libkern/libkern/OSCrossEndian.h

   1 /*
   2  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /*
  25  * This private header exports 3 APIs.
  26  *      _OSRosettaCheck() -     An inline function that returns true if we are
  27  *                              currently running under Rosetta.
  28  *      IF_ROSETTA() -          Which is used to as a regular conditional
  29  *                              expression that is true only if the current
  30  *                              code is executing in the Rosetta
  31  *                              translation space.
  32  *      ROSETTA_ONLY(exprs) -   Which is used to create a block code that only
  33  *                              executes if we are running in Rosetta.
  34  *
  35  * for example
  36  *
  37  * IF_ROSETTA() {
  38  *      // Do Cross endian swapping of input data
  39  *      outdata = OSSwap??(indata);
  40  * }
  41  * else {
  42  *      // Do straight through
  43  *      outdata = indata;
  44  * }
  45  *
  46  * outdata = indata;
  47  * ROSETTA_ONLY(
  48  *      // Do Cross endian swapping of input data
  49  *      outdata = OSSwap??(outdata);
  50  * );
  51  */
  52
  53 #ifndef _LIBKERN_OSCROSSENDIAN_H
  54 #define _LIBKERN_OSCROSSENDIAN_H
  55
  56 #if __ppc__
  57
  58 static __inline__ int _OSRosettaCheck(void)
  59 {
  60     int isCrossEndian;
  61
  62     __asm__ (  "b 0f\n"
  63             "   .long 0x14400004\n"
  64             "   li %0,1\n"
  65             "0:"
  66         : "=r" (isCrossEndian) : "0" (0)
  67     );
  68
  69     return isCrossEndian;
  70 }
  71
  72 #else
  73
  74 static __inline__ int _OSRosettaCheck(void) { return 0; }
  75
  76 #endif
  77
  78 #define IF_ROSETTA() if (__builtin_expect(_OSRosettaCheck(), 0) )
  79
  80 #define ROSETTA_ONLY(exprs)     \
  81 do {                            \
  82     IF_ROSETTA() {              \
  83         exprs                   \
  84     }                           \
  85 } while(0)
  86
  87 #endif /*  _LIBKERN_OSCROSSENDIAN_H */