fs/jffs2/pushpull.h

   1 /*
   2  * JFFS2 -- Journalling Flash File System, Version 2.
   3  *
   4  * Copyright (C) 2001, 2002 Red Hat, Inc.
   5  *
   6  * Created by David Woodhouse <dwmw2@infradead.org>
   7  *
   8  * For licensing information, see the file 'LICENCE' in this directory.
   9  *
  10  * $Id: pushpull.h,v 1.10 2004/11/16 20:36:11 dwmw2 Exp $
  11  *
  12  */
  13
  14 #ifndef __PUSHPULL_H__
  15 #define __PUSHPULL_H__
  16
  17 #include <linux/errno.h>
  18
  19 struct pushpull {
  20         unsigned char *buf;
  21         unsigned int buflen;
  22         unsigned int ofs;
  23         unsigned int reserve;
  24 };
  25
  26
  27 static inline void init_pushpull(struct pushpull *pp, char *buf, unsigned buflen, unsigned ofs, unsigned reserve)
  28 {
  29         pp->buf = buf;
  30         pp->buflen = buflen;
  31         pp->ofs = ofs;
  32         pp->reserve = reserve;
  33 }
  34
  35 static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
  36 {
  37         if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve)) {
  38                 return -ENOSPC;
  39         }
  40
  41         if (bit) {
  42                 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs &7)));
  43         }
  44         else {
  45                 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs &7)));
  46         }
  47         pp->ofs++;
  48
  49         return 0;
  50 }
  51
  52 static inline int pushedbits(struct pushpull *pp)
  53 {
  54         return pp->ofs;
  55 }
  56
  57 static inline int pullbit(struct pushpull *pp)
  58 {
  59         int bit;
  60
  61         bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
  62
  63         pp->ofs++;
  64         return bit;
  65 }
  66
  67 static inline int pulledbits(struct pushpull *pp)
  68 {
  69         return pp->ofs;
  70 }
  71
  72 #endif /* __PUSHPULL_H__ */