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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkAutoMalloc_DEFINED
#define SkAutoMalloc_DEFINED
#include "SkMacros.h"
#include "SkMalloc.h"
#include "SkNoncopyable.h"
#include "SkTypes.h"
#include <memory>
/**
* Manage an allocated block of heap memory. This object is the sole manager of
* the lifetime of the block, so the caller must not call sk_free() or delete
* on the block, unless release() was called.
*/
class SkAutoMalloc : SkNoncopyable {
public:
explicit SkAutoMalloc(size_t size = 0)
: fPtr(size ? sk_malloc_throw(size) : nullptr), fSize(size) {}
/**
* Passed to reset to specify what happens if the requested size is smaller
* than the current size (and the current block was dynamically allocated).
*/
enum OnShrink {
/**
* If the requested size is smaller than the current size, and the
* current block is dynamically allocated, free the old block and
* malloc a new block of the smaller size.
*/
kAlloc_OnShrink,
/**
* If the requested size is smaller than the current size, and the
* current block is dynamically allocated, just return the old
* block.
*/
kReuse_OnShrink
};
/**
* Reallocates the block to a new size. The ptr may or may not change.
*/
void* reset(size_t size = 0, OnShrink shrink = kAlloc_OnShrink) {
if (size != fSize && (size > fSize || kReuse_OnShrink != shrink)) {
fPtr.reset(size ? sk_malloc_throw(size) : nullptr);
fSize = size;
}
return fPtr.get();
}
/**
* Return the allocated block.
*/
void* get() { return fPtr.get(); }
const void* get() const { return fPtr.get(); }
/** Transfer ownership of the current ptr to the caller, setting the
internal reference to null. Note the caller is reponsible for calling
sk_free on the returned address.
*/
void* release() {
fSize = 0;
return fPtr.release();
}
private:
struct WrapFree {
void operator()(void* p) { sk_free(p); }
};
std::unique_ptr<void, WrapFree> fPtr;
size_t fSize; // can be larger than the requested size (see kReuse)
};
#define SkAutoMalloc(...) SK_REQUIRE_LOCAL_VAR(SkAutoMalloc)
/**
* Manage an allocated block of memory. If the requested size is <= kSizeRequested (or slightly
* more), then the allocation will come from the stack rather than the heap. This object is the
* sole manager of the lifetime of the block, so the caller must not call sk_free() or delete on
* the block.
*/
template <size_t kSizeRequested> class SkAutoSMalloc : SkNoncopyable {
public:
/**
* Creates initially empty storage. get() returns a ptr, but it is to a zero-byte allocation.
* Must call reset(size) to return an allocated block.
*/
SkAutoSMalloc() {
fPtr = fStorage;
fSize = kSize;
}
/**
* Allocate a block of the specified size. If size <= kSizeRequested (or slightly more), then
* the allocation will come from the stack, otherwise it will be dynamically allocated.
*/
explicit SkAutoSMalloc(size_t size) {
fPtr = fStorage;
fSize = kSize;
this->reset(size);
}
/**
* Free the allocated block (if any). If the block was small enough to have been allocated on
* the stack, then this does nothing.
*/
~SkAutoSMalloc() {
if (fPtr != (void*)fStorage) {
sk_free(fPtr);
}
}
/**
* Return the allocated block. May return non-null even if the block is of zero size. Since
* this may be on the stack or dynamically allocated, the caller must not call sk_free() on it,
* but must rely on SkAutoSMalloc to manage it.
*/
void* get() const { return fPtr; }
/**
* Return a new block of the requested size, freeing (as necessary) any previously allocated
* block. As with the constructor, if size <= kSizeRequested (or slightly more) then the return
* block may be allocated locally, rather than from the heap.
*/
void* reset(size_t size,
SkAutoMalloc::OnShrink shrink = SkAutoMalloc::kAlloc_OnShrink,
bool* didChangeAlloc = nullptr) {
size = (size < kSize) ? kSize : size;
bool alloc = size != fSize && (SkAutoMalloc::kAlloc_OnShrink == shrink || size > fSize);
if (didChangeAlloc) {
*didChangeAlloc = alloc;
}
if (alloc) {
if (fPtr != (void*)fStorage) {
sk_free(fPtr);
}
if (size == kSize) {
SkASSERT(fPtr != fStorage); // otherwise we lied when setting didChangeAlloc.
fPtr = fStorage;
} else {
fPtr = sk_malloc_throw(size);
}
fSize = size;
}
SkASSERT(fSize >= size && fSize >= kSize);
SkASSERT((fPtr == fStorage) || fSize > kSize);
return fPtr;
}
private:
// Align up to 32 bits.
static const size_t kSizeAlign4 = SkAlign4(kSizeRequested);
#if defined(SK_BUILD_FOR_GOOGLE3)
// Stack frame size is limited for SK_BUILD_FOR_GOOGLE3. 4k is less than the actual max, but some functions
// have multiple large stack allocations.
static const size_t kMaxBytes = 4 * 1024;
static const size_t kSize = kSizeRequested > kMaxBytes ? kMaxBytes : kSizeAlign4;
#else
static const size_t kSize = kSizeAlign4;
#endif
void* fPtr;
size_t fSize; // can be larger than the requested size (see kReuse)
uint32_t fStorage[kSize >> 2];
};
// Can't guard the constructor because it's a template class.
#endif
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