libkern/libkern/OSCrossEndian.h

   1 /*
   2  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_OSREFERENCE_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
  10  * License may not be used to create, or enable the creation or
  11  * redistribution of, unlawful or unlicensed copies of an Apple operating
  12  * system, or to circumvent, violate, or enable the circumvention or
  13  * violation of, any terms of an Apple operating system software license
  14  * agreement.
  15  *
  16  * Please obtain a copy of the License at
  17  * http://www.opensource.apple.com/apsl/ and read it before using this
  18  * file.
  19  *
  20  * The Original Code and all software distributed under the License are
  21  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  22  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  23  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  25  * Please see the License for the specific language governing rights and
  26  * limitations under the License.
  27  *
  28  * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
  29  */
  30
  31 /*
  32  * This private header exports 3 APIs.
  33  *      _OSRosettaCheck() -     An inline function that returns true if we are
  34  *                              currently running under Rosetta.
  35  *      IF_ROSETTA() -          Which is used to as a regular conditional
  36  *                              expression that is true only if the current
  37  *                              code is executing in the Rosetta
  38  *                              translation space.
  39  *      ROSETTA_ONLY(exprs) -   Which is used to create a block code that only
  40  *                              executes if we are running in Rosetta.
  41  *
  42  * for example
  43  *
  44  * IF_ROSETTA() {
  45  *      // Do Cross endian swapping of input data
  46  *      outdata = OSSwap??(indata);
  47  * }
  48  * else {
  49  *      // Do straight through
  50  *      outdata = indata;
  51  * }
  52  *
  53  * outdata = indata;
  54  * ROSETTA_ONLY(
  55  *      // Do Cross endian swapping of input data
  56  *      outdata = OSSwap??(outdata);
  57  * );
  58  */
  59
  60 #ifndef _LIBKERN_OSCROSSENDIAN_H
  61 #define _LIBKERN_OSCROSSENDIAN_H
  62
  63 #if __ppc__
  64
  65 static __inline__ int _OSRosettaCheck(void)
  66 {
  67     int isCrossEndian;
  68
  69     __asm__ (  "b 0f\n"
  70             "   .long 0x14400004\n"
  71             "   li %0,1\n"
  72             "0:"
  73         : "=r" (isCrossEndian) : "0" (0)
  74     );
  75
  76     return isCrossEndian;
  77 }
  78
  79 #else
  80
  81 static __inline__ int _OSRosettaCheck(void) { return 0; }
  82
  83 #endif
  84
  85 #define IF_ROSETTA() if (__builtin_expect(_OSRosettaCheck(), 0) )
  86
  87 #define ROSETTA_ONLY(exprs)     \
  88 do {                            \
  89     IF_ROSETTA() {              \
  90         exprs                   \
  91     }                           \
  92 } while(0)
  93
  94 #endif /*  _LIBKERN_OSCROSSENDIAN_H */