diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/include/core/SkMath.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gfx/skia/trunk/include/core/SkMath.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,224 @@ + +/* + * 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" + +/** + * 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. + */ +int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom); + +/** + * 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) + +// 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; +} + +/////////////////////////////////////////////////////////////////////////////// + +//! Returns the number of leading zero bits (0...32) +int SkCLZ_portable(uint32_t); + +#ifndef SkCLZ + #if defined(_MSC_VER) && _MSC_VER >= 1400 + #include + + static inline int SkCLZ(uint32_t mask) { + if (mask) { + DWORD index; + _BitScanReverse(&index, mask); + return index ^ 0x1F; + } else { + return 32; + } + } + #elif defined(SK_CPU_ARM) || 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 +inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) { +#ifdef SK_CPU_ARM + // 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(d); + *mod = static_cast(numer-d*denom); +#else + // On x86 this will just be a single idiv. + *div = static_cast(numer/denom); + *mod = static_cast(numer%denom); +#endif // SK_CPU_ARM +} + +#endif