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1 /*
2  * Copyright 2006 The Android Open Source Project
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #ifndef SkTypes_DEFINED
9 #define SkTypes_DEFINED
10 
11 // IWYU pragma: begin_exports
12 #include "SkPreConfig.h"
13 #include "SkUserConfig.h"
14 #include "SkPostConfig.h"
15 #include <stddef.h>
16 #include <stdint.h>
17 
18 #if defined(SK_ARM_HAS_NEON)
19     #include <arm_neon.h>
20 #elif SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
21     #include <immintrin.h>
22 #endif
23 // IWYU pragma: end_exports
24 
25 #include <string.h>
26 
27 /**
28  *  sk_careful_memcpy() is just like memcpy(), but guards against undefined behavior.
29  *
30  * It is undefined behavior to call memcpy() with null dst or src, even if len is 0.
31  * If an optimizer is "smart" enough, it can exploit this to do unexpected things.
32  *     memcpy(dst, src, 0);
33  *     if (src) {
34  *         printf("%x\n", *src);
35  *     }
36  * In this code the compiler can assume src is not null and omit the if (src) {...} check,
37  * unconditionally running the printf, crashing the program if src really is null.
38  * Of the compilers we pay attention to only GCC performs this optimization in practice.
39  */
sk_careful_memcpy(void * dst,const void * src,size_t len)40 static inline void* sk_careful_memcpy(void* dst, const void* src, size_t len) {
41     // When we pass >0 len we had better already be passing valid pointers.
42     // So we just need to skip calling memcpy when len == 0.
43     if (len) {
44         memcpy(dst,src,len);
45     }
46     return dst;
47 }
48 
49 /** \file SkTypes.h
50 */
51 
52 /** See SkGraphics::GetVersion() to retrieve these at runtime
53  */
54 #define SKIA_VERSION_MAJOR  1
55 #define SKIA_VERSION_MINOR  0
56 #define SKIA_VERSION_PATCH  0
57 
58 /*
59     memory wrappers to be implemented by the porting layer (platform)
60 */
61 
62 /** Called internally if we run out of memory. The platform implementation must
63     not return, but should either throw an exception or otherwise exit.
64 */
65 SK_API extern void sk_out_of_memory(void);
66 /** Called internally if we hit an unrecoverable error.
67     The platform implementation must not return, but should either throw
68     an exception or otherwise exit.
69 */
70 SK_API extern void sk_abort_no_print(void);
71 
72 enum {
73     SK_MALLOC_TEMP  = 0x01, //!< hint to sk_malloc that the requested memory will be freed in the scope of the stack frame
74     SK_MALLOC_THROW = 0x02  //!< instructs sk_malloc to call sk_throw if the memory cannot be allocated.
75 };
76 /** Return a block of memory (at least 4-byte aligned) of at least the
77     specified size. If the requested memory cannot be returned, either
78     return null (if SK_MALLOC_TEMP bit is clear) or throw an exception
79     (if SK_MALLOC_TEMP bit is set). To free the memory, call sk_free().
80 */
81 SK_API extern void* sk_malloc_flags(size_t size, unsigned flags);
82 /** Same as sk_malloc(), but hard coded to pass SK_MALLOC_THROW as the flag
83 */
84 SK_API extern void* sk_malloc_throw(size_t size);
85 /** Same as standard realloc(), but this one never returns null on failure. It will throw
86     an exception if it fails.
87 */
88 SK_API extern void* sk_realloc_throw(void* buffer, size_t size);
89 /** Free memory returned by sk_malloc(). It is safe to pass null.
90 */
91 SK_API extern void sk_free(void*);
92 
93 /** Much like calloc: returns a pointer to at least size zero bytes, or NULL on failure.
94  */
95 SK_API extern void* sk_calloc(size_t size);
96 
97 /** Same as sk_calloc, but throws an exception instead of returning NULL on failure.
