| /* |
| * 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 sk_64_isS32(lastFx) && (unsigned)SkFixedFloorToInt(sk_64_asS32(lastFx)) < max; |
| } |
| |
| #endif /* #ifndef SkBitmapProcState_utils_DEFINED */ |
