jpeg_blob = mem;
  38   sparrow->shared->blob_size = length;
  39 }
  40
  41 static void
  42 unload_images(GstSparrow *sparrow){
  43   int munmap(sparrow->shared->jpeg_blob, sparrow->shared->blob_size);
  44 }
  45
  46 GStaticRWLock blob_lock = G_STATIC_RW_LOCK_INIT;
  47 GStaticRWLock index_lock = G_STATIC_RW_LOCK_INIT;
  48
  49 /* not using the reader locks (?)
  50   g_static_rw_lock_reader_lock ();
  51   g_static_rw_lock_reader_unlock ();
  52 */
  53
  54 void
  55 maybe_load_images(GstSparrow *sparrow)
  56 {
  57   if (g_static_rw_lock_writer_trylock(&blob_lock)){
  58     if (sparrow->shared->jpeg_blob == NULL){
  59       load_images(sparrow);
  60     }
  61     else {
  62       GST_WARNING("trying to load images that are already loaded !!\n");
  63     }
  64     g_static_rw_lock_writer_unlock(&blob_lock);
  65   }
  66 }
  67
  68 INVISIBLE void
  69 maybe_unload_images(GstSparrow *sparrow){
  70   if (g_static_rw_lock_writer_trylock(&blob_lock)){
  71     if (sparrow->shared->jpeg_blob){
  72       unload_images(sparrow);
  73       sparrow->shared->jpeg_blob = NULL;
  74     }
  75     g_static_rw_lock_writer_unlock(&blob_lock);
  76   }
  77 }
  78
  79