libfat/cache.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2004-2008 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * cache.c
  15  *
  16  * Simple sector cache
  17  */
  18
  19 #include <stdlib.h>
  20 #include "libfatint.h"
  21
  22 void *libfat_get_sector(struct libfat_filesystem *fs, libfat_sector_t n)
  23 {
  24     struct libfat_sector *ls;
  25
  26     for (ls = fs->sectors; ls; ls = ls->next) {
  27         if (ls->n == n)
  28             return ls->data;    /* Found in cache */
  29     }
  30
  31     /* Not found in cache */
  32     ls = malloc(sizeof(struct libfat_sector));
  33     if (!ls) {
  34         libfat_flush(fs);
  35         ls = malloc(sizeof(struct libfat_sector));
  36
  37         if (!ls)
  38             return NULL;        /* Can't allocate memory */
  39     }
  40
  41     if (fs->read(fs->readptr, ls->data, LIBFAT_SECTOR_SIZE, n)
  42         != LIBFAT_SECTOR_SIZE) {
  43         free(ls);
  44         return NULL;            /* I/O error */
  45     }
  46
  47     ls->n = n;
  48     ls->next = fs->sectors;
  49     fs->sectors = ls;
  50
  51     return ls->data;
  52 }
  53
  54 void libfat_flush(struct libfat_filesystem *fs)
  55 {
  56     struct libfat_sector *ls, *lsnext;
  57
  58     lsnext = fs->sectors;
  59     fs->sectors = NULL;
  60
  61     for (ls = lsnext; ls; ls = lsnext) {
  62         lsnext = ls->next;
  63         free(ls);
  64     }
  65 }