icuSources/layout/LESwaps.h

   1
   2 /*
   3  * @(#)LESwaps.h        1.3 00/03/15
   4  *
   5  * (C) Copyright IBM Corp. 1998-2003 - All Rights Reserved
   6  *
   7  */
   8
   9 #ifndef __LESWAPS_H
  10 #define __LESWAPS_H
  11
  12 #include "LETypes.h"
  13
  14 U_NAMESPACE_BEGIN
  15
  16 /**
  17  * A convenience macro which invokes the swapWord member function
  18  * from a concise call.
  19  *
  20  * @draft ICU 2.2
  21  */
  22 #define SWAPW(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapWord(value))
  23
  24
  25 /**
  26  * A convenience macro which invokes the swapLong member function
  27  * from a concise call.
  28  *
  29  * @draft ICU 2.2
  30  */
  31 #define SWAPL(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapLong(value))
  32
  33 /**
  34  * This class is used to access data which stored in big endian order
  35  * regardless of the conventions of the platform. It has been designed
  36  * to automatically detect the endian-ness of the platform, so that a
  37  * compilation flag is not needed.
  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  * @draft ICU 2.2
  43  */
  44 class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
  45 public:
  46
  47     /**
  48      * This method detects the endian-ness of the platform by
  49      * casting a pointer to a word to a pointer to a byte. On
  50      * big endian platforms the FF will be in the byte with the
  51      * lowest address. On little endian platforms, the FF will
  52      * be in the byte with the highest address.
  53      *
  54      * @return true if the platform is big endian
  55      *
  56      * @draft ICU 2.2
  57      */
  58     static le_bool isBigEndian()
  59     {
  60         const le_uint16 word = 0xFF00;
  61
  62         return *((le_uint8 *) &word);
  63     };
  64
  65     /**
  66      * This method does the byte swap required on little endian platforms
  67      * to correctly access a (16-bit) word.
  68      *
  69      * @param value - the word to be byte swapped
  70      *
  71      * @return the byte swapped word
  72      *
  73      * @draft ICU 2.2
  74      */
  75     static le_uint16 swapWord(le_uint16 value)
  76     {
  77         return (((le_uint8) (value >> 8)) | (value << 8));
  78     };
  79
  80     /**
  81      * This method does the byte swapping required on little endian platforms
  82      * to correctly access a (32-bit) long.
  83      *
  84      * @param value - the long to be byte swapped
  85      *
  86      * @return the byte swapped long
  87      *
  88      * @draft ICU 2.2
  89      */
  90     static le_uint32 swapLong(le_uint32 value)
  91     {
  92         return swapWord((le_uint16) (value >> 16)) | (swapWord((le_uint16) value) << 16);
  93     };
  94
  95 private:
  96     LESwaps() {} // private - forbid instantiation
  97 };
  98
  99 U_NAMESPACE_END
 100 #endif