diff options
Diffstat (limited to 'gfx/skia/skia/include/private/SkFloatBits.h')
-rw-r--r-- | gfx/skia/skia/include/private/SkFloatBits.h | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/gfx/skia/skia/include/private/SkFloatBits.h b/gfx/skia/skia/include/private/SkFloatBits.h new file mode 100644 index 0000000000..89eea4b9e3 --- /dev/null +++ b/gfx/skia/skia/include/private/SkFloatBits.h @@ -0,0 +1,91 @@ +/* + * Copyright 2008 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 SkFloatBits_DEFINED +#define SkFloatBits_DEFINED + +#include "include/core/SkTypes.h" +#include "include/private/SkSafe_math.h" + +#include <float.h> + +/** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement + int. This also converts -0 (0x80000000) to 0. Doing this to a float allows + it to be compared using normal C operators (<, <=, etc.) +*/ +static inline int32_t SkSignBitTo2sCompliment(int32_t x) { + if (x < 0) { + x &= 0x7FFFFFFF; + x = -x; + } + return x; +} + +/** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float). + This undoes the result of SkSignBitTo2sCompliment(). + */ +static inline int32_t Sk2sComplimentToSignBit(int32_t x) { + int sign = x >> 31; + // make x positive + x = (x ^ sign) - sign; + // set the sign bit as needed + x |= SkLeftShift(sign, 31); + return x; +} + +union SkFloatIntUnion { + float fFloat; + int32_t fSignBitInt; +}; + +// Helper to see a float as its bit pattern (w/o aliasing warnings) +static inline int32_t SkFloat2Bits(float x) { + SkFloatIntUnion data; + data.fFloat = x; + return data.fSignBitInt; +} + +// Helper to see a bit pattern as a float (w/o aliasing warnings) +static inline float SkBits2Float(int32_t floatAsBits) { + SkFloatIntUnion data; + data.fSignBitInt = floatAsBits; + return data.fFloat; +} + +constexpr int32_t gFloatBits_exponent_mask = 0x7F800000; +constexpr int32_t gFloatBits_matissa_mask = 0x007FFFFF; + +static inline bool SkFloatBits_IsFinite(int32_t bits) { + return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask; +} + +static inline bool SkFloatBits_IsInf(int32_t bits) { + return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) && + (bits & gFloatBits_matissa_mask) == 0; +} + +/** Return the float as a 2s compliment int. Just to be used to compare floats + to each other or against positive float-bit-constants (like 0). This does + not return the int equivalent of the float, just something cheaper for + compares-only. + */ +static inline int32_t SkFloatAs2sCompliment(float x) { + return SkSignBitTo2sCompliment(SkFloat2Bits(x)); +} + +/** Return the 2s compliment int as a float. This undos the result of + SkFloatAs2sCompliment + */ +static inline float Sk2sComplimentAsFloat(int32_t x) { + return SkBits2Float(Sk2sComplimentToSignBit(x)); +} + +// Scalar wrappers for float-bit routines + +#define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) + +#endif |