1 /*
2 * Copyright 2017 Google Inc.
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 SkMalloc_DEFINED
9 #define SkMalloc_DEFINED
10
11 #include <cstddef>
12 #include <cstring>
13
14 #include "SkPreConfig.h"
15
16 /*
17 memory wrappers to be implemented by the porting layer (platform)
18 */
19
20 enum {
21 SK_MALLOC_TEMP = 0x01, //!< hint to sk_malloc that the requested memory will be freed in the scope of the stack frame
22 SK_MALLOC_THROW = 0x02 //!< instructs sk_malloc to call sk_throw if the memory cannot be allocated.
23 };
24 /** Return a block of memory (at least 4-byte aligned) of at least the
25 specified size. If the requested memory cannot be returned, either
26 return null (if SK_MALLOC_TEMP bit is clear) or throw an exception
27 (if SK_MALLOC_TEMP bit is set). To free the memory, call sk_free().
28 */
29 SK_API extern void* sk_malloc_flags(size_t size, unsigned flags);
30 /** Same as sk_malloc(), but hard coded to pass SK_MALLOC_THROW as the flag
31 */
32 SK_API extern void* sk_malloc_throw(size_t size);
33 /** Same as standard realloc(), but this one never returns null on failure. It will throw
34 an exception if it fails.
35 */
36 SK_API extern void* sk_realloc_throw(void* buffer, size_t size);
37 /** Free memory returned by sk_malloc(). It is safe to pass null.
38 */
39 SK_API extern void sk_free(void*);
40
41 /** Much like calloc: returns a pointer to at least size zero bytes, or NULL on failure.
42 */
43 SK_API extern void* sk_calloc(size_t size);
44
45 /** Same as sk_calloc, but throws an exception instead of returning NULL on failure.
46 */
47 SK_API extern void* sk_calloc_throw(size_t size);
48
49 /** Called internally if we run out of memory. The platform implementation must
50 not return, but should either throw an exception or otherwise exit.
51 */
52 SK_API extern void sk_out_of_memory(void);
53
54 // bzero is safer than memset, but we can't rely on it, so... sk_bzero()
sk_bzero(void * buffer,size_t size)55 static inline void sk_bzero(void* buffer, size_t size) {
56 // Please c.f. sk_careful_memcpy. It's undefined behavior to call memset(null, 0, 0).
57 if (size) {
58 memset(buffer, 0, size);
59 }
60 }
61
62 /**
63 * sk_careful_memcpy() is just like memcpy(), but guards against undefined behavior.
64 *
65 * It is undefined behavior to call memcpy() with null dst or src, even if len is 0.
66 * If an optimizer is "smart" enough, it can exploit this to do unexpected things.
67 * memcpy(dst, src, 0);
68 * if (src) {
69 * printf("%x\n", *src);
70 * }
71 * In this code the compiler can assume src is not null and omit the if (src) {...} check,
72 * unconditionally running the printf, crashing the program if src really is null.
73 * Of the compilers we pay attention to only GCC performs this optimization in practice.
74 */
sk_careful_memcpy(void * dst,const void * src,size_t len)75 static inline void* sk_careful_memcpy(void* dst, const void* src, size_t len) {
76 // When we pass >0 len we had better already be passing valid pointers.
77 // So we just need to skip calling memcpy when len == 0.
78 if (len) {
79 memcpy(dst,src,len);
80 }
81 return dst;
82 }
83
84 #endif // SkMalloc_DEFINED
85