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authorThe Android Open Source Project <initial-contribution@android.com>2009-03-03 19:30:35 -0800
committerThe Android Open Source Project <initial-contribution@android.com>2009-03-03 19:30:35 -0800
commit0910916c0f7b951ee55c4b7c6358295b9bca0565 (patch)
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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
+