icuSources/layout/LESwaps.h

   1
   2 /*
   3  *
   4  * (C) Copyright IBM Corp. 1998-2004 - All Rights Reserved
   5  *
   6  */
   7
   8 #ifndef __LESWAPS_H
   9 #define __LESWAPS_H
  10
  11 #include "LETypes.h"
  12
  13 U_NAMESPACE_BEGIN
  14
  15 /**
  16  * A convenience macro which invokes the swapWord member function
  17  * from a concise call.
  18  *
  19  * @stable ICU 2.8
  20  */
  21 #if defined(U_IS_BIG_ENDIAN)
  22     #if U_IS_BIG_ENDIAN
  23         #define SWAPW(value) (value)
  24     #else
  25         #define SWAPW(value) LESwaps::swapWord(value)
  26     #endif
  27 #else
  28     #define SWAPW(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapWord(value))
  29 #endif
  30
  31 /**
  32  * A convenience macro which invokes the swapLong member function
  33  * from a concise call.
  34  *
  35  * @stable ICU 2.8
  36  */
  37 #if defined(U_IS_BIG_ENDIAN)
  38     #if U_IS_BIG_ENDIAN
  39         #define SWAPL(value) (value)
  40     #else
  41         #define SWAPL(value) LESwaps::swapLong(value)
  42     #endif
  43 #else
  44     #define SWAPL(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapLong(value))
  45 #endif
  46
  47 /**
  48  * This class is used to access data which stored in big endian order
  49  * regardless of the conventions of the platform. It has been designed
  50  * to automatically detect the endian-ness of the platform, so that a
  51  * compilation flag is not needed.
  52  *
  53  * All methods are static and inline in an attempt to induce the compiler
  54  * to do most of the calculations at compile time.
  55  *
  56  * @stable ICU 2.8
  57  */
  58 class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
  59 public:
  60
  61 #if !defined(U_IS_BIG_ENDIAN)
  62     /**
  63      * This method detects the endian-ness of the platform by
  64      * casting a pointer to a word to a pointer to a byte. On
  65      * big endian platforms the FF will be in the byte with the
  66      * lowest address. On little endian platforms, the FF will
  67      * be in the byte with the highest address.
  68      *
  69      * @return TRUE if the platform is big endian
  70      *
  71      * @stable ICU 2.8
  72      */
  73     static le_uint8 isBigEndian()
  74     {
  75         const le_uint16 word = 0xFF00;
  76
  77         return *((le_uint8 *) &word);
  78     };
  79 #endif
  80
  81     /**
  82      * This method does the byte swap required on little endian platforms
  83      * to correctly access a (16-bit) word.
  84      *
  85      * @param value - the word to be byte swapped
  86      *
  87      * @return the byte swapped word
  88      *
  89      * @stable ICU 2.8
  90      */
  91     static le_uint16 swapWord(le_uint16 value)
  92     {
  93         return (((le_uint8) (value >> 8)) | (value << 8));
  94     };
  95
  96     /**
  97      * This method does the byte swapping required on little endian platforms
  98      * to correctly access a (32-bit) long.
  99      *
 100      * @param value - the long to be byte swapped
 101      *
 102      * @return the byte swapped long
 103      *
 104      * @stable ICU 2.8
 105      */
 106     static le_uint32 swapLong(le_uint32 value)
 107     {
 108         return swapWord((le_uint16) (value >> 16)) | (swapWord((le_uint16) value) << 16);
 109     };
 110
 111 private:
 112     LESwaps() {} // private - forbid instantiation
 113 };
 114
 115 U_NAMESPACE_END
 116 #endif