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📄 dlmalloc-2.6.6.c

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      All together, these considerations should lead you to use mmap
      only for relatively large requests.  


*/



#ifndef DEFAULT_MMAP_MAX
#if HAVE_MMAP
#define DEFAULT_MMAP_MAX       (64)
#else
#define DEFAULT_MMAP_MAX       (0)
#endif
#endif

/*
    M_MMAP_MAX is the maximum number of requests to simultaneously 
      service using mmap. This parameter exists because:

         1. Some systems have a limited number of internal tables for
            use by mmap.
         2. In most systems, overreliance on mmap can degrade overall
            performance.
         3. If a program allocates many large regions, it is probably
            better off using normal sbrk-based allocation routines that
            can reclaim and reallocate normal heap memory. Using a
            small value allows transition into this mode after the
            first few allocations.

      Setting to 0 disables all use of mmap.  If HAVE_MMAP is not set,
      the default value is 0, and attempts to set it to non-zero values
      in mallopt will fail.
*/




/* 
    USE_DL_PREFIX will prefix all public routines with the string 'dl'.
      Useful to quickly avoid procedure declaration conflicts and linker
      symbol conflicts with existing memory allocation routines.

*/

/* #define USE_DL_PREFIX */




/* 

  Special defines for linux libc

  Except when compiled using these special defines for Linux libc
  using weak aliases, this malloc is NOT designed to work in
  multithreaded applications.  No semaphores or other concurrency
  control are provided to ensure that multiple malloc or free calls
  don't run at the same time, which could be disasterous. A single
  semaphore could be used across malloc, realloc, and free (which is
  essentially the effect of the linux weak alias approach). It would
  be hard to obtain finer granularity.

*/


#ifdef INTERNAL_LINUX_C_LIB

#if __STD_C

Void_t * __default_morecore_init (ptrdiff_t);
Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init;

#else

Void_t * __default_morecore_init ();
Void_t *(*__morecore)() = __default_morecore_init;

#endif

#define MORECORE (*__morecore)
#define MORECORE_FAILURE 0
#define MORECORE_CLEARS 1 

#else /* INTERNAL_LINUX_C_LIB */

#if __STD_C
extern Void_t*     sbrk(ptrdiff_t);
#else
extern Void_t*     sbrk();
#endif

#ifndef MORECORE
#define MORECORE sbrk
#endif

#ifndef MORECORE_FAILURE
#define MORECORE_FAILURE -1
#endif

#ifndef MORECORE_CLEARS
#define MORECORE_CLEARS 1
#endif

#endif /* INTERNAL_LINUX_C_LIB */

#if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__)

#define cALLOc		__libc_calloc
#define fREe		__libc_free
#define mALLOc		__libc_malloc
#define mEMALIGn	__libc_memalign
#define rEALLOc		__libc_realloc
#define vALLOc		__libc_valloc
#define pvALLOc		__libc_pvalloc
#define mALLINFo	__libc_mallinfo
#define mALLOPt		__libc_mallopt

#pragma weak calloc = __libc_calloc
#pragma weak free = __libc_free
#pragma weak cfree = __libc_free
#pragma weak malloc = __libc_malloc
#pragma weak memalign = __libc_memalign
#pragma weak realloc = __libc_realloc
#pragma weak valloc = __libc_valloc
#pragma weak pvalloc = __libc_pvalloc
#pragma weak mallinfo = __libc_mallinfo
#pragma weak mallopt = __libc_mallopt

#else

#ifdef USE_DL_PREFIX
#define cALLOc		dlcalloc
#define fREe		dlfree
#define mALLOc		dlmalloc
#define mEMALIGn	dlmemalign
#define rEALLOc		dlrealloc
#define vALLOc		dlvalloc
#define pvALLOc		dlpvalloc
#define mALLINFo	dlmallinfo
#define mALLOPt		dlmallopt
#else /* USE_DL_PREFIX */
#define cALLOc		calloc
#define fREe		free
#define mALLOc		malloc
#define mEMALIGn	memalign
#define rEALLOc		realloc
#define vALLOc		valloc
#define pvALLOc		pvalloc
#define mALLINFo	mallinfo
#define mALLOPt		mallopt
#endif /* USE_DL_PREFIX */

#endif

/* Public routines */

#if __STD_C

Void_t* mALLOc(size_t);
void    fREe(Void_t*);
Void_t* rEALLOc(Void_t*, size_t);
Void_t* mEMALIGn(size_t, size_t);
Void_t* vALLOc(size_t);
Void_t* pvALLOc(size_t);
Void_t* cALLOc(size_t, size_t);
void    cfree(Void_t*);
int     malloc_trim(size_t);
size_t  malloc_usable_size(Void_t*);
void    malloc_stats();
int     mALLOPt(int, int);
struct mallinfo mALLINFo(void);
#else
Void_t* mALLOc();
void    fREe();
Void_t* rEALLOc();
Void_t* mEMALIGn();
Void_t* vALLOc();
Void_t* pvALLOc();
Void_t* cALLOc();
void    cfree();
int     malloc_trim();
size_t  malloc_usable_size();
void    malloc_stats();
int     mALLOPt();
struct mallinfo mALLINFo();
#endif


#ifdef __cplusplus
};  /* end of extern "C" */
#endif

/* ---------- To make a malloc.h, end cutting here ------------ */


/* 
  Emulation of sbrk for WIN32
  All code within the ifdef WIN32 is untested by me.

