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nsprpub/pr/include/prbit.h@7e26c7da4463 (annotated)

nsprpub/pr/include/prbit.h

Wed, 31 Dec 2014 06:55:50 +0100

author
Michael Schloh von Bennewitz <michael@schloh.com>
date
Wed, 31 Dec 2014 06:55:50 +0100
changeset 2
7e26c7da4463
permissions
-rw-r--r--

Added tag UPSTREAM_283F7C6 for changeset ca08bd8f51b2

michael@0 1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0 2 /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0 3 * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0 5
michael@0 6 #ifndef prbit_h___
michael@0 7 #define prbit_h___
michael@0 8
michael@0 9 #include "prtypes.h"
michael@0 10 PR_BEGIN_EXTERN_C
michael@0 11
michael@0 12 /*
michael@0 13 ** Replace compare/jump/add/shift sequence with compiler built-in/intrinsic
michael@0 14 ** functions.
michael@0 15 */
michael@0 16 #if defined(_WIN32) && (_MSC_VER >= 1300) && \
michael@0 17 (defined(_M_IX86) || defined(_M_AMD64) || defined(_M_ARM))
michael@0 18 unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask);
michael@0 19 unsigned char _BitScanReverse(unsigned long * Index, unsigned long Mask);
michael@0 20 # pragma intrinsic(_BitScanForward,_BitScanReverse)
michael@0 21 __forceinline static int __prBitScanForward32(unsigned int val)
michael@0 22 {
michael@0 23 unsigned long idx;
michael@0 24 _BitScanForward(&idx, (unsigned long)val);
michael@0 25 return( (int)idx );
michael@0 26 }
michael@0 27 __forceinline static int __prBitScanReverse32(unsigned int val)
michael@0 28 {
michael@0 29 unsigned long idx;
michael@0 30 _BitScanReverse(&idx, (unsigned long)val);
michael@0 31 return( (int)(31-idx) );
michael@0 32 }
michael@0 33 # define pr_bitscan_ctz32(val) __prBitScanForward32(val)
michael@0 34 # define pr_bitscan_clz32(val) __prBitScanReverse32(val)
michael@0 35 # define PR_HAVE_BUILTIN_BITSCAN32
michael@0 36 #elif ((__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) && \
michael@0 37 (defined(__i386__) || defined(__x86_64__) || defined(__arm__))
michael@0 38 # define pr_bitscan_ctz32(val) __builtin_ctz(val)
michael@0 39 # define pr_bitscan_clz32(val) __builtin_clz(val)
michael@0 40 # define PR_HAVE_BUILTIN_BITSCAN32
michael@0 41 #endif /* MSVC || GCC */
michael@0 42
michael@0 43 /*
michael@0 44 ** A prbitmap_t is a long integer that can be used for bitmaps
michael@0 45 */
michael@0 46 typedef unsigned long prbitmap_t;
michael@0 47
michael@0 48 #define PR_TEST_BIT(_map,_bit) \
michael@0 49 ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] & (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
michael@0 50 #define PR_SET_BIT(_map,_bit) \
michael@0 51 ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] |= (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
michael@0 52 #define PR_CLEAR_BIT(_map,_bit) \
michael@0 53 ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] &= ~(1L << ((_bit) & (PR_BITS_PER_LONG-1))))
michael@0 54
michael@0 55 /*
michael@0 56 ** Compute the log of the least power of 2 greater than or equal to n
michael@0 57 */
michael@0 58 NSPR_API(PRIntn) PR_CeilingLog2(PRUint32 i);
michael@0 59
michael@0 60 /*
michael@0 61 ** Compute the log of the greatest power of 2 less than or equal to n
michael@0 62 */
michael@0 63 NSPR_API(PRIntn) PR_FloorLog2(PRUint32 i);
michael@0 64
michael@0 65 /*
michael@0 66 ** Macro version of PR_CeilingLog2: Compute the log of the least power of
michael@0 67 ** 2 greater than or equal to _n. The result is returned in _log2.
michael@0 68 */
michael@0 69 #ifdef PR_HAVE_BUILTIN_BITSCAN32
