libkern/libkern/OSCrossEndian.h

   1 /*
   2  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22
  23 /*
  24  * This private header exports 3 APIs.
  25  *      _OSRosettaCheck() -     An inline function that returns true if we are
  26  *                              currently running under Rosetta.
  27  *      IF_ROSETTA() -          Which is used to as a regular conditional
  28  *                              expression that is true only if the current
  29  *                              code is executing in the Rosetta
  30  *                              translation space.
  31  *      ROSETTA_ONLY(exprs) -   Which is used to create a block code that only
  32  *                              executes if we are running in Rosetta.
  33  *
  34  * for example
  35  *
  36  * IF_ROSETTA() {
  37  *      // Do Cross endian swapping of input data
  38  *      outdata = OSSwap??(indata);
  39  * }
  40  * else {
  41  *      // Do straight through
  42  *      outdata = indata;
  43  * }
  44  *
  45  * outdata = indata;
  46  * ROSETTA_ONLY(
  47  *      // Do Cross endian swapping of input data
  48  *      outdata = OSSwap??(outdata);
  49  * );
  50  */
  51
  52 #ifndef _LIBKERN_OSCROSSENDIAN_H
  53 #define _LIBKERN_OSCROSSENDIAN_H
  54
  55 #if __ppc__
  56
  57 static __inline__ int _OSRosettaCheck(void)
  58 {
  59     int isCrossEndian;
  60
  61     __asm__ (  "b 0f\n"
  62             "   .long 0x14400004\n"
  63             "   li %0,1\n"
  64             "0:"
  65         : "=r" (isCrossEndian) : "0" (0)
  66     );
  67
  68     return isCrossEndian;
  69 }
  70
  71 #else
  72
  73 static __inline__ int _OSRosettaCheck(void) { return 0; }
  74
  75 #endif
  76
  77 #define IF_ROSETTA() if (__builtin_expect(_OSRosettaCheck(), 0) )
  78
  79 #define ROSETTA_ONLY(exprs)     \
  80 do {                            \
  81     IF_ROSETTA() {              \
  82         exprs                   \
  83     }                           \
  84 } while(0)
  85
  86 #endif /*  _LIBKERN_OSCROSSENDIAN_H */