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 */ isBigEndian()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 */ swapWord(le_uint16 value)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 */ swapLong(le_uint32 value)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: LESwaps()117 LESwaps() {} // private - forbid instantiation 118 }; 119 120 U_NAMESPACE_END 121 #endif 122