1 /*
2 * Copyright 2019 Google Inc.
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 "src/core/SkDescriptor.h"
9
10 #include <new>
11
12 #include "include/core/SkTypes.h"
13 #include "include/private/SkTo.h"
14 #include "src/core/SkOpts.h"
15
Alloc(size_t length)16 std::unique_ptr<SkDescriptor> SkDescriptor::Alloc(size_t length) {
17 SkASSERT(SkAlign4(length) == length);
18 void* allocation = ::operator new (length);
19 return std::unique_ptr<SkDescriptor>(new (allocation) SkDescriptor{});
20 }
21
operator delete(void * p)22 void SkDescriptor::operator delete(void* p) { ::operator delete(p); }
operator new(size_t)23 void* SkDescriptor::operator new(size_t) {
24 SK_ABORT("Descriptors are created with placement new.");
25 }
26
addEntry(uint32_t tag,size_t length,const void * data)27 void* SkDescriptor::addEntry(uint32_t tag, size_t length, const void* data) {
28 SkASSERT(tag);
29 SkASSERT(SkAlign4(length) == length);
30 SkASSERT(this->findEntry(tag, nullptr) == nullptr);
31
32 Entry* entry = (Entry*)((char*)this + fLength);
33 entry->fTag = tag;
34 entry->fLen = SkToU32(length);
35 if (data) {
36 memcpy(entry + 1, data, length);
37 }
38
39 fCount += 1;
40 fLength = SkToU32(fLength + sizeof(Entry) + length);
41 return (entry + 1); // return its data
42 }
43
computeChecksum()44 void SkDescriptor::computeChecksum() {
45 fChecksum = SkDescriptor::ComputeChecksum(this);
46 }
47
findEntry(uint32_t tag,uint32_t * length) const48 const void* SkDescriptor::findEntry(uint32_t tag, uint32_t* length) const {
49 const Entry* entry = (const Entry*)(this + 1);
50 int count = fCount;
51
52 while (--count >= 0) {
53 if (entry->fTag == tag) {
54 if (length) {
55 *length = entry->fLen;
56 }
57 return entry + 1;
58 }
59 entry = (const Entry*)((const char*)(entry + 1) + entry->fLen);
60 }
61 return nullptr;
62 }
63
copy() const64 std::unique_ptr<SkDescriptor> SkDescriptor::copy() const {
65 std::unique_ptr<SkDescriptor> desc = SkDescriptor::Alloc(fLength);
66 memcpy(desc.get(), this, fLength);
67 return desc;
68 }
69
operator ==(const SkDescriptor & other) const70 bool SkDescriptor::operator==(const SkDescriptor& other) const {
71
72 // the first value we should look at is the checksum, so this loop
73 // should terminate early if they descriptors are different.
74 // NOTE: if we wrote a sentinel value at the end of each, we could
75 // remove the aa < stop test in the loop...
76 const uint32_t* aa = (const uint32_t*)this;
77 const uint32_t* bb = (const uint32_t*)&other;
78 const uint32_t* stop = (const uint32_t*)((const char*)aa + fLength);
79 do {
80 if (*aa++ != *bb++)
81 return false;
82 } while (aa < stop);
83 return true;
84 }
85
ComputeChecksum(const SkDescriptor * desc)86 uint32_t SkDescriptor::ComputeChecksum(const SkDescriptor* desc) {
87 const uint32_t* ptr = (const uint32_t*)desc + 1; // skip the checksum field
88 size_t len = desc->fLength - sizeof(uint32_t);
89 return SkOpts::hash(ptr, len);
90 }
91
isValid() const92 bool SkDescriptor::isValid() const {
93 uint32_t count = fCount;
94 size_t lengthRemaining = this->fLength;
95 if (lengthRemaining < sizeof(SkDescriptor)) {
96 return false;
97 }
98 lengthRemaining -= sizeof(SkDescriptor);
99 size_t offset = sizeof(SkDescriptor);
100
101 while (lengthRemaining > 0 && count > 0) {
102 if (lengthRemaining < sizeof(Entry)) {
103 return false;
104 }
105 lengthRemaining -= sizeof(Entry);
106
107 const Entry* entry = (const Entry*)(reinterpret_cast<const char*>(this) + offset);
108
109 if (lengthRemaining < entry->fLen) {
110 return false;
111 }
112 lengthRemaining -= entry->fLen;
113
114 // rec tags are always a known size.
115 if (entry->fTag == kRec_SkDescriptorTag && entry->fLen != sizeof(SkScalerContextRec)) {
116 return false;
117 }
118
119 offset += sizeof(Entry) + entry->fLen;
120 count--;
121 }
122 return lengthRemaining == 0 && count == 0;
123 }
124
125 SkAutoDescriptor::SkAutoDescriptor() = default;
SkAutoDescriptor(size_t size)126 SkAutoDescriptor::SkAutoDescriptor(size_t size) { this->reset(size); }
SkAutoDescriptor(const SkDescriptor & desc)127 SkAutoDescriptor::SkAutoDescriptor(const SkDescriptor& desc) { this->reset(desc); }
SkAutoDescriptor(const SkAutoDescriptor & ad)128 SkAutoDescriptor::SkAutoDescriptor(const SkAutoDescriptor& ad) {
129 this->reset(*ad.getDesc());
130 }
operator =(const SkAutoDescriptor & ad)131 SkAutoDescriptor& SkAutoDescriptor::operator=(const SkAutoDescriptor& ad) {
132 this->reset(*ad.getDesc());
133 return *this;
134 }
135
~SkAutoDescriptor()136 SkAutoDescriptor::~SkAutoDescriptor() { this->free(); }
137
reset(size_t size)138 void SkAutoDescriptor::reset(size_t size) {
139 this->free();
140 if (size <= sizeof(fStorage)) {
141 fDesc = new (&fStorage) SkDescriptor{};
142 } else {
143 fDesc = SkDescriptor::Alloc(size).release();
144 }
145 }
146
reset(const SkDescriptor & desc)147 void SkAutoDescriptor::reset(const SkDescriptor& desc) {
148 size_t size = desc.getLength();
149 this->reset(size);
150 memcpy(fDesc, &desc, size);
151 }
152
free()153 void SkAutoDescriptor::free() {
154 if (fDesc != (SkDescriptor*)&fStorage) {
155 delete fDesc;
156 }
157 }
158
159
160