1a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 2ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com/* 3ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com * Copyright 2011 Google Inc. 4ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com * 5ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com * Use of this source code is governed by a BSD-style license that can be 6ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com * found in the LICENSE file. 7a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com */ 8a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 9a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 10ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976eepoger@google.com 11a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com#ifndef SkTLazy_DEFINED 12a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com#define SkTLazy_DEFINED 13a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 14a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com#include "SkTypes.h" 15b81be7a7809fb0c24ff7d589d537c38b04b772f1bungeman@google.com#include <new> 16a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 17c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.comtemplate <typename T> class SkTLazy; 18c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.comtemplate <typename T> void* operator new(size_t, SkTLazy<T>* lazy); 19c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com 20a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com/** 21a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * Efficient way to defer allocating/initializing a class until it is needed 22a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * (if ever). 23a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com */ 24a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.comtemplate <typename T> class SkTLazy { 25a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.compublic: 26a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com SkTLazy() : fPtr(NULL) {} 27a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 28a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com explicit SkTLazy(const T* src) : fPtr(NULL) { 29a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com if (src) { 30a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com fPtr = new (fStorage) T(*src); 31a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 32a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 33a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 34a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com SkTLazy(const SkTLazy<T>& src) : fPtr(NULL) { 358c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com if (src.isValid()) { 368c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com fPtr = new (fStorage) T(*src->get()); 378c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com } else { 388c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com fPtr = NULL; 39a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 40a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 41a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 42a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com ~SkTLazy() { 438c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com if (this->isValid()) { 44a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com fPtr->~T(); 45a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 46a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 47a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 48a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com /** 492c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org * Return a pointer to a default-initialized instance of the class. If a 50c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com * previous instance had been initialized (either from init() or set()) it 512c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org * will first be destroyed, so that a freshly initialized instance is 522c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org * always returned. 532c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org */ 542c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org T* init() { 558c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com if (this->isValid()) { 562c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org fPtr->~T(); 572c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org } 58cff323ecd8e9addbd55b34ce81db07bbe757977absalomon@google.com fPtr = new (SkTCast<T*>(fStorage)) T; 592c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org return fPtr; 602c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org } 618c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com 622c8fc5a7038cdfbb28a8364fd0057f3c21f90bfdmike@reedtribe.org /** 63a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * Copy src into this, and return a pointer to a copy of it. Note this 64a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * will always return the same pointer, so if it is called on a lazy that 65a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * has already been initialized, then this will copy over the previous 66a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com * contents. 67a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com */ 68a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com T* set(const T& src) { 698c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com if (this->isValid()) { 70a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com *fPtr = src; 71a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } else { 72cff323ecd8e9addbd55b34ce81db07bbe757977absalomon@google.com fPtr = new (SkTCast<T*>(fStorage)) T(src); 73a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 74a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com return fPtr; 75a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com } 768c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com 778c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com /** 786f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org * Destroy the lazy object (if it was created via init() or set()) 796f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org */ 806f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org void reset() { 816f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org if (this->isValid()) { 826f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org fPtr->~T(); 836f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org fPtr = NULL; 846f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org } 856f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org } 866f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org 876f954b956fc5c36ebbcac404d93ba9349fb0355fcommit-bot@chromium.org /** 888c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com * Returns true if a valid object has been initialized in the SkTLazy, 898c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com * false otherwise. 908c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com */ 9149f085dddff10473b6ebf832a974288300224e60bsalomon bool isValid() const { return SkToBool(fPtr); } 92fbfcd5602128ec010c82cb733c9cdc0a3254f9f3rmistry@google.com 93a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com /** 94bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org * Returns the object. This version should only be called when the caller 95bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org * knows that the object has been initialized. 96a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com */ 978c2fe99ed2c210317786683e8c1f1e86cff0be49bsalomon@google.com T* get() const { SkASSERT(this->isValid()); return fPtr; } 9805a2ee052c9ef4c781b7b590b00b3d2da3b3449askia.committer@gmail.com 99bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org /** 100bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org * Like above but doesn't assert if object isn't initialized (in which case 101bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org * NULL is returned). 102bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org */ 103bb5c46591c50d05418467cd1c4e927ceb85c2ba9commit-bot@chromium.org T* getMaybeNull() const { return fPtr; } 104fbfcd5602128ec010c82cb733c9cdc0a3254f9f3rmistry@google.com 105a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.comprivate: 106c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com friend void* operator new<T>(size_t, SkTLazy* lazy); 107c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com 108a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com T* fPtr; // NULL or fStorage 109a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com char fStorage[sizeof(T)]; 110a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com}; 111a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com 112c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com// Use the below macro (SkNEW_IN_TLAZY) rather than calling this directly 113c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.comtemplate <typename T> void* operator new(size_t, SkTLazy<T>* lazy) { 114c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com SkASSERT(!lazy->isValid()); 115c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com lazy->fPtr = reinterpret_cast<T*>(lazy->fStorage); 116c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com return lazy->fPtr; 117c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com} 118c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com 119c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com// Skia doesn't use C++ exceptions but it may be compiled with them enabled. Having an op delete 120c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com// to match the op new silences warnings about missing op delete when a constructor throws an 121c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com// exception. 1225ee708a235926b87958ae03ba7301112c4f127b7robertphillips@google.comtemplate <typename T> void operator delete(void*, SkTLazy<T>*) { SK_CRASH(); } 123c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com 124c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com// Use this to construct a T inside an SkTLazy using a non-default constructor. 125c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com#define SkNEW_IN_TLAZY(tlazy_ptr, type_name, args) (new (tlazy_ptr) type_name args) 126c78188896e28a4ae49e406a7422b345ae177dafebsalomon@google.com 1275dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com/** 1285dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * A helper built on top of SkTLazy to do copy-on-first-write. The object is initialized 1295dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * with a const pointer but provides a non-const pointer accessor. The first time the 1305dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * accessor is called (if ever) the object is cloned. 1315dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * 1325dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * In the following example at most one copy of constThing is made: 1335dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * 1345dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * SkTCopyOnFirstWrite<Thing> thing(&constThing); 1355dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * ... 1365dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * function_that_takes_a_const_thing_ptr(thing); // constThing is passed 1375dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * ... 1385dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * if (need_to_modify_thing()) { 1395dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * thing.writable()->modifyMe(); // makes a copy of constThing 1405dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * } 1415dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * ... 1425dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * x = thing->readSomething(); 1435dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * ... 1445dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * if (need_to_modify_thing_now()) { 1455dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * thing.writable()->changeMe(); // makes a copy of constThing if we didn't call modifyMe() 1465dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * } 1475dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * 1485dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * consume_a_thing(thing); // could be constThing or a modified copy. 1495dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com */ 1505dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.comtemplate <typename T> 1515dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.comclass SkTCopyOnFirstWrite { 1525dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.compublic: 1535dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com SkTCopyOnFirstWrite(const T& initial) : fObj(&initial) {} 1545dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 15545a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com // Constructor for delayed initialization. 15645a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com SkTCopyOnFirstWrite() : fObj(NULL) {} 15745a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com 15845a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com // Should only be called once, and only if the default constructor was used. 15945a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com void init(const T& initial) { 16045a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com SkASSERT(NULL == fObj); 16145a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com SkASSERT(!fLazy.isValid()); 16245a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com fObj = &initial; 16345a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com } 16445a15f551b5b3c6c747d8eaf6466b7d3b76a8faebsalomon@google.com 1655dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com /** 1665dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * Returns a writable T*. The first time this is called the initial object is cloned. 1675dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com */ 1685dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com T* writable() { 16949f085dddff10473b6ebf832a974288300224e60bsalomon SkASSERT(fObj); 1705dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com if (!fLazy.isValid()) { 1715dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com fLazy.set(*fObj); 1725dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com fObj = fLazy.get(); 1735dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com } 1745dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com return const_cast<T*>(fObj); 1755dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com } 1765dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 1775dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com /** 1785dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com * Operators for treating this as though it were a const pointer. 1795dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com */ 1805dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 1815dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com const T *operator->() const { return fObj; } 1825dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 1835dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com operator const T*() const { return fObj; } 1845dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 1855dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com const T& operator *() const { return *fObj; } 1865dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 1875dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.comprivate: 1885dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com const T* fObj; 1895dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com SkTLazy<T> fLazy; 1905dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com}; 1915dc26b97366934ba0f896cea02a3fec027d5d5c1bsalomon@google.com 192a076e9be17654a60310e72c4f70fcd5337f56dbfreed@google.com#endif 193