icuSources/layout/LESwaps.h

   1
   2 /*
   3  *
   4  * (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved
   5  *
   6  */
   7
   8 #ifndef __LESWAPS_H
   9 #define __LESWAPS_H
  10
  11 #include "LETypes.h"
  12
  13 /**
  14  * \file
  15  * \brief C++ API: Endian independent access to data for LayoutEngine
  16  */
  17
  18 U_NAMESPACE_BEGIN
  19
  20 /**
  21  * A convenience macro which invokes the swapWord member function
  22  * from a concise call.
  23  *
  24  * @stable ICU 2.8
  25  */
  26 #if defined(U_IS_BIG_ENDIAN)
  27     #if U_IS_BIG_ENDIAN
  28         #define SWAPW(value) (value)
  29     #else
  30         #define SWAPW(value) LESwaps::swapWord(value)
  31     #endif
  32 #else
  33     #define SWAPW(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapWord(value))
  34 #endif
  35
  36 /**
  37  * A convenience macro which invokes the swapLong member function
  38  * from a concise call.
  39  *
  40  * @stable ICU 2.8
  41  */
  42 #if defined(U_IS_BIG_ENDIAN)
  43     #if U_IS_BIG_ENDIAN
  44         #define SWAPL(value) (value)
  45     #else
  46         #define SWAPL(value) LESwaps::swapLong(value)
  47     #endif
  48 #else
  49     #define SWAPL(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapLong(value))
  50 #endif
  51
  52 /**
  53  * This class is used to access data which stored in big endian order
  54  * regardless of the conventions of the platform. It has been designed
  55  * to automatically detect the endian-ness of the platform, so that a
  56  * compilation flag is not needed.
  57  *
  58  * All methods are static and inline in an attempt to induce the compiler
  59  * to do most of the calculations at compile time.
  60  *
  61  * @stable ICU 2.8
  62  */
  63 class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
  64 public:
  65
  66 #if !defined(U_IS_BIG_ENDIAN)
  67     /**
  68      * This method detects the endian-ness of the platform by
  69      * casting a pointer to a word to a pointer to a byte. On
  70      * big endian platforms the FF will be in the byte with the
  71      * lowest address. On little endian platforms, the FF will
  72      * be in the byte with the highest address.
  73      *
  74      * @return TRUE if the platform is big endian
  75      *
  76      * @stable ICU 2.8
  77      */
  78     static le_uint8 isBigEndian()
  79     {
  80         const le_uint16 word = 0xFF00;
  81
  82         return *((le_uint8 *) &word);
  83     };
  84 #endif
  85
  86     /**
  87      * This method does the byte swap required on little endian platforms
  88      * to correctly access a (16-bit) word.
  89      *
  90      * @param value - the word to be byte swapped
  91      *
  92      * @return the byte swapped word
  93      *
  94      * @stable ICU 2.8
  95      */
  96     static le_uint16 swapWord(le_uint16 value)
  97     {
  98         return (((le_uint8) (value >> 8)) | (value << 8));
  99     };
 100
 101     /**
 102      * This method does the byte swapping required on little endian platforms
 103      * to correctly access a (32-bit) long.
 104      *
 105      * @param value - the long to be byte swapped
 106      *
 107      * @return the byte swapped long
 108      *
 109      * @stable ICU 2.8
 110      */
 111     static le_uint32 swapLong(le_uint32 value)
 112     {
 113         return swapWord((le_uint16) (value >> 16)) | (swapWord((le_uint16) value) << 16);
 114     };
 115
 116 private:
 117     LESwaps() {} // private - forbid instantiation
 118 };
 119
 120 U_NAMESPACE_END
 121 #endif