98  */
99 SK_API extern void* sk_calloc_throw(size_t size);
100 
101 // bzero is safer than memset, but we can't rely on it, so... sk_bzero()
sk_bzero(void * buffer,size_t size)102 static inline void sk_bzero(void* buffer, size_t size) {
103     // Please c.f. sk_careful_memcpy.  It's undefined behavior to call memset(null, 0, 0).
104     if (size) {
105         memset(buffer, 0, size);
106     }
107 }
108 
109 ///////////////////////////////////////////////////////////////////////////////
110 
111 #ifdef override_GLOBAL_NEW
112 #include <new>
113 
new(size_t size)114 inline void* operator new(size_t size) {
115     return sk_malloc_throw(size);
116 }
117 
delete(void * p)118 inline void operator delete(void* p) {
119     sk_free(p);
120 }
121 #endif
122 
123 ///////////////////////////////////////////////////////////////////////////////
124 
125 #define SK_INIT_TO_AVOID_WARNING    = 0
126 
127 #ifndef SkDebugf
128     SK_API void SkDebugf(const char format[], ...);
129 #endif
130 
131 #define SkASSERT_RELEASE(cond)          if(!(cond)) { SK_ABORT(#cond); }
132 
133 #ifdef SK_DEBUG
134     #define SkASSERT(cond)              SkASSERT_RELEASE(cond)
135     #define SkDEBUGFAIL(message)        SkASSERT(false && message)
136     #define SkDEBUGFAILF(fmt, ...)      SkASSERTF(false, fmt, ##__VA_ARGS__)
137     #define SkDEBUGCODE(code)           code
138     #define SkDECLAREPARAM(type, var)   , type var
139     #define SkPARAM(var)                , var
140 //  #define SkDEBUGF(args       )       SkDebugf##args
141     #define SkDEBUGF(args       )       SkDebugf args
142     #define SkAssertResult(cond)        SkASSERT(cond)
143 #else
144     #define SkASSERT(cond)
145     #define SkDEBUGFAIL(message)
146     #define SkDEBUGCODE(code)
147     #define SkDEBUGF(args)
148     #define SkDECLAREPARAM(type, var)
149     #define SkPARAM(var)
150 
151     // unlike SkASSERT, this guy executes its condition in the non-debug build
152     #define SkAssertResult(cond)        cond
153 #endif
154 
155 // Legacy macro names for SK_ABORT
156 #define SkFAIL(message)                 SK_ABORT(message)
157 #define sk_throw()                      SK_ABORT("sk_throw")
158 
159 // We want to evaluate cond only once, and inside the SkASSERT somewhere so we see its string form.
160 // So we use the comma operator to make an SkDebugf that always returns false: we'll evaluate cond,
161 // and if it's true the assert passes; if it's false, we'll print the message and the assert fails.
162 #define SkASSERTF(cond, fmt, ...)       SkASSERT((cond) || (SkDebugf(fmt"\n", __VA_ARGS__), false))
163 
164 #ifdef SK_DEVELOPER
165     #define SkDEVCODE(code)             code
166 #else
167     #define SkDEVCODE(code)
168 #endif
169 
170 #ifdef SK_IGNORE_TO_STRING
171     #define SK_TO_STRING_NONVIRT()
172     #define SK_TO_STRING_VIRT()
173     #define SK_TO_STRING_PUREVIRT()
174     #define SK_TO_STRING_OVERRIDE()
175 #else
176     class SkString;
177     // the 'toString' helper functions convert Sk* objects to human-readable
178     // form in developer mode
179     #define SK_TO_STRING_NONVIRT() void toString(SkString* str) const;
180     #define SK_TO_STRING_VIRT() virtual void toString(SkString* str) const;
181     #define SK_TO_STRING_PUREVIRT() virtual void toString(SkString* str) const = 0;
182     #define SK_TO_STRING_OVERRIDE() void toString(SkString* str) const override;
183 #endif
184 
185 /*
186  *  Usage:  SK_MACRO_CONCAT(a, b)   to construct the symbol ab
187  *
188  *  SK_MACRO_CONCAT_IMPL_PRIV just exists to make this work. Do not use directly
189  *
190  */
191 #define SK_MACRO_CONCAT(X, Y)           SK_MACRO_CONCAT_IMPL_PRIV(X, Y)
192 #define SK_MACRO_CONCAT_IMPL_PRIV(X, Y)  X ## Y
193 
194 /*
195  *  Usage: SK_MACRO_APPEND_LINE(foo)    to make foo123, where 123 is the current
196  *                                      line number. Easy way to construct
197  *                                      unique names for local functions or
198  *                                      variables.
