mirror of
https://github.com/lwip-tcpip/lwip.git
synced 2024-10-05 22:29:49 +00:00
- Changed mem_malloc(): near fit behaves like exact fit since mem->next is always used
- Included some more alignment statements - Every malloced block is at least MIN_SIZE big (can be overridden, can be used to work against fragmentation) - Added many comments so that the next developer knows what I was thinking :-)
This commit is contained in:
parent
9cf1390dc6
commit
6f4056cf99
227
src/core/mem.c
227
src/core/mem.c
@ -50,44 +50,38 @@
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#if (MEM_LIBC_MALLOC == 0)
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/* lwIP replacement for your libc malloc() */
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/* This does not have to be aligned since for getting its size,
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* we only use the macro SIZEOF_STRUCT_MEM, which automatically alignes.
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*/
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struct mem {
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mem_size_t next, prev;
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#if MEM_ALIGNMENT == 1
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mem_size_t next;
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mem_size_t prev;
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u8_t used;
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#elif MEM_ALIGNMENT == 2
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u16_t used;
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#elif MEM_ALIGNMENT == 4
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u32_t used;
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#elif MEM_ALIGNMENT == 8
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u64_t used;
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#else
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#error "unhandled MEM_ALIGNMENT size"
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#endif /* MEM_ALIGNMENT */
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};
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/* All allocated blocks will be MIN_SIZE bytes big, at least! */
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#define MIN_SIZE MEM_ALIGN_SIZE(12)
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#define SIZEOF_STRUCT_MEM MEM_ALIGN_SIZE(sizeof(struct mem))
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#define MEM_SIZE_ALIGNED MEM_ALIGN_SIZE(MEM_SIZE)
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static struct mem *ram_end;
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#if 0
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/* Adam original */
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static u8_t ram[MEM_SIZE + (2*sizeof(struct mem) + MEM_ALIGNMENT)];
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#else
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/* Christiaan alignment fix */
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static u8_t *ram;
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static struct mem ram_heap[1 + ( (MEM_SIZE + sizeof(struct mem) - 1) / sizeof(struct mem))];
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#endif
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#define MIN_SIZE 12
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#if 1 /* this one does not align correctly for some, resulting in crashes */
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#define SIZEOF_STRUCT_MEM (unsigned int)MEM_ALIGN_SIZE(sizeof(struct mem))
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#else
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#define SIZEOF_STRUCT_MEM (sizeof(struct mem) + \
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(((sizeof(struct mem) % MEM_ALIGNMENT) == 0)? 0 : \
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(4 - (sizeof(struct mem) % MEM_ALIGNMENT))))
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#endif
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static struct mem *lfree; /* pointer to the lowest free block */
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static sys_sem_t mem_sem;
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/* the heap. we need one struct mem at the end and some room for alignment */
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static u8_t ram_heap[MEM_SIZE_ALIGNED + SIZEOF_STRUCT_MEM + MEM_ALIGNMENT];
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static u8_t *ram; /* for alignment, ram is now a pointer instead of an array */
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static struct mem *lfree; /* pointer to the lowest free block */
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static sys_sem_t mem_sem; /* concurrent access protection */
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/*
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* "Plug holes" by combining adjacent empty struct mems.
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* After this function is through, there should not exist
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* one empty struct mem pointing to another empty struct mem.
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*
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* @param mem this points to a struct mem which just has been freed
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* @internal this function is only called by mem_free() and mem_realloc()
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*
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* This assumes access to the heap is protected by the calling function
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* already.
