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      1 //===- SwapByteOrder.h - Generic and optimized byte swaps -------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file declares generic and optimized functions to swap the byte order of
     11 // an integral type.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_SUPPORT_SWAPBYTEORDER_H
     16 #define LLVM_SUPPORT_SWAPBYTEORDER_H
     17 
     18 #include "llvm/Support/Compiler.h"
     19 #include "llvm/Support/DataTypes.h"
     20 #include <cstddef>
     21 #include <limits>
     22 
     23 namespace llvm {
     24 namespace sys {
     25 
     26 /// SwapByteOrder_16 - This function returns a byte-swapped representation of
     27 /// the 16-bit argument.
     28 inline uint16_t SwapByteOrder_16(uint16_t value) {
     29 #if defined(_MSC_VER) && !defined(_DEBUG)
     30   // The DLL version of the runtime lacks these functions (bug!?), but in a
     31   // release build they're replaced with BSWAP instructions anyway.
     32   return _byteswap_ushort(value);
     33 #else
     34   uint16_t Hi = value << 8;
     35   uint16_t Lo = value >> 8;
     36   return Hi | Lo;
     37 #endif
     38 }
     39 
     40 /// SwapByteOrder_32 - This function returns a byte-swapped representation of
     41 /// the 32-bit argument.
     42 inline uint32_t SwapByteOrder_32(uint32_t value) {
     43 #if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
     44   return __builtin_bswap32(value);
     45 #elif defined(_MSC_VER) && !defined(_DEBUG)
     46   return _byteswap_ulong(value);
     47 #else
     48   uint32_t Byte0 = value & 0x000000FF;
     49   uint32_t Byte1 = value & 0x0000FF00;
     50   uint32_t Byte2 = value & 0x00FF0000;
     51   uint32_t Byte3 = value & 0xFF000000;
     52   return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
     53 #endif
     54 }
     55 
     56 /// SwapByteOrder_64 - This function returns a byte-swapped representation of
     57 /// the 64-bit argument.
     58 inline uint64_t SwapByteOrder_64(uint64_t value) {
     59 #if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
     60   return __builtin_bswap64(value);
     61 #elif defined(_MSC_VER) && !defined(_DEBUG)
     62   return _byteswap_uint64(value);
     63 #else
     64   uint64_t Hi = SwapByteOrder_32(uint32_t(value));
     65   uint32_t Lo = SwapByteOrder_32(uint32_t(value >> 32));
     66   return (Hi << 32) | Lo;
     67 #endif
     68 }
     69 
     70 inline unsigned char  getSwappedBytes(unsigned char C) { return C; }
     71 inline   signed char  getSwappedBytes(signed char C) { return C; }
     72 inline          char  getSwappedBytes(char C) { return C; }
     73 
     74 inline unsigned short getSwappedBytes(unsigned short C) { return SwapByteOrder_16(C); }
     75 inline   signed short getSwappedBytes(  signed short C) { return SwapByteOrder_16(C); }
     76 
     77 inline unsigned int   getSwappedBytes(unsigned int   C) { return SwapByteOrder_32(C); }
     78 inline   signed int   getSwappedBytes(  signed int   C) { return SwapByteOrder_32(C); }
     79 
     80 #if __LONG_MAX__ == __INT_MAX__
     81 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_32(C); }
     82 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_32(C); }
     83 #elif __LONG_MAX__ == __LONG_LONG_MAX__
     84 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_64(C); }
     85 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_64(C); }
     86 #else
     87 #error "Unknown long size!"
     88 #endif
     89 
     90 inline unsigned long long getSwappedBytes(unsigned long long C) {
     91   return SwapByteOrder_64(C);
     92 }
     93 inline signed long long getSwappedBytes(signed long long C) {
     94   return SwapByteOrder_64(C);
     95 }
     96 
     97 inline float getSwappedBytes(float C) {
     98   union {
     99     uint32_t i;
    100     float f;
    101   } in, out;
    102   in.f = C;
    103   out.i = SwapByteOrder_32(in.i);
    104   return out.f;
    105 }
    106 
    107 inline double getSwappedBytes(double C) {
    108   union {
    109     uint64_t i;
    110     double d;
    111   } in, out;
    112   in.d = C;
    113   out.i = SwapByteOrder_64(in.i);
    114   return out.d;
    115 }
    116 
    117 template<typename T>
    118 inline void swapByteOrder(T &Value) {
    119   Value = getSwappedBytes(Value);
    120 }
    121 
    122 } // end namespace sys
    123 } // end namespace llvm
    124 
    125 #endif
    126