199  */
200 #define SK_MACRO_APPEND_LINE(name)  SK_MACRO_CONCAT(name, __LINE__)
201 
202 /**
203  * For some classes, it's almost always an error to instantiate one without a name, e.g.
204  *   {
205  *       SkAutoMutexAcquire(&mutex);
206  *       <some code>
207  *   }
208  * In this case, the writer meant to hold mutex while the rest of the code in the block runs,
209  * but instead the mutex is acquired and then immediately released.  The correct usage is
210  *   {
211  *       SkAutoMutexAcquire lock(&mutex);
212  *       <some code>
213  *   }
214  *
215  * To prevent callers from instantiating your class without a name, use SK_REQUIRE_LOCAL_VAR
216  * like this:
217  *   class classname {
218  *       <your class>
219  *   };
220  *   #define classname(...) SK_REQUIRE_LOCAL_VAR(classname)
221  *
222  * This won't work with templates, and you must inline the class' constructors and destructors.
223  * Take a look at SkAutoFree and SkAutoMalloc in this file for examples.
224  */
225 #define SK_REQUIRE_LOCAL_VAR(classname) \
226     static_assert(false, "missing name for " #classname)
227 
228 ///////////////////////////////////////////////////////////////////////
229 
230 /**
231  *  Fast type for signed 8 bits. Use for parameter passing and local variables,
232  *  not for storage.
233  */
234 typedef int S8CPU;
235 
236 /**
237  *  Fast type for unsigned 8 bits. Use for parameter passing and local
238  *  variables, not for storage
239  */
240 typedef unsigned U8CPU;
241 
242 /**
243  *  Fast type for signed 16 bits. Use for parameter passing and local variables,
244  *  not for storage
245  */
246 typedef int S16CPU;
247 
248 /**
249  *  Fast type for unsigned 16 bits. Use for parameter passing and local
250  *  variables, not for storage
251  */
252 typedef unsigned U16CPU;
253 
254 /**
255  *  Meant to be a small version of bool, for storage purposes. Will be 0 or 1
256  */
257 typedef uint8_t SkBool8;
258 
259 #ifdef SK_DEBUG
260     SK_API int8_t      SkToS8(intmax_t);
261     SK_API uint8_t     SkToU8(uintmax_t);
262     SK_API int16_t     SkToS16(intmax_t);
263     SK_API uint16_t    SkToU16(uintmax_t);
264     SK_API int32_t     SkToS32(intmax_t);
265     SK_API uint32_t    SkToU32(uintmax_t);
266     SK_API int         SkToInt(intmax_t);
267     SK_API unsigned    SkToUInt(uintmax_t);
268     SK_API size_t      SkToSizeT(uintmax_t);
269 #else
270     #define SkToS8(x)   ((int8_t)(x))
271     #define SkToU8(x)   ((uint8_t)(x))
272     #define SkToS16(x)  ((int16_t)(x))
273     #define SkToU16(x)  ((uint16_t)(x))
274     #define SkToS32(x)  ((int32_t)(x))
275     #define SkToU32(x)  ((uint32_t)(x))
276     #define SkToInt(x)  ((int)(x))
277     #define SkToUInt(x) ((unsigned)(x))
278     #define SkToSizeT(x) ((size_t)(x))
279 #endif
280 
281 /** Returns 0 or 1 based on the condition
282 */
283 #define SkToBool(cond)  ((cond) != 0)
284 
285 #define SK_MaxS16   32767
286 #define SK_MinS16   -32767
287 #define SK_MaxU16   0xFFFF
288 #define SK_MinU16   0
289 #define SK_MaxS32   0x7FFFFFFF
290 #define SK_MinS32   -SK_MaxS32
