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 /* * 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 SkFDot6_DEFINED #define SkFDot6_DEFINED #include "SkFixed.h" #include "SkScalar.h" #include "SkMath.h" typedef int32_t SkFDot6; /* This uses the magic number approach suggested here: * http://stereopsis.com/sree/fpu2006.html and used in * _cairo_fixed_from_double. It does banker's rounding * (i.e. round to nearest even) */ inline SkFDot6 SkScalarRoundToFDot6(SkScalar x, int shift = 0) { union { double fDouble; int32_t fBits[2]; } tmp; int fractionalBits = 6 + shift; double magic = (1LL << (52 - (fractionalBits))) * 1.5; tmp.fDouble = SkScalarToDouble(x) + magic; #ifdef SK_CPU_BENDIAN return tmp.fBits[1]; #else return tmp.fBits[0]; #endif } #define SK_FDot6One (64) #define SK_FDot6Half (32) #ifdef SK_DEBUG inline SkFDot6 SkIntToFDot6(S16CPU x) { SkASSERT(SkToS16(x) == x); return x << 6; } #else #define SkIntToFDot6(x) ((x) << 6) #endif #define SkFDot6Floor(x) ((x) >> 6) #define SkFDot6Ceil(x) (((x) + 63) >> 6) #define SkFDot6Round(x) (((x) + 32) >> 6) #define SkFixedToFDot6(x) ((x) >> 10) inline SkFixed SkFDot6ToFixed(SkFDot6 x) { SkASSERT((SkLeftShift(x, 10) >> 10) == x); return SkLeftShift(x, 10); } #define SkScalarToFDot6(x) (SkFDot6)((x) * 64) #define SkFDot6ToScalar(x) ((SkScalar)(x) * 0.015625f) #define SkFDot6ToFloat SkFDot6ToScalar inline SkFixed SkFDot6Div(SkFDot6 a, SkFDot6 b) { SkASSERT(b != 0); if (a == (int16_t)a) { return SkLeftShift(a, 16) / b; } else { return SkFixedDiv(a, b); } } #include "SkFDot6Constants.h" class QuickFDot6Inverse { public: inline static SkFixed Lookup(SkFDot6 x) { SkASSERT(SkAbs32(x) < kInverseTableSize); return gFDot6INVERSE[kInverseTableSize + x]; } }; static inline SkFixed QuickSkFDot6Div(SkFDot6 a, SkFDot6 b) { const int kMinBits = 3; // abs(b) should be at least (1 << kMinBits) for quick division const int kMaxBits = 31; // Number of bits available in signed int // Given abs(b) <= (1 << kMinBits), the inverse of abs(b) is at most 1 << (22 - kMinBits) in // SkFixed format. Hence abs(a) should be less than kMaxAbsA const int kMaxAbsA = 1 << (kMaxBits - (22 - kMinBits)); SkFDot6 abs_a = SkAbs32(a); SkFDot6 abs_b = SkAbs32(b); if (abs_b >= (1 << kMinBits) && abs_b < kInverseTableSize && abs_a < kMaxAbsA) { SkASSERT((int64_t)a * QuickFDot6Inverse::Lookup(b) <= SK_MaxS32 && (int64_t)a * QuickFDot6Inverse::Lookup(b) >= SK_MinS32); SkFixed ourAnswer = (a * QuickFDot6Inverse::Lookup(b)) >> 6; #ifdef SK_DEBUG SkFixed directAnswer = SkFDot6Div(a, b); SkASSERT( (directAnswer == 0 && ourAnswer == 0) || SkFixedDiv(SkAbs32(directAnswer - ourAnswer), SkAbs32(directAnswer)) <= 1 << 10 ); #endif return ourAnswer; } else { return SkFDot6Div(a, b); } } #endif