1 /*
2  * Copyright 2007 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 #include "SkMask.h"
9 #include "SkMalloc.h"
10 #include "SkSafeMath.h"
11 
12 /** returns the product if it is positive and fits in 31 bits. Otherwise this
13     returns 0.
14  */
15 static int32_t safeMul32(int32_t a, int32_t b) {
16     int64_t size = sk_64_mul(a, b);
17     if (size > 0 && sk_64_isS32(size)) {
18         return sk_64_asS32(size);
19     }
20     return 0;
21 }
22 
23 size_t SkMask::computeImageSize() const {
24     return safeMul32(fBounds.height(), fRowBytes);
25 }
26 
27 size_t SkMask::computeTotalImageSize() const {
28     size_t size = this->computeImageSize();
29     if (fFormat == SkMask::k3D_Format) {
30         size = safeMul32(SkToS32(size), 3);
31     }
32     return size;
33 }
34 
35 /** We explicitly use this allocator for SkBimap pixels, so that we can
36     freely assign memory allocated by one class to the other.
37 */
38 uint8_t* SkMask::AllocImage(size_t size, AllocType at) {
39     size_t aligned_size = SkSafeMath::Align4(size);
40     unsigned flags = SK_MALLOC_THROW;
41     if (at == kZeroInit_Alloc) {
42         flags |= SK_MALLOC_ZERO_INITIALIZE;
43     }
44     return static_cast<uint8_t*>(sk_malloc_flags(aligned_size, flags));
45 }
46 
47 /** We explicitly use this allocator for SkBimap pixels, so that we can
48     freely assign memory allocated by one class to the other.
49 */
50 void SkMask::FreeImage(void* image) {
51     sk_free(image);
52 }
53 
54 ///////////////////////////////////////////////////////////////////////////////
55 
56 static const int gMaskFormatToShift[] = {
57     ~0, // BW -- not supported
58     0,  // A8
59     0,  // 3D
60     2,  // ARGB32
61     1,  // LCD16
62 };
63 
64 static int maskFormatToShift(SkMask::Format format) {
65     SkASSERT((unsigned)format < SK_ARRAY_COUNT(gMaskFormatToShift));
66     SkASSERT(SkMask::kBW_Format != format);
67     return gMaskFormatToShift[format];
68 }
69 
70 void* SkMask::getAddr(int x, int y) const {
71     SkASSERT(kBW_Format != fFormat);
72     SkASSERT(fBounds.contains(x, y));
73     SkASSERT(fImage);
74 
75     char* addr = (char*)fImage;
76     addr += (y - fBounds.fTop) * fRowBytes;
77     addr += (x - fBounds.fLeft) << maskFormatToShift(fFormat);
78     return addr;
79 }
80