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167 lines
4.3 KiB
C++
167 lines
4.3 KiB
C++
#pragma once
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#include <Common/Arena.h>
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#include <Common/Allocator.h>
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namespace DB
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{
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/// Allocator which proxies all allocations to Arena. Used in aggregate functions.
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class ArenaAllocator
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{
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public:
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static void * alloc(size_t size, Arena * arena)
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{
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return arena->alloc(size);
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}
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static void * realloc(void * buf, size_t old_size, size_t new_size, Arena * arena)
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{
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char const * data = reinterpret_cast<char *>(buf);
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// Invariant should be maintained: new_size > old_size
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if (data + old_size == arena->head->pos)
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{
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// Consecutive optimization
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arena->allocContinue(new_size - old_size, data);
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return reinterpret_cast<void *>(const_cast<char *>(data));
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}
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else
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{
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return arena->realloc(data, old_size, new_size);
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}
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}
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static void free(void * /*buf*/, size_t /*size*/)
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{
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// Do nothing, trash in arena remains.
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}
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protected:
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static constexpr size_t getStackThreshold()
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{
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return 0;
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}
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};
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/// Allocates in Arena with proper alignment.
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template <size_t alignment>
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class AlignedArenaAllocator
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{
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public:
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static void * alloc(size_t size, Arena * arena)
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{
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return arena->alignedAlloc(size, alignment);
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}
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static void * realloc(void * buf, size_t old_size, size_t new_size, Arena * arena)
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{
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char const * data = reinterpret_cast<char *>(buf);
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if (data + old_size == arena->head->pos)
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{
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arena->allocContinue(new_size - old_size, data, alignment);
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return reinterpret_cast<void *>(const_cast<char *>(data));
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}
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else
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{
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return arena->alignedRealloc(data, old_size, new_size, alignment);
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}
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}
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static void free(void * /*buf*/, size_t /*size*/)
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{
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}
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protected:
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static constexpr size_t getStackThreshold()
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{
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return 0;
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}
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};
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/// Switches to ordinary Allocator after REAL_ALLOCATION_TRESHOLD bytes to avoid fragmentation and trash in Arena.
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template <size_t REAL_ALLOCATION_TRESHOLD = 4096, typename TRealAllocator = Allocator<false>, typename TArenaAllocator = ArenaAllocator, size_t alignment = 0>
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class MixedArenaAllocator : private TRealAllocator
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{
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public:
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void * alloc(size_t size, Arena * arena)
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{
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return (size < REAL_ALLOCATION_TRESHOLD) ? TArenaAllocator::alloc(size, arena) : TRealAllocator::alloc(size, alignment);
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}
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void * realloc(void * buf, size_t old_size, size_t new_size, Arena * arena)
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{
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// Invariant should be maintained: new_size > old_size
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if (new_size < REAL_ALLOCATION_TRESHOLD)
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return TArenaAllocator::realloc(buf, old_size, new_size, arena);
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if (old_size >= REAL_ALLOCATION_TRESHOLD)
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return TRealAllocator::realloc(buf, old_size, new_size, alignment);
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void * new_buf = TRealAllocator::alloc(new_size, alignment);
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memcpy(new_buf, buf, old_size);
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return new_buf;
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}
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void free(void * buf, size_t size)
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{
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if (size >= REAL_ALLOCATION_TRESHOLD)
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TRealAllocator::free(buf, size);
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}
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protected:
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static constexpr size_t getStackThreshold()
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{
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return 0;
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}
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};
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template <size_t alignment, size_t REAL_ALLOCATION_TRESHOLD = 4096>
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using MixedAlignedArenaAllocator = MixedArenaAllocator<REAL_ALLOCATION_TRESHOLD, Allocator<false>, AlignedArenaAllocator<alignment>, alignment>;
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template <size_t N = 64, typename Base = ArenaAllocator>
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class ArenaAllocatorWithStackMemory : public Base
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{
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char stack_memory[N];
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public:
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void * alloc(size_t size, Arena * arena)
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{
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return (size > N) ? Base::alloc(size, arena) : stack_memory;
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}
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void * realloc(void * buf, size_t old_size, size_t new_size, Arena * arena)
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{
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/// Was in stack_memory, will remain there.
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if (new_size <= N)
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return buf;
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/// Already was big enough to not fit in stack_memory.
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if (old_size > N)
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return Base::realloc(buf, old_size, new_size, arena);
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/// Was in stack memory, but now will not fit there.
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void * new_buf = Base::alloc(new_size, arena);
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memcpy(new_buf, buf, old_size);
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return new_buf;
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}
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void free(void * /*buf*/, size_t /*size*/) {}
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protected:
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static constexpr size_t getStackThreshold()
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{
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return N;
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}
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};
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}
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