michael@0: #ifndef SkBitmapProcState_utils_DEFINED
michael@0: #define SkBitmapProcState_utils_DEFINED
michael@0: 
michael@0: // Helper to ensure that when we shift down, we do it w/o sign-extension
michael@0: // so the caller doesn't have to manually mask off the top 16 bits
michael@0: //
michael@0: static unsigned SK_USHIFT16(unsigned x) {
michael@0:     return x >> 16;
michael@0: }
michael@0: 
michael@0: /*
michael@0:  *  The decal_ functions require that
michael@0:  *  1. dx > 0
michael@0:  *  2. [fx, fx+dx, fx+2dx, fx+3dx, ... fx+(count-1)dx] are all <= maxX
michael@0:  *
michael@0:  *  In addition, we use SkFractionalInt to keep more fractional precision than
michael@0:  *  just SkFixed, so we will abort the decal_ call if dx is very small, since
michael@0:  *  the decal_ function just operates on SkFixed. If that were changed, we could
michael@0:  *  skip the very_small test here.
michael@0:  */
michael@0: static inline bool can_truncate_to_fixed_for_decal(SkFractionalInt frX,
michael@0:                                                    SkFractionalInt frDx,
michael@0:                                                    int count, unsigned max) {
michael@0:     SkFixed dx = SkFractionalIntToFixed(frDx);
michael@0: 
michael@0:     // if decal_ kept SkFractionalInt precision, this would just be dx <= 0
michael@0:     // I just made up the 1/256. Just don't want to perceive accumulated error
michael@0:     // if we truncate frDx and lose its low bits.
michael@0:     if (dx <= SK_Fixed1 / 256) {
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     // We cast to unsigned so we don't have to check for negative values, which
michael@0:     // will now appear as very large positive values, and thus fail our test!
michael@0:     SkFixed fx = SkFractionalIntToFixed(frX);
michael@0:     return (unsigned)SkFixedFloorToInt(fx) <= max &&
michael@0:            (unsigned)SkFixedFloorToInt(fx + dx * (count - 1)) < max;
michael@0: }
michael@0: 
michael@0: #endif /* #ifndef SkBitmapProcState_utils_DEFINED */