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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 "include/private/base/SkAssert.h"
#include "include/private/base/SkCPUTypes.h"
#include "include/private/base/SkTemplates.h"
#include <cstddef>
#include <cstdint>
/**
* Return the integer square root of value, with a bias of bitBias
*/
int32_t SkSqrtBits(int32_t value, int bitBias);
/** Return the integer square root of n, treated as a SkFixed (16.16)
*/
static inline int32_t SkSqrt32(int32_t n) { return SkSqrtBits(n, 15); }
/**
* Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
*/
static inline int SkClampPos(int value) {
return value & ~(value >> 31);
}
/**
* Stores numer/denom and numer%denom into div and mod respectively.
*/
template <typename In, typename Out>
inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
#ifdef SK_CPU_ARM32
// If we wrote this as in the else branch, GCC won't fuse the two into one
// divmod call, but rather a div call followed by a divmod. Silly! This
// version is just as fast as calling __aeabi_[u]idivmod manually, but with
// prettier code.
//
// This benches as around 2x faster than the code in the else branch.
const In d = numer/denom;
*div = static_cast<Out>(d);
*mod = static_cast<Out>(numer-d*denom);
#else
// On x86 this will just be a single idiv.
*div = static_cast<Out>(numer/denom);
*mod = static_cast<Out>(numer%denom);
#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;
}
// If a signed int holds min_int (e.g. 0x80000000) it is undefined what happens when
// we negate it (even though we *know* we're 2's complement and we'll get the same
// value back). So we create this helper function that casts to size_t (unsigned) first,
// to avoid the complaint.
static inline size_t sk_negate_to_size_t(int32_t value) {
#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
}
///////////////////////////////////////////////////////////////////////////////
/** 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;
}
/**
* Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa.
*/
#if defined(_MSC_VER)
#include <stdlib.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
/*
* Return the number of set bits (i.e., the population count) in the provided uint32_t.
*/
int SkPopCount_portable(uint32_t n);
#if defined(__GNUC__) || defined(__clang__)
static inline int SkPopCount(uint32_t n) {
return __builtin_popcount(n);
}
#else
static inline int SkPopCount(uint32_t n) {
return SkPopCount_portable(n);
}
#endif
/*
* Return the 0-based index of the nth bit set in target
* Returns 32 if there is no nth bit set.
*/
int SkNthSet(uint32_t target, int n);
//! Returns the number of leading zero bits (0...32)
// From Hacker's Delight 2nd Edition
constexpr int SkCLZ_portable(uint32_t x) {
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);
}
static_assert(32 == SkCLZ_portable(0));
static_assert(31 == SkCLZ_portable(1));
static_assert( 1 == SkCLZ_portable(1 << 30));
static_assert( 1 == SkCLZ_portable((1 << 30) | (1 << 24) | 1));
static_assert( 0 == SkCLZ_portable(~0U));
#if defined(SK_BUILD_FOR_WIN)
#include <intrin.h>
static inline int SkCLZ(uint32_t mask) {
if (mask) {
unsigned long index = 0;
_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
static inline int SkCLZ(uint32_t mask) {
return SkCLZ_portable(mask);
}
#endif
//! Returns the number of trailing zero bits (0...32)
// From Hacker's Delight 2nd Edition
constexpr int SkCTZ_portable(uint32_t x) {
return 32 - SkCLZ_portable(~x & (x - 1));
}
static_assert(32 == SkCTZ_portable(0));
static_assert( 0 == SkCTZ_portable(1));
static_assert(30 == SkCTZ_portable(1 << 30));
static_assert( 2 == SkCTZ_portable((1 << 30) | (1 << 24) | (1 << 2)));
static_assert( 0 == SkCTZ_portable(~0U));
#if defined(SK_BUILD_FOR_WIN)
#include <intrin.h>
static inline int SkCTZ(uint32_t mask) {
if (mask) {
unsigned long index = 0;
_BitScanForward(&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;
} else {
return 32;
}
}
#elif defined(SK_CPU_ARM32) || defined(__GNUC__) || defined(__clang__)
static inline int SkCTZ(uint32_t mask) {
// __builtin_ctz(0) is undefined, so we have to detect that case.
return mask ? __builtin_ctz(mask) : 32;
}
#else
static inline int SkCTZ(uint32_t mask) {
return SkCTZ_portable(mask);
}
#endif
/**
* 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);
}
constexpr int SkNextLog2_portable(uint32_t value) {
SkASSERT(value != 0);
return 32 - SkCLZ_portable(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);
}
constexpr int SkPrevLog2_portable(uint32_t value) {
SkASSERT(value != 0);
return 32 - SkCLZ_portable(value >> 1);
}
/**
* 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 << SkNextLog2(static_cast<uint32_t>(value));
}
constexpr int SkNextPow2_portable(int value) {
SkASSERT(value > 0);
return 1 << SkNextLog2_portable(static_cast<uint32_t>(value));
}
/**
* 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 << SkPrevLog2(static_cast<uint32_t>(value));
}
constexpr int SkPrevPow2_portable(int value) {
SkASSERT(value > 0);
return 1 << SkPrevLog2_portable(static_cast<uint32_t>(value));
}
///////////////////////////////////////////////////////////////////////////////
/**
* Return the smallest 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;
}
// conservative check. will return false for very large values that "could" fit
template <typename T> static inline bool SkFitsInFixed(T x) {
return SkTAbs(x) <= 32767.0f;
}
#endif