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author | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 19:30:35 -0800 |
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committer | The Android Open Source Project <initial-contribution@android.com> | 2009-03-03 19:30:35 -0800 |
commit | 0910916c0f7b951ee55c4b7c6358295b9bca0565 (patch) | |
tree | 059e9645510636ae148ba4594b3d6009918655e2 /include/core/SkMath.h | |
parent | 6eb364108744656fcd23a96a478aa772cd4e85bc (diff) | |
download | external_skia-0910916c0f7b951ee55c4b7c6358295b9bca0565.zip external_skia-0910916c0f7b951ee55c4b7c6358295b9bca0565.tar.gz external_skia-0910916c0f7b951ee55c4b7c6358295b9bca0565.tar.bz2 |
auto import from //depot/cupcake/@135843
Diffstat (limited to 'include/core/SkMath.h')
-rw-r--r-- | include/core/SkMath.h | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/include/core/SkMath.h b/include/core/SkMath.h new file mode 100644 index 0000000..5c2b475 --- /dev/null +++ b/include/core/SkMath.h @@ -0,0 +1,230 @@ +/* + * Copyright (C) 2006 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifndef SkMath_DEFINED +#define SkMath_DEFINED + +#include "SkTypes.h" + +//! Returns the number of leading zero bits (0...32) +int SkCLZ_portable(uint32_t); + +/** Computes the 64bit product of a * b, and then shifts the answer down by + shift bits, returning the low 32bits. shift must be [0..63] + e.g. to perform a fixedmul, call SkMulShift(a, b, 16) +*/ +int32_t SkMulShift(int32_t a, int32_t b, unsigned shift); + +/** 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) + +/** Return the integer cube root of value, with a bias of bitBias + */ +int32_t SkCubeRootBits(int32_t value, int bitBias); + +/** 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; +} + +/** 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. + Note: only works as long as max - value doesn't wrap around + @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); + // ensure that if value is negative, max - value doesn't wrap around + SkASSERT(value >= 0 || max - value > 0); + +#ifdef SK_CPU_HAS_CONDITIONAL_INSTR + if (value < 0) { + value = 0; + } + if (value > max) { + value = max; + } + return value; +#else + + int diff = max - value; + // clear diff if diff is positive + diff &= diff >> 31; + + // clear the result if value < 0 + return (value + diff) & ~(value >> 31); +#endif +} + +/** 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) { +#ifdef SK_CPU_HAS_CONDITIONAL_INSTR + if (value > max) { + value = max; + } + return value; +#else + int diff = max - value; + // clear diff if diff is positive + diff &= diff >> 31; + + return value + diff; +#endif +} + +/////////////////////////////////////////////////////////////////////////////// + +#if defined(__arm__) && !defined(__thumb__) + #define SkCLZ(x) __builtin_clz(x) +#endif + +#ifndef SkCLZ + #define SkCLZ(x) SkCLZ_portable(x) +#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 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); +} + +/////////////////////////////////////////////////////////////////////////////// + +/** 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. +*/ +#if defined(__arm__) && !defined(__thumb__) + 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/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 = SkMulS16(a, b) + 1; + return (prod + (prod >> 8)) >> 8; +} + +/** Return a*b/255, rounding any fractional bits. Only valid if both + a and b are 0..255 + */ +static inline U8CPU SkMulDiv255Round(U8CPU a, U8CPU b) { + SkASSERT((uint8_t)a == a); + SkASSERT((uint8_t)b == b); + unsigned prod = SkMulS16(a, b) + 128; + return (prod + (prod >> 8)) >> 8; +} + +/** 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(unsigned a, unsigned 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; +} + +/////////////////////////////////////////////////////////////////////////////// + +#ifdef SK_DEBUG + class SkMath { + public: + static void UnitTest(); + }; +#endif + +#endif + |