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*/
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static void
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plug_holes(struct mem *mem)
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{
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@ -99,10 +93,11 @@ plug_holes(struct mem *mem)
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LWIP_ASSERT("plug_holes: mem->used == 0", mem->used == 0);
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/* plug hole forward */
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LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE", mem->next <= MEM_SIZE);
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LWIP_ASSERT("plug_holes: mem->next <= MEM_SIZE_ALIGNED", mem->next <= MEM_SIZE_ALIGNED);
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nmem = (struct mem *)&ram[mem->next];
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if (mem != nmem && nmem->used == 0 && (u8_t *)nmem != (u8_t *)ram_end) {
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/* if mem->next is unused and not end of ram, combine mem and mem->next */
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if (lfree == nmem) {
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lfree = mem;
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}
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@ -113,6 +108,7 @@ plug_holes(struct mem *mem)
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/* plug hole backward */
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pmem = (struct mem *)&ram[mem->prev];
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if (pmem != mem && pmem->used == 0) {
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/* if mem->prev is unused, combine mem and mem->prev */
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if (lfree == mem) {
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lfree = pmem;
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}
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@ -121,38 +117,45 @@ plug_holes(struct mem *mem)
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}
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}
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/*
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* Zero the heap and initialize start, end and lowest-free
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*/
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void
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mem_init(void)
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{
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struct mem *mem;
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LWIP_ASSERT("Sanity check alignment", (SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
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LWIP_ASSERT("Sanity check alignment",
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(SIZEOF_STRUCT_MEM & (MEM_ALIGNMENT-1)) == 0);
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#if 0
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/* Adam original */
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#else
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/* Christiaan alignment fix */
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ram = (u8_t*)ram_heap;
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#endif
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memset(ram, 0, MEM_SIZE);
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/* align the heap */
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ram = MEM_ALIGN(ram_heap);
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memset(ram, 0, MEM_SIZE_ALIGNED);
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/* initialize the start of the heap */
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mem = (struct mem *)ram;
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mem->next = MEM_SIZE;
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mem->next = MEM_SIZE_ALIGNED;
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mem->prev = 0;
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mem->used = 0;
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ram_end = (struct mem *)&ram[MEM_SIZE];
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/* initialize the end of the heap */
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ram_end = (struct mem *)&ram[MEM_SIZE_ALIGNED];
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ram_end->used = 1;
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ram_end->next = MEM_SIZE;
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ram_end->prev = MEM_SIZE;
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ram_end->next = MEM_SIZE_ALIGNED;
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ram_end->prev = MEM_SIZE_ALIGNED;
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mem_sem = sys_sem_new(1);
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/* initialize the lowest-free pointer to the start of the heap */
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lfree = (struct mem *)ram;
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#if MEM_STATS
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lwip_stats.mem.avail = MEM_SIZE;
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lwip_stats.mem.avail = MEM_SIZE_ALIGNED;
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#endif /* MEM_STATS */
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}
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/* Put a struct mem back on the heap
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* @param rmem is the data portion of a struct mem as returned by a previous
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* call to mem_malloc()
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*/
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void
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mem_free(void *rmem)
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{
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@ -162,8 +165,9 @@ mem_free(void *rmem)
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LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_TRACE | 2, ("mem_free(p == NULL) was called.\n"));
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return;
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}
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LWIP_ASSERT("Sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
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LWIP_ASSERT("mem_free: sanity check alignment", (((mem_ptr_t)rmem) & (MEM_ALIGNMENT-1)) == 0);
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/* protect the heap from concurrent access */
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sys_sem_wait(mem_sem);
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LWIP_ASSERT("mem_free: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
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@ -177,20 +181,23 @@ mem_free(void *rmem)
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sys_sem_signal(mem_sem);
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return;
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}
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/* Get the corresponding struct mem ... */
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mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
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/* ... which has to be in a used state ... */
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LWIP_ASSERT("mem_free: mem->used", mem->used);
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/* ... and is now unused. */
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mem->used = 0;
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if (mem < lfree) {
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/* the newly freed struct is now the lowest */
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lfree = mem;
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}
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#if MEM_STATS
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lwip_stats.mem.used -= mem->next - ((u8_t *)mem - ram);
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#endif /* MEM_STATS */
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/* finally, see if prev or next are free also */
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plug_holes(mem);
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sys_sem_signal(mem_sem);
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}
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@ -208,15 +215,16 @@ mem_realloc(void *rmem, mem_size_t newsize)
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/* Expand the size of the allocated memory region so that we can
