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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMathPriv_DEFINED
#define SkMathPriv_DEFINED
#include "SkMath.h"
#if defined(SK_BUILD_FOR_IOS) && (defined(SK_BUILD_FOR_ARM32) || defined(SK_BUILD_FOR_ARM64))
// iOS on ARM starts processes with the Flush-To-Zero (FTZ) and
// Denormals-Are-Zero (DAZ) bits in the fpscr register set.
// Algorithms that rely on denormalized numbers need alternative implementations.
// This can also be controlled in SSE with the MXCSR register,
// x87 with FSTCW/FLDCW, and mips with FCSR. This should be detected at runtime,
// or the library built one way or the other more generally (by the build).
#define SK_CPU_FLUSH_TO_ZERO
#endif
/** Returns -1 if n < 0, else returns 0
*/
#define SkExtractSign(n) ((int32_t)(n) >> 31)
/** If sign == -1, returns -n, else sign must be 0, and returns n.
Typically used in conjunction with SkExtractSign().
*/
static inline int32_t SkApplySign(int32_t n, int32_t sign) {
SkASSERT(sign == 0 || sign == -1);
return (n ^ sign) - sign;
}
/** Return x with the sign of y */
static inline int32_t SkCopySign32(int32_t x, int32_t y) {
return SkApplySign(x, SkExtractSign(x ^ y));
}
/** 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
@return max if value >= max, else value
*/
static inline unsigned SkClampUMax(unsigned value, unsigned max) {
if (value > max) {
value = max;
}
return value;
}
///////////////////////////////////////////////////////////////////////////////
/** Return a*b/255, truncating away any fractional bits. Only valid if both
a and b are 0..255
*/
static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
SkASSERT((uint8_t)a == a);
SkASSERT((uint8_t)b == b);
unsigned prod = a*b + 1;
return (prod + (prod >> 8)) >> 8;
}
/** 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.
*/
static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
SkASSERT((uint8_t)a == a);
SkASSERT((uint8_t)b == b);
unsigned prod = a*b + 255;
return (prod + (prod >> 8)) >> 8;
}
/** Just the rounding step in SkDiv255Round: round(value / 255)
*/
static inline unsigned SkDiv255Round(unsigned prod) {
prod += 128;
return (prod + (prod >> 8)) >> 8;
}
static inline float SkPinToUnitFloat(float x) {
return SkTMin(SkTMax(x, 0.0f), 1.0f);
}
/**
* Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa.
*/
#if defined(_MSC_VER)
#include <intrin.h>
static inline uint32_t SkBSwap32(uint32_t v) { return _byteswap_ulong(v); }
#else
static inline uint32_t SkBSwap32(uint32_t v) { return __builtin_bswap32(v); }
#endif
//! Returns the number of leading zero bits (0...32)
int SkCLZ_portable(uint32_t);
#ifndef SkCLZ
#if defined(SK_BUILD_FOR_WIN32)
#include <intrin.h>
static inline int SkCLZ(uint32_t mask) {
if (mask) {
unsigned long index;
_BitScanReverse(&index, mask);
// Suppress this bogus /analyze warning. The check for non-zero
// guarantees that _BitScanReverse will succeed.
#pragma warning(suppress : 6102) // Using 'index' from failed function call
return index ^ 0x1F;
} else {
return 32;
}
}
#elif defined(SK_CPU_ARM32) || defined(__GNUC__) || defined(__clang__)
static inline int SkCLZ(uint32_t mask) {
// __builtin_clz(0) is undefined, so we have to detect that case.
return mask ? __builtin_clz(mask) : 32;
}
#else
#define SkCLZ(x) SkCLZ_portable(x)
#endif
#endif
/**
* 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.
*/
static inline int SkNextPow2(int value) {
SkASSERT(value > 0);
return 1 << (32 - SkCLZ(value - 1));
}
/**
* 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.
*/
static inline int SkPrevPow2(int value) {
SkASSERT(value > 0);
return 1 << (32 - SkCLZ(value >> 1));
}
/**
* 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
*/
static inline int SkNextLog2(uint32_t value) {
SkASSERT(value != 0);
return 32 - SkCLZ(value - 1);
}
/**
* 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
*/
static inline int SkPrevLog2(uint32_t value) {
SkASSERT(value != 0);
return 32 - SkCLZ(value >> 1);
}
///////////////////////////////////////////////////////////////////////////////
/**
* Return the next power of 2 >= n.
*/
static inline uint32_t GrNextPow2(uint32_t n) {
return n ? (1 << (32 - SkCLZ(n - 1))) : 1;
}
/**
* Returns the next power of 2 >= n or n if the next power of 2 can't be represented by size_t.
*/
static inline size_t GrNextSizePow2(size_t n) {
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;
}
#endif
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