/* * 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" // 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; } /////////////////////////////////////////////////////////////////////////////// /** * 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. */ static inline int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom) { SkASSERT(denom); int64_t tmp = sk_64_mul(numer1, numer2) / denom; return sk_64_asS32(tmp); } /** * 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) //! 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