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 */
138
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