/*
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* Copyright 2012 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkMathPriv_DEFINED
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#define SkMathPriv_DEFINED
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#include "SkMath.h"
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/**
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* Return the integer square root of value, with a bias of bitBias
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*/
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int32_t SkSqrtBits(int32_t value, int bitBias);
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/** Return the integer square root of n, treated as a SkFixed (16.16)
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*/
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static inline int32_t SkSqrt32(int32_t n) { return SkSqrtBits(n, 15); }
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/**
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* Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
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*/
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static inline int SkClampPos(int value) {
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return value & ~(value >> 31);
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}
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/**
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* Stores numer/denom and numer%denom into div and mod respectively.
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*/
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template <typename In, typename Out>
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inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
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#ifdef SK_CPU_ARM32
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// If we wrote this as in the else branch, GCC won't fuse the two into one
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// divmod call, but rather a div call followed by a divmod. Silly! This
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// version is just as fast as calling __aeabi_[u]idivmod manually, but with
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// prettier code.
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//
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// This benches as around 2x faster than the code in the else branch.
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const In d = numer/denom;
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*div = static_cast<Out>(d);
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*mod = static_cast<Out>(numer-d*denom);
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#else
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// On x86 this will just be a single idiv.
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*div = static_cast<Out>(numer/denom);
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*mod = static_cast<Out>(numer%denom);
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#endif
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}
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/** Returns -1 if n < 0, else returns 0
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*/
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#define SkExtractSign(n) ((int32_t)(n) >> 31)
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/** If sign == -1, returns -n, else sign must be 0, and returns n.
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Typically used in conjunction with SkExtractSign().
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*/
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static inline int32_t SkApplySign(int32_t n, int32_t sign) {
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SkASSERT(sign == 0 || sign == -1);
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return (n ^ sign) - sign;
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}
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/** Return x with the sign of y */
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static inline int32_t SkCopySign32(int32_t x, int32_t y) {
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return SkApplySign(x, SkExtractSign(x ^ y));
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}
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/** Given a positive value and a positive max, return the value
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pinned against max.
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Note: only works as long as max - value doesn't wrap around
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@return max if value >= max, else value
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*/
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static inline unsigned SkClampUMax(unsigned value, unsigned max) {
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if (value > max) {
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value = max;
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}
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return value;
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}
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// If a signed int holds min_int (e.g. 0x80000000) it is undefined what happens when
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// we negate it (even though we *know* we're 2's complement and we'll get the same
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// value back). So we create this helper function that casts to size_t (unsigned) first,
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// to avoid the complaint.
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static inline size_t sk_negate_to_size_t(int32_t value) {
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#if defined(_MSC_VER)
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#pragma warning(push)
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#pragma warning(disable : 4146) // Thanks MSVC, we know what we're negating an unsigned
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#endif
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return -static_cast<size_t>(value);
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#if defined(_MSC_VER)
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#pragma warning(pop)
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#endif
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}
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///////////////////////////////////////////////////////////////////////////////
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/** Return a*b/255, truncating away any fractional bits. Only valid if both
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a and b are 0..255
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*/
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static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
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SkASSERT((uint8_t)a == a);
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SkASSERT((uint8_t)b == b);
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unsigned prod = a*b + 1;
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return (prod + (prod >> 8)) >> 8;
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}
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/** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if
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both a and b are 0..255. The expected result equals (a * b + 254) / 255.
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*/
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static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
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SkASSERT((uint8_t)a == a);
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SkASSERT((uint8_t)b == b);
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unsigned prod = a*b + 255;
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return (prod + (prod >> 8)) >> 8;
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}
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/** Just the rounding step in SkDiv255Round: round(value / 255)
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*/
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static inline unsigned SkDiv255Round(unsigned prod) {
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prod += 128;
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return (prod + (prod >> 8)) >> 8;
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}
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static inline float SkPinToUnitFloat(float x) {
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return SkTMin(SkTMax(x, 0.0f), 1.0f);
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}
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/**
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* Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa.