291 #define SK_MaxU32   0xFFFFFFFF
292 #define SK_MinU32   0
293 #define SK_NaN32    (1 << 31)
294 
295 /** Returns true if the value can be represented with signed 16bits
296  */
SkIsS16(long x)297 static inline bool SkIsS16(long x) {
298     return (int16_t)x == x;
299 }
300 
301 /** Returns true if the value can be represented with unsigned 16bits
302  */
SkIsU16(long x)303 static inline bool SkIsU16(long x) {
304     return (uint16_t)x == x;
305 }
306 
SkLeftShift(int32_t value,int32_t shift)307 static inline int32_t SkLeftShift(int32_t value, int32_t shift) {
308     return (int32_t) ((uint32_t) value << shift);
309 }
310 
SkLeftShift(int64_t value,int32_t shift)311 static inline int64_t SkLeftShift(int64_t value, int32_t shift) {
312     return (int64_t) ((uint64_t) value << shift);
313 }
314 
315 //////////////////////////////////////////////////////////////////////////////
316 
317 /** Returns the number of entries in an array (not a pointer) */
318 template <typename T, size_t N> char (&SkArrayCountHelper(T (&array)[N]))[N];
319 #define SK_ARRAY_COUNT(array) (sizeof(SkArrayCountHelper(array)))
320 
321 // Can be used to bracket data types that must be dense, e.g. hash keys.
322 #if defined(__clang__)  // This should work on GCC too, but GCC diagnostic pop didn't seem to work!
323     #define SK_BEGIN_REQUIRE_DENSE _Pragma("GCC diagnostic push") \
324                                    _Pragma("GCC diagnostic error \"-Wpadded\"")
325     #define SK_END_REQUIRE_DENSE   _Pragma("GCC diagnostic pop")
326 #else
327     #define SK_BEGIN_REQUIRE_DENSE
328     #define SK_END_REQUIRE_DENSE
329 #endif
330 
331 #define SkAlign2(x)     (((x) + 1) >> 1 << 1)
332 #define SkIsAlign2(x)   (0 == ((x) & 1))
333 
334 #define SkAlign4(x)     (((x) + 3) >> 2 << 2)
335 #define SkIsAlign4(x)   (0 == ((x) & 3))
336 
337 #define SkAlign8(x)     (((x) + 7) >> 3 << 3)
338 #define SkIsAlign8(x)   (0 == ((x) & 7))
339 
340 #define SkAlignPtr(x)   (sizeof(void*) == 8 ?   SkAlign8(x) :   SkAlign4(x))
341 #define SkIsAlignPtr(x) (sizeof(void*) == 8 ? SkIsAlign8(x) : SkIsAlign4(x))
342 
343 typedef uint32_t SkFourByteTag;
344 #define SkSetFourByteTag(a, b, c, d)    (((a) << 24) | ((b) << 16) | ((c) << 8) | (d))
345 
346 /** 32 bit integer to hold a unicode value
347 */
348 typedef int32_t SkUnichar;
349 /** 32 bit value to hold a millisecond count
350 */
351 typedef uint32_t SkMSec;
352 /** 1 second measured in milliseconds
353 */
354 #define SK_MSec1 1000
355 /** maximum representable milliseconds
356 */
357 #define SK_MSecMax 0x7FFFFFFF
358 /** Returns a < b for milliseconds, correctly handling wrap-around from 0xFFFFFFFF to 0
359 */
360 #define SkMSec_LT(a, b)     ((int32_t)(a) - (int32_t)(b) < 0)
361 /** Returns a <= b for milliseconds, correctly handling wrap-around from 0xFFFFFFFF to 0
362 */
363 #define SkMSec_LE(a, b)     ((int32_t)(a) - (int32_t)(b) <= 0)
364 
365 /** The generation IDs in Skia reserve 0 has an invalid marker.
366  */
367 #define SK_InvalidGenID     0
368 /** The unique IDs in Skia reserve 0 has an invalid marker.
