LXR syslinux/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
  22void *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
  54void 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}
  66