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adjust for alignment. */
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if ((newsize % MEM_ALIGNMENT) != 0) {
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newsize += MEM_ALIGNMENT - ((newsize + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT);
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}
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newsize = MEM_ALIGN_SIZE(newsize);
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if (newsize > MEM_SIZE) {
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if (newsize > MEM_SIZE_ALIGNED) {
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return NULL;
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}
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sys_sem_wait(mem_sem);
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if(newsize < MIN_SIZE) {
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/* every data block must be at least MIN_SIZE long */
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newsize = MIN_SIZE;
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}
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LWIP_ASSERT("mem_realloc: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
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(u8_t *)rmem < (u8_t *)ram_end);
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@ -225,29 +233,60 @@ mem_realloc(void *rmem, mem_size_t newsize)
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LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_realloc: illegal memory\n"));
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return rmem;
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}
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/* Get the corresponding struct mem ... */
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mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
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/* ... and its offset pointer */
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ptr = (u8_t *)mem - ram;
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size = mem->next - ptr - SIZEOF_STRUCT_MEM;
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LWIP_ASSERT("mem_realloc can only shrink memory", newsize <= size);
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if (newsize > size) {
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/* not supported */
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return NULL;
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}
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if (newsize == size) {
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/* No change in size, simply return */
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return rmem;
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}
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/* protect the heap from concurrent access */
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sys_sem_wait(mem_sem);
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#if MEM_STATS
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lwip_stats.mem.used -= (size - newsize);
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#endif /* MEM_STATS */
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if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE < size) {
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mem2 = (struct mem *)&ram[mem->next];
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if(mem2->used == 0) {
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/* The next struct is unused, we can simply move it at little */
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mem_size_t next;
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/* remember the old next pointer */
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next = mem2->next;
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ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
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mem2 = (struct mem *)&ram[ptr2];
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mem2->used = 0;
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mem2->next = next;
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mem2->prev = ptr;
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mem->next = ptr2;
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if (mem2->next != MEM_SIZE_ALIGNED) {
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((struct mem *)&ram[mem2->next])->prev = ptr2;
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}
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} else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE < size) {
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/* There's room for another struct mem with at least MIN_SIZE of data. */
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ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
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mem2 = (struct mem *)&ram[ptr2];
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mem2->used = 0;
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mem2->next = mem->next;
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mem2->prev = ptr;
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mem->next = ptr2;
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if (mem2->next != MEM_SIZE) {
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if (mem2->next != MEM_SIZE_ALIGNED) {
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((struct mem *)&ram[mem2->next])->prev = ptr2;
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}
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plug_holes(mem2);
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/* mem->next is used, so no need to plug holes! */
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}
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/* else {
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the remaining space stays unused since it is too small
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} */
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sys_sem_signal(mem_sem);
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return rmem;
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}
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@ -273,13 +312,13 @@ mem_malloc(mem_size_t size)
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size += MEM_ALIGNMENT - ((size + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT);
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}
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if (size > MEM_SIZE) {
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if (size > MEM_SIZE_ALIGNED) {
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return NULL;
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}
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sys_sem_wait(mem_sem);
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for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE; ptr = ((struct mem *)&ram[ptr])->next) {
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for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED; ptr = ((struct mem *)&ram[ptr])->next) {
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mem = (struct mem *)&ram[ptr];
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if (!mem->used &&
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mem->next - (ptr + SIZEOF_STRUCT_MEM) >= size + SIZEOF_STRUCT_MEM) {
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@ -289,7 +328,7 @@ mem_malloc(mem_size_t size)
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mem2->prev = ptr;
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mem2->next = mem->next;
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mem->next = ptr2;
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if (mem2->next != MEM_SIZE) {
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if (mem2->next != MEM_SIZE_ALIGNED) {
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((struct mem *)&ram[mem2->next])->prev = ptr2;
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}
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@ -330,6 +369,11 @@ mem_malloc(mem_size_t size)
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#else
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/**
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* Adam's mem_malloc() plus solution for bug #17922
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*
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* Allocate a block of memory with a minimum of 'size' bytes.
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* @param size is the minimum size of the requested block in bytes.
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*
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* Note that the returned value will always be aligned.
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*/
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void *
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mem_malloc(mem_size_t size)
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@ -343,28 +387,36 @@ mem_malloc(mem_size_t size)
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/* Expand the size of the allocated memory region so that we can
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adjust for alignment. */
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if ((size % MEM_ALIGNMENT) != 0) {
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size += MEM_ALIGNMENT - ((size + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT);
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size = MEM_ALIGN_SIZE(size);
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if(size < MIN_SIZE) {
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/* every data block must be at least MIN_SIZE long */
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size = MIN_SIZE;
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}
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if (size > MEM_SIZE) {
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if (size > MEM_SIZE_ALIGNED) {
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return NULL;
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}
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/* protect the heap from concurrent access */
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sys_sem_wait(mem_sem);
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for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE - size; ptr = ((struct mem *)&ram[ptr])->next) {
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/* Scan through the heap searching for a free block that is big enough,
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* beginning with the lowest free block.
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*/
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for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED - size;
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ptr = ((struct mem *)&ram[ptr])->next) {
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mem = (struct mem *)&ram[ptr];
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if ((!mem->used) &&
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(mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
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/* mem is not used and at least perfect fit is possible */
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if (mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) > size) {
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if (mem->next - (ptr + (2*SIZEOF_STRUCT_MEM) + MIN_SIZE) >= size) {
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/* split large block, create empty remainder,
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remainder must be large enough to contain data: if
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remainder must be large enough to contain MIN_SIZE data: if
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mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
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struct mem will fit in but no data between mem2 and mem2->next
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struct mem would fit in but no data between mem2 and mem2->next
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*/
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ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
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/* create mem2 struct */
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@ -372,35 +424,18 @@ mem_malloc(mem_size_t size)
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mem2->used = 0;
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mem2->next = mem->next;
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mem2->prev = ptr;
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/* and insert it between mem and mem->next */
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mem->next = ptr2;
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mem->used = 1;
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if (mem2->next != MEM_SIZE) {
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if (mem2->next != MEM_SIZE_ALIGNED) {
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((struct mem *)&ram[mem2->next])->prev = ptr2;
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}
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} else if (mem->next - (ptr + SIZEOF_STRUCT_MEM) > size) {
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/* near fit: do not split but move mem->next directly behind mem */
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mem2 = (struct mem *)&ram[mem->next];
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if (mem2->used) {
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/* can't move mem2, splitting not possible
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-> memory between mem and mem2 will be 'lost' */
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mem->used = 1;
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} else {
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mem_size_t next2;
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/* remember the next pointer */
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next2 = mem2->next;
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ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
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/* create mem2 struct */
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mem2 = (struct mem *)&ram[ptr2];
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mem2->used = 0;
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/* insert the old next pointer */
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mem2->next = next2;
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mem2->prev = ptr;
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mem->next = ptr2;
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mem->used = 1;
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}
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} else {
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/* exact fit: do not split, no mem2 creation */
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/* near fit or excact fit: do not split, no mem2 creation
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* also can't move mem->next directly behind mem, since mem->next
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* will always be used at this point!
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*/
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mem->used = 1;
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}
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@ -411,7 +446,7 @@ mem_malloc(mem_size_t size)
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}
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#endif /* MEM_STATS */
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if (mem == lfree) {
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/* Find next free block after mem */
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/* Find next free block after mem and update lowest free pointer */
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while (lfree->used && lfree != ram_end) {
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lfree = (struct mem *)&ram[lfree->next];
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}
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@ -422,7 +457,9 @@ mem_malloc(mem_size_t size)
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(mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
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LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
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(unsigned long)((u8_t *)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
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LWIP_ASSERT("Sanity check alignment", (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
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LWIP_ASSERT("mem_malloc: sanity check alignment",
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(((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);
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return (u8_t *)mem + SIZEOF_STRUCT_MEM;
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}
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}
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extern "C" {
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#endif
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/* MEM_SIZE would have to be aligned, but using 64000 here instead of
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* 65535 leaves some room for alignment...
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*/
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#if MEM_SIZE > 64000l
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typedef u32_t mem_size_t;
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#define MEM_SIZE_F U32_F
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