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* Copyright 2006 The Android Open Source Project
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkDescriptor_DEFINED
#define SkDescriptor_DEFINED
#include <memory>
#include "SkMacros.h"
#include "SkNoncopyable.h"
#include "SkScalerContext.h"
class SkDescriptor : SkNoncopyable {
static size_t ComputeOverhead(int entryCount) {
SkASSERT(entryCount >= 0);
return sizeof(SkDescriptor) + entryCount * sizeof(Entry);
static std::unique_ptr<SkDescriptor> Alloc(size_t length);
// Ensure the unsized delete is called.
void operator delete(void* p);
void init() {
fLength = sizeof(SkDescriptor);
fCount = 0;
uint32_t getLength() const { return fLength; }
void* addEntry(uint32_t tag, size_t length, const void* data = nullptr);
void computeChecksum();
// Assumes that getLength <= capacity of this SkDescriptor.
bool isValid() const;
#ifdef SK_DEBUG
void assertChecksum() const {
SkASSERT(SkDescriptor::ComputeChecksum(this) == fChecksum);
const void* findEntry(uint32_t tag, uint32_t* length) const;
std::unique_ptr<SkDescriptor> copy() const;
// This assumes that all memory added has a length that is a multiple of 4. This is checked
// by the assert in addEntry.
bool operator==(const SkDescriptor& other) const;
bool operator!=(const SkDescriptor& other) const { return !(*this == other); }
uint32_t getChecksum() const { return fChecksum; }
struct Entry {
uint32_t fTag;
uint32_t fLen;
#ifdef SK_DEBUG
uint32_t getCount() const { return fCount; }
// private so no one can create one except our factories
SkDescriptor() = default;
friend class SkDescriptorTestHelper;
static uint32_t ComputeChecksum(const SkDescriptor* desc);
uint32_t fChecksum; // must be first
uint32_t fLength; // must be second
uint32_t fCount;
class SkAutoDescriptor : SkNoncopyable {
SkAutoDescriptor(size_t size);
SkAutoDescriptor(const SkDescriptor& desc);
SkAutoDescriptor(SkAutoDescriptor&&) = delete;
SkAutoDescriptor& operator =(SkAutoDescriptor&&) = delete;
void reset(size_t size);
void reset(const SkDescriptor& desc);
SkDescriptor* getDesc() const { SkASSERT(fDesc); return fDesc; }
void free();
static constexpr size_t kStorageSize
= sizeof(SkDescriptor)
+ sizeof(SkDescriptor::Entry) + sizeof(SkScalerContextRec) // for rec
+ sizeof(SkDescriptor::Entry) + sizeof(void*) // for typeface
+ 32; // slop for occasional small extras
SkDescriptor* fDesc{nullptr};
std::aligned_storage<kStorageSize, alignof(uint32_t)>::type fStorage;
#endif //SkDescriptor_DEFINED