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      1 /*
      2  * Copyright 2008 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 
      9 #ifndef SkFloatBits_DEFINED
     10 #define SkFloatBits_DEFINED
     11 
     12 #include "SkTypes.h"
     13 #include "SkSafe_math.h"
     14 
     15 /** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement
     16     int. This also converts -0 (0x80000000) to 0. Doing this to a float allows
     17     it to be compared using normal C operators (<, <=, etc.)
     18 */
     19 static inline int32_t SkSignBitTo2sCompliment(int32_t x) {
     20     if (x < 0) {
     21         x &= 0x7FFFFFFF;
     22         x = -x;
     23     }
     24     return x;
     25 }
     26 
     27 /** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float).
     28     This undoes the result of SkSignBitTo2sCompliment().
     29  */
     30 static inline int32_t Sk2sComplimentToSignBit(int32_t x) {
     31     int sign = x >> 31;
     32     // make x positive
     33     x = (x ^ sign) - sign;
     34     // set the sign bit as needed
     35     x |= SkLeftShift(sign, 31);
     36     return x;
     37 }
     38 
     39 union SkFloatIntUnion {
     40     float   fFloat;
     41     int32_t fSignBitInt;
     42 };
     43 
     44 // Helper to see a float as its bit pattern (w/o aliasing warnings)
     45 static inline int32_t SkFloat2Bits(float x) {
     46     SkFloatIntUnion data;
     47     data.fFloat = x;
     48     return data.fSignBitInt;
     49 }
     50 
     51 // Helper to see a bit pattern as a float (w/o aliasing warnings)
     52 static inline float SkBits2Float(int32_t floatAsBits) {
     53     SkFloatIntUnion data;
     54     data.fSignBitInt = floatAsBits;
     55     return data.fFloat;
     56 }
     57 
     58 /** Return the float as a 2s compliment int. Just to be used to compare floats
     59     to each other or against positive float-bit-constants (like 0). This does
     60     not return the int equivalent of the float, just something cheaper for
     61     compares-only.
     62  */
     63 static inline int32_t SkFloatAs2sCompliment(float x) {
     64     return SkSignBitTo2sCompliment(SkFloat2Bits(x));
     65 }
     66 
     67 /** Return the 2s compliment int as a float. This undos the result of
     68     SkFloatAs2sCompliment
     69  */
     70 static inline float Sk2sComplimentAsFloat(int32_t x) {
     71     return SkBits2Float(Sk2sComplimentToSignBit(x));
     72 }
     73 
     74 static inline int32_t pin_double_to_int(double x) {
     75     return (int32_t)SkTPin<double>(x, SK_MinS32, SK_MaxS32);
     76 }
     77 
     78 /** Return the floor of the float as an int.
     79     If the value is out of range, or NaN, return +/- SK_MaxS32
     80 */
     81 static inline int32_t SkFloatToIntFloor(float x) {
     82     return pin_double_to_int(floor(x));
     83 }
     84 
     85 /** Return the float rounded to an int.
     86     If the value is out of range, or NaN, return +/- SK_MaxS32
     87 */
     88 static inline int32_t SkFloatToIntRound(float x) {
     89     return pin_double_to_int(floor((double)x + 0.5));
     90 }
     91 
     92 /** Return the ceiling of the float as an int.
     93     If the value is out of range, or NaN, return +/- SK_MaxS32
     94 */
     95 static inline int32_t SkFloatToIntCeil(float x) {
     96     return pin_double_to_int(ceil(x));
     97 }
     98 
     99 //  Scalar wrappers for float-bit routines
    100 
    101 #define SkScalarAs2sCompliment(x)    SkFloatAs2sCompliment(x)
    102 #define Sk2sComplimentAsScalar(x)    Sk2sComplimentAsFloat(x)
    103 
    104 #endif
    105