SkMathPriv.h File Reference

#include "include/private/base/SkAssert.h"
#include "include/private/base/SkCPUTypes.h"
#include "include/private/base/SkTemplates.h"
#include <cstddef>
#include <cstdint>

Go to the source code of this file.

Macros
#define	SkExtractSign(n)   ((int32_t)(n) >> 31)

Functions
int32_t	SkSqrtBits (int32_t value, int bitBias)
static int32_t	SkSqrt32 (int32_t n)
static int	SkClampPos (int value)
template<typename In , typename Out >
void	SkTDivMod (In numer, In denom, Out *div, Out *mod)
static int32_t	SkApplySign (int32_t n, int32_t sign)
static int32_t	SkCopySign32 (int32_t x, int32_t y)
static unsigned	SkClampUMax (unsigned value, unsigned max)
static size_t	sk_negate_to_size_t (int32_t value)
static U8CPU	SkMulDiv255Trunc (U8CPU a, U8CPU b)
static U8CPU	SkMulDiv255Ceiling (U8CPU a, U8CPU b)
static unsigned	SkDiv255Round (unsigned prod)
static uint32_t	SkBSwap32 (uint32_t v)
int	SkPopCount_portable (uint32_t n)
static int	SkPopCount (uint32_t n)
int	SkNthSet (uint32_t target, int n)
constexpr int	SkCLZ_portable (uint32_t x)
	Returns the number of leading zero bits (0...32) More...
static int	SkCLZ (uint32_t mask)
constexpr int	SkCTZ_portable (uint32_t x)
	Returns the number of trailing zero bits (0...32) More...
static int	SkCTZ (uint32_t mask)
static int	SkNextLog2 (uint32_t value)
constexpr int	SkNextLog2_portable (uint32_t value)
static int	SkPrevLog2 (uint32_t value)
constexpr int	SkPrevLog2_portable (uint32_t value)
static int	SkNextPow2 (int value)
constexpr int	SkNextPow2_portable (int value)
static int	SkPrevPow2 (int value)
constexpr int	SkPrevPow2_portable (int value)
static uint32_t	GrNextPow2 (uint32_t n)
static size_t	GrNextSizePow2 (size_t n)
template<typename T >
static bool	SkFitsInFixed (T x)

Macro Definition Documentation

SkExtractSign

#define SkExtractSign

(

n

)

((int32_t)(n) >> 31)

Returns -1 if n < 0, else returns 0

Definition at line 45 of file SkMathPriv.h.

Function Documentation

GrNextPow2()

static uint32_t GrNextPow2 ( uint32_t  n )

inlinestatic

Return the smallest power-of-2 >= n.

Definition at line 302 of file SkMathPriv.h.

                                              {
    return n ? (1 << (32 - SkCLZ(n - 1))) : 1;
}

GrNextSizePow2()

static size_t GrNextSizePow2 ( size_t  n )

inlinestatic

Returns the next power of 2 >= n or n if the next power of 2 can't be represented by size_t.

Definition at line 309 of file SkMathPriv.h.

                                              {
    constexpr int kNumSizeTBits = 8 * sizeof(size_t);
    constexpr size_t kHighBitSet = size_t(1) << (kNumSizeTBits - 1);
 
    if (!n) {
        return 1;
    } else if (n >= kHighBitSet) {
        return n;
    }
 
    n--;
    uint32_t shift = 1;
    while (shift < kNumSizeTBits) {
        n |= n >> shift;
        shift <<= 1;
    }
    return n + 1;
}

sk_negate_to_size_t()

static size_t sk_negate_to_size_t ( int32_t  value )

inlinestatic

Definition at line 76 of file SkMathPriv.h.

                                                        {
#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4146)  // Thanks MSVC, we know what we're negating an unsigned
#endif
    return -static_cast<size_t>(value);
#if defined(_MSC_VER)
#pragma warning(pop)
#endif
}

SkApplySign()

static int32_t SkApplySign ( int32_t  n, int32_t  sign  )

inlinestatic

If sign == -1, returns -n, else sign must be 0, and returns n. Typically used in conjunction with SkExtractSign().

Definition at line 50 of file SkMathPriv.h.

                                                           {
    SkASSERT(sign == 0 || sign == -1);
    return (n ^ sign) - sign;
}

SkBSwap32()

static uint32_t SkBSwap32 ( uint32_t  v )

inlinestatic

Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa.

Definition at line 123 of file SkMathPriv.h.

