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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/DataTypes.h"
     19 #include <cstddef>
     20 #include <limits>
     21 
     22 namespace llvm {
     23 namespace sys {
     24 
     25 /// SwapByteOrder_16 - This function returns a byte-swapped representation of
     26 /// the 16-bit argument.
     27 inline uint16_t SwapByteOrder_16(uint16_t value) {
     28 #if defined(_MSC_VER) && !defined(_DEBUG)
     29   // The DLL version of the runtime lacks these functions (bug!?), but in a
     30   // release build they're replaced with BSWAP instructions anyway.
     31   return _byteswap_ushort(value);
     32 #else
     33   uint16_t Hi = value << 8;
     34   uint16_t Lo = value >> 8;
     35   return Hi | Lo;
     36 #endif
     37 }
     38 
     39 /// SwapByteOrder_32 - This function returns a byte-swapped representation of
     40 /// the 32-bit argument.
     41 inline uint32_t SwapByteOrder_32(uint32_t value) {
     42 #if defined(__llvm__) || \
     43 (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) && !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__) || \
     60 (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) && !defined(__ICC)
     61   return __builtin_bswap64(value);
     62 #elif defined(_MSC_VER) && !defined(_DEBUG)
     63   return _byteswap_uint64(value);
     64 #else
     65   uint64_t Hi = SwapByteOrder_32(uint32_t(value));
     66   uint32_t Lo = SwapByteOrder_32(uint32_t(value >> 32));
     67   return (Hi << 32) | Lo;
     68 #endif
     69 }
     70 
     71 inline unsigned char  SwapByteOrder(unsigned char C) { return C; }
     72 inline   signed char  SwapByteOrder(signed char C) { return C; }
     73 inline          char  SwapByteOrder(char C) { return C; }
     74 
     75 inline unsigned short SwapByteOrder(unsigned short C) { return SwapByteOrder_16(C); }
     76 inline   signed short SwapByteOrder(  signed short C) { return SwapByteOrder_16(C); }
     77 
     78 inline unsigned int   SwapByteOrder(unsigned int   C) { return SwapByteOrder_32(C); }
     79 inline   signed int   SwapByteOrder(  signed int   C) { return SwapByteOrder_32(C); }
     80 
     81 #if __LONG_MAX__ == __INT_MAX__
     82 inline unsigned long  SwapByteOrder(unsigned long  C) { return SwapByteOrder_32(C); }
     83 inline   signed long  SwapByteOrder(  signed long  C) { return SwapByteOrder_32(C); }
     84 #elif __LONG_MAX__ == __LONG_LONG_MAX__
     85 inline unsigned long  SwapByteOrder(unsigned long  C) { return SwapByteOrder_64(C); }
     86 inline   signed long  SwapByteOrder(  signed long  C) { return SwapByteOrder_64(C); }
     87 #else
     88 #error "Unknown long size!"
     89 #endif
     90 
     91 inline unsigned long long SwapByteOrder(unsigned long long C) {
     92   return SwapByteOrder_64(C);
     93 }
     94 inline signed long long SwapByteOrder(signed long long C) {
     95   return SwapByteOrder_64(C);
     96 }
     97 
     98 } // end namespace sys
     99 } // end namespace llvm
    100 
    101 #endif
    102