eebf5cb6c0
fix addArc to not wrap around if the sweepAngle is close to 360 but lost precision when convert to radians (and then to unit vectors ala sin/cos) git-svn-id: http://skia.googlecode.com/svn/trunk@495 2bbb7eff-a529-9590-31e7-b0007b416f81
236 lines
6.9 KiB
C
236 lines
6.9 KiB
C
/*
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* Copyright (C) 2006 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef SkMath_DEFINED
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#define SkMath_DEFINED
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#include "SkTypes.h"
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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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/** Computes the 64bit product of a * b, and then shifts the answer down by
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shift bits, returning the low 32bits. shift must be [0..63]
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e.g. to perform a fixedmul, call SkMulShift(a, b, 16)
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*/
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int32_t SkMulShift(int32_t a, int32_t b, unsigned shift);
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/** Computes numer1 * numer2 / denom in full 64 intermediate precision.
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It is an error for denom to be 0. There is no special handling if
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the result overflows 32bits.
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*/
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int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom);
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/** Computes (numer1 << shift) / denom in full 64 intermediate precision.
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It is an error for denom to be 0. There is no special handling if
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the result overflows 32bits.
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*/
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int32_t SkDivBits(int32_t numer, int32_t denom, int shift);
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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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#define SkSqrt32(n) SkSqrtBits(n, 15)
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/** Return the integer cube root of value, with a bias of bitBias
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*/
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int32_t SkCubeRootBits(int32_t value, int bitBias);
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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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/** 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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/** Given an integer and a positive (max) integer, return the value
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pinned against 0 and max, inclusive.
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Note: only works as long as max - value doesn't wrap around
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@param value The value we want returned pinned between [0...max]
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@param max The positive max value
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@return 0 if value < 0, max if value > max, else value
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*/
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static inline int SkClampMax(int value, int max) {
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// ensure that max is positive
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SkASSERT(max >= 0);
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// ensure that if value is negative, max - value doesn't wrap around
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SkASSERT(value >= 0 || max - value > 0);
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#ifdef SK_CPU_HAS_CONDITIONAL_INSTR
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if (value < 0) {
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value = 0;
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}
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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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#else
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int diff = max - value;
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// clear diff if diff is positive
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diff &= diff >> 31;
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// clear the result if value < 0
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return (value + diff) & ~(value >> 31);
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#endif
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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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#ifdef SK_CPU_HAS_CONDITIONAL_INSTR
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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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#else
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int diff = max - value;
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// clear diff if diff is positive
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diff &= diff >> 31;
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return value + diff;
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#endif
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}
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///////////////////////////////////////////////////////////////////////////////
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#if defined(__arm__) && !defined(__thumb__)
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#define SkCLZ(x) __builtin_clz(x)
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#endif
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#ifndef SkCLZ
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#define SkCLZ(x) SkCLZ_portable(x)
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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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/** 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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/** SkMulS16(a, b) multiplies a * b, but requires that a and b are both int16_t.
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With this requirement, we can generate faster instructions on some
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architectures.
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*/
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#if defined(__arm__) \
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&& !defined(__thumb__) \
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&& !defined(__ARM_ARCH_4T__) \
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&& !defined(__ARM_ARCH_5T__)
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static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
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SkASSERT((int16_t)x == x);
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SkASSERT((int16_t)y == y);
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int32_t product;
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asm("smulbb %0, %1, %2 \n"
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: "=r"(product)
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: "r"(x), "r"(y)
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);
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return product;
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}
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#else
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#ifdef SK_DEBUG
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static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
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SkASSERT((int16_t)x == x);
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SkASSERT((int16_t)y == y);
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return x * y;
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}
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#else
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#define SkMulS16(x, y) ((x) * (y))
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#endif
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#endif
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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 = SkMulS16(a, b) + 1;
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return (prod + (prod >> 8)) >> 8;
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}
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/** Return a*b/255, rounding 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 SkMulDiv255Round(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 = SkMulS16(a, b) + 128;
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return (prod + (prod >> 8)) >> 8;
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}
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/** Return a*b/((1 << shift) - 1), rounding any fractional bits.
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Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
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*/
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static inline unsigned SkMul16ShiftRound(unsigned a, unsigned b, int shift) {
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SkASSERT(a <= 32767);
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SkASSERT(b <= 32767);
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SkASSERT(shift > 0 && shift <= 8);
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unsigned prod = SkMulS16(a, b) + (1 << (shift - 1));
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return (prod + (prod >> shift)) >> shift;
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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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#endif
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