aligned_alloc
https://en.cppreference.com/w/c/memory/aligned_alloc
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| #include <cstdlib>
double *aligned_ptr = static_cast<double *>(std::aligned_alloc(256, 4096 * sizeof(double)));
free(aligned_ptr)
|
vector+自定义allocator
自定义可设置AlignSize的allocator，很奇怪，deallocator里用delete[] 会报free() invalid pointer的错，无奈之下用malloc和free了。
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| #include <vector>
#include <cstdio>
#include <cstdlib>
#include <iostream>
template <typename T, size_t AlignSize>
class AlignedAllocator
{
private:
void *adjust(void *p)
{
return reinterpret_cast<void *>((reinterpret_cast<size_t>(p) + sizeof(T *)) | (AlignSize - 1) + 1);
}
public:
using value_type = T;
template <typename U>
struct rebind
{
using other = AlignedAllocator<U, AlignSize>;
};
T *allocate(size_t n)
{
const size_t allocateSize = n * sizeof(T) + AlignSize + sizeof(T *);
__u_char *rawPtr = reinterpret_cast<__u_char *>(malloc(allocateSize));
T *alignedPtr = reinterpret_cast<T *>(adjust(rawPtr));
reinterpret_cast<T **>(alignedPtr)[-1] = reinterpret_cast<T *>(rawPtr);
return alignedPtr;
}
void deallocate(T *p)
{
free(reinterpret_cast<T **>(p)[-1]);
}
void deallocate(T *p, size_t n)
{
free(reinterpret_cast<T **>(p)[-1]);
}
void construct(T *p, const T &val)
{
new (p) T(val);
}
void destroy(T *p)
{
p->~T();
}
};
class Test
{
public:
Test()
{
std::cout << "Test construct.\n";
}
Test(const Test &other)
{
std::cout << "Test copy construct.\n";
}
~Test()
{
std::cout << "Test destroy.\n";
}
};
template <typename T, size_t AlignSize>
using AlignedVector = std::vector<T, AlignedAllocator<T, AlignSize>>;
int main(int argc, char *argv[])
{
constexpr size_t CacheLineSizeByte = 128;
AlignedVector<Test, CacheLineSizeByte> testVector(10);
return 0;
}
|