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/*
* libc/stdlib/malloc/malloc.h -- small malloc implementation
*
* Copyright (C) 2002 NEC Corporation
* Copyright (C) 2002 Miles Bader <miles@gnu.org>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License. See the file COPYING.LIB in the main
* directory of this archive for more details.
*
* Written by Miles Bader <miles@gnu.org>
*/
/* The alignment we guarantee for malloc return values. */
#define MALLOC_ALIGNMENT (sizeof (double))
/* The system pagesize we assume; we really ought to get it with
getpagesize, but gee, how annoying. */
#define MALLOC_PAGE_SIZE 4096
/* The minimum size of block we request from the the system to extend the
heap for small allocations (we may request a bigger block if necessary to
satisfy a particularly big request). */
#define MALLOC_HEAP_EXTEND_SIZE MALLOC_PAGE_SIZE
/* When a heap free-area grows above this size, try to unmap it, releasing
the memory back to the system. */
#define MALLOC_UNMAP_THRESHOLD (8*MALLOC_PAGE_SIZE)
/* When unmapping a free-area, retain this many bytes if it's the only one,
to avoid completely emptying the heap. This is only a heuristic -- the
existance of another free area, even if it's smaller than
MALLOC_MIN_SIZE, will cause us not to reserve anything. */
#define MALLOC_MIN_SIZE (2*MALLOC_PAGE_SIZE)
/* For systems with an MMU, use sbrk to map/unmap memory for the malloc
heap, instead of mmap/munmap. This is a tradeoff -- sbrk is faster than
mmap/munmap, and guarantees contiguous allocation, but is also less
flexible, and causes the heap to only be shrinkable from the end. */
#ifdef __UCLIBC_HAS_MMU__
# define MALLOC_USE_SBRK
#endif
/* The size of a malloc allocation is stored in a size_t word
MALLOC_ALIGNMENT bytes prior to the start address of the allocation:
+--------+---------+-------------------+
| SIZE |(unused) | allocation ... |
+--------+---------+-------------------+
^ BASE ^ ADDR
^ ADDR - MALLOC_ALIGN
*/
/* The amount of extra space used by the malloc header. */
#define MALLOC_HEADER_SIZE MALLOC_ALIGNMENT
/* Return base-address of a malloc allocation, given the user address. */
#define MALLOC_BASE(addr) ((void *)((char *)addr - MALLOC_HEADER_SIZE))
/* Return the size of a malloc allocation, given the user address. */
#define MALLOC_SIZE(addr) (*(size_t *)MALLOC_BASE(addr))
/* Sets the size of a malloc allocation, given the user address. */
#define MALLOC_SET_SIZE(addr, size) (*(size_t *)MALLOC_BASE(addr) = (size))
/* Return the user address of a malloc allocation, given the base address. */
#define MALLOC_ADDR(base) ((void *)((char *)base + MALLOC_HEADER_SIZE))
/* Locking for multithreaded apps. */
#ifdef __UCLIBC_HAS_THREADS__
# include <pthread.h>
# define MALLOC_USE_LOCKING
typedef pthread_mutex_t malloc_mutex_t;
# define MALLOC_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
/* The main malloc lock. This must be hold while accessing __malloc_heap,
and in order to gain __malloc_sbrk_lock. */
extern malloc_mutex_t __malloc_lock;
# define __malloc_lock() pthread_mutex_lock (&__malloc_lock)
# define __malloc_unlock() pthread_mutex_unlock (&__malloc_lock)
# ifdef MALLOC_USE_SBRK
/* This lock is used to serialize uses of the `sbrk' function (in both
malloc and free, sbrk may be used several times in succession, and
things will break if these multiple calls are interleaved with another
thread's use of sbrk!). */
extern malloc_mutex_t __malloc_sbrk_lock;
# define __malloc_lock_sbrk() pthread_mutex_lock (&__malloc_sbrk_lock)
# define __malloc_unlock_sbrk() pthread_mutex_unlock (&__malloc_sbrk_lock)
# endif /* MALLOC_USE_SBRK */
#else /* !__UCLIBC_HAS_THREADS__ */
/* Without threads, mutex operations are a nop. */
# define __malloc_lock() (void)0
# define __malloc_unlock() (void)0
# define __malloc_lock_sbrk() (void)0
# define __malloc_unlock_sbrk() (void)0
#endif /* __UCLIBC_HAS_THREADS__ */
/* Change this to `#if 1' to cause malloc to emit debugging info to stderr. */
#if 0
#include <stdio.h>
#define MALLOC_DEBUG(fmt, args...) fprintf (stderr, fmt , ##args)
#else
#define MALLOC_DEBUG(fmt, args...) (void)0
#endif
/* Return SZ rounded down to POWER_OF_2_SIZE (which must be power of 2). */
#define MALLOC_ROUND_DOWN(sz, power_of_2_size) \
((sz) & ~(power_of_2_size - 1))
/* Return SZ rounded to POWER_OF_2_SIZE (which must be power of 2). */
#define MALLOC_ROUND_UP(sz, power_of_2_size) \
MALLOC_ROUND_DOWN ((sz) + (power_of_2_size - 1), (power_of_2_size))
/* Return SZ rounded down to a multiple MALLOC_PAGE_SIZE. */
#define MALLOC_ROUND_DOWN_TO_PAGE_SIZE(sz) \
MALLOC_ROUND_DOWN (sz, MALLOC_PAGE_SIZE)
/* Return SZ rounded up to a multiple MALLOC_PAGE_SIZE. */
#define MALLOC_ROUND_UP_TO_PAGE_SIZE(sz) \
MALLOC_ROUND_UP (sz, MALLOC_PAGE_SIZE)
/* The malloc heap. */
extern struct heap __malloc_heap;
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