3 * Copyright 2006 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #ifndef SkTemplates_DEFINED
11 #define SkTemplates_DEFINED
16 /** \file SkTemplates.h
18 This file contains light-weight template classes for type-safe and exception-safe
23 * Marks a local variable as known to be unused (to avoid warnings).
24 * Note that this does *not* prevent the local variable from being optimized away.
26 template<typename T> inline void sk_ignore_unused_variable(const T&) { }
29 * SkTIsConst<T>::value is true if the type T is const.
30 * The type T is constrained not to be an array or reference type.
32 template <typename T> struct SkTIsConst {
34 static uint16_t test(const volatile void*);
35 static uint32_t test(volatile void *);
36 static const bool value = (sizeof(uint16_t) == sizeof(test(t)));
40 /** SkTConstType<T, CONST>::type will be 'const T' if CONST is true, 'T' otherwise. */
41 template <typename T, bool CONST> struct SkTConstType {
44 template <typename T> struct SkTConstType<T, true> {
50 * Returns a pointer to a D which comes immediately after S[count].
52 template <typename D, typename S> static D* SkTAfter(S* ptr, size_t count = 1) {
53 return reinterpret_cast<D*>(ptr + count);
57 * Returns a pointer to a D which comes byteOffset bytes after S.
59 template <typename D, typename S> static D* SkTAddOffset(S* ptr, size_t byteOffset) {
60 // The intermediate char* has the same const-ness as D as this produces better error messages.
61 // This relies on the fact that reinterpret_cast can add constness, but cannot remove it.
62 return reinterpret_cast<D*>(
63 reinterpret_cast<typename SkTConstType<char, SkTIsConst<D>::value>::type*>(ptr) + byteOffset
67 /** \class SkAutoTCallVProc
69 Call a function when this goes out of scope. The template uses two
70 parameters, the object, and a function that is to be called in the destructor.
71 If detach() is called, the object reference is set to null. If the object
72 reference is null when the destructor is called, we do not call the
75 template <typename T, void (*P)(T*)> class SkAutoTCallVProc : SkNoncopyable {
77 SkAutoTCallVProc(T* obj): fObj(obj) {}
78 ~SkAutoTCallVProc() { if (fObj) P(fObj); }
79 T* detach() { T* obj = fObj; fObj = NULL; return obj; }
84 /** \class SkAutoTCallIProc
86 Call a function when this goes out of scope. The template uses two
87 parameters, the object, and a function that is to be called in the destructor.
88 If detach() is called, the object reference is set to null. If the object
89 reference is null when the destructor is called, we do not call the
92 template <typename T, int (*P)(T*)> class SkAutoTCallIProc : SkNoncopyable {
94 SkAutoTCallIProc(T* obj): fObj(obj) {}
95 ~SkAutoTCallIProc() { if (fObj) P(fObj); }
96 T* detach() { T* obj = fObj; fObj = NULL; return obj; }
101 /** \class SkAutoTDelete
102 An SkAutoTDelete<T> is like a T*, except that the destructor of SkAutoTDelete<T>
103 automatically deletes the pointer it holds (if any). That is, SkAutoTDelete<T>
104 owns the T object that it points to. Like a T*, an SkAutoTDelete<T> may hold
105 either NULL or a pointer to a T object. Also like T*, SkAutoTDelete<T> is
106 thread-compatible, and once you dereference it, you get the threadsafety
109 The size of a SkAutoTDelete is small: sizeof(SkAutoTDelete<T>) == sizeof(T*)
111 template <typename T> class SkAutoTDelete : SkNoncopyable {
113 SkAutoTDelete(T* obj = NULL) : fObj(obj) {}
114 ~SkAutoTDelete() { SkDELETE(fObj); }
116 T* get() const { return fObj; }
117 T& operator*() const { SkASSERT(fObj); return *fObj; }
118 T* operator->() const { SkASSERT(fObj); return fObj; }
128 * Delete the owned object, setting the internal pointer to NULL.
136 * Transfer ownership of the object to the caller, setting the internal
137 * pointer to NULL. Note that this differs from get(), which also returns
138 * the pointer, but it does not transfer ownership.
150 // Calls ~T() in the destructor.
151 template <typename T> class SkAutoTDestroy : SkNoncopyable {
153 SkAutoTDestroy(T* obj = NULL) : fObj(obj) {}
160 T* get() const { return fObj; }
161 T& operator*() const { SkASSERT(fObj); return *fObj; }
162 T* operator->() const { SkASSERT(fObj); return fObj; }
168 template <typename T> class SkAutoTDeleteArray : SkNoncopyable {
170 SkAutoTDeleteArray(T array[]) : fArray(array) {}
171 ~SkAutoTDeleteArray() { SkDELETE_ARRAY(fArray); }
173 T* get() const { return fArray; }
174 void free() { SkDELETE_ARRAY(fArray); fArray = NULL; }
175 T* detach() { T* array = fArray; fArray = NULL; return array; }
181 /** Allocate an array of T elements, and free the array in the destructor
183 template <typename T> class SkAutoTArray : SkNoncopyable {
187 SkDEBUGCODE(fCount = 0;)
189 /** Allocate count number of T elements
191 explicit SkAutoTArray(int count) {
192 SkASSERT(count >= 0);
195 fArray = SkNEW_ARRAY(T, count);
197 SkDEBUGCODE(fCount = count;)
200 /** Reallocates given a new count. Reallocation occurs even if new count equals old count.