369  */
370 #define SK_InvalidUniqueID  0
371 
372 /****************************************************************************
373     The rest of these only build with C++
374 */
375 #ifdef __cplusplus
376 
377 /** Faster than SkToBool for integral conditions. Returns 0 or 1
378 */
Sk32ToBool(uint32_t n)379 static inline int Sk32ToBool(uint32_t n) {
380     return (n | (0-n)) >> 31;
381 }
382 
383 /** Generic swap function. Classes with efficient swaps should specialize this function to take
384     their fast path. This function is used by SkTSort. */
SkTSwap(T & a,T & b)385 template <typename T> inline void SkTSwap(T& a, T& b) {
386     T c(a);
387     a = b;
388     b = c;
389 }
390 
SkAbs32(int32_t value)391 static inline int32_t SkAbs32(int32_t value) {
392     SkASSERT(value != SK_NaN32);  // The most negative int32_t can't be negated.
393     if (value < 0) {
394         value = -value;
395     }
396     return value;
397 }
398 
SkTAbs(T value)399 template <typename T> inline T SkTAbs(T value) {
400     if (value < 0) {
401         value = -value;
402     }
403     return value;
404 }
405 
SkMax32(int32_t a,int32_t b)406 static inline int32_t SkMax32(int32_t a, int32_t b) {
407     if (a < b)
408         a = b;
409     return a;
410 }
411 
SkMin32(int32_t a,int32_t b)412 static inline int32_t SkMin32(int32_t a, int32_t b) {
413     if (a > b)
414         a = b;
415     return a;
416 }
417 
SkTMin(const T & a,const T & b)418 template <typename T> const T& SkTMin(const T& a, const T& b) {
419     return (a < b) ? a : b;
420 }
421 
SkTMax(const T & a,const T & b)422 template <typename T> const T& SkTMax(const T& a, const T& b) {
423     return (b < a) ? a : b;
424 }
425 
SkSign32(int32_t a)426 static inline int32_t SkSign32(int32_t a) {
427     return (a >> 31) | ((unsigned) -a >> 31);
428 }
429 
SkFastMin32(int32_t value,int32_t max)430 static inline int32_t SkFastMin32(int32_t value, int32_t max) {
431     if (value > max) {
432         value = max;
433     }
434     return value;
435 }
436 
437 /** Returns value pinned between min and max, inclusively. */
SkTPin(const T & value,const T & min,const T & max)438 template <typename T> static inline const T& SkTPin(const T& value, const T& min, const T& max) {
439     return SkTMax(SkTMin(value, max), min);
440 }
441 
442 
443 ///////////////////////////////////////////////////////////////////////////////
444 
445 /**
446  *  Indicates whether an allocation should count against a cache budget.
447  */
448 enum class SkBudgeted : bool {
449     kNo  = false,
450     kYes = true
451 };
452 
453 ///////////////////////////////////////////////////////////////////////////////
454 
455 /** Use to combine multiple bits in a bitmask in a type safe way.
456  */
457 template <typename T>
SkTBitOr(T a,T b)458 T SkTBitOr(T a, T b) {
459     return (T)(a | b);
460 }
461 
462 /**
463  *  Use to cast a pointer to a different type, and maintaining strict-aliasing
464  */
SkTCast(const void * ptr)465 template <typename Dst> Dst SkTCast(const void* ptr) {
466     union {
467         const void* src;
468         Dst dst;
469     } data;
470     data.src = ptr;
471     return data.dst;
472 }
473 
474 //////////////////////////////////////////////////////////////////////////////
475 
476 /** \class SkNoncopyable
477 
478 SkNoncopyable is the base class for objects that do not want to
479 be copied. It hides its copy-constructor and its assignment-operator.
