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/*
* Copyright 2012, The Android Open Source Project
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef ANDROID_LINEARALLOCATOR_H
#define ANDROID_LINEARALLOCATOR_H
#include <stddef.h>
#include <type_traits>
#include <vector>
namespace android {
namespace uirenderer {
/**
* A memory manager that internally allocates multi-kbyte buffers for placing objects in. It avoids
* the overhead of malloc when many objects are allocated. It is most useful when creating many
* small objects with a similar lifetime, and doesn't add significant overhead for large
* allocations.
*/
class LinearAllocator {
public:
LinearAllocator();
~LinearAllocator();
/**
* Reserves and returns a region of memory of at least size 'size', aligning as needed.
* Typically this is used in an object's overridden new() method or as a replacement for malloc.
*
* The lifetime of the returned buffers is tied to that of the LinearAllocator. If calling
* delete() on an object stored in a buffer is needed, it should be overridden to use
* rewindIfLastAlloc()
*
* Note that unlike create, for alloc the type is purely for compile-time error
* checking and does not affect size.
*/
template<class T>
void* alloc(size_t size) {
static_assert(std::is_trivially_destructible<T>::value,
"Error, type is non-trivial! did you mean to use create()?");
return allocImpl(size);
}
/**
* Allocates an instance of the template type with the given construction parameters
* and adds it to the automatic destruction list.
*/
template<class T, typename... Params>
T* create(Params&&... params) {
T* ret = new (allocImpl(sizeof(T))) T(std::forward<Params>(params)...);
if (!std::is_trivially_destructible<T>::value) {
auto dtor = [](void* ret) { ((T*)ret)->~T(); };
addToDestructionList(dtor, ret);
}
return ret;
}
template<class T, typename... Params>
T* create_trivial(Params&&... params) {
static_assert(std::is_trivially_destructible<T>::value,
"Error, called create_trivial on a non-trivial type");
return new (allocImpl(sizeof(T))) T(std::forward<Params>(params)...);
}
template<class T>
T* create_trivial_array(int count) {
static_assert(std::is_trivially_destructible<T>::value,
"Error, called create_trivial_array on a non-trivial type");
return reinterpret_cast<T*>(allocImpl(sizeof(T) * count));
}
/**
* Attempt to deallocate the given buffer, with the LinearAllocator attempting to rewind its
* state if possible.
*/
void rewindIfLastAlloc(void* ptr, size_t allocSize);
/**
* Same as rewindIfLastAlloc(void*, size_t)
*/
template<class T>
void rewindIfLastAlloc(T* ptr) {
rewindIfLastAlloc((void*)ptr, sizeof(T));
}
/**
* Dump memory usage statistics to the log (allocated and wasted space)
*/
void dumpMemoryStats(const char* prefix = "");
/**
* The number of bytes used for buffers allocated in the LinearAllocator (does not count space
* wasted)
*/
size_t usedSize() const { return mTotalAllocated - mWastedSpace; }
private:
LinearAllocator(const LinearAllocator& other);
class Page;
typedef void (*Destructor)(void* addr);
struct DestructorNode {
Destructor dtor;
void* addr;
DestructorNode* next = nullptr;
};
void* allocImpl(size_t size);
void addToDestructionList(Destructor, void* addr);
void runDestructorFor(void* addr);
Page* newPage(size_t pageSize);
bool fitsInCurrentPage(size_t size);
void ensureNext(size_t size);
void* start(Page *p);
void* end(Page* p);
size_t mPageSize;
size_t mMaxAllocSize;
void* mNext;
Page* mCurrentPage;
Page* mPages;
DestructorNode* mDtorList = nullptr;
// Memory usage tracking
size_t mTotalAllocated;
size_t mWastedSpace;
size_t mPageCount;
size_t mDedicatedPageCount;
};
template <class T>
class LinearStdAllocator {
public:
typedef T value_type; // needed to implement std::allocator
typedef T* pointer; // needed to implement std::allocator
LinearStdAllocator(LinearAllocator& allocator)
: linearAllocator(allocator) {}
LinearStdAllocator(const LinearStdAllocator& other)
: linearAllocator(other.linearAllocator) {}
~LinearStdAllocator() {}
// rebind marks that allocators can be rebound to different types
template <class U>
struct rebind {
typedef LinearStdAllocator<U> other;
};
// enable allocators to be constructed from other templated types
template <class U>
LinearStdAllocator(const LinearStdAllocator<U>& other)
: linearAllocator(other.linearAllocator) {}
T* allocate(size_t num, const void* = 0) {
return (T*)(linearAllocator.alloc<void*>(num * sizeof(T)));
}
void deallocate(pointer p, size_t num) {
// attempt to rewind, but no guarantees
linearAllocator.rewindIfLastAlloc(p, num * sizeof(T));
}
// public so template copy constructor can access
LinearAllocator& linearAllocator;
};
// return that all specializations of LinearStdAllocator are interchangeable
template <class T1, class T2>
bool operator== (const LinearStdAllocator<T1>&, const LinearStdAllocator<T2>&) { return true; }
template <class T1, class T2>
bool operator!= (const LinearStdAllocator<T1>&, const LinearStdAllocator<T2>&) { return false; }
template <class T>
class LsaVector : public std::vector<T, LinearStdAllocator<T>> {
public:
LsaVector(const LinearStdAllocator<T>& allocator)
: std::vector<T, LinearStdAllocator<T>>(allocator) {}
};
}; // namespace uirenderer
}; // namespace android
#endif // ANDROID_LINEARALLOCATOR_H
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