PublicUtility/CABitOperations.h
/* |
File: CABitOperations.h |
Abstract: Part of CoreAudio Utility Classes |
Version: 1.2.2 |
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*/ |
#ifndef _CABitOperations_h_ |
#define _CABitOperations_h_ |
#if !defined(__COREAUDIO_USE_FLAT_INCLUDES__) |
//#include <CoreServices/../Frameworks/CarbonCore.framework/Headers/MacTypes.h> |
#include <CoreFoundation/CFBase.h> |
#else |
// #include <MacTypes.h> |
#include "CFBase.h" |
#endif |
#include <TargetConditionals.h> |
// return whether a number is a power of two |
inline UInt32 IsPowerOfTwo(UInt32 x) |
{ |
return (x & (x-1)) == 0; |
} |
// count the leading zeros in a word |
// Metrowerks Codewarrior. powerpc native count leading zeros instruction: |
// I think it's safe to remove this ... |
//#define CountLeadingZeroes(x) ((int)__cntlzw((unsigned int)x)) |
inline UInt32 CountLeadingZeroes(UInt32 arg) |
{ |
// GNUC / LLVM has a builtin |
#if defined(__GNUC__) |
// on llvm and clang the result is defined for 0 |
#if (TARGET_CPU_X86 || TARGET_CPU_X86_64) && !defined(__llvm__) |
if (arg == 0) return 32; |
#endif // TARGET_CPU_X86 || TARGET_CPU_X86_64 |
return __builtin_clz(arg); |
#elif TARGET_OS_WIN32 |
UInt32 tmp; |
__asm{ |
bsr eax, arg |
mov ecx, 63 |
cmovz eax, ecx |
xor eax, 31 |
mov tmp, eax // this moves the result in tmp to return. |
} |
return tmp; |
#else |
#error "Unsupported architecture" |
#endif // defined(__GNUC__) |
} |
// Alias (with different spelling) |
#define CountLeadingZeros CountLeadingZeroes |
inline UInt32 CountLeadingZeroesLong(UInt64 arg) |
{ |
// GNUC / LLVM has a builtin |
#if defined(__GNUC__) |
#if (TARGET_CPU_X86 || TARGET_CPU_X86_64) && !defined(__llvm__) |
if (arg == 0) return 64; |
#endif // TARGET_CPU_X86 || TARGET_CPU_X86_64 |
return __builtin_clzll(arg); |
#elif TARGET_OS_WIN32 |
UInt32 x = CountLeadingZeroes((UInt32)(arg >> 32)); |
if(x < 32) |
return x; |
else |
return 32+CountLeadingZeroes((UInt32)arg); |
#else |
#error "Unsupported architecture" |
#endif // defined(__GNUC__) |
} |
#define CountLeadingZerosLong CountLeadingZeroesLong |
// count trailing zeroes |
inline UInt32 CountTrailingZeroes(UInt32 x) |
{ |
return 32 - CountLeadingZeroes(~x & (x-1)); |
} |
// count leading ones |
inline UInt32 CountLeadingOnes(UInt32 x) |
{ |
return CountLeadingZeroes(~x); |
} |
// count trailing ones |
inline UInt32 CountTrailingOnes(UInt32 x) |
{ |
return 32 - CountLeadingZeroes(x & (~x-1)); |
} |
// number of bits required to represent x. |
inline UInt32 NumBits(UInt32 x) |
{ |
return 32 - CountLeadingZeroes(x); |
} |
// base 2 log of next power of two greater or equal to x |
inline UInt32 Log2Ceil(UInt32 x) |
{ |
return 32 - CountLeadingZeroes(x - 1); |
} |
// base 2 log of next power of two less or equal to x |
inline UInt32 Log2Floor(UInt32 x) |
{ |
return 32 - CountLeadingZeroes(x) - 1; |
} |
// next power of two greater or equal to x |
inline UInt32 NextPowerOfTwo(UInt32 x) |
{ |
return 1 << Log2Ceil(x); |
} |
// counting the one bits in a word |
inline UInt32 CountOnes(UInt32 x) |
{ |
// secret magic algorithm for counting bits in a word. |
UInt32 t; |
x = x - ((x >> 1) & 0x55555555); |
t = ((x >> 2) & 0x33333333); |
x = (x & 0x33333333) + t; |
x = (x + (x >> 4)) & 0x0F0F0F0F; |
x = x + (x << 8); |
x = x + (x << 16); |
return x >> 24; |
} |
// counting the zero bits in a word |
inline UInt32 CountZeroes(UInt32 x) |
{ |
return CountOnes(~x); |
} |
// return the bit position (0..31) of the least significant bit |
inline UInt32 LSBitPos(UInt32 x) |
{ |
return CountTrailingZeroes(x & -(SInt32)x); |
} |
// isolate the least significant bit |
inline UInt32 LSBit(UInt32 x) |
{ |
return x & -(SInt32)x; |
} |
// return the bit position (0..31) of the most significant bit |
inline UInt32 MSBitPos(UInt32 x) |
{ |
return 31 - CountLeadingZeroes(x); |
} |
// isolate the most significant bit |
inline UInt32 MSBit(UInt32 x) |
{ |
return 1 << MSBitPos(x); |
} |
// Division optimized for power of 2 denominators |
inline UInt32 DivInt(UInt32 numerator, UInt32 denominator) |
{ |
if(IsPowerOfTwo(denominator)) |
return numerator >> (31 - CountLeadingZeroes(denominator)); |
else |
return numerator/denominator; |
} |
#endif |
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