480 */
481 class SK_API SkNoncopyable {
482 public:
SkNoncopyable()483     SkNoncopyable() {}
484 
485 private:
486     SkNoncopyable(const SkNoncopyable&);
487     SkNoncopyable& operator=(const SkNoncopyable&);
488 };
489 
490 class SkAutoFree : SkNoncopyable {
491 public:
SkAutoFree()492     SkAutoFree() : fPtr(NULL) {}
SkAutoFree(void * ptr)493     explicit SkAutoFree(void* ptr) : fPtr(ptr) {}
~SkAutoFree()494     ~SkAutoFree() { sk_free(fPtr); }
495 
496     /** Return the currently allocate buffer, or null
497     */
get()498     void* get() const { return fPtr; }
499 
500     /** Assign a new ptr allocated with sk_malloc (or null), and return the
501         previous ptr. Note it is the caller's responsibility to sk_free the
502         returned ptr.
503     */
set(void * ptr)504     void* set(void* ptr) {
505         void* prev = fPtr;
506         fPtr = ptr;
507         return prev;
508     }
509 
510     /** Transfer ownership of the current ptr to the caller, setting the
511         internal reference to null. Note the caller is reponsible for calling
512         sk_free on the returned address.
513     */
detach()514     void* detach() { return this->set(NULL); }
515 
516     /** Free the current buffer, and set the internal reference to NULL. Same
517         as calling sk_free(detach())
518     */
free()519     void free() {
520         sk_free(fPtr);
521         fPtr = NULL;
522     }
523 
524 private:
525     void* fPtr;
526     // illegal
527     SkAutoFree(const SkAutoFree&);
528     SkAutoFree& operator=(const SkAutoFree&);
529 };
530 #define SkAutoFree(...) SK_REQUIRE_LOCAL_VAR(SkAutoFree)
531 
532 /**
533  *  Manage an allocated block of heap memory. This object is the sole manager of
534  *  the lifetime of the block, so the caller must not call sk_free() or delete
535  *  on the block, unless detach() was called.
536  */
537 class SkAutoMalloc : SkNoncopyable {
538 public:
539     explicit SkAutoMalloc(size_t size = 0) {
540         fPtr = size ? sk_malloc_throw(size) : NULL;
541         fSize = size;
542     }
543 
~SkAutoMalloc()544     ~SkAutoMalloc() {
545         sk_free(fPtr);
546     }
547 
548     /**
549      *  Passed to reset to specify what happens if the requested size is smaller
550      *  than the current size (and the current block was dynamically allocated).
551      */
552     enum OnShrink {
553         /**
554          *  If the requested size is smaller than the current size, and the
555          *  current block is dynamically allocated, free the old block and
556          *  malloc a new block of the smaller size.
557          */
558         kAlloc_OnShrink,
559 
560         /**
561          *  If the requested size is smaller than the current size, and the
562          *  current block is dynamically allocated, just return the old
563          *  block.
564          */
565         kReuse_OnShrink
566     };
567 
568     /**
569      *  Reallocates the block to a new size. The ptr may or may not change.
570      */
571     void* reset(size_t size, OnShrink shrink = kAlloc_OnShrink,  bool* didChangeAlloc = NULL) {
572         if (size == fSize || (kReuse_OnShrink == shrink && size < fSize)) {
573             if (didChangeAlloc) {
574                 *didChangeAlloc = false;
575             }
576             return fPtr;
577         }
578 
579         sk_free(fPtr);
580         fPtr = size ? sk_malloc_throw(size) : NULL;
581         fSize = size;
582         if (didChangeAlloc) {
583             *didChangeAlloc = true;
584         }
585 
586         return fPtr;
587     }
588 
589     /**
590      *  Releases the block back to the heap
591      */
free()592     void free() {
593         this->reset(0);
594     }
595 
596     /**
597      *  Return the allocated block.
598      */
get()599     void* get() { return fPtr; }
get()600     const void* get() const { return fPtr; }
601 
602    /** Transfer ownership of the current ptr to the caller, setting the
603        internal reference to null. Note the caller is reponsible for calling
604        sk_free on the returned address.
