fs/ufs/swab.h

   1 /*
   2  *  linux/fs/ufs/swab.h
   3  *
   4  * Copyright (C) 1997, 1998 Francois-Rene Rideau <fare@tunes.org>
   5  * Copyright (C) 1998 Jakub Jelinek <jj@ultra.linux.cz>
   6  */
   7
   8 #ifndef _UFS_SWAB_H
   9 #define _UFS_SWAB_H
  10
  11 /*
  12  * Notes:
  13  *    HERE WE ASSUME EITHER BIG OR LITTLE ENDIAN UFSes
  14  *    in case there are ufs implementations that have strange bytesexes,
  15  *    you'll need to modify code here as well as in ufs_super.c and ufs_fs.h
  16  *    to support them.
  17  *
  18  *    WE ALSO ASSUME A REMOTELY SANE ARCHITECTURE BYTESEX.
  19  *    We are not ready to confront insane bytesexual perversions where
  20  *    conversion to/from little/big-endian is not an involution.
  21  *    That is, we require that XeYZ_to_cpu(x) == cpu_to_XeYZ(x)
  22  *
  23  *    NOTE that swab macros depend on a variable (or macro) swab being in
  24  *    scope and properly initialized (usually from sb->u.ufs_sb.s_swab).
  25  *    Its meaning depends on whether the architecture is sane-endian or not.
  26  *    For sane architectures, it's a flag taking values UFS_NATIVE_ENDIAN (0)
  27  *    or UFS_SWABBED_ENDIAN (1), indicating whether to swab or not.
  28  *    For pervert architectures, it's either UFS_LITTLE_ENDIAN or
  29  *    UFS_BIG_ENDIAN whose meaning you'll have to guess.
  30  *
  31  *    It is important to keep these conventions in synch with ufs_fs.h
  32  *    and super.c. Failure to do so (initializing swab to 0 both for
  33  *    NATIVE_ENDIAN and LITTLE_ENDIAN) led to nasty crashes on big endian
  34  *    machines reading little endian UFSes. Search for "swab =" in super.c.
  35  *
  36  *    I also suspect the whole UFS code to trust the on-disk structures
  37  *    much too much, which might lead to losing badly when mounting
  38  *    inconsistent partitions as UFS filesystems. fsck required (but of
  39  *    course, no fsck.ufs has yet to be ported from BSD to Linux as of 199808).
  40  */
  41
  42 #include <linux/ufs_fs.h>
  43 #include <asm/byteorder.h>
  44
  45 /*
  46  * These are only valid inside ufs routines,
  47  * after swab has been initialized to sb->u.ufs_sb.s_swab
  48  */
  49 #define SWAB16(x) ufs_swab16(swab,x)
  50 #define SWAB32(x) ufs_swab32(swab,x)
  51 #define SWAB64(x) ufs_swab64(swab,x)
  52
  53 /*
  54  * We often use swabing, when we want to increment/decrement some value,
  55  * so these macros might become handy and increase readability. (Daniel)
  56  */
  57 #define INC_SWAB16(x)   ((x)=ufs_swab16_add(swab,x,1))
  58 #define INC_SWAB32(x)   ((x)=ufs_swab32_add(swab,x,1))
  59 #define INC_SWAB64(x)   ((x)=ufs_swab64_add(swab,x,1))
  60 #define DEC_SWAB16(x)   ((x)=ufs_swab16_add(swab,x,-1))
  61 #define DEC_SWAB32(x)   ((x)=ufs_swab32_add(swab,x,-1))
  62 #define DEC_SWAB64(x)   ((x)=ufs_swab64_add(swab,x,-1))
  63 #define ADD_SWAB16(x,y) ((x)=ufs_swab16_add(swab,x,y))
  64 #define ADD_SWAB32(x,y) ((x)=ufs_swab32_add(swab,x,y))
  65 #define ADD_SWAB64(x,y) ((x)=ufs_swab64_add(swab,x,y))
  66 #define SUB_SWAB16(x,y) ((x)=ufs_swab16_add(swab,x,-(y)))
  67 #define SUB_SWAB32(x,y) ((x)=ufs_swab32_add(swab,x,-(y)))
  68 #define SUB_SWAB64(x,y) ((x)=ufs_swab64_add(swab,x,-(y)))
  69
  70 #if defined(__LITTLE_ENDIAN) || defined(__BIG_ENDIAN) /* sane bytesex */
  71 extern __inline__ __const__ __u16 ufs_swab16(unsigned swab, __u16 x) {
  72         if (swab)
  73                 return swab16(x);
  74         else
  75                 return x;
  76 }
  77 extern __inline__ __const__ __u32 ufs_swab32(unsigned swab, __u32 x) {
  78         if (swab)
  79                 return swab32(x);
  80         else
  81                 return x;
  82 }
  83 extern __inline__ __const__ __u64 ufs_swab64(unsigned swab, __u64 x) {
  84         if (swab)
  85                 return swab64(x);
  86         else
  87                 return x;
  88 }
  89 extern __inline__ __const__ __u16 ufs_swab16_add(unsigned swab, __u16 x, __u16 y) {
  90         if (swab)
  91                 return swab16(swab16(x)+y);
  92         else
  93                 return x + y;
  94 }
  95 extern __inline__ __const__ __u32 ufs_swab32_add(unsigned swab, __u32 x, __u32 y) {
  96         if (swab)
  97                 return swab32(swab32(x)+y);
  98         else
  99                 return x + y;
 100 }
 101 extern __inline__ __const__ __u64 ufs_swab64_add(unsigned swab, __u64 x, __u64 y) {
 102         if (swab)
 103                 return swab64(swab64(x)+y);
 104         else
 105                 return x + y;
 106 }
 107 #else /* bytesexual perversion -- BEWARE! Read note at top of file! */
 108 extern __inline__ __const__ __u16 ufs_swab16(unsigned swab, __u16 x) {
 109         if (swab == UFS_LITTLE_ENDIAN)
 110                 return le16_to_cpu(x);
 111         else
 112                 return be16_to_cpu(x);
 113 }
 114 extern __inline__ __const__ __u32 ufs_swab32(unsigned swab, __u32 x) {
 115         if (swab == UFS_LITTLE_ENDIAN)
 116                 return le32_to_cpu(x);
 117         else
 118                 return be32_to_cpu(x);
 119 }
 120 extern __inline__ __const__ __u64 ufs_swab64(unsigned swab, __u64 x) {
 121         if (swab == UFS_LITTLE_ENDIAN)
 122                 return le64_to_cpu(x);
 123         else
 124                 return be64_to_cpu(x);
 125 }
 126 extern __inline__ __const__ __u16 ufs_swab16_add(unsigned swab, __u16 x, __u16 y) {
 127         return ufs_swab16(swab, ufs_swab16(swab, x) + y);
 128 }
 129 extern __inline__ __const__ __u32 ufs_swab32_add(unsigned swab, __u32 x, __u32 y) {
 130         return ufs_swab32(swab, ufs_swab32(swab, x) + y);
 131 }
 132 extern __inline__ __const__ __u64 ufs_swab64_add(unsigned swab, __u64 x, __u64 y) {
 133         return ufs_swab64(swab, ufs_swab64(swab, x) + y);
 134 }
 135 #endif /* byte sexuality */
 136
 137 #endif /* _UFS_SWAB_H */