libfat/ulint.h

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2001-2004 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
  33 read8(le8_t *_p)
  34 {
  35   return *_p;
  36 }
  37
  38 static inline void
  39 write8(le8_t *_p, uint8_t _v)
  40 {
  41   *_p = _v;
  42 }
  43
  44 #if defined(__i386__) || defined(__x86_64__)
  45
  46 /* Littleendian architectures which support unaligned memory accesses */
  47
  48 static inline unsigned short
  49 read16(le16_t *_p)
  50 {
  51   return *((const uint16_t *)_p);
  52 }
  53
  54 static inline void
  55 write16(le16_t *_p, unsigned short _v)
  56 {
  57   *((uint16_t *)_p) = _v;
  58 }
  59
  60 static inline unsigned int
  61 read32(le32_t *_p)
  62 {
  63   return *((const uint32_t *)_p);
  64 }
  65
  66 static inline void
  67 write32(le32_t *_p, uint32_t _v)
  68 {
  69   *((uint32_t *)_p) = _v;
  70 }
  71
  72 #else
  73
  74 /* Generic, mostly portable versions */
  75
  76 static inline unsigned short
  77 read16(le16_t *_p)
  78 {
  79   uint16_t _v;
  80
  81   _v  = p[0];
  82   _v |= p[1] << 8;
  83   return _v;
  84 }
  85
  86 static inline void
  87 write16(le16_t *_p, uint16_t _v)
  88 {
  89   _p[0] = _v & 0xFF;
  90   _p[1] = (_v >> 8) & 0xFF;
  91 }
  92
  93 static inline unsigned int
  94 read32(le32_t *_p)
  95 {
  96   _v  = _p[0];
  97   _v |= _p[1] << 8;
  98   _v |= _p[2] << 16;
  99   _v |= _p[3] << 24;
 100   return _v;
 101 }
 102
 103 static inline void
 104 write32(le32_t *_p, uint32_t _v)
 105 {
 106   _p[0] = _v & 0xFF;
 107   _p[1] = (_v >> 8) & 0xFF;
 108   _p[2] = (_v >> 16) & 0xFF;
 109   _p[3] = (_v >> 24) & 0xFF;
 110 }
 111
 112 #endif
 113
 114 #endif /* ULINT_H */