nsprpub/pr/include/prbit.h

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  15  * The Original Code is the Netscape Portable Runtime (NSPR).
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  37
  38 #ifndef prbit_h___
  39 #define prbit_h___
  40
  41 #include "prtypes.h"
  42 PR_BEGIN_EXTERN_C
  43
  44 /*
  45 ** A prbitmap_t is a long integer that can be used for bitmaps
  46 */
  47 typedef unsigned long prbitmap_t;
  48
  49 #define PR_TEST_BIT(_map,_bit) \
  50     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] & (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
  51 #define PR_SET_BIT(_map,_bit) \
  52     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] |= (1L << ((_bit) & (PR_BITS_PER_LONG-1))))
  53 #define PR_CLEAR_BIT(_map,_bit) \
  54     ((_map)[(_bit)>>PR_BITS_PER_LONG_LOG2] &= ~(1L << ((_bit) & (PR_BITS_PER_LONG-1))))
  55
  56 /*
  57 ** Compute the log of the least power of 2 greater than or equal to n
  58 */
  59 NSPR_API(PRIntn) PR_CeilingLog2(PRUint32 i);
  60
  61 /*
  62 ** Compute the log of the greatest power of 2 less than or equal to n
  63 */
  64 NSPR_API(PRIntn) PR_FloorLog2(PRUint32 i);
  65
  66 /*
  67 ** Macro version of PR_CeilingLog2: Compute the log of the least power of
  68 ** 2 greater than or equal to _n. The result is returned in _log2.
  69 */
  70 #define PR_CEILING_LOG2(_log2,_n)   \
  71   PR_BEGIN_MACRO                    \
  72     PRUint32 j_ = (PRUint32)(_n);       \
  73     (_log2) = 0;                    \
  74     if ((j_) & ((j_)-1))            \
  75         (_log2) += 1;               \
  76     if ((j_) >> 16)                 \
  77         (_log2) += 16, (j_) >>= 16; \
  78     if ((j_) >> 8)                  \
  79         (_log2) += 8, (j_) >>= 8;   \
  80     if ((j_) >> 4)                  \
  81         (_log2) += 4, (j_) >>= 4;   \
  82     if ((j_) >> 2)                  \
  83         (_log2) += 2, (j_) >>= 2;   \
  84     if ((j_) >> 1)                  \
  85         (_log2) += 1;               \
  86   PR_END_MACRO
  87
  88 /*
  89 ** Macro version of PR_FloorLog2: Compute the log of the greatest power of
  90 ** 2 less than or equal to _n. The result is returned in _log2.
  91 **
  92 ** This is equivalent to finding the highest set bit in the word.
  93 */
  94 #define PR_FLOOR_LOG2(_log2,_n)   \
  95   PR_BEGIN_MACRO                    \
  96     PRUint32 j_ = (PRUint32)(_n);       \
  97     (_log2) = 0;                    \
  98     if ((j_) >> 16)                 \
  99         (_log2) += 16, (j_) >>= 16; \
 100     if ((j_) >> 8)                  \
 101         (_log2) += 8, (j_) >>= 8;   \
 102     if ((j_) >> 4)                  \
 103         (_log2) += 4, (j_) >>= 4;   \
 104     if ((j_) >> 2)                  \
 105         (_log2) += 2, (j_) >>= 2;   \
 106     if ((j_) >> 1)                  \
 107         (_log2) += 1;               \
 108   PR_END_MACRO
 109
 110 /*
 111 ** Macros for rotate left and right. The argument 'a' must be an unsigned
 112 ** 32-bit integer type such as PRUint32.
 113 **
 114 ** There is no rotate operation in the C Language, so the construct
 115 ** (a << 4) | (a >> 28) is frequently used instead. Most compilers convert
 116 ** this to a rotate instruction, but MSVC doesn't without a little help.
 117 ** To get MSVC to generate a rotate instruction, we have to use the _rotl
 118 ** or _rotr intrinsic and use a pragma to make it inline.
 119 **
 120 ** Note: MSVC in VS2005 will do an inline rotate instruction on the above
 121 ** construct.
 122 */
 123
 124 #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \
 125     defined(_M_X64))
 126 #include <stdlib.h>
 127 #pragma intrinsic(_rotl, _rotr)
 128 #define PR_ROTATE_LEFT32(a, bits) _rotl(a, bits)
 129 #define PR_ROTATE_RIGHT32(a, bits) _rotr(a, bits)
 130 #else
 131 #define PR_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits))))
 132 #define PR_ROTATE_RIGHT32(a, bits) (((a) >> (bits)) | ((a) << (32 - (bits))))
 133 #endif
 134
 135 PR_END_EXTERN_C
 136 #endif /* prbit_h___ */