  Thanks to Martin Fong and others for supplying this.
*/


#ifdef WIN32

#define AlignPage(add) (((add) + (malloc_getpagesize-1)) & \~(malloc_getpagesize-1))
#define AlignPage64K(add) (((add) + (0x10000 - 1)) & ~(0x10000 - 1))

/* resrve 64MB to insure large contiguous space */ 
#define RESERVED_SIZE (1024*1024*64)
#define NEXT_SIZE (2048*1024)
#define TOP_MEMORY ((unsigned long)2*1024*1024*1024)

struct GmListElement;
typedef struct GmListElement GmListElement;

struct GmListElement 
{
	GmListElement* next;
	void* base;
};

static GmListElement* head = 0;
static unsigned int gNextAddress = 0;
static unsigned int gAddressBase = 0;
static unsigned int gAllocatedSize = 0;

static
GmListElement* makeGmListElement (void* bas)
{
	GmListElement* this;
	this = (GmListElement*)(void*)LocalAlloc (0, sizeof (GmListElement));
	assert (this);
	if (this)
	{
		this->base = bas;
		this->next = head;
		head = this;
	}
	return this;
}

void gcleanup ()
{
	BOOL rval;
	assert ( (head == NULL) || (head->base == (void*)gAddressBase));
	if (gAddressBase && (gNextAddress - gAddressBase))
	{
		rval = VirtualFree ((void*)gAddressBase, 
							gNextAddress - gAddressBase, 
							MEM_DECOMMIT);
        assert (rval);
	}
	while (head)
	{
		GmListElement* next = head->next;
		rval = VirtualFree (head->base, 0, MEM_RELEASE);
		assert (rval);
		LocalFree (head);
		head = next;
	}
}
		
static
void* findRegion (void* start_address, unsigned long size)
{
	MEMORY_BASIC_INFORMATION info;
	if (size >= TOP_MEMORY) return NULL;

	while ((unsigned long)start_address + size < TOP_MEMORY)
	{
		VirtualQuery (start_address, &info, sizeof (info));
		if ((info.State == MEM_FREE) && (info.RegionSize >= size))
			return start_address;
		else
		{
			// Requested region is not available so see if the
			// next region is available.  Set 'start_address'
			// to the next region and call 'VirtualQuery()'
			// again.

			start_address = (char*)info.BaseAddress + info.RegionSize; 

			// Make sure we start looking for the next region
			// on the *next* 64K boundary.  Otherwise, even if
			// the new region is free according to
			// 'VirtualQuery()', the subsequent call to
			// 'VirtualAlloc()' (which follows the call to
			// this routine in 'wsbrk()') will round *down*
			// the requested address to a 64K boundary which
			// we already know is an address in the
			// unavailable region.  Thus, the subsequent call
			// to 'VirtualAlloc()' will fail and bring us back
			// here, causing us to go into an infinite loop.

			start_address =
				(void *) AlignPage64K((unsigned long) start_address);
		}
	}
	return NULL;
	
}


void* wsbrk (long size)
{
	void* tmp;
	if (size > 0)
	{
		if (gAddressBase == 0)
		{
			gAllocatedSize = max (RESERVED_SIZE, AlignPage (size));
			gNextAddress = gAddressBase = 
				(unsigned int)VirtualAlloc (NULL, gAllocatedSize, 
											MEM_RESERVE, PAGE_NOACCESS);
		} else if (AlignPage (gNextAddress + size) > (gAddressBase +
gAllocatedSize))
		{
			long new_size = max (NEXT_SIZE, AlignPage (size));
			void* new_address = (void*)(gAddressBase+gAllocatedSize);
			do 
			{
				new_address = findRegion (new_address, new_size);
				
				if (new_address == 0)
					return (void*)-1;

				gAddressBase = gNextAddress =
					(unsigned int)VirtualAlloc (new_address, new_size,
												MEM_RESERVE, PAGE_NOACCESS);
				// repeat in case of race condition
				// The region that we found has been snagged 
				// by another thread
			}
			while (gAddressBase == 0);

			assert (new_address == (void*)gAddressBase);

			gAllocatedSize = new_size;

			if (!makeGmListElement ((void*)gAddressBase))
				return (void*)-1;
		}
		if ((size + gNextAddress) > AlignPage (gNextAddress))
		{
			void* res;
			res = VirtualAlloc ((void*)AlignPage (gNextAddress),
								(size + gNextAddress - 
								 AlignPage (gNextAddress)), 
								MEM_COMMIT, PAGE_READWRITE);
			if (res == 0)
				return (void*)-1;
		}
		tmp = (void*)gNextAddress;
		gNextAddress = (unsigned int)tmp + size;
		return tmp;
	}
	else if (size < 0)
	{
		unsigned int alignedGoal = AlignPage (gNextAddress + size);
		/* Trim by releasing the virtual memory */
		if (alignedGoal >= gAddressBase)
		{
			VirtualFree ((void*)alignedGoal, gNextAddress - alignedGoal,  
						 MEM_DECOMMIT);
			gNextAddress = gNextAddress + size;
			return (void*)gNextAddress;
		}
		else 
		{

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