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#include "allocator.hpp"
#include <string.h>
#include <assert.h>
// Low-level allocation functions
#if defined(_WIN32) || defined(_WIN64)
# ifdef __MWERKS__
# pragma ANSI_strict off // disable ANSI strictness to include windows.h
# pragma cpp_extensions on // enable some extensions to include windows.h
# endif
# if defined(_MSC_VER)
# pragma warning(disable: 4201) // nonstandard extension used: nameless struct/union
# endif
# ifdef _XBOX_VER
# define NOD3D
# include <xtl.h>
# else
# include <windows.h>
# endif
namespace
{
const size_t page_size = 4096;
size_t align_to_page(size_t value)
{
return (value + page_size - 1) & ~(page_size - 1);
}
void* allocate_page_aligned(size_t size)
{
// We can't use VirtualAlloc because it has 64Kb granularity so we run out of address space quickly
// We can't use malloc because of occasional problems with CW on CRT termination
static HANDLE heap = HeapCreate(0, 0, 0);
void* result = HeapAlloc(heap, 0, size + page_size);
return reinterpret_cast<void*>(align_to_page(reinterpret_cast<size_t>(result)));
}
void* allocate(size_t size)
{
size_t aligned_size = align_to_page(size);
void* ptr = allocate_page_aligned(aligned_size + page_size);
if (!ptr) return 0;
char* end = static_cast<char*>(ptr) + aligned_size;
DWORD old_flags;
VirtualProtect(end, page_size, PAGE_NOACCESS, &old_flags);
return end - size;
}
void deallocate(void* ptr, size_t size)
{
size_t aligned_size = align_to_page(size);
void* rptr = static_cast<char*>(ptr) + size - aligned_size;
DWORD old_flags;
VirtualProtect(rptr, aligned_size + page_size, PAGE_NOACCESS, &old_flags);
}
}
#elif defined(__APPLE__) || defined(__linux__)
# include <sys/mman.h>
namespace
{
const size_t page_size = 4096;
size_t align_to_page(size_t value)
{
return (value + page_size - 1) & ~(page_size - 1);
}
void* allocate_page_aligned(size_t size)
{
return mmap(0, size + page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
}
void* allocate(size_t size)
{
size_t aligned_size = align_to_page(size);
void* ptr = allocate_page_aligned(aligned_size + page_size);
if (!ptr) return 0;
char* end = static_cast<char*>(ptr) + aligned_size;
int res = mprotect(end, page_size, PROT_NONE);
assert(res == 0);
(void)!res;
return end - size;
}
void deallocate(void* ptr, size_t size)
{
size_t aligned_size = align_to_page(size);
void* rptr = static_cast<char*>(ptr) + size - aligned_size;
int res = mprotect(rptr, aligned_size + page_size, PROT_NONE);
assert(res == 0);
(void)!res;
}
}
#else
# include <stdlib.h>
namespace
{
void* allocate(size_t size)
{
return malloc(size);
}
void deallocate(void* ptr, size_t size)
{
(void)size;
free(ptr);
}
}
#endif
// High-level allocation functions
void* memory_allocate(size_t size)
{
void* result = allocate(size + sizeof(size_t));
if (!result) return 0;
memcpy(result, &size, sizeof(size_t));
return static_cast<size_t*>(result) + 1;
}
size_t memory_size(void* ptr)
{
assert(ptr);
size_t result;
memcpy(&result, static_cast<size_t*>(ptr) - 1, sizeof(size_t));
return result;
}
void memory_deallocate(void* ptr)
{
if (!ptr) return;
size_t size = memory_size(ptr);
deallocate(static_cast<size_t*>(ptr) - 1, size + sizeof(size_t));
}
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