605     */
detach()606     void* detach() {
607         void* ptr = fPtr;
608         fPtr = NULL;
609         fSize = 0;
610         return ptr;
611     }
612 
613 private:
614     void*   fPtr;
615     size_t  fSize;  // can be larger than the requested size (see kReuse)
616 };
617 #define SkAutoMalloc(...) SK_REQUIRE_LOCAL_VAR(SkAutoMalloc)
618 
619 /**
620  *  Manage an allocated block of memory. If the requested size is <= kSizeRequested (or slightly
621  *  more), then the allocation will come from the stack rather than the heap. This object is the
622  *  sole manager of the lifetime of the block, so the caller must not call sk_free() or delete on
623  *  the block.
624  */
625 template <size_t kSizeRequested> class SkAutoSMalloc : SkNoncopyable {
626 public:
627     /**
628      *  Creates initially empty storage. get() returns a ptr, but it is to a zero-byte allocation.
629      *  Must call reset(size) to return an allocated block.
630      */
SkAutoSMalloc()631     SkAutoSMalloc() {
632         fPtr = fStorage;
633         fSize = kSize;
634     }
635 
636     /**
637      *  Allocate a block of the specified size. If size <= kSizeRequested (or slightly more), then
638      *  the allocation will come from the stack, otherwise it will be dynamically allocated.
639      */
SkAutoSMalloc(size_t size)640     explicit SkAutoSMalloc(size_t size) {
641         fPtr = fStorage;
642         fSize = kSize;
643         this->reset(size);
644     }
645 
646     /**
647      *  Free the allocated block (if any). If the block was small enough to have been allocated on
648      *  the stack, then this does nothing.
649      */
~SkAutoSMalloc()650     ~SkAutoSMalloc() {
651         if (fPtr != (void*)fStorage) {
652             sk_free(fPtr);
653         }
654     }
655 
656     /**
657      *  Return the allocated block. May return non-null even if the block is of zero size. Since
658      *  this may be on the stack or dynamically allocated, the caller must not call sk_free() on it,
659      *  but must rely on SkAutoSMalloc to manage it.
660      */
get()661     void* get() const { return fPtr; }
662 
663     /**
664      *  Return a new block of the requested size, freeing (as necessary) any previously allocated
665      *  block. As with the constructor, if size <= kSizeRequested (or slightly more) then the return
666      *  block may be allocated locally, rather than from the heap.
667      */
668     void* reset(size_t size,
669                 SkAutoMalloc::OnShrink shrink = SkAutoMalloc::kAlloc_OnShrink,
670                 bool* didChangeAlloc = NULL) {
671         size = (size < kSize) ? kSize : size;
672         bool alloc = size != fSize && (SkAutoMalloc::kAlloc_OnShrink == shrink || size > fSize);
673         if (didChangeAlloc) {
674             *didChangeAlloc = alloc;
675         }
676         if (alloc) {
677             if (fPtr != (void*)fStorage) {
678                 sk_free(fPtr);
679             }
680 
681             if (size == kSize) {
682                 SkASSERT(fPtr != fStorage); // otherwise we lied when setting didChangeAlloc.
683                 fPtr = fStorage;
684             } else {
685                 fPtr = sk_malloc_flags(size, SK_MALLOC_THROW | SK_MALLOC_TEMP);
686             }
687 
688             fSize = size;
689         }
690         SkASSERT(fSize >= size && fSize >= kSize);
691         SkASSERT((fPtr == fStorage) || fSize > kSize);
692         return fPtr;
693     }
694 
695 private:
696     // Align up to 32 bits.
697     static const size_t kSizeAlign4 = SkAlign4(kSizeRequested);
698 #if defined(GOOGLE3)
699     // Stack frame size is limited for GOOGLE3. 4k is less than the actual max, but some functions
700     // have multiple large stack allocations.
701     static const size_t kMaxBytes = 4 * 1024;
702     static const size_t kSize = kSizeRequested > kMaxBytes ? kMaxBytes : kSizeAlign4;
703 #else
704     static const size_t kSize = kSizeAlign4;
705 #endif
706 
707     void*       fPtr;
708     size_t      fSize;  // can be larger than the requested size (see kReuse)
709     uint32_t    fStorage[kSize >> 2];
710 };
711 // Can't guard the constructor because it's a template class.
712 
713 #endif /* C++ */
714 
715 #endif
716