SkTCopyOnFirstWrite< T > Class Template Reference

#include <SkTLazy.h>

Public Member Functions
	SkTCopyOnFirstWrite (const T &initial)
	SkTCopyOnFirstWrite (const T *initial)
	SkTCopyOnFirstWrite ()
	SkTCopyOnFirstWrite (const SkTCopyOnFirstWrite &that)
	SkTCopyOnFirstWrite (SkTCopyOnFirstWrite &&that)
SkTCopyOnFirstWrite &	operator= (const SkTCopyOnFirstWrite &that)
SkTCopyOnFirstWrite &	operator= (SkTCopyOnFirstWrite &&that)
void	init (const T &initial)
template<typename... Args>
void	initIfNeeded (Args &&... args)
T *	writable ()
const T *	get () const
const T *	operator-> () const
	operator const T * () const
const T &	operator* () const

Detailed Description

template<typename T>
class SkTCopyOnFirstWrite< T >

A helper built on top of std::optional to do copy-on-first-write. The object is initialized with a const pointer but provides a non-const pointer accessor. The first time the accessor is called (if ever) the object is cloned.

In the following example at most one copy of constThing is made:

SkTCopyOnFirstWrite<Thing> thing(&constThing); ... function_that_takes_a_const_thing_ptr(thing); // constThing is passed ... if (need_to_modify_thing()) { thing.writable()->modifyMe(); // makes a copy of constThing } ... x = thing->readSomething(); ... if (need_to_modify_thing_now()) { thing.writable()->changeMe(); // makes a copy of constThing if we didn't call modifyMe() }

consume_a_thing(thing); // could be constThing or a modified copy.

Definition at line 139 of file SkTLazy.h.

Constructor & Destructor Documentation

SkTCopyOnFirstWrite() [1/5]

template<typename T >

SkTCopyOnFirstWrite< T >::SkTCopyOnFirstWrite ( const T &  initial )

inlineexplicit

Definition at line 141 of file SkTLazy.h.

: fObj(&initial) {}

SkTCopyOnFirstWrite() [2/5]

template<typename T >

SkTCopyOnFirstWrite< T >::SkTCopyOnFirstWrite ( const T *  initial )

inlineexplicit

Definition at line 143 of file SkTLazy.h.

: fObj(initial) {}

SkTCopyOnFirstWrite() [3/5]

template<typename T >

SkTCopyOnFirstWrite< T >::SkTCopyOnFirstWrite ( )

inline

Definition at line 146 of file SkTLazy.h.

: fObj(nullptr) {}

SkTCopyOnFirstWrite() [4/5]

template<typename T >

SkTCopyOnFirstWrite< T >::SkTCopyOnFirstWrite ( const SkTCopyOnFirstWrite< T > &  that )

inline

Definition at line 148 of file SkTLazy.h.

{ *this = that;            }

SkTCopyOnFirstWrite() [5/5]

template<typename T >

SkTCopyOnFirstWrite< T >::SkTCopyOnFirstWrite ( SkTCopyOnFirstWrite< T > &&  that )

inline

Definition at line 149 of file SkTLazy.h.

{ *this = std::move(that); }

Member Function Documentation

get()

template<typename T >

const T * SkTCopyOnFirstWrite< T >::get ( ) const

inline

Definition at line 191 of file SkTLazy.h.

{ return fObj; }

init()

template<typename T >

void SkTCopyOnFirstWrite< T >::init ( const T &  initial )

inline

Definition at line 164 of file SkTLazy.h.

                                {
        SkASSERT(!fObj);
        SkASSERT(!fLazy.has_value());
        fObj = &initial;
    }

initIfNeeded()

template<typename T >

template<typename... Args>

void SkTCopyOnFirstWrite< T >::initIfNeeded ( Args &&...  args )

inline

Definition at line 172 of file SkTLazy.h.

                                      {
        if (!fObj) {
            SkASSERT(!fLazy.has_value());
            fObj = &fLazy.emplace(std::forward<Args>(args)...);
        }
    }

operator const T *()

template<typename T >

SkTCopyOnFirstWrite< T >::operator const T * ( ) const

inline

Definition at line 199 of file SkTLazy.h.

{ return fObj; }

operator*()

template<typename T >

const T & SkTCopyOnFirstWrite< T >::operator* ( ) const

inline

Definition at line 201 of file SkTLazy.h.

{ return *fObj; }

operator->()

template<typename T >

const T * SkTCopyOnFirstWrite< T >::operator-> ( ) const

inline

Operators for treating this as though it were a const pointer.

Definition at line 197 of file SkTLazy.h.

{ return fObj; }

operator=() [1/2]

template<typename T >

SkTCopyOnFirstWrite & SkTCopyOnFirstWrite< T >::operator= ( const SkTCopyOnFirstWrite< T > &  that )

inline

Definition at line 151 of file SkTLazy.h.

                                                                    {
        fLazy = that.fLazy;
        fObj  = fLazy.has_value() ? &fLazy.value() : that.fObj;
        return *this;
    }

operator=() [2/2]

template<typename T >

SkTCopyOnFirstWrite & SkTCopyOnFirstWrite< T >::operator= ( SkTCopyOnFirstWrite< T > &&  that )

inline

Definition at line 157 of file SkTLazy.h.

                                                               {
        fLazy = std::move(that.fLazy);
        fObj  = fLazy.has_value() ? &fLazy.value() : that.fObj;
        return *this;
    }

writable()

template<typename T >

T * SkTCopyOnFirstWrite< T >::writable ( )

inline

Returns a writable T*. The first time this is called the initial object is cloned.

Definition at line 182 of file SkTLazy.h.

                  {
        SkASSERT(fObj);
        if (!fLazy.has_value()) {
            fLazy = *fObj;
            fObj = &fLazy.value();
        }
        return &fLazy.value();
    }

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The documentation for this class was generated from the following file:

• third_party/skia/src/base/SkTLazy.h