202 void reset(int count) {
203 SkDELETE_ARRAY(fArray);
204 SkASSERT(count >= 0);
207 fArray = SkNEW_ARRAY(T, count);
209 SkDEBUGCODE(fCount = count;)
213 SkDELETE_ARRAY(fArray);
216 /** Return the array of T elements. Will be NULL if count == 0
218 T* get() const { return fArray; }
220 /** Return the nth element in the array
222 T& operator[](int index) const {
223 SkASSERT((unsigned)index < (unsigned)fCount);
224 return fArray[index];
229 SkDEBUGCODE(int fCount;)
232 /** Wraps SkAutoTArray, with room for up to N elements preallocated
234 template <int N, typename T> class SkAutoSTArray : SkNoncopyable {
236 /** Initialize with no objects */
242 /** Allocate count number of T elements
244 SkAutoSTArray(int count) {
254 /** Destroys previous objects in the array and default constructs count number of objects */
255 void reset(int count) {
257 T* iter = start + fCount;
258 while (iter > start) {
262 if (fCount != count) {
264 // 'fArray' was allocated last time so free it now
265 SkASSERT((T*) fStorage != fArray);
270 fArray = (T*) sk_malloc_throw(count * sizeof(T));
271 } else if (count > 0) {
272 fArray = (T*) fStorage;
281 T* stop = fArray + count;
282 while (iter < stop) {
283 SkNEW_PLACEMENT(iter++, T);
287 /** Return the number of T elements in the array
289 int count() const { return fCount; }
291 /** Return the array of T elements. Will be NULL if count == 0
293 T* get() const { return fArray; }
295 /** Return the nth element in the array
297 T& operator[](int index) const {
298 SkASSERT(index < fCount);
299 return fArray[index];
305 // since we come right after fArray, fStorage should be properly aligned
306 char fStorage[N * sizeof(T)];
309 /** Manages an array of T elements, freeing the array in the destructor.
310 * Does NOT call any constructors/destructors on T (T must be POD).
312 template <typename T> class SkAutoTMalloc : SkNoncopyable {
314 /** Takes ownership of the ptr. The ptr must be a value which can be passed to sk_free. */
315 explicit SkAutoTMalloc(T* ptr = NULL) {
319 /** Allocates space for 'count' Ts. */
320 explicit SkAutoTMalloc(size_t count) {
321 fPtr = (T*)sk_malloc_flags(count * sizeof(T), SK_MALLOC_THROW | SK_MALLOC_TEMP);
328 /** Resize the memory area pointed to by the current ptr preserving contents. */
329 void realloc(size_t count) {
330 fPtr = reinterpret_cast<T*>(sk_realloc_throw(fPtr, count * sizeof(T)));
333 /** Resize the memory area pointed to by the current ptr without preserving contents. */
334 void reset(size_t count) {
336 fPtr = (T*)sk_malloc_flags(count * sizeof(T), SK_MALLOC_THROW | SK_MALLOC_TEMP);
339 T* get() const { return fPtr; }
345 operator const T*() const {
349 T& operator[](int index) {
353 const T& operator[](int index) const {
358 * Transfer ownership of the ptr to the caller, setting the internal
359 * pointer to NULL. Note that this differs from get(), which also returns
360 * the pointer, but it does not transfer ownership.
372 template <size_t N, typename T> class SkAutoSTMalloc : SkNoncopyable {
378 SkAutoSTMalloc(size_t count) {
380 fPtr = (T*)sk_malloc_flags(count * sizeof(T), SK_MALLOC_THROW | SK_MALLOC_TEMP);
389 if (fPtr != fTStorage) {
394 // doesn't preserve contents
395 T* reset(size_t count) {
396 if (fPtr != fTStorage) {
400 fPtr = (T*)sk_malloc_flags(count * sizeof(T), SK_MALLOC_THROW | SK_MALLOC_TEMP);
409 T* get() const { return fPtr; }
415 operator const T*() const {
419 T& operator[](int index) {
423 const T& operator[](int index) const {
430 uint32_t fStorage32[(N*sizeof(T) + 3) >> 2];
431 T fTStorage[1]; // do NOT want to invoke T::T()
436 * Reserves memory that is aligned on double and pointer boundaries.
437 * Hopefully this is sufficient for all practical purposes.
439 template <size_t N> class SkAlignedSStorage : SkNoncopyable {
441 void* get() { return fData; }
451 * Reserves memory that is aligned on double and pointer boundaries.
452 * Hopefully this is sufficient for all practical purposes. Otherwise,
453 * we have to do some arcane trickery to determine alignment of non-POD
454 * types. Lifetime of the memory is the lifetime of the object.
456 template <int N, typename T> class SkAlignedSTStorage : SkNoncopyable {
459 * Returns void* because this object does not initialize the
460 * memory. Use placement new for types that require a cons.
462 void* get() { return fStorage.get(); }
464 SkAlignedSStorage<sizeof(T)*N> fStorage;