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/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMath_DEFINED
#define SkMath_DEFINED
#include "SkTypes.h"
// 64bit -> 32bit utilities
/**
* Return true iff the 64bit value can exactly be represented in signed 32bits
*/
static inline bool sk_64_isS32(int64_t value) {
return (int32_t)value == value;
}
/**
* Return the 64bit argument as signed 32bits, asserting in debug that the arg
* exactly fits in signed 32bits. In the release build, no checks are preformed
* and the return value if the arg does not fit is undefined.
*/
static inline int32_t sk_64_asS32(int64_t value) {
SkASSERT(sk_64_isS32(value));
return (int32_t)value;
}
// Handy util that can be passed two ints, and will automatically promote to
// 64bits before the multiply, so the caller doesn't have to remember to cast
// e.g. (int64_t)a * b;
static inline int64_t sk_64_mul(int64_t a, int64_t b) {
return a * b;
}
///////////////////////////////////////////////////////////////////////////////
/**
* Computes numer1 * numer2 / denom in full 64 intermediate precision.
* It is an error for denom to be 0. There is no special handling if
* the result overflows 32bits.
*/
static inline int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom) {
SkASSERT(denom);
int64_t tmp = sk_64_mul(numer1, numer2) / denom;
return sk_64_asS32(tmp);
}
/**
* Computes (numer1 << shift) / denom in full 64 intermediate precision.
* It is an error for denom to be 0. There is no special handling if
* the result overflows 32bits.
*/
int32_t SkDivBits(int32_t numer, int32_t denom, int shift);
/**
* 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)
*/
#define SkSqrt32(n) SkSqrtBits(n, 15)
//! Returns the number of leading zero bits (0...32)
int SkCLZ_portable(uint32_t);
#ifndef SkCLZ
#if defined(_MSC_VER) && _MSC_VER >= 1400
#include <intrin.h>
static inline int SkCLZ(uint32_t mask) {
if (mask) {
DWORD index;
_BitScanReverse(&index, mask);
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 (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
*/
static inline int SkClampPos(int value) {
return value & ~(value >> 31);
}
/** Given an integer and a positive (max) integer, return the value
* pinned against 0 and max, inclusive.
* @param value The value we want returned pinned between [0...max]
* @param max The positive max value
* @return 0 if value < 0, max if value > max, else value
*/
static inline int SkClampMax(int value, int max) {
// ensure that max is positive
SkASSERT(max >= 0);
if (value < 0) {
value = 0;
}
if (value > max) {
value = max;
}
return value;
}
/**
* 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 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 true if value is a power of 2. Does not explicitly check for
* value <= 0.
*/
static inline bool SkIsPow2(int value) {
return (value & (value - 1)) == 0;
}
///////////////////////////////////////////////////////////////////////////////
/**
* SkMulS16(a, b) multiplies a * b, but requires that a and b are both int16_t.
* With this requirement, we can generate faster instructions on some
* architectures.
*/
#ifdef SK_ARM_HAS_EDSP
static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
SkASSERT((int16_t)x == x);
SkASSERT((int16_t)y == y);
int32_t product;
asm("smulbb %0, %1, %2 \n"
: "=r"(product)
: "r"(x), "r"(y)
);
return product;
}
#else
#ifdef SK_DEBUG
static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
SkASSERT((int16_t)x == x);
SkASSERT((int16_t)y == y);
return x * y;
}
#else
#define SkMulS16(x, y) ((x) * (y))
#endif
#endif
/**
* Return a*b/((1 << shift) - 1), rounding any fractional bits.
* Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
*/
static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
SkASSERT(a <= 32767);
SkASSERT(b <= 32767);
SkASSERT(shift > 0 && shift <= 8);
unsigned prod = SkMulS16(a, b) + (1 << (shift - 1));
return (prod + (prod >> shift)) >> shift;
}
/**
* Return a*b/255, rounding any fractional bits.
* Only valid if a and b are unsigned and <= 32767.
*/
static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
SkASSERT(a <= 32767);
SkASSERT(b <= 32767);
unsigned prod = SkMulS16(a, b) + 128;
return (prod + (prod >> 8)) >> 8;
}
/**
* 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
}
#endif
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