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*/
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#if defined(_MSC_VER)
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#include <stdlib.h>
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static inline uint32_t SkBSwap32(uint32_t v) { return _byteswap_ulong(v); }
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#else
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static inline uint32_t SkBSwap32(uint32_t v) { return __builtin_bswap32(v); }
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#endif
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//! Returns the number of leading zero bits (0...32)
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int SkCLZ_portable(uint32_t);
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#ifndef SkCLZ
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#if defined(SK_BUILD_FOR_WIN)
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#include <intrin.h>
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static inline int SkCLZ(uint32_t mask) {
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if (mask) {
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unsigned long index;
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_BitScanReverse(&index, mask);
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// Suppress this bogus /analyze warning. The check for non-zero
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// guarantees that _BitScanReverse will succeed.
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#pragma warning(suppress : 6102) // Using 'index' from failed function call
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return index ^ 0x1F;
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} else {
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return 32;
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}
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}
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#elif defined(SK_CPU_ARM32) || defined(__GNUC__) || defined(__clang__)
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static inline int SkCLZ(uint32_t mask) {
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// __builtin_clz(0) is undefined, so we have to detect that case.
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return mask ? __builtin_clz(mask) : 32;
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}
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#else
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#define SkCLZ(x) SkCLZ_portable(x)
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#endif
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#endif
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/**
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* Returns the smallest power-of-2 that is >= the specified value. If value
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* is already a power of 2, then it is returned unchanged. It is undefined
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* if value is <= 0.
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*/
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static inline int SkNextPow2(int value) {
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SkASSERT(value > 0);
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return 1 << (32 - SkCLZ(value - 1));
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}
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/**
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* Returns the largest power-of-2 that is <= the specified value. If value
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* is already a power of 2, then it is returned unchanged. It is undefined
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* if value is <= 0.
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*/
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static inline int SkPrevPow2(int value) {
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SkASSERT(value > 0);
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return 1 << (32 - SkCLZ(value >> 1));
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}
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/**
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* Returns the log2 of the specified value, were that value to be rounded up
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* to the next power of 2. It is undefined to pass 0. Examples:
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* SkNextLog2(1) -> 0
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* SkNextLog2(2) -> 1
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* SkNextLog2(3) -> 2
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* SkNextLog2(4) -> 2
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* SkNextLog2(5) -> 3
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*/
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static inline int SkNextLog2(uint32_t value) {
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SkASSERT(value != 0);
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return 32 - SkCLZ(value - 1);
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}
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/**
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* Returns the log2 of the specified value, were that value to be rounded down
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* to the previous power of 2. It is undefined to pass 0. Examples:
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* SkPrevLog2(1) -> 0
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* SkPrevLog2(2) -> 1
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* SkPrevLog2(3) -> 1
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* SkPrevLog2(4) -> 2
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* SkPrevLog2(5) -> 2
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*/
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static inline int SkPrevLog2(uint32_t value) {
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SkASSERT(value != 0);
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return 32 - SkCLZ(value >> 1);
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}
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///////////////////////////////////////////////////////////////////////////////
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/**
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* Return the next power of 2 >= n.
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*/
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static inline uint32_t GrNextPow2(uint32_t n) {
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return n ? (1 << (32 - SkCLZ(n - 1))) : 1;
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}
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/**
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* Returns the next power of 2 >= n or n if the next power of 2 can't be represented by size_t.
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*/
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static inline size_t GrNextSizePow2(size_t n) {
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constexpr int kNumSizeTBits = 8 * sizeof(size_t);
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constexpr size_t kHighBitSet = size_t(1) << (kNumSizeTBits - 1);
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if (!n) {
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return 1;
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} else if (n >= kHighBitSet) {
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return n;
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}
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n--;
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uint32_t shift = 1;
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while (shift < kNumSizeTBits) {
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n |= n >> shift;
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shift <<= 1;
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}
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return n + 1;
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}
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// conservative check. will return false for very large values that "could" fit
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template <typename T> static inline bool SkFitsInFixed(T x) {
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return SkTAbs(x) <= 32767.0f;
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}
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#endif
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