{ return __builtin_bswap32(v); }

SkClampPos()

static int SkClampPos ( int  value )

inlinestatic

Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)

Definition at line 30 of file SkMathPriv.h.

                                        {
    return value & ~(value >> 31);
}

SkClampUMax()

static unsigned SkClampUMax ( unsigned  value, unsigned  max  )

inlinestatic

Given a positive value and a positive max, return the value pinned against max. Note: only works as long as max - value doesn't wrap around

Returns

max if value >= max, else value

Definition at line 65 of file SkMathPriv.h.

                                                                 {
    if (value > max) {
        value = max;
    }
    return value;
}

SkCLZ()

static int SkCLZ ( uint32_t  mask )

inlinestatic

Definition at line 186 of file SkMathPriv.h.

                                           {
        return SkCLZ_portable(mask);
    }

SkCLZ_portable()

constexpr int SkCLZ_portable ( uint32_t  x )

constexpr

Returns the number of leading zero bits (0...32)

Definition at line 149 of file SkMathPriv.h.

                                         {
    int n = 32;
    uint32_t y = x >> 16; if (y != 0) {n -= 16; x = y;}
             y = x >>  8; if (y != 0) {n -=  8; x = y;}
             y = x >>  4; if (y != 0) {n -=  4; x = y;}
             y = x >>  2; if (y != 0) {n -=  2; x = y;}
             y = x >>  1; if (y != 0) {return n - 2;}
    return n - static_cast<int>(x);
}

SkCopySign32()

static int32_t SkCopySign32 ( int32_t  x, int32_t  y  )

inlinestatic

Return x with the sign of y

Definition at line 56 of file SkMathPriv.h.

                                                         {
    return SkApplySign(x, SkExtractSign(x ^ y));
}

SkCTZ()

static int SkCTZ ( uint32_t  mask )

inlinestatic

Definition at line 224 of file SkMathPriv.h.

                                           {
        return SkCTZ_portable(mask);
    }

SkCTZ_portable()

constexpr int SkCTZ_portable ( uint32_t  x )

constexpr

Returns the number of trailing zero bits (0...32)

Definition at line 193 of file SkMathPriv.h.

                                         {
    return 32 - SkCLZ_portable(~x & (x - 1));
}

SkDiv255Round()

static unsigned SkDiv255Round ( unsigned  prod )

inlinestatic

Just the rounding step in SkDiv255Round: round(value / 255)

Definition at line 111 of file SkMathPriv.h.

                                                    {
    prod += 128;
    return (prod + (prod >> 8)) >> 8;
}

SkFitsInFixed()

template<typename T >

static bool SkFitsInFixed ( T  x )

inlinestatic

Definition at line 329 of file SkMathPriv.h.

                                                            {
    return SkTAbs(x) <= 32767.0f;
}

SkMulDiv255Ceiling()

static U8CPU SkMulDiv255Ceiling ( U8CPU  a, U8CPU  b  )

inlinestatic

Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if both a and b are 0..255. The expected result equals (a * b + 254) / 255.

Definition at line 102 of file SkMathPriv.h.

                                                         {
    SkASSERT((uint8_t)a == a);
    SkASSERT((uint8_t)b == b);
    unsigned prod = a*b + 255;
    return (prod + (prod >> 8)) >> 8;
}

SkMulDiv255Trunc()

static U8CPU SkMulDiv255Trunc ( U8CPU  a, U8CPU  b  )

inlinestatic

Return a*b/255, truncating away any fractional bits. Only valid if both a and b are 0..255

Definition at line 92 of file SkMathPriv.h.

                                                       {
    SkASSERT((uint8_t)a == a);
    SkASSERT((uint8_t)b == b);
    unsigned prod = a*b + 1;
    return (prod + (prod >> 8)) >> 8;
}

SkNextLog2()

static int SkNextLog2 ( uint32_t  value )

inlinestatic

Returns the log2 of the specified value, were that value to be rounded up to the next power of 2. It is undefined to pass 0. Examples: SkNextLog2(1) -> 0 SkNextLog2(2) -> 1 SkNextLog2(3) -> 2 SkNextLog2(4) -> 2 SkNextLog2(5) -> 3

Definition at line 238 of file SkMathPriv.h.

                                             {
    SkASSERT(value != 0);
    return 32 - SkCLZ(value - 1);
}

SkNextLog2_portable()

constexpr int SkNextLog2_portable ( uint32_t  value )

constexpr

Definition at line 243 of file SkMathPriv.h.

