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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMalloc_DEFINED
#define SkMalloc_DEFINED
#include <cstddef>
#include <cstring>
#include "SkTypes.h"
/*
memory wrappers to be implemented by the porting layer (platform)
*/
/** Free memory returned by sk_malloc(). It is safe to pass null. */
SK_API extern void sk_free(void*);
/**
* Called internally if we run out of memory. The platform implementation must
* not return, but should either throw an exception or otherwise exit.
*/
SK_API extern void sk_out_of_memory(void);
enum {
/**
* If this bit is set, the returned buffer must be zero-initialized. If this bit is not set
* the buffer can be uninitialized.
*/
SK_MALLOC_ZERO_INITIALIZE = 1 << 0,
/**
* If this bit is set, the implementation must throw/crash/quit if the request cannot
* be fulfilled. If this bit is not set, then it should return nullptr on failure.
*/
SK_MALLOC_THROW = 1 << 1,
};
/**
* Return a block of memory (at least 4-byte aligned) of at least the specified size.
* If the requested memory cannot be returned, either return nullptr or throw/exit, depending
* on the SK_MALLOC_THROW bit. If the allocation succeeds, the memory will be zero-initialized
* if the SK_MALLOC_ZERO_INITIALIZE bit was set.
*
* To free the memory, call sk_free()
*/
SK_API extern void* sk_malloc_flags(size_t size, unsigned flags);
/** Same as standard realloc(), but this one never returns null on failure. It will throw
* an exception if it fails.
*/
SK_API extern void* sk_realloc_throw(void* buffer, size_t size);
static inline void* sk_malloc_throw(size_t size) {
return sk_malloc_flags(size, SK_MALLOC_THROW);
}
static inline void* sk_calloc_throw(size_t size) {
return sk_malloc_flags(size, SK_MALLOC_THROW | SK_MALLOC_ZERO_INITIALIZE);
}
static inline void* sk_calloc_canfail(size_t size) {
#if defined(IS_FUZZING_WITH_LIBFUZZER)
// The Libfuzzer environment is very susceptible to OOM, so to avoid those
// just pretend we can't allocate more than 200kb.
if (size > 200000) {
return nullptr;
}
#endif
return sk_malloc_flags(size, SK_MALLOC_ZERO_INITIALIZE);
}
// Performs a safe multiply count * elemSize, checking for overflow
SK_API extern void* sk_calloc_throw(size_t count, size_t elemSize);
SK_API extern void* sk_malloc_throw(size_t count, size_t elemSize);
SK_API extern void* sk_realloc_throw(void* buffer, size_t count, size_t elemSize);
/**
* These variants return nullptr on failure
*/
static inline void* sk_malloc_canfail(size_t size) {
#if defined(IS_FUZZING_WITH_LIBFUZZER)
// The Libfuzzer environment is very susceptible to OOM, so to avoid those
// just pretend we can't allocate more than 200kb.
if (size > 200000) {
return nullptr;
}
#endif
return sk_malloc_flags(size, 0);
}
SK_API extern void* sk_malloc_canfail(size_t count, size_t elemSize);
// bzero is safer than memset, but we can't rely on it, so... sk_bzero()
static inline void sk_bzero(void* buffer, size_t size) {
// Please c.f. sk_careful_memcpy. It's undefined behavior to call memset(null, 0, 0).
if (size) {
memset(buffer, 0, size);
}
}
/**
* sk_careful_memcpy() is just like memcpy(), but guards against undefined behavior.
*
* It is undefined behavior to call memcpy() with null dst or src, even if len is 0.
* If an optimizer is "smart" enough, it can exploit this to do unexpected things.
* memcpy(dst, src, 0);
* if (src) {
* printf("%x\n", *src);
* }
* In this code the compiler can assume src is not null and omit the if (src) {...} check,
* unconditionally running the printf, crashing the program if src really is null.
* Of the compilers we pay attention to only GCC performs this optimization in practice.
*/
static inline void* sk_careful_memcpy(void* dst, const void* src, size_t len) {
// When we pass >0 len we had better already be passing valid pointers.
// So we just need to skip calling memcpy when len == 0.
if (len) {
memcpy(dst,src,len);
}
return dst;
}
#endif // SkMalloc_DEFINED
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