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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkBitmapProcState_utils_DEFINED
#define SkBitmapProcState_utils_DEFINED
// Helper to ensure that when we shift down, we do it w/o sign-extension
// so the caller doesn't have to manually mask off the top 16 bits
//
static inline unsigned SK_USHIFT16(unsigned x) {
return x >> 16;
}
/*
* The decal_ functions require that
* 1. dx > 0
* 2. [fx, fx+dx, fx+2dx, fx+3dx, ... fx+(count-1)dx] are all <= maxX
*
* In addition, we use SkFractionalInt to keep more fractional precision than
* just SkFixed, so we will abort the decal_ call if dx is very small, since
* the decal_ function just operates on SkFixed. If that were changed, we could
* skip the very_small test here.
*/
static inline bool can_truncate_to_fixed_for_decal(SkFixed fx,
SkFixed dx,
int count, unsigned max) {
SkASSERT(count > 0);
// if decal_ kept SkFractionalInt precision, this would just be dx <= 0
// I just made up the 1/256. Just don't want to perceive accumulated error
// if we truncate frDx and lose its low bits.
if (dx <= SK_Fixed1 / 256) {
return false;
}
// Note: it seems the test should be (fx <= max && lastFx <= max); but
// historically it's been a strict inequality check, and changing produces
// unexpected diffs. Further investigation is needed.
// We cast to unsigned so we don't have to check for negative values, which
// will now appear as very large positive values, and thus fail our test!
if ((unsigned)SkFixedFloorToInt(fx) >= max) {
return false;
}
// Promote to 64bit (48.16) to avoid overflow.
const uint64_t lastFx = fx + sk_64_mul(dx, count - 1);
return SkTFitsIn<int32_t>(lastFx) && (unsigned)SkFixedFloorToInt(SkTo<int32_t>(lastFx)) < max;
}
#endif /* #ifndef SkBitmapProcState_utils_DEFINED */
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