                                                  {
    SkASSERT(value != 0);
    return 32 - SkCLZ_portable(value - 1);
}

SkNextPow2()

static int SkNextPow2 ( int  value )

inlinestatic

Returns the smallest power-of-2 that is >= the specified value. If value is already a power of 2, then it is returned unchanged. It is undefined if value is <= 0.

Definition at line 272 of file SkMathPriv.h.

                                        {
    SkASSERT(value > 0);
    return 1 << SkNextLog2(static_cast<uint32_t>(value));
}

SkNextPow2_portable()

constexpr int SkNextPow2_portable ( int  value )

constexpr

Definition at line 277 of file SkMathPriv.h.

                                             {
    SkASSERT(value > 0);
    return 1 << SkNextLog2_portable(static_cast<uint32_t>(value));
}

SkNthSet()

int SkNthSet	(	uint32_t	target,
		int	n
	)

Definition at line 53 of file SkMathPriv.cpp.

                                     {
    SkASSERT(n < SkPopCount(target));
 
    for (int i = 0; i < n; ++i) {
        target &= (target - 1); // Remove the lowest bit in the integer.
    }
 
    return SkCTZ(target);
}

SkPopCount()

static int SkPopCount ( uint32_t  n )

inlinestatic

Definition at line 136 of file SkMathPriv.h.

                                             {
        return SkPopCount_portable(n);
    }

SkPopCount_portable()

int SkPopCount_portable

(

uint32_t

n

)

Definition at line 42 of file SkMathPriv.cpp.

                                    {
    int count = 0;
 
    while (n) {
        n &= (n - 1); // Remove the lowest bit in the integer.
        count++;
    }
    return count;
}

SkPrevLog2()

static int SkPrevLog2 ( uint32_t  value )

inlinestatic

Returns the log2 of the specified value, were that value to be rounded down to the previous power of 2. It is undefined to pass 0. Examples: SkPrevLog2(1) -> 0 SkPrevLog2(2) -> 1 SkPrevLog2(3) -> 1 SkPrevLog2(4) -> 2 SkPrevLog2(5) -> 2

Definition at line 257 of file SkMathPriv.h.

                                             {
    SkASSERT(value != 0);
    return 32 - SkCLZ(value >> 1);
}

SkPrevLog2_portable()

constexpr int SkPrevLog2_portable ( uint32_t  value )

constexpr

Definition at line 262 of file SkMathPriv.h.

                                                  {
    SkASSERT(value != 0);
    return 32 - SkCLZ_portable(value >> 1);
}

SkPrevPow2()

static int SkPrevPow2 ( int  value )

inlinestatic

Returns the largest power-of-2 that is <= the specified value. If value is already a power of 2, then it is returned unchanged. It is undefined if value is <= 0.

Definition at line 287 of file SkMathPriv.h.

                                        {
    SkASSERT(value > 0);
    return 1 << SkPrevLog2(static_cast<uint32_t>(value));
}

SkPrevPow2_portable()

constexpr int SkPrevPow2_portable ( int  value )

constexpr

Definition at line 292 of file SkMathPriv.h.

                                             {
    SkASSERT(value > 0);
    return 1 << SkPrevLog2_portable(static_cast<uint32_t>(value));
}

SkSqrt32()

static int32_t SkSqrt32 ( int32_t  n )

inlinestatic

Return the integer square root of n, treated as a SkFixed (16.16)

Definition at line 25 of file SkMathPriv.h.

{ return SkSqrtBits(n, 15); }

SkSqrtBits()

int32_t SkSqrtBits	(	int32_t	value,
		int	bitBias
	)

Return the integer square root of value, with a bias of bitBias

Definition at line 18 of file SkMathPriv.cpp.

                                         {
    SkASSERT(x >= 0 && count > 0 && (unsigned)count <= 30);
 
    uint32_t    root = 0;
    uint32_t    remHi = 0;
    uint32_t    remLo = x;
 
    do {
        root <<= 1;
 
        remHi = (remHi<<2) | (remLo>>30);
        remLo <<= 2;
 
        uint32_t testDiv = (root << 1) + 1;
        if (remHi >= testDiv) {
            remHi -= testDiv;
            root++;
        }
    } while (--count >= 0);
 
    return root;
}

SkTDivMod()

template<typename In , typename Out >

void SkTDivMod ( In  numer, In  denom, Out *  div, Out *  mod  )

inline

Stores numer/denom and numerdenom into div and mod respectively.

Definition at line 38 of file SkMathPriv.h.

                                                              {
    *div = static_cast<Out>(numer/denom);
    *mod = static_cast<Out>(numer%denom);
}