icuSources/layout/LESwaps.h

   1 /*
   2  *
   3  * (C) Copyright IBM Corp. 1998-2011 - All Rights Reserved
   4  *
   5  */
   6
   7 #ifndef __LESWAPS_H
   8 #define __LESWAPS_H
   9
  10 #include "LETypes.h"
  11
  12 /**
  13  * \file
  14  * \brief C++ API: Endian independent access to data for LayoutEngine
  15  */
  16
  17 U_NAMESPACE_BEGIN
  18
  19 /**
  20  * A convenience macro which invokes the swapWord member function
  21  * from a concise call.
  22  *
  23  * @stable ICU 2.8
  24  */
  25 #define SWAPW(value) LESwaps::swapWord((le_uint16)(value))
  26
  27 /**
  28  * A convenience macro which invokes the swapLong member function
  29  * from a concise call.
  30  *
  31  * @stable ICU 2.8
  32  */
  33 #define SWAPL(value) LESwaps::swapLong((le_uint32)(value))
  34
  35 /**
  36  * This class is used to access data which stored in big endian order
  37  * regardless of the conventions of the platform.
  38  *
  39  * All methods are static and inline in an attempt to induce the compiler
  40  * to do most of the calculations at compile time.
  41  *
  42  * @stable ICU 2.8
  43  */
  44 class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
  45 public:
  46
  47     /**
  48      * Reads a big-endian 16-bit word and returns a native-endian value.
  49      * No-op on a big-endian platform, byte-swaps on a little-endian platform.
  50      *
  51      * @param value - the word to be byte swapped
  52      *
  53      * @return the byte swapped word
  54      *
  55      * @stable ICU 2.8
  56      */
  57     static le_uint16 swapWord(le_uint16 value)
  58     {
  59 #if (defined(U_IS_BIG_ENDIAN) && U_IS_BIG_ENDIAN) || \
  60     (defined(BYTE_ORDER) && defined(BIG_ENDIAN) && (BYTE_ORDER == BIG_ENDIAN)) || \
  61     defined(__BIG_ENDIAN__)
  62         // Fastpath when we know that the platform is big-endian.
  63         return value;
  64 #else
  65         // Reads a big-endian value on any platform.
  66         const le_uint8 *p = reinterpret_cast<const le_uint8 *>(&value);
  67         return (le_uint16)((p[0] << 8) | p[1]);
  68 #endif
  69     };
  70
  71     /**
  72      * Reads a big-endian 32-bit word and returns a native-endian value.
  73      * No-op on a big-endian platform, byte-swaps on a little-endian platform.
  74      *
  75      * @param value - the long to be byte swapped
  76      *
  77      * @return the byte swapped long
  78      *
  79      * @stable ICU 2.8
  80      */
  81     static le_uint32 swapLong(le_uint32 value)
  82     {
  83 #if (defined(U_IS_BIG_ENDIAN) && U_IS_BIG_ENDIAN) || \
  84     (defined(BYTE_ORDER) && defined(BIG_ENDIAN) && (BYTE_ORDER == BIG_ENDIAN)) || \
  85     defined(__BIG_ENDIAN__)
  86         // Fastpath when we know that the platform is big-endian.
  87         return value;
  88 #else
  89         // Reads a big-endian value on any platform.
  90         const le_uint8 *p = reinterpret_cast<const le_uint8 *>(&value);
  91         return (le_uint32)((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
  92 #endif
  93     };
  94
  95 private:
  96     LESwaps() {} // private - forbid instantiation
  97 };
  98
  99 U_NAMESPACE_END
 100 #endif