michael@0 70 #define PR_CEILING_LOG2(_log2,_n) \
michael@0 71 PR_BEGIN_MACRO \
michael@0 72 PRUint32 j_ = (PRUint32)(_n); \
michael@0 73 (_log2) = (j_ <= 1 ? 0 : 32 - pr_bitscan_clz32(j_ - 1)); \
michael@0 74 PR_END_MACRO
michael@0 75 #else
michael@0 76 #define PR_CEILING_LOG2(_log2,_n) \
michael@0 77 PR_BEGIN_MACRO \
michael@0 78 PRUint32 j_ = (PRUint32)(_n); \
michael@0 79 (_log2) = 0; \
michael@0 80 if ((j_) & ((j_)-1)) \
michael@0 81 (_log2) += 1; \
michael@0 82 if ((j_) >> 16) \
michael@0 83 (_log2) += 16, (j_) >>= 16; \
michael@0 84 if ((j_) >> 8) \
michael@0 85 (_log2) += 8, (j_) >>= 8; \
michael@0 86 if ((j_) >> 4) \
michael@0 87 (_log2) += 4, (j_) >>= 4; \
michael@0 88 if ((j_) >> 2) \
michael@0 89 (_log2) += 2, (j_) >>= 2; \
michael@0 90 if ((j_) >> 1) \
michael@0 91 (_log2) += 1; \
michael@0 92 PR_END_MACRO
michael@0 93 #endif /* PR_HAVE_BUILTIN_BITSCAN32 */
michael@0 94
michael@0 95 /*
michael@0 96 ** Macro version of PR_FloorLog2: Compute the log of the greatest power of
michael@0 97 ** 2 less than or equal to _n. The result is returned in _log2.
michael@0 98 **
michael@0 99 ** This is equivalent to finding the highest set bit in the word.
michael@0 100 */
michael@0 101 #ifdef PR_HAVE_BUILTIN_BITSCAN32
michael@0 102 #define PR_FLOOR_LOG2(_log2,_n) \
michael@0 103 PR_BEGIN_MACRO \
michael@0 104 PRUint32 j_ = (PRUint32)(_n); \
michael@0 105 (_log2) = 31 - pr_bitscan_clz32((j_) | 1); \
michael@0 106 PR_END_MACRO
michael@0 107 #else
michael@0 108 #define PR_FLOOR_LOG2(_log2,_n) \
michael@0 109 PR_BEGIN_MACRO \
michael@0 110 PRUint32 j_ = (PRUint32)(_n); \
michael@0 111 (_log2) = 0; \
michael@0 112 if ((j_) >> 16) \
michael@0 113 (_log2) += 16, (j_) >>= 16; \
michael@0 114 if ((j_) >> 8) \
michael@0 115 (_log2) += 8, (j_) >>= 8; \
michael@0 116 if ((j_) >> 4) \
michael@0 117 (_log2) += 4, (j_) >>= 4; \
michael@0 118 if ((j_) >> 2) \
michael@0 119 (_log2) += 2, (j_) >>= 2; \
michael@0 120 if ((j_) >> 1) \
michael@0 121 (_log2) += 1; \
michael@0 122 PR_END_MACRO
michael@0 123 #endif /* PR_HAVE_BUILTIN_BITSCAN32 */
michael@0 124
michael@0 125 /*
michael@0 126 ** Macros for rotate left and right. The argument 'a' must be an unsigned
michael@0 127 ** 32-bit integer type such as PRUint32.
michael@0 128 **
michael@0 129 ** There is no rotate operation in the C Language, so the construct
michael@0 130 ** (a << 4) | (a >> 28) is frequently used instead. Most compilers convert
michael@0 131 ** this to a rotate instruction, but MSVC doesn't without a little help.
michael@0 132 ** To get MSVC to generate a rotate instruction, we have to use the _rotl
michael@0 133 ** or _rotr intrinsic and use a pragma to make it inline.
michael@0 134 **
michael@0 135 ** Note: MSVC in VS2005 will do an inline rotate instruction on the above
michael@0 136 ** construct.
michael@0 137 */
michael@0 138
michael@0 139 #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \
michael@0 140 defined(_M_X64) || defined(_M_ARM))
michael@0 141 #include <stdlib.h>
michael@0 142 #pragma intrinsic(_rotl, _rotr)
michael@0 143 #define PR_ROTATE_LEFT32(a, bits) _rotl(a, bits)
michael@0 144 #define PR_ROTATE_RIGHT32(a, bits) _rotr(a, bits)
michael@0 145 #else
michael@0 146 #define PR_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits))))
michael@0 147 #define PR_ROTATE_RIGHT32(a, bits) (((a) >> (bits)) | ((a) << (32 - (bits))))
michael@0 148 #endif
michael@0 149
michael@0 150 PR_END_EXTERN_C
michael@0 151 #endif /* prbit_h___ */

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