/**
* Put a struct mem back on the heap
*
* @param rmem is the data portion of a struct mem as returned by a previous
* call to mem_malloc()
*/
void
mem_free(void *rmem)
{
struct mem *mem;
LWIP_MEM_FREE_DECL_PROTECT();
if (rmem == NULL) {
LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("mem_free(p == NULL) was called.\n"));
return;
}
LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
(u8_t *)rmem < (u8_t *)ram_end);
if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
SYS_ARCH_DECL_PROTECT(lev);
LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_free: illegal memory\n"));
/* protect mem stats from concurrent access */
SYS_ARCH_PROTECT(lev);
MEM_STATS_INC(illegal);
SYS_ARCH_UNPROTECT(lev);
return;
}
/* protect the heap from concurrent access */
LWIP_MEM_FREE_PROTECT();
/* Get the corresponding struct mem ... */
mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
/* ... which has to be in a used state ... */
LWIP_ASSERT("mem_free: mem->used", mem->used);
/* ... and is now unused. */
mem->used = 0;
if (mem < lfree) {
/* the newly freed struct is now the lowest */
lfree = mem;
}
MEM_STATS_DEC_USED(used, mem->next - (mem_size_t)(((u8_t *)mem - ram)));
/* finally, see if prev or next are free also */
plug_holes(mem);
#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
mem_free_count = 1;
#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
LWIP_MEM_FREE_UNPROTECT();
}
/**
* Shrink memory returned by mem_malloc().
*
* @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
* @param newsize required size after shrinking (needs to be smaller than or
* equal to the previous size)
* @return for compatibility reasons: is always == rmem, at the moment
* or NULL if newsize is > old size, in which case rmem is NOT touched
* or freed!
*/
void *
mem_trim(void *rmem, mem_size_t newsize)
{
mem_size_t size;
mem_size_t ptr, ptr2;
struct mem *mem, *mem2;
/* use the FREE_PROTECT here: it protects with sem OR SYS_ARCH_PROTECT */
LWIP_MEM_FREE_DECL_PROTECT();
/* Expand the size of the allocated memory region so that we can
adjust for alignment. */
newsize = LWIP_MEM_ALIGN_SIZE(newsize);
if(newsize < MIN_SIZE_ALIGNED) {
/* every data block must be at least MIN_SIZE_ALIGNED long */
newsize = MIN_SIZE_ALIGNED;
}
if (newsize > MEM_SIZE_ALIGNED) {
return NULL;
}
LWIP_ASSERT("mem_trim: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
(u8_t *)rmem < (u8_t *)ram_end);
if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
SYS_ARCH_DECL_PROTECT(lev);
LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SEVERE, ("mem_trim: illegal memory\n"));
/* protect mem stats from concurrent access */
SYS_ARCH_PROTECT(lev);
MEM_STATS_INC(illegal);
SYS_ARCH_UNPROTECT(lev);
return rmem;
}
/* Get the corresponding struct mem ... */
mem = (struct mem *)(void *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
/* ... and its offset pointer */
ptr = (mem_size_t)((u8_t *)mem - ram);
size = mem->next - ptr - SIZEOF_STRUCT_MEM;
LWIP_ASSERT("mem_trim can only shrink memory", newsize <= size);
if (newsize > size) {
/* not supported */
return NULL;
}
if (newsize == size) {
/* No change in size, simply return */
return rmem;
}
/* protect the heap from concurrent access */
LWIP_MEM_FREE_PROTECT();
mem2 = (struct mem *)(void *)&ram[mem->next];
if(mem2->used == 0) {
/* The next struct is unused, we can simply move it at little */
mem_size_t next;
/* remember the old next pointer */
next = mem2->next;
/* create new struct mem which is moved directly after the shrinked mem */
ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
if (lfree == mem2) {
lfree = (struct mem *)(void *)&ram[ptr2];
}
mem2 = (struct mem *)(void *)&ram[ptr2];
mem2->used = 0;
/* restore the next pointer */
mem2->next = next;
/* link it back to mem */
mem2->prev = ptr;
/* link mem to it */
mem->next = ptr2;
/* last thing to restore linked list: as we have moved mem2,
* let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
* the end of the heap */
if (mem2->next != MEM_SIZE_ALIGNED) {
((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
}
MEM_STATS_DEC_USED(used, (size - newsize));
/* no need to plug holes, we've already done that */
} else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
/* Next struct is used but there's room for another struct mem with
* at least MIN_SIZE_ALIGNED of data.
* Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
* ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
* @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
* region that couldn't hold data, but when mem->next gets freed,
* the 2 regions would be combined, resulting in more free memory */
ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
mem2 = (struct mem *)(void *)&ram[ptr2];
if (mem2 < lfree) {
lfree = mem2;
}
mem2->used = 0;
mem2->next = mem->next;
mem2->prev = ptr;
mem->next = ptr2;
if (mem2->next != MEM_SIZE_ALIGNED) {
((struct mem *)(void *)&ram[mem2->next])->prev = ptr2;
}
MEM_STATS_DEC_USED(used, (size - newsize));
/* the original mem->next is used, so no need to plug holes! */
}
/* else {
next struct mem is used but size between mem and mem2 is not big enough
to create another struct mem
-> don't do anyhting.
-> the remaining space stays unused since it is too small
} */
#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT
mem_free_count = 1;
#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */
LWIP_MEM_FREE_UNPROTECT();
return rmem;
}