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/*
* This file is from CPython's Modules/_ctypes/malloc_closure.c
* and has received some edits.
*/
#include <ffi.h>
#ifdef MS_WIN32
#include <windows.h>
#else
#include <sys/mman.h>
#include <unistd.h>
# if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
# define MAP_ANONYMOUS MAP_ANON
# endif
#endif
/* 'allocate_num_pages' is dynamically adjusted starting from one
page. It grows by a factor of PAGE_ALLOCATION_GROWTH_RATE. This is
meant to handle both the common case of not needing a lot of pages,
and the rare case of needing many of them. Systems in general have a
limit of how many mmap'd blocks can be open.
*/
#define PAGE_ALLOCATION_GROWTH_RATE 1.3
static Py_ssize_t allocate_num_pages = 0;
/* #define MALLOC_CLOSURE_DEBUG */ /* enable for some debugging output */
/******************************************************************/
union mmaped_block {
ffi_closure closure;
union mmaped_block *next;
};
static union mmaped_block *free_list = 0;
static Py_ssize_t _pagesize = 0;
static void more_core(void)
{
union mmaped_block *item;
Py_ssize_t count, i;
/* determine the pagesize */
#ifdef MS_WIN32
if (!_pagesize) {
SYSTEM_INFO systeminfo;
GetSystemInfo(&systeminfo);
_pagesize = systeminfo.dwPageSize;
}
#else
if (!_pagesize) {
#ifdef _SC_PAGESIZE
_pagesize = sysconf(_SC_PAGESIZE);
#else
_pagesize = getpagesize();
#endif
}
#endif
if (_pagesize <= 0)
_pagesize = 4096;
/* bump 'allocate_num_pages' */
allocate_num_pages = 1 + (
(Py_ssize_t)(allocate_num_pages * PAGE_ALLOCATION_GROWTH_RATE));
/* calculate the number of mmaped_blocks to allocate */
count = (allocate_num_pages * _pagesize) / sizeof(union mmaped_block);
/* allocate a memory block */
#ifdef MS_WIN32
item = (union mmaped_block *)VirtualAlloc(NULL,
count * sizeof(union mmaped_block),
MEM_COMMIT,
PAGE_EXECUTE_READWRITE);
if (item == NULL)
return;
#else
item = (union mmaped_block *)mmap(NULL,
allocate_num_pages * _pagesize,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS,
-1,
0);
if (item == (void *)MAP_FAILED)
return;
#endif
#ifdef MALLOC_CLOSURE_DEBUG
printf("block at %p allocated (%ld bytes), %ld mmaped_blocks\n",
item, (long)(allocate_num_pages * _pagesize), (long)count);
#endif
/* put them into the free list */
for (i = 0; i < count; ++i) {
item->next = free_list;
free_list = item;
++item;
}
}
/******************************************************************/
/* put the item back into the free list */
static void cffi_closure_free(ffi_closure *p)
{
union mmaped_block *item = (union mmaped_block *)p;
item->next = free_list;
free_list = item;
}
/* return one item from the free list, allocating more if needed */
static ffi_closure *cffi_closure_alloc(void)
{
union mmaped_block *item;
if (!free_list)
more_core();
if (!free_list)
return NULL;
item = free_list;
free_list = item->next;
return &item->closure;
}
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