michael@0: 
michael@0: /*
michael@0:  * Copyright 2008 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: #ifndef SkFloatBits_DEFINED
michael@0: #define SkFloatBits_DEFINED
michael@0: 
michael@0: #include "SkTypes.h"
michael@0: 
michael@0: /** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement
michael@0:     int. This also converts -0 (0x80000000) to 0. Doing this to a float allows
michael@0:     it to be compared using normal C operators (<, <=, etc.)
michael@0: */
michael@0: static inline int32_t SkSignBitTo2sCompliment(int32_t x) {
michael@0:     if (x < 0) {
michael@0:         x &= 0x7FFFFFFF;
michael@0:         x = -x;
michael@0:     }
michael@0:     return x;
michael@0: }
michael@0: 
michael@0: /** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float).
michael@0:     This undoes the result of SkSignBitTo2sCompliment().
michael@0:  */
michael@0: static inline int32_t Sk2sComplimentToSignBit(int32_t x) {
michael@0:     int sign = x >> 31;
michael@0:     // make x positive
michael@0:     x = (x ^ sign) - sign;
michael@0:     // set the sign bit as needed
michael@0:     x |= sign << 31;
michael@0:     return x;
michael@0: }
michael@0: 
michael@0: /** Given the bit representation of a float, return its value cast to an int.
michael@0:     If the value is out of range, or NaN, return return +/- SK_MaxS32
michael@0: */
michael@0: int32_t SkFloatBits_toIntCast(int32_t floatBits);
michael@0: 
michael@0: /** Given the bit representation of a float, return its floor as an int.
michael@0:     If the value is out of range, or NaN, return return +/- SK_MaxS32
michael@0:  */
michael@0: SK_API int32_t SkFloatBits_toIntFloor(int32_t floatBits);
michael@0: 
michael@0: /** Given the bit representation of a float, return it rounded to an int.
michael@0:     If the value is out of range, or NaN, return return +/- SK_MaxS32
michael@0:  */
michael@0: SK_API int32_t SkFloatBits_toIntRound(int32_t floatBits);
michael@0: 
michael@0: /** Given the bit representation of a float, return its ceiling as an int.
michael@0:     If the value is out of range, or NaN, return return +/- SK_MaxS32
michael@0:  */
michael@0: SK_API int32_t SkFloatBits_toIntCeil(int32_t floatBits);
michael@0: 
michael@0: 
michael@0: union SkFloatIntUnion {
michael@0:     float   fFloat;
michael@0:     int32_t fSignBitInt;
michael@0: };
michael@0: 
michael@0: // Helper to see a float as its bit pattern (w/o aliasing warnings)
michael@0: static inline int32_t SkFloat2Bits(float x) {
michael@0:     SkFloatIntUnion data;
michael@0:     data.fFloat = x;
michael@0:     return data.fSignBitInt;
michael@0: }
michael@0: 
michael@0: // Helper to see a bit pattern as a float (w/o aliasing warnings)
michael@0: static inline float SkBits2Float(int32_t floatAsBits) {
michael@0:     SkFloatIntUnion data;
michael@0:     data.fSignBitInt = floatAsBits;
michael@0:     return data.fFloat;
michael@0: }
michael@0: 
michael@0: /** Return the float as a 2s compliment int. Just to be used to compare floats
michael@0:     to each other or against positive float-bit-constants (like 0). This does
michael@0:     not return the int equivalent of the float, just something cheaper for
michael@0:     compares-only.
michael@0:  */
michael@0: static inline int32_t SkFloatAs2sCompliment(float x) {
michael@0:     return SkSignBitTo2sCompliment(SkFloat2Bits(x));
michael@0: }
michael@0: 
michael@0: /** Return the 2s compliment int as a float. This undos the result of
michael@0:     SkFloatAs2sCompliment
michael@0:  */
michael@0: static inline float Sk2sComplimentAsFloat(int32_t x) {
michael@0:     return SkBits2Float(Sk2sComplimentToSignBit(x));
michael@0: }
michael@0: 
michael@0: /** Return x cast to a float (i.e. (float)x)
michael@0: */
michael@0: float SkIntToFloatCast(int x);
michael@0: float SkIntToFloatCast_NoOverflowCheck(int x);
michael@0: 
michael@0: /** Return the float cast to an int.
michael@0:     If the value is out of range, or NaN, return +/- SK_MaxS32
michael@0: */
michael@0: static inline int32_t SkFloatToIntCast(float x) {
michael@0:     return SkFloatBits_toIntCast(SkFloat2Bits(x));
michael@0: }
michael@0: 
michael@0: /** Return the floor of the float as an int.
michael@0:     If the value is out of range, or NaN, return +/- SK_MaxS32
michael@0: */
michael@0: static inline int32_t SkFloatToIntFloor(float x) {
michael@0:     return SkFloatBits_toIntFloor(SkFloat2Bits(x));
michael@0: }
michael@0: 
michael@0: /** Return the float rounded to an int.
michael@0:     If the value is out of range, or NaN, return +/- SK_MaxS32
michael@0: */
michael@0: static inline int32_t SkFloatToIntRound(float x) {
michael@0:     return SkFloatBits_toIntRound(SkFloat2Bits(x));
michael@0: }
michael@0: 
michael@0: /** Return the ceiling of the float as an int.
michael@0:     If the value is out of range, or NaN, return +/- SK_MaxS32
michael@0: */
michael@0: static inline int32_t SkFloatToIntCeil(float x) {
michael@0:     return SkFloatBits_toIntCeil(SkFloat2Bits(x));
michael@0: }
michael@0: 
michael@0: //  Scalar wrappers for float-bit routines
michael@0: 
michael@0: #define SkScalarAs2sCompliment(x)    SkFloatAs2sCompliment(x)
michael@0: #define Sk2sComplimentAsScalar(x)    Sk2sComplimentAsFloat(x)
michael@0: 
michael@0: #endif