libkern/libkern/OSCrossEndian.h

   1 /*
   2  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_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. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*
  30  * This private header exports 3 APIs.
  31  *      _OSRosettaCheck() -     An inline function that returns true if we are
  32  *                              currently running under Rosetta.
  33  *      IF_ROSETTA() -          Which is used to as a regular conditional
  34  *                              expression that is true only if the current
  35  *                              code is executing in the Rosetta
  36  *                              translation space.
  37  *      ROSETTA_ONLY(exprs) -   Which is used to create a block code that only
  38  *                              executes if we are running in Rosetta.
  39  *
  40  * for example
  41  *
  42  * IF_ROSETTA() {
  43  *      // Do Cross endian swapping of input data
  44  *      outdata = OSSwap??(indata);
  45  * }
  46  * else {
  47  *      // Do straight through
  48  *      outdata = indata;
  49  * }
  50  *
  51  * outdata = indata;
  52  * ROSETTA_ONLY(
  53  *      // Do Cross endian swapping of input data
  54  *      outdata = OSSwap??(outdata);
  55  * );
  56  */
  57
  58 #ifndef _LIBKERN_OSCROSSENDIAN_H
  59 #define _LIBKERN_OSCROSSENDIAN_H
  60
  61 #if __ppc__
  62
  63 static __inline__ int _OSRosettaCheck(void)
  64 {
  65     int isCrossEndian;
  66
  67     __asm__ (  "b 0f\n"
  68             "   .long 0x14400004\n"
  69             "   li %0,1\n"
  70             "0:"
  71         : "=r" (isCrossEndian) : "0" (0)
  72     );
  73
  74     return isCrossEndian;
  75 }
  76
  77 #else
  78
  79 static __inline__ int _OSRosettaCheck(void) { return 0; }
  80
  81 #endif
  82
  83 #define IF_ROSETTA() if (__builtin_expect(_OSRosettaCheck(), 0) )
  84
  85 #define ROSETTA_ONLY(exprs)     \
  86 do {                            \
  87     IF_ROSETTA() {              \
  88         exprs                   \
  89     }                           \
  90 } while(0)
  91
  92 #endif /*  _LIBKERN_OSCROSSENDIAN_H */