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authorThe Android Open Source Project <initial-contribution@android.com>2009-03-03 18:28:36 -0800
committerThe Android Open Source Project <initial-contribution@android.com>2009-03-03 18:28:36 -0800
commit6eb364108744656fcd23a96a478aa772cd4e85bc (patch)
tree4b825dc642cb6eb9a060e54bf8d69288fbee4904 /include/core/SkMath.h
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auto import from //depot/cupcake/@135843
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diff --git a/include/core/SkMath.h b/include/core/SkMath.h
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--- a/include/core/SkMath.h
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-/*
- * 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
-