libfat/ulint.h

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2001-2008 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., 675 Mass Ave, Cambridge MA 02139,
   8  *   USA; either version 2 of the License, or (at your option) any later
   9  *   version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * ulint.h
  15  *
  16  * Basic operations on unaligned, littleendian integers
  17  */
  18
  19 #ifndef ULINT_H
  20 #define ULINT_H
  21
  22 #include <inttypes.h>
  23
  24 /* These are unaligned, littleendian integer types */
  25
  26 typedef uint8_t le8_t;          /*  8-bit byte */
  27 typedef uint8_t le16_t[2];      /* 16-bit word */
  28 typedef uint8_t le32_t[4];      /* 32-bit dword */
  29
  30 /* Read/write these quantities */
  31
  32 static inline unsigned char read8(le8_t * _p)
  33 {
  34     return *_p;
  35 }
  36
  37 static inline void write8(le8_t * _p, uint8_t _v)
  38 {
  39     *_p = _v;
  40 }
  41
  42 #if defined(__i386__) || defined(__x86_64__)
  43
  44 /* Littleendian architectures which support unaligned memory accesses */
  45
  46 static inline unsigned short read16(le16_t * _p)
  47 {
  48     return *((const uint16_t *)_p);
  49 }
  50
  51 static inline void write16(le16_t * _p, unsigned short _v)
  52 {
  53     *((uint16_t *) _p) = _v;
  54 }
  55
  56 static inline unsigned int read32(le32_t * _p)
  57 {
  58     return *((const uint32_t *)_p);
  59 }
  60
  61 static inline void write32(le32_t * _p, uint32_t _v)
  62 {
  63     *((uint32_t *) _p) = _v;
  64 }
  65
  66 #else
  67
  68 /* Generic, mostly portable versions */
  69
  70 static inline unsigned short read16(le16_t * _pp)
  71 {
  72     uint8_t *_p = *_pp;
  73     uint16_t _v;
  74
  75     _v = _p[0];
  76     _v |= _p[1] << 8;
  77     return _v;
  78 }
  79
  80 static inline void write16(le16_t * _pp, uint16_t _v)
  81 {
  82     uint8_t *_p = *_pp;
  83
  84     _p[0] = _v & 0xFF;
  85     _p[1] = (_v >> 8) & 0xFF;
  86 }
  87
  88 static inline unsigned int read32(le32_t * _pp)
  89 {
  90     uint8_t *_p = *_pp;
  91     uint32_t _v;
  92
  93     _v = _p[0];
  94     _v |= _p[1] << 8;
  95     _v |= _p[2] << 16;
  96     _v |= _p[3] << 24;
  97     return _v;
  98 }
  99
 100 static inline void write32(le32_t * _pp, uint32_t _v)
 101 {
 102     uint8_t *_p = *_pp;
 103
 104     _p[0] = _v & 0xFF;
 105     _p[1] = (_v >> 8) & 0xFF;
 106     _p[2] = (_v >> 16) & 0xFF;
 107     _p[3] = (_v >> 24) & 0xFF;
 108 }
 109
 110 #endif
 111
 112 #endif /* ULINT_H */