The Tor Browser: gfx/skia/trunk/include/core/SkTLazy.h@129ffea94266 (annotated)

gfx/skia/trunk/include/core/SkTLazy.h@129ffea94266 (annotated)

gfx/skia/trunk/include/core/SkTLazy.h

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkTLazy_DEFINED
 #define SkTLazy_DEFINED
 #include "SkTypes.h"
 #include <new>
 template <typename T> class SkTLazy;
 template <typename T> void* operator new(size_t, SkTLazy<T>* lazy);
 /**
  *  Efficient way to defer allocating/initializing a class until it is needed
  *  (if ever).
  */
 template <typename T> class SkTLazy {
 public:
     SkTLazy() : fPtr(NULL) {}
     explicit SkTLazy(const T* src) : fPtr(NULL) {
         if (src) {
             fPtr = new (fStorage) T(*src);
         }
     }
     SkTLazy(const SkTLazy<T>& src) : fPtr(NULL) {
         if (src.isValid()) {
             fPtr = new (fStorage) T(*src->get());
         } else {
             fPtr = NULL;
         }
     }
     ~SkTLazy() {
         if (this->isValid()) {
             fPtr->~T();
         }
     }
     /**
      *  Return a pointer to a default-initialized instance of the class. If a
      *  previous instance had been initialized (either from init() or set()) it
      *  will first be destroyed, so that a freshly initialized instance is
      *  always returned.
      */
     T* init() {
         if (this->isValid()) {
             fPtr->~T();
         }
         fPtr = new (SkTCast<T*>(fStorage)) T;
         return fPtr;
     }
     /**
      *  Copy src into this, and return a pointer to a copy of it. Note this
      *  will always return the same pointer, so if it is called on a lazy that
      *  has already been initialized, then this will copy over the previous
      *  contents.
      */
     T* set(const T& src) {
         if (this->isValid()) {
             *fPtr = src;
         } else {
             fPtr = new (SkTCast<T*>(fStorage)) T(src);
         }
         return fPtr;
     }
     /**
      * Destroy the lazy object (if it was created via init() or set())
      */
     void reset() {
         if (this->isValid()) {
             fPtr->~T();
             fPtr = NULL;
         }
     }
     /**
      *  Returns true if a valid object has been initialized in the SkTLazy,
      *  false otherwise.
      */
     bool isValid() const { return NULL != fPtr; }
     /**
      * Returns the object. This version should only be called when the caller
      * knows that the object has been initialized.
      */
     T* get() const { SkASSERT(this->isValid()); return fPtr; }
     /**
      * Like above but doesn't assert if object isn't initialized (in which case
      * NULL is returned).
      */
     T* getMaybeNull() const { return fPtr; }
 private:
     friend void* operator new<T>(size_t, SkTLazy* lazy);
     T*   fPtr; // NULL or fStorage
     char fStorage[sizeof(T)];
 };
 // Use the below macro (SkNEW_IN_TLAZY) rather than calling this directly
 template <typename T> void* operator new(size_t, SkTLazy<T>* lazy) {
     SkASSERT(!lazy->isValid());
     lazy->fPtr = reinterpret_cast<T*>(lazy->fStorage);
     return lazy->fPtr;
 }
 // Skia doesn't use C++ exceptions but it may be compiled with them enabled. Having an op delete
 // to match the op new silences warnings about missing op delete when a constructor throws an
 // exception.
 template <typename T> void operator delete(void*, SkTLazy<T>*) { SK_CRASH(); }
 // Use this to construct a T inside an SkTLazy using a non-default constructor.
 #define SkNEW_IN_TLAZY(tlazy_ptr, type_name, args) (new (tlazy_ptr) type_name args)
 /**
  * A helper built on top of SkTLazy 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.
  */
 template <typename T>
 class SkTCopyOnFirstWrite {
 public:
     SkTCopyOnFirstWrite(const T& initial) : fObj(&initial) {}
     // Constructor for delayed initialization.
     SkTCopyOnFirstWrite() : fObj(NULL) {}
     // Should only be called once, and only if the default constructor was used.
     void init(const T& initial) {
         SkASSERT(NULL == fObj);
         SkASSERT(!fLazy.isValid());
         fObj = &initial;
     }
     /**
      * Returns a writable T*. The first time this is called the initial object is cloned.
      */
     T* writable() {
         SkASSERT(NULL != fObj);
         if (!fLazy.isValid()) {
             fLazy.set(*fObj);
             fObj = fLazy.get();
         }
         return const_cast<T*>(fObj);
     }
     /**
      * Operators for treating this as though it were a const pointer.
      */
     const T *operator->() const { return fObj; }
     operator const T*() const { return fObj; }
     const T& operator *() const { return *fObj; }
 private:
     const T*    fObj;
     SkTLazy<T>  fLazy;
 };
 #endif

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gfx/skia/trunk/include/core/SkTLazy.h@129ffea94266 (annotated)

gfx/skia/trunk/include/core/SkTLazy.h