1 /* 2 * Copyright 2006 The Android Open Source Project 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkFDot6_DEFINED 9 #define SkFDot6_DEFINED 10 11 #include "include/core/SkMath.h" 12 #include "include/core/SkScalar.h" 13 #include "include/private/SkFixed.h" 14 #include "include/private/SkTo.h" 15 16 typedef int32_t SkFDot6; 17 18 /* This uses the magic number approach suggested here: 19 * http://stereopsis.com/sree/fpu2006.html and used in 20 * _cairo_fixed_from_double. It does banker's rounding 21 * (i.e. round to nearest even) 22 */ 23 inline SkFDot6 SkScalarRoundToFDot6(SkScalar x, int shift = 0) 24 { 25 union { 26 double fDouble; 27 int32_t fBits[2]; 28 } tmp; 29 int fractionalBits = 6 + shift; 30 double magic = (1LL << (52 - (fractionalBits))) * 1.5; 31 32 tmp.fDouble = SkScalarToDouble(x) + magic; 33 #ifdef SK_CPU_BENDIAN 34 return tmp.fBits[1]; 35 #else 36 return tmp.fBits[0]; 37 #endif 38 } 39 40 #define SK_FDot6One (64) 41 #define SK_FDot6Half (32) 42 43 #ifdef SK_DEBUG SkIntToFDot6(int x)44 inline SkFDot6 SkIntToFDot6(int x) { 45 SkASSERT(SkToS16(x) == x); 46 return x << 6; 47 } 48 #else 49 #define SkIntToFDot6(x) ((x) << 6) 50 #endif 51 52 #define SkFDot6Floor(x) ((x) >> 6) 53 #define SkFDot6Ceil(x) (((x) + 63) >> 6) 54 #define SkFDot6Round(x) (((x) + 32) >> 6) 55 56 #define SkFixedToFDot6(x) ((x) >> 10) 57 SkFDot6ToFixed(SkFDot6 x)58inline SkFixed SkFDot6ToFixed(SkFDot6 x) { 59 SkASSERT((SkLeftShift(x, 10) >> 10) == x); 60 61 return SkLeftShift(x, 10); 62 } 63 64 #define SkScalarToFDot6(x) (SkFDot6)((x) * 64) 65 #define SkFDot6ToScalar(x) ((SkScalar)(x) * 0.015625f) 66 #define SkFDot6ToFloat SkFDot6ToScalar 67 SkFDot6Div(SkFDot6 a,SkFDot6 b)68inline SkFixed SkFDot6Div(SkFDot6 a, SkFDot6 b) { 69 SkASSERT(b != 0); 70 71 if (SkTFitsIn<int16_t>(a)) { 72 return SkLeftShift(a, 16) / b; 73 } else { 74 return SkFixedDiv(a, b); 75 } 76